Cheapest way for me to diagnose car troubles.
May 29, 2009 6:43 AM Subscribe
Engine is turning over slowly and I think it might be the battery. Affordable way to check this myself or just take it into the garage?
The other day, I went to start my 2002 Toyota echo, and the engine had a really slow turn over before it finally started. I notice if I give it a bit of gas, it starts right away. No check engine or battery lights come on while driving around town. From the research I have been doing, it seems to suggest either the battery or the alternator. My wife bought the car used 3 years ago, so there is a good chance it is the original battery, so i am leaning toward a dying battery. Is there a cheap way to figure this out? I don't own a battery charger or a voltmeter, and am trying to figure out if it's cheaper to just have the dealer check it out when we bring the car in for an oil change tomorrow or pick up some items at the auto store and test it myself tonight (and get some tools in the process). Suggestions?
The other day, I went to start my 2002 Toyota echo, and the engine had a really slow turn over before it finally started. I notice if I give it a bit of gas, it starts right away. No check engine or battery lights come on while driving around town. From the research I have been doing, it seems to suggest either the battery or the alternator. My wife bought the car used 3 years ago, so there is a good chance it is the original battery, so i am leaning toward a dying battery. Is there a cheap way to figure this out? I don't own a battery charger or a voltmeter, and am trying to figure out if it's cheaper to just have the dealer check it out when we bring the car in for an oil change tomorrow or pick up some items at the auto store and test it myself tonight (and get some tools in the process). Suggestions?
Most auto places will check a battery for free - autozone, parks, pepboys, etc.
posted by anti social order at 6:52 AM on May 29, 2009
posted by anti social order at 6:52 AM on May 29, 2009
Best answer: Most tyre and exhaust type places will test a battery for free. First point of call, though, is to check the connections are clean and tight, as this will very much affect cranking speed.
It is not at all cheaper to put a battery in than check a battery or alternator. You can get a voltmeter for about $5-10 and this will easily tell you if the alternator is screwed (it should read above 12V when the engine is sitting at a fast idle) and if the battery is screwed (if the alternator is working, the battery should be sitting at 11.8-12V with the engine off and not drop enormously from that voltage when cranking to start).
However, it is unlikely to be your alternator if the light is not on (it tells you when it's not charging) so a new battery is likely but, as I said, a lot of places will test this for free on the chance of making a sale on a battery. It takes about 5 seconds to do.
posted by Brockles at 6:55 AM on May 29, 2009 [3 favorites]
It is not at all cheaper to put a battery in than check a battery or alternator. You can get a voltmeter for about $5-10 and this will easily tell you if the alternator is screwed (it should read above 12V when the engine is sitting at a fast idle) and if the battery is screwed (if the alternator is working, the battery should be sitting at 11.8-12V with the engine off and not drop enormously from that voltage when cranking to start).
However, it is unlikely to be your alternator if the light is not on (it tells you when it's not charging) so a new battery is likely but, as I said, a lot of places will test this for free on the chance of making a sale on a battery. It takes about 5 seconds to do.
posted by Brockles at 6:55 AM on May 29, 2009 [3 favorites]
Take it to one of the auto parts store - they test the electrical stuff for free. And will usually install a new battery if that ends up being it. I have my money on it being a battery. Usually if it is that old - I'll go ahead and replace it (if it is starting slow - etc).
posted by jaythebull at 7:07 AM on May 29, 2009
posted by jaythebull at 7:07 AM on May 29, 2009
Response by poster: Thanks everyone! Couple things I need clarification on (sorry, I'm slow)
1) When I was considering picking up a voltmeter, some articles seem to suggest that the battery has to be charged (assuming it will take a charge) before this route would work. Is this so?
2) Taking it into a parts store for testing: would I need to pull the battery or do they bring a tester to the car? Does the battery have to be charged to be tested at the store?
posted by scarello at 7:19 AM on May 29, 2009
1) When I was considering picking up a voltmeter, some articles seem to suggest that the battery has to be charged (assuming it will take a charge) before this route would work. Is this so?
