Help me diagnose this car issue
October 7, 2023 8:14 AM Subscribe
My 2008 Kia Rio (base) has lately been difficult to start in the morning. The "check engine" light is off. The engine cranks fine but doesn't "catch". It sometimes takes four or five turns of the key before the car starts. Once the car starts, it runs fine, and subsequent starts during the day are uneventful. How do I pinpoint the problem?
I have a buddy who is a retired mechanic. He briefly looked at the car yesterday and didn't find anything obviously wrong with it. He said that the battery, alternator, and starter are all good. And, of course, the car started easily for him on five separate tries, but the engine was warm at the time (I had driven the car home from work).
What do I do next to diagnose the problem, short of taking the car to an auto repair shop? If I can figure out the source of the problem, my friend the mechanic can replace the Finnigan pin or whatever.
I have a buddy who is a retired mechanic. He briefly looked at the car yesterday and didn't find anything obviously wrong with it. He said that the battery, alternator, and starter are all good. And, of course, the car started easily for him on five separate tries, but the engine was warm at the time (I had driven the car home from work).
What do I do next to diagnose the problem, short of taking the car to an auto repair shop? If I can figure out the source of the problem, my friend the mechanic can replace the Finnigan pin or whatever.
Response by poster: I'm not sure about the age of the battery. I think my friend the mechanic tested it, but I'm not positive. If the battery were in bad shape, wouldn't you expect a problem with cranking the engine? That doesn't happen. I suppose I can take the car to Advance Auto Parts and have them check the battery.
posted by akk2014 at 9:20 AM on October 7, 2023
posted by akk2014 at 9:20 AM on October 7, 2023
Best answer: Agreed that it's possible for a marginal battery to be strong enough to crank the engine, but not strong enough to make the engine control ECU happy. Load testing the battery or measuring the voltage across the battery while the car is being cranked would be the most scientific way to check for this.
Could be that the fuel system is losing pressure/bleeding down after sitting overnight due to a dribbling fuel injector etc.. You can try cycling the key _without _cranking the engine- e.g. turn it from off to on, leave in in the on position, pause a second, repeat this 3 or 4 times and then try cranking the car. if it starts right up, that would be clue to check to see if the fuel rail is holding pressure. (The fuel pump runs for a second when the key is first turned on to 'prime' the system.)
Good luck!
posted by Larry David Syndrome at 9:34 AM on October 7, 2023 [1 favorite]
Could be that the fuel system is losing pressure/bleeding down after sitting overnight due to a dribbling fuel injector etc.. You can try cycling the key _without _cranking the engine- e.g. turn it from off to on, leave in in the on position, pause a second, repeat this 3 or 4 times and then try cranking the car. if it starts right up, that would be clue to check to see if the fuel rail is holding pressure. (The fuel pump runs for a second when the key is first turned on to 'prime' the system.)
Good luck!
posted by Larry David Syndrome at 9:34 AM on October 7, 2023 [1 favorite]
Fuel system/tired fuel pump?
If you can, video the problem for your mechanic to see what's happening.
posted by 2N2222 at 9:35 AM on October 7, 2023
If you can, video the problem for your mechanic to see what's happening.
posted by 2N2222 at 9:35 AM on October 7, 2023
Could be a temperature sensor - when cold, most cars use a richer mix of fuel/air ratio to enable easier starting. If your sensor is misreading "hot" when actually cold, this could explain the symptoms.
posted by soylent00FF00 at 9:43 AM on October 7, 2023
posted by soylent00FF00 at 9:43 AM on October 7, 2023
When was your last oil & filters change?
I recently fixed an old (1990's) diesel engine that hadn't been run for a few years. Batteries were kept charged and it would turnover okay, but it wouldn't catch (although it would restart well when still warm from the last run, and it used to start well when run once a month prior to sitting unused).
The only effective 'hack' to get it running from cold was a hot air blower into the air intake to warm things up prior to starting, and then often some ethanol spray into the air intake as it was turning over too. That was about enough to help it splutter into action.
But replacing all the engine oil, and replaced both the oil & fuel filters. It was back to starting first time again even from cold, consistently.
posted by many-things at 10:42 AM on October 7, 2023
I recently fixed an old (1990's) diesel engine that hadn't been run for a few years. Batteries were kept