old car won't start -- help!
November 10, 2010 2:34 PM   Subscribe

Old car ('91 Tercel) won't start on cold, wet mornings. Trusted mechanic can't find anything wrong. Since this trouble began ten months ago, have replaced MAP sensor, starter, battery and ignition coil. Any hacks or diagnostic tips?

I'm no mechanic (although I change my own oil). Have some electrical knowledge, and a voltmeter, so I could take some measurements. Vehicle just passed its smog check. Precise symptoms: starter spins, just won't ignite. I've learned that if it doesn't start up immediately, continuing to crank the starter is futile. Usually the car starts fine, later in the day, when things warm up (although today seems to be an exception). And starting (after a spell where it won't) is very rough, with some visible exhaust -- but otherwaise this car runs great and I don't want to replace it.

Maybe a new fuel pump? But I'm guessing my mechanic would've replaced that by now.

And I'm not flooding it -- I don't touch the gas pedal because it doesn't seem to make any difference, until after the engine actually starts.

Any advice? And by hacks, I remember how my brother used to remove his Oldsmobile's air cleaner and, using a medicine dropper, he'd deposit a few drops of gasoline into the carburetor when that car wouldn't start. Since it feels like nothing's being delivered to ignite in my engine, I'm tempted to remove the most convenient spark plug and add some gas, like my bro did. But my machine is fuel injected.
posted by Rash to Travel & Transportation (24 answers total)
My first thought is 'spark plug'. They're cheep and easy to replace and old/dirty ones can keep your engine from turning over easily. Maybe check them, and see about replacing your distributor cap/cables as well. Good luck.
posted by Pecinpah at 2:43 PM on November 10, 2010

Spray the spark plug wires and the coil wire with WD-40. It sounds like they are getting damp and dry out as the day gets warmer.
posted by Old Geezer at 2:54 PM on November 10, 2010

If it is always cold wet mornings, I'd change the electrics all out - (delete as appropriate) spark plugs, leads, distributor cap and arm. The main thing that damp air does is allow dissipation of high voltage, so this would be something I'd hit as a priority. Being as you have already replaced the coil (but didn't mention anything else) I am assuming you haven't already done these.

However, your comment that if it doesn't immediately start then it won't, means I wonder if it is something else. Usually a weak spark will fire eventually, so cranking wouldn't be futile in that instance. Lumpy start up with smoke does, however, support poor spark as a possibility.

Another option is the cold start circuit (again, if the car has one) which is an extra injector that squirts more fuel into the cylinder when the engine is very cold. Now, if dry cold starts fine and wet cold doesn't start, then it isn't this.

Is it always wet cold that is the issue? Or are you not able to be that specific?

Fuel delivery could be an issue, but the wet cold is kind of an odd symptom unless there is some corrosion on tehe fuel pump terminals, but it seems an outside chance to me.
posted by Brockles at 3:01 PM on November 10, 2010 [1 favorite]

I'd look at the cold start injector (CSI) circuit and its accompanying components: the cold start injector, the cold start injector timer, and the EFI computer.

On a carbureted motor, pumping the carb before starting the motor does serve to prime the motor. On a fuel injected motor, the cold start injector does that same task.

Note that because it is fuel injected, it doesn't matter what you do with the gas pedal before you start the motor, although the most reliable way to start an EFI motor is to keep your foot off the gas pedal until is fires up.

The cold start injector is controlled by the EFI computer. The EFI computer has several sensors that tell the CSI when and how long to inject fuel. Read page 20 of this document for a comprehensive description of the Toyota CSI circuit.
posted by mosk at 3:02 PM on November 10, 2010 [1 favorite]

Cap and spark lug wires. Both cheap to replace, and if there's a crack anywhere getting moisture in, that'll cause your trouble. Did you mean MAF sensor? That's an expensive thing to have had replaced for this kind of problem; ditto the battery and starter (since it's cranking, why would the starter and battery need to be replaced?)

So once you've replaced the cap and wires, and it starts working just fine, you might want to start looking for a new "trusted" mechanic (or at least get some second opinions going forward.)
posted by davejay at 3:03 PM on November 10, 2010 [1 favorite]

As former owner of older Toyota, Nthing distributor cap. That was ALWAYS the problem when my care wouldn't start.
posted by mneekadon at 3:06 PM on November 10, 2010

I have a 90 Camry that used to give me fits when it was damp/wet. Finally had the cap & rotator arm replaced along with the plug wires. No more problems.