2) Taking it into a parts store for testing: would I need to pull the battery or do they bring a tester to the car? Does the battery have to be charged to be tested at the store?
posted by scarello at 7:19 AM on May 29, 2009
Best answer: If you want to do it yourself, grab a voltmeter, and touch its leads to the battery terminals while the car is not running. You should see ~11-13 VDC. Any lower and your battery's likely weak or discharged. Now, start the car. Touch the leads to the battery terminals again. You should see ~13-14 VDC. If you don't see an increase in voltage, then your alternator is likely operating improperly and not charging the battery. If you do see an increase, your alternator is operating properly and the battery isn't taking a charge.
If you want to take it into a parts store, they keep the battery testers on little carts. You can either bring your battery in, or let them wheel the cart out into the parking lot. Your choice.
posted by TheNewWazoo at 7:24 AM on May 29, 2009
If you want to take it into a parts store, they keep the battery testers on little carts. You can either bring your battery in, or let them wheel the cart out into the parking lot. Your choice.
posted by TheNewWazoo at 7:24 AM on May 29, 2009
Every time I have been to a parts store, they have the tester on a cart. So they bring it out to the car and test it. Bonus: They will be able to help you pull the battery and replace right there if it is needed!!
posted by snoelle at 7:34 AM on May 29, 2009
posted by snoelle at 7:34 AM on May 29, 2009
Make sure the battery terminals are clean. You'd be surprised how often a poor connection causes the starting circuit to perform poorly. One "wet finger in the air" way to check for a poor connection is to see if the headlights are bright with the engine off. If the battery is weak, the headlights will be dim (if they are xenons, though, this won't work as they just won't start at all without sufficient current).
If the headlights are bright but the starting circuit is starved/slow, try cleaning the terminals or, using a crosspoint or Phillips head screwdriver, gently tap the point of the screwdriver in a few positions about the seam between the battery post and the connector. This will usually improve the connection dramatically. Be gentle, though.
If the starter is still slow, I'd suspect the battery has reached the end of its lifespan. They usually only last about five years. Shorter, by about a third, in warm climates.
posted by bz at 8:38 AM on May 29, 2009
If the headlights are bright but the starting circuit is starved/slow, try cleaning the terminals or, using a crosspoint or Phillips head screwdriver, gently tap the point of the screwdriver in a few positions about the seam between the battery post and the connector. This will usually improve the connection dramatically. Be gentle, though.
If the starter is still slow, I'd suspect the battery has reached the end of its lifespan. They usually only last about five years. Shorter, by about a third, in warm climates.
posted by bz at 8:38 AM on May 29, 2009
A jump start is a good test. If you can get someone to jumpstart your car with theirs, and this actually starts the car, then drive the car to the auto parts store. Once there, stop the car, wait a few minutes, and try starting it. If, in spite of the fact that you have given it a chance to charge on the drive, the car has a hard time cranking, then the battery is probably toast. (Use caution when jumping. An exploding battery will ruin your day.)
Less common is that the alternator is not charging. In that case, you should probably have a dash board gauge or idiot light telling you that there is a problem.
posted by Midnight Skulker at 8:57 AM on May 29, 2009
Less common is that the alternator is not charging. In that case, you should probably have a dash board gauge or idiot light telling you that there is a problem.
posted by Midnight Skulker at 8:57 AM on May 29, 2009
Best answer: If you've had the car for three years and don't know the age of the current battery, just replace it. CRC makes a great pair of products: a battery terminal cleaner and a battery terminal protector. Clean up your terminals before you install the battery, and then apply the protector after you've bolted everything up. It does a great job of preventing the corrosion.
You're going to need, if I remember correctly, a 10 or 12mm socket for the terminals and a 10mm for the battery tie-down bracket. Get some wd40 because the bracket bolts are going to be rusty and crappy. Be careful not to drop the tie-down bolts deep into the engine bay. They're just a J shaped piece of metal with threads on top that loop under the battery tray. Don't be lazy and leave them out, either. The battery will bounce around, short against the hood and suffer from excessive vibration.
When removing, remove the NEGATIVE terminal first, and when installing, put the POSITIVE on first. The reason being, the ground side gernarlly won't arc as aggressively.
posted by Jon-o at 9:27 AM on May 29, 2009 [1 favorite]
You're going to need, if I remember correctly, a 10 or 12mm socket for the terminals and a 10mm for the battery tie-down bracket. Get some wd40 because the bracket bolts are going to be rusty and crappy. Be careful not to drop the tie-down bolts deep into the engine bay. They're just a J shaped piece of metal with threads on top that loop under the battery tray. Don't be lazy and leave them out, either. The battery will bounce around, short against the hood and suffer from excessive vibration.
When removing, remove the NEGATIVE terminal first, and when installing, put the POSITIVE on first. The reason being, the ground side gernarlly won't arc as aggressively.
posted by Jon-o at 9:27 AM on May 29, 2009 [1 favorite]
Take it to Sears would be my recommendation. You just drive right in, they test it and your alternator for free and they have some of the better replacement batteries around. The whole process of getting a new battery there is extremely simple.
posted by caddis at 11:16 AM on May 29, 2009
posted by caddis at 11:16 AM on May 29, 2009
Response by poster: Well, I ran some tests with a voltmeter and the battery and alternator seem fine. Not sure what if could be....starter motor?
posted by scarello at 3:40 PM on May 29, 2009
posted by scarello at 3:40 PM on May 29, 2009
I think it is unlikely that it is the starter motor. My experience has been that they either work or they don't...
posted by HuronBob at 4:21 PM on May 29, 2009
posted by HuronBob at 4:21 PM on May 29, 2009
Can you define the battery checks you did? The important element is not just the held voltage, but also how much the voltage drops when it cranks (during actual starting).
It could still be the starter or any of the connections inbetween, including the earth strap to the body from the battery. Check them all and get someone to crank the engine while you watch the voltmeter and see what it does. Is there any reason you didn't get someone to put a battery tester on it? That would have tested it for voltage and load performance too, see...
posted by Brockles at 4:36 PM on May 29, 2009
It could still be the starter or any of the connections inbetween, including the earth strap to the body from the battery. Check them all and get someone to crank the engine while you watch the voltmeter and see what it does. Is there any reason you didn't get someone to put a battery tester on it? That would have tested it for voltage and load performance too, see...
posted by Brockles at 4:36 PM on May 29, 2009
Response by poster: Yeah, I just tested the battery with the car off and got a reading of about 13 volts or so and then tested with the car running and the voltage remained steady. Didn't have anyone around to start the engine so I could watch the meter on start up though. I'll drop by someplace tonight and have them test the battery for me. . Otherwise, it's going in for an oil change tomorrow, so worst case scenario I will see what they say. I know the car is overdue for its regular oil change so it may be sticking fuel injectors or dirty filter, the list goes on it seems. Thanks for all of the help.
posted by scarello at 4:57 PM on May 29, 2009
posted by scarello at 4:57 PM on May 29, 2009
so it may be sticking fuel injectors or dirty filter, the list goes on it seems.
Nope. Slow cranking can only be caused by the battery, the charge within it (hence the alternator), the starter and the connections between them. Batteries can often hold 12V yet go all jelly-tastic and weak when given a load (like starting an engine) to deal with. They tend to bluff before they give in, if you get the analogy...
posted by Brockles at 8:08 PM on May 29, 2009
Nope. Slow cranking can only be caused by the battery, the charge within it (hence the alternator), the starter and the connections between them. Batteries can often hold 12V yet go all jelly-tastic and weak when given a load (like starting an engine) to deal with. They tend to bluff before they give in, if you get the analogy...
posted by Brockles at 8:08 PM on May 29, 2009
Response by poster:
Nope. Slow cranking can only be caused by the battery, the charge within it (hence the alternator), the starter and the connections between them. Batteries can often hold 12V yet go all jelly-tastic and weak when given a load (like starting an engine) to deal with. They tend to bluff before they give in, if you get the analogy..