Good Luck.

posted by sandpine at 3:08 PM on November 10, 2010

Looks like two other people have beat me to distributor cap. "won't start on cold, wet mornings" usually means that condensation is getting under the cap.

You can replace the cap yourself fairly easily - just make sure you keep track of which spark plug wire goes to which terminal on the cap. Easiest way is to just unclip the old cap from the distributor, clip on the new cap, and then transfer the wires from the old cap to the corresponding terminal on the new cap one at a time.
posted by zombiedance at 3:15 PM on November 10, 2010

Response by poster:

It burned up a couple months ago in a rather peculiar low-idle situation involving dieseling after ignition switch cut-off -- probably unrelated.

posted by Rash at 3:22 PM on November 10, 2010

> It burned up a couple months ago...

Which "it" are you referring to? The car? The motor? Components on the motor?
posted by mosk at 3:32 PM on November 10, 2010

Response by poster: Sorry, "it" was the starter.
posted by Rash at 4:04 PM on November 10, 2010

Response by poster: More details:

Troubles began in January when I noticed occasional fading during acceleration. Then, one cold morning, the car wouldn't start no matter what -- so after my first tow, the mechanic replaced the very expensive MAP (not MAF) sensor. When I still had trouble starting, mechanic replaced plugs, cables, battery and ignition coil (but I'm not sure about the distributor cap). Car then ran well all summer, but as I feared now that the cold, rainy California winter is here, more troubles.

The car doesn't exactly live outside, but not in a garage, either -- my parking space is roofed over.
posted by Rash at 4:20 PM on November 10, 2010

It sounds like your mechanic took the shotgun approach to fixing things by replacing a lot of the "usual suspect" components, but it's unclear if he did any actual troubleshooting of the problem. Motors need three things to run: fuel, air, and spark. Not enough of any of those, or too much air or fuel, and it won't start. Would it/will it exhibit this behavior for your mechanic? Did he do any testing?

I think that the correct next step is to see if it's a spark problem (too little getting to the cylinders at startup when the weather is bad) or a fuel problem (too much/too little at startup when the weather conditions are bad).

The spark situation is easy for a mechanic to determine with an engine analyzer, but harder for you to determine on your own if you don't know what you are doing. (There are some low tech ways to check spark, but I don't want to recommend them to someone who hasn't done much shade tree wrenching, as you could get shocked.)

The fuel situation is a bit tougher to test on your own because the EFI system pressurizes fuel, andyou should not be messing around with fuel injectors and pressurized fuel if you don't know what you are doing.

Bottom line: a simple visual inspection of the contact surfaces inside the distributor cap and on the top and tip of the rotor should indicate if they are new or worn; if they are worn, replace them and see if that solves the problem. (Tip: get these parts from NAPA or the dealer, not AutoZone or the equivalent). However, to really fix the root cause of the problem you should consider taking it to a mechanic that has an engine analyzer and having them troubleshoot...and for best results, you'd like to take it the night before a storm so the mechanic can see it in the morning when the weather is rainy and it (presumably) won't start.
posted by mosk at 4:45 PM on November 10, 2010

Response by poster: Is it always wet cold that is the issue? Or are you not able to be that specific?

Definitely cold, definitely after sitting overnight, but not every night. Moisture seems to guarantee I'll be having difficulty in the morning.
posted by Rash at 5:23 PM on November 10, 2010

Here's how you can test this yourself.
Fill a spray bottle with water.
Start the car and open the hood. Identify the distributer cap. Spritz liberally with water. If the car begins to run rough, then it's a sure bet that a new distributer cap and rotor will solve this problem. This way, you don't need to wait for a rainy day to test you hypotheses.

If you brought your car to me and said, "When it's wet out, the car doesn't start" this would be my first diagnostic procedure, no matter what other sophisticated diagnostic equipment I have in my tool box. "Verify the concern" and "simulate the conditions" are the two foundations of any deliberate diagnosis. Anything else is shotgunning parts and guessing.
posted by Jon-o at 5:24 PM on November 10, 2010 [5 favorites]

nthing plugs, wires, and distributor.
posted by TrialByMedia at 7:39 PM on November 10, 2010

Here's the nice part about replacing the distributor cap and rotor - they're cheap parts. They're also insanely easy to replace.
posted by azpenguin at 7:48 PM on November 10, 2010

My Tercel is long-gone, and it was carbureted, so I'm not even sure whether you have similar parts. But mine had an exhaust gas recirculation (EGR) valve that caused cold-start issues when it failed. If that part still exists on the fuel injected version of the engine, and Autozone indicates it does, I'd look at that.