Well, I don't know what to say then. Just got back from the shop and the battery and alternator are fine. Had them replace the spark plugs since they were near time for replacement and it's still cranking slow. They said it may be the fuel injectors sticking, but would have to bring it in for a diagnostic during the week to be sure. Not sure what else I can do.
posted by scarello at 8:27 AM on May 30, 2009
Nope. Slow cranking can only be caused by the battery, the charge within it (hence the alternator), the starter and the connections between them. Batteries can often hold 12V yet go all jelly-tastic and weak when given a load (like starting an engine) to deal with. They tend to bluff before they give in, if you get the analogy..
Well, I don't know what to say then. Just got back from the shop and the battery and alternator are fine. Had them replace the spark plugs since they were near time for replacement and it's still cranking slow. They said it may be the fuel injectors sticking, but would have to bring it in for a diagnostic during the week to be sure. Not sure what else I can do.
posted by scarello at 8:27 AM on May 30, 2009
There is no way the injectors can affect the speed of cranking the engine - none at all. So either they are trying to fleece you, or this is a terminology issue:
By cranking, do you mean the speed at which the engine is rotating while purely on the starter motor (before it fires up and runs)? This is the correct use of the phrase.
Or do you mean the amount of time the engine turns only on the starter motor before it fires - industry would refer to this as 'slow starting' or 'takes a while to fire up' or similar.
If the engine turns over slowly (that "Chu-chu-chu" sound before the "BRum" that means its started), it is only affected by the starter and the current fed to it if the engine is otherwise in a condition that it will run - ie if it starts at all, it can only be the starter, battery and leads between them.
posted by Brockles at 9:05 AM on May 30, 2009
By cranking, do you mean the speed at which the engine is rotating while purely on the starter motor (before it fires up and runs)? This is the correct use of the phrase.
Or do you mean the amount of time the engine turns only on the starter motor before it fires - industry would refer to this as 'slow starting' or 'takes a while to fire up' or similar.
If the engine turns over slowly (that "Chu-chu-chu" sound before the "BRum" that means its started), it is only affected by the starter and the current fed to it if the engine is otherwise in a condition that it will run - ie if it starts at all, it can only be the starter, battery and leads between them.
posted by Brockles at 9:05 AM on May 30, 2009
Response by poster: As to whether the dealer is trying to fleece me, I wonder sometimes, as every time I go for an oil change there is a problem with my car, but that's another matter...lets see if maybe I am explaining this all wrong...I get in the car, turn the key and it does the chu chu chu you are referring to. It will do this until I give some gas from the pedal and then the engine starts up (sometimes I have to try twice). So it take a longer time to fire up the engine than it usually does and won't start at all without gas, which is unusual for a fuel injected vehicle. This only started a few days ago and it's been raining here alot (not sure if that makes any difference, but thought I would add that detail anyways). Thanks for the patience!
posted by scarello at 10:33 AM on May 30, 2009
posted by scarello at 10:33 AM on May 30, 2009
Ok, then the problem is we've been trying to answer completely the wrong question due to incorrect terminology and not enough detail!
ho hum. These things happen surprisingly often. It is important, when asking advice on a topic you are (openly) not very knowledgeable about, to try and remove any of the assumptions you (or other people of the same knowledge level) have made. In another instance you could have wasted a lot of time or money asking the garage to investigate the wrong issue and also opened yourself up to an opportunity for fleecing as they fix the mythical problem in a way that is plausible but quite possibly unrelated. You can't really have too much information and background when trying to diagnose this kind of thing over an internet forum, that's for sure.
So, this has nothing at all to do with alternators, starter motors, batteries or connections. None of the advice above (including mine) is at all relevant to your issue. Other that that, I think we are doing swimmingly.
So yes, it could be dirty injectors. It could be a faulty cold start valve (basically a fifth injector for starting a cold engine, if your car has one) or it could be a faulty Air Flow meter or any number of issues. It's pretty hard to get further into diagnosing your issue without getting hands on with the car, to be honest, but clearly there is some kind of issue with fuel/air mixture at start speeds.
Are there any other symptoms (no matter how unrelated you think they are)? Hesitation when pulling away from traffic light or on large changes of throttle position (ie overtaking)? Does the car feel generally down on power? All that kind of stuff may help, but as I say it is very hard to diagnose an electronic management system without poking around with it and disconnecting things to see what happens.
posted by Brockles at 10:49 AM on May 30, 2009
ho hum. These things happen surprisingly often. It is important, when asking advice on a topic you are (openly) not very knowledgeable about, to try and remove any of the assumptions you (or other people of the same knowledge level) have made. In another instance you could have wasted a lot of time or money asking the garage to investigate the wrong issue and also opened yourself up to an opportunity for fleecing as they fix the mythical problem in a way that is plausible but quite possibly unrelated. You can't really have too much information and background when trying to diagnose this kind of thing over an internet forum, that's for sure.
So, this has nothing at all to do with alternators, starter motors, batteries or connections. None of the advice above (including mine) is at all relevant to your issue. Other that that, I think we are doing swimmingly.
So yes, it could be dirty injectors. It could be a faulty cold start valve (basically a fifth injector for starting a cold engine, if your car has one) or it could be a faulty Air Flow meter or any number of issues. It's pretty hard to get further into diagnosing your issue without getting hands on with the car, to be honest, but clearly there is some kind of issue with fuel/air mixture at start speeds.
Are there any other symptoms (no matter how unrelated you think they are)? Hesitation when pulling away from traffic light or on large changes of throttle position (ie overtaking)? Does the car feel generally down on power? All that kind of stuff may help, but as I say it is very hard to diagnose an electronic management system without poking around with it and disconnecting things to see what happens.
posted by Brockles at 10:49 AM on May 30, 2009
Oh, it could also be weak spark from poor quality leads/coil/plugs, I guess, if the wet is related. It could be coincidental, but if it dries up and the problem goes away it could be worth mentioning. I'd be inclined (if the problem seems consistent) to persevere and see if you can get any more data/coincidences nailed down before you spend any more money on them trying to find it. It's a bit of a risk, as the problem may potentially leave you stranded, so it mostly hinges on how brave you are and how dependent on your car you are if it doesn't start. Intermittent or slight issues are always a hell of a job to find, and this can be expensive in terms of labour at the dealer/garage.
Also another possibly related symptom: low idle speed when it first start? Does it idle as smoothly as it used to when it is running with your feet off the pedals (stationary)?
posted by Brockles at 10:53 AM on May 30, 2009
Also another possibly related symptom: low idle speed when it first start? Does it idle as smoothly as it used to when it is running with your feet off the pedals (stationary)?
posted by Brockles at 10:53 AM on May 30, 2009
Response by poster: Ahhh, ok, sorry if it wasn't worded properly. I thought I had painted a clear picture, but I guess it was clear to someone who doesn't know what they're talking about (me). Spark plugs were changed today, so I know that's not the issue. They were past due for their change, and I had hoped it would fix it, but no luck. Car itself seems to run normally once we get it going. No hesitation or anything like that. Out of curiosity, I bought a bottle of fuel injector cleaner and dumped it into the gas tank. Car actually seemed to run a bit differently, almost smoother in a way, but that could just be psychological. What i did notice, was when I parked the car and then tried restarting it right after, it popped right on, only with a minimum of lag. But alas, when I tried to start the car again later, after letting it sit a while, it was the same old problem. Not much else I can think about in terms of troubles. Its warm and dry here now, so the car has dried off nicely.
posted by scarello at 11:08 AM on May 30, 2009
posted by scarello at 11:08 AM on May 30, 2009
Best answer: Hmmm. Starting so easily again when hot is not all that surprising. Injector cleaner should be enough, especially if the car runs evenly, as an injector that is clogged most often causes lumpy running by the point it affects starting.
My guess is one of the following:
Idle circuit issue (some sensors are used/not used just in start up - it's likely that one of those is off for these symptoms. I can't be more specific without knowing your management system more thoroughly).