It's not something crazy stupid like a cracked distributor body letting moisture in, is it? Or a part that you've already replaced but it got damaged somehow? On mornings where it doesn't start, could you make it go by directing a hairdryer at the distributor for a couple minutes?

If none of this works, you might be able to save yourself a lot of grief by just taking the car to a shop that can talk to the electronics in your fuel injection system. It consists of many, many parts; experienced MeFites above have suggested parts that you've already replaced, but there's a lot left to do via trial and error. That's going to get expensive, eventually.
posted by richyoung at 9:03 PM on November 10, 2010

MAP sensor, indeed! I have learned something today.
posted by davejay at 9:18 PM on November 10, 2010

2nding the diagnostic thing. Sounds like lack of spark, so remove a plug lead from the plug, stick a screwdriver up the plug end of the lead, and with someone cranking the engine and you holding the plastic/rubber/wood handle of the screwdriver, move the shaft of the screwdriver so it almost touches a bolt or other convenient metal part of the engine - if all is ok you will see and hear a big spark jumping from the screwdriver shaft across to the engine. No spark? Ignition off, check that the blade of the screwdriver is making contact with the metal clip right up inside the connector, then repeat the cranking exercise. Note, be very careful not to touch the metal of the screwdriver while cranking, or the high voltage current will earth through you - not pleasant, don't ask me how I know this ... but it is a most unambiguous way to confirm the state of the ignition system.

If there is still no spark, this is the problem. Replace all the components not already replaced - plugs, all leads, distributor cap, and distributor rotor. Make sure the little spring loaded button that projects from the inside of the distributor cap is long enough to make contact with the rotor. When replacing the rotor, note that will be a keyway or similar to locate it at the right angle, make sure the rotor is engaging this and seated properly (it might take a bit of a push). There is (if I remember my distributors) a capacitor in the distributor, make sure that all the connections are done up properly and no loose wires around.

If it is not spark, and the engine is fuel injected, you are probably beyond what a basic guy can troubleshoot and fix, unless it is something obvious like you can't hear the fuel pump as you normally can. In that case, the new maechanic suggestion sounds pretty good to me.

Good luck.
posted by GeeEmm at 3:19 AM on November 11, 2010 [1 favorite]

Response by poster: I did receive a new Distributor Cap in Janauary, tried Jon-o's water spray test; no difference when the engine is running.

So I think it must be some part of the cold start injector (CSI) circuit and its accompanying components: the cold start injector, the cold start injector timer, or the EFI computer.

Thanks for all your ideas and advice!
posted by Rash at 10:09 AM on November 11, 2010

Although it may well be the cold start injector (or the EGR or another system, for that matter), I don't think you can rule out the distributor cap based on the test you did, as the "spray water on it" test isn't really a valid test.

Your situation is that it won't start on rainy or "wet" mornings. This may be because, overnight, condensation creeps into the cap, either through a crack in the cap or distributor, or because the O-ring at the base of cap isn't sealing well. When there is moisture inside the cap, this shorts the circuit before the spark can travel from the rotor to the lead for each spark plug/cylinder.

If the motor is already running, there is enough energy/heat inside the cap to keep the motor running. You can't adequately simulate the condition when the fault occurs by spraying a running, warm engine with water. What you want to test is the situation when the motor is NOT running, and the air inside/around the cap is cold and damp.

BTW, if you do encounter the situation of the engine not starting, a simple means of testing the cap is to remove it and spray the inside lightly with WD-40 and reinstall it. WD-40 displaces water -- that's what the "WD" stands for -- and if it starts after WD-40 is applied, it's definitely your cap that's leaking.
posted by mosk at 12:30 PM on November 11, 2010

Response by poster: Well I'll try that one as well. But it seems my problem's not just wet mornings, though damp air seems to guarantee trouble.

Last night I left my car at the shop in hopes it wouldn't start this morning but alas, cranked right up, wasn't cold enough. Mechanic says it could be my Head Temperature Sensor but since everything check out okay, he didn't do anything. Guess I'll just be repeating that move when it gets colder.
posted by Rash at 12:31 PM on November 12, 2010

Response by poster: Finally got my mechanic to see the problem, after another tow following a couple cold days when it wouldn't even start once things warmed up. He swapped out my spark plug wires and distributer cap, now all's well.
posted by Rash at 3:30 PM on January 14, 2011

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