Air flow Meter
Cold Start valve
Fuel pressure regulator (it may be allowing the fuel pressure in the rail to drop too far so it takes time to build up - try cycling the ignition a few times before starting it to see if there is any difference in the need to apply throttle to get it to start. The fuel pump will run for a few seconds on each time the ignition is turned on, and you can use this to 'charge' the fuel pressure in teh rail up to help this). I find this one unlikely, though.
Hmmm. Again, it could be a number of things, and without some means of diagnosing hands on or with a computer, I think we're not going to solve this without coincidental anecdotal stories from other owners. At least we've stopped you wasting money on alternators and batteries, I guess.
posted by Brockles at 11:17 AM on May 30, 2009
My guess is one of the following:
Idle circuit issue (some sensors are used/not used just in start up - it's likely that one of those is off for these symptoms. I can't be more specific without knowing your management system more thoroughly).
Air flow Meter
Cold Start valve
Fuel pressure regulator (it may be allowing the fuel pressure in the rail to drop too far so it takes time to build up - try cycling the ignition a few times before starting it to see if there is any difference in the need to apply throttle to get it to start. The fuel pump will run for a few seconds on each time the ignition is turned on, and you can use this to 'charge' the fuel pressure in teh rail up to help this). I find this one unlikely, though.
Hmmm. Again, it could be a number of things, and without some means of diagnosing hands on or with a computer, I think we're not going to solve this without coincidental anecdotal stories from other owners. At least we've stopped you wasting money on alternators and batteries, I guess.
posted by Brockles at 11:17 AM on May 30, 2009
Response by poster: Thanks alot Brockles, really appreciate you taking some time out to help me try to figure this out. I'd love to try and fix it on my own, but I think I may have to dole out for the diagnostics. The wife takes this car on the highway every day, so it's worth it to be sure she is safe.
What did strike me as interesting is the point you make about the fuel regulator. I do notice that if it doesn't start the first time, it usually starts the second (still with a shot of gas). Hmmm...
posted by scarello at 12:03 PM on May 30, 2009
What did strike me as interesting is the point you make about the fuel regulator. I do notice that if it doesn't start the first time, it usually starts the second (still with a shot of gas). Hmmm...
posted by scarello at 12:03 PM on May 30, 2009
A bad fuel pressure regulator is typically going to cause problems accross the board. On your 02 Echo, the pressure regulator is just a little mechanical diaphragm that controls the fuel return from the rail to the tank, thus maintaining pressure. The diaphragm is controlled via intake manifold pressure signal. For example, at idle there's less pressure in the manifold, 400milibar and that negative pressure pulls the diaphragm open, allowing fuel to bypass. At wide open throttle, you'll have closer to 1000milibar in the manifold, not enough negative pressure to effect a change on the diaphragm and no fuel bypasses, ensuring that maximum pressure is available at the injectors to accelerate the engine. If you had a pressure regulator that had failed, you would likely have hard starting AND poor performance.
On a modern car, when you press the pedal while starting, you're not actually applying more fuel to the engine like you were in a pre fuel-injected car. These days, you're mostly just allowing more air to flow to the engine by opening the throttle. Given your description, I'm going to say that you have a clogged fuel injector. It hasn't clogged shut, causing a misfire or lack of fuel. There's an injector that is contaminated and stuck slightly open, allowing the flooding of fuel into the engine, causing hard starting while otherwise functioning well enough that the car runs OK.
posted by Jon-o at 4:15 AM on June 2, 2009
On a modern car, when you press the pedal while starting, you're not actually applying more fuel to the engine like you were in a pre fuel-injected car. These days, you're mostly just allowing more air to flow to the engine by opening the throttle. Given your description, I'm going to say that you have a clogged fuel injector. It hasn't clogged shut, causing a misfire or lack of fuel. There's an injector that is contaminated and stuck slightly open, allowing the flooding of fuel into the engine, causing hard starting while otherwise functioning well enough that the car runs OK.
posted by Jon-o at 4:15 AM on June 2, 2009
Jon-o: I've never seen a vacuum controlled pressure regulator on an injected car. They've all been a restricting valve working on spring pressure balanced against an ambient pressure outlet (a teeny pipe on top) and not connected to the vacuum system at all. In addition, I have been unable to find an Echo specific pressure regulator on any online parts site that is different in configuration from any pressure regulator that I would consider typical.
Can you please cite some sources for your version of how the regulator works?
Injectors need a constant pressure to function normally - they won't fire at all if the pressure is too low, no matter if they are electrically activated or not. Pressure is held in the fuel rail by a restricting valve (the pressure regulator) that opens only over the standard rail pressure, thus ensuring a constant head of pressure at the back of the injectors. Fuel flow and correct atomisation on injector firing is thus kept consistent and controlled by duration of the firing pulse. I have not heard of any automotive injector that would cope at all with varying pressures as you describe - starting would be the worst possible time for varying pressure, too, which makes it illogical, from my understanding.
There's an injector that is contaminated and stuck slightly open, allowing the flooding of fuel into the engine, causing hard starting while otherwise functioning well enough that the car runs OK.
This doesn't fit with the 'starts fine hot but not when its been sat for a while' scenario. If the injector was leaking into the bore, it would only do so until rail pressure leaks down to ambient pressure; ie for a finite time after stopping the engine. The fuel in the bore would either evaporate (if an exhaust or inlet valve was open) or run past the pistons if the car was left long enough and the car would start relatively normally (albeit, perhaps lumpily with the poorly functioning injector). Given enough time, and with a cold engine, there would be almost zero fuel in the cylinder in initial cranking to cause an issue and it is more likely to cause a problem when restarting from semi-hot (as petrol would evaporate and remain in the bore, rather than trickle out).
If the car started reluctantly at times, and ran rough for the first few seconds, I'd agree it is a possible solution, issue, but it is not consistent with the symptoms, to my mind. In addition, I see no reason for a slightly clogged injector to produce no other symptoms - why would it not cause a slight misfire, being as it would not be misting the fuel correctly?
A regulator with a slight leak (a full, banzai, leak would give different symptoms) can cause this problem as follows:
Rail pressure drops over time to below the pressure required to fire the injector as fuel is allowed to continue over time to bleed pressure back down the return line. Consequently, when the car is cranked for starting, the injectors either don't fire until full pressure is maintained in the rail (taking a little longer than normal to regain pressure than the initial burst of the fuel pump on ignition on that usually happens) or they fire in an inefficient manner and don't atmomise the fuel correctly, meaning that a difficult to start fuel charge is injected (it being mostly dribbly fuel and not enough fuel droplets/mist like normal).
This means that while the engine is cranking, a very rich mixture that is difficult to ignite in a cold engine is in the piston. Opening the throttle and increasing the air supply will begin to rectify the incorrect air/fuel ratio in the piston. The time taken for all this to happen will also allow the fuel rail pressure to return to close to normal and so the better misted fuel is able to ignite with the extra air charge (Despite the greater amount of raw fuel in the piston).
posted by Brockles at 5:26 AM on June 2, 2009
Can you please cite some sources for your version of how the regulator works?
Injectors need a constant pressure to function normally - they won't fire at all if the pressure is too low, no matter if they are electrically activated or not. Pressure is held in the fuel rail by a restricting valve (the pressure regulator) that opens only over the standard rail pressure, thus ensuring a constant head of pressure at the back of the injectors. Fuel flow and correct atomisation on injector firing is thus kept consistent and controlled by duration of the firing pulse. I have not heard of any automotive injector that would cope at all with varying pressures as you describe - starting would be the worst possible time for varying pressure, too, which makes it illogical, from my understanding.
There's an injector that is contaminated and stuck slightly open, allowing the flooding of fuel into the engine, causing hard starting while otherwise functioning well enough that the car runs OK.
This doesn't fit with the 'starts fine hot but not when its been sat for a while' scenario. If the injector was leaking into the bore, it would only do so until rail pressure leaks down to ambient pressure; ie for a finite time after stopping the engine. The fuel in the bore would either evaporate (if an exhaust or inlet valve was open) or run past the pistons if the car was left long enough and the car would start relatively normally (albeit, perhaps lumpily with the poorly functioning injector). Given enough time, and with a cold engine, there would be almost zero fuel in the cylinder in initial cranking to cause an issue and it is more likely to cause a problem when restarting from semi-hot (as petrol would evaporate and remain in the bore, rather than trickle out).
If the car started reluctantly at times, and ran rough for the first few seconds, I'd agree it is a possible solution, issue, but it is not consistent with the symptoms, to my mind. In addition, I see no reason for a slightly clogged injector to produce no other symptoms - why would it not cause a slight misfire, being as it would not be misting the fuel correctly?
A regulator with a slight leak (a full, banzai, leak would give different symptoms) can cause this problem as follows:
Rail pressure drops over time to below the pressure required to fire the injector as fuel is allowed to continue over time to bleed pressure back down the return line. Consequently, when the car is cranked for starting, the injectors either don't fire until full pressure is maintained in the rail (taking a little longer than normal to regain pressure than the initial burst of the fuel pump on ignition on that usually happens) or they fire in an inefficient manner and don't atmomise the fuel correctly, meaning that a difficult to start fuel charge is injected (it being mostly dribbly fuel and not enough fuel droplets/mist like normal).
This means that while the engine is cranking, a very rich mixture that is difficult to ignite in a cold engine is in the piston. Opening the throttle and increasing the air supply will begin to rectify the incorrect air/fuel ratio in the piston. The time taken for all this to happen will also allow the fuel rail pressure to return to close to normal and so the better misted fuel is able to ignite with the extra air charge (Despite the greater amount of raw fuel in the piston).
posted by Brockles at 5:26 AM on June 2, 2009
Response by poster: Hey guys! No check engine light at all. Here is the thing...the other day I pulled the negative terminal off the battery while the car was running just to double check the alternator. After I was done, I re-tightened the cable and voila, the car starts fine and has been starting fine since. However, I now notice a strong smell of gas when I start the car and rev the engine. The wife commented on the smell as well when she started the car at work... It's almost like a sensor was reset someplace, as the cable was always quite snug before.
posted by scarello at 6:10 PM on June 4, 2009
posted by scarello at 6:10 PM on June 4, 2009
You could have removed some surface corrosion when you reinstalled that terminal.
If, at some point, the battery was disconnected and the vehicle was off, something would have reset. Sensors don't typically reset, but a modern Engine Control Module stores adapted values for fuel delivery (it can compensate for small air leaks and stuff through adaptation). That data would have been erased and the ECM will start its adaptations from scratch until it works everything out. So, a little extra stinkyness could be attributed to the ECM relearning its fuel trim.
Your car will always run richer at a cold start. A little stinkyness isn't too unusal, especially on a high mileage car. Is it colder out that usual?
Unless the fuel smell persists when the vehicle is warm, don't worry about it.
But if the gas odor is really strong, get it looked at.
posted by Jon-o at 2:23 PM on June 5, 2009
If, at some point, the battery was disconnected and the vehicle was off, something would have reset. Sensors don't typically reset, but a modern Engine Control Module stores adapted values for fuel delivery (it can compensate for small air leaks and stuff through adaptation). That data would have been erased and the ECM will start its adaptations from scratch until it works everything out. So, a little extra stinkyness could be attributed to the ECM relearning its fuel trim.
Your car will always run richer at a cold start. A little stinkyness isn't too unusal, especially on a high mileage car. Is it colder out that usual?
Unless the fuel smell persists when the vehicle is warm, don't worry about it.
But if the gas odor is really strong, get it looked at.
posted by Jon-o at 2:23 PM on June 5, 2009
Response by poster: Weather has been pretty nice actually, although it does get cooler at night. Usually once the car gets going, the smell goes away, it's just after the initial start. What's odd about the battery, is that when we took it in for an oil change, they looked at the battery and cleaned the terminals...I dont know, its odd. I guess I will just file this one away as a hiccup and keep an eye that the smell/problem does not return or intensify. Thanks again for all of the help!
posted by scarello at 3:18 PM on June 5, 2009
posted by scarello at 3:18 PM on June 5, 2009
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posted by Ery at 6:48 AM on May 29, 2009 [1 favorite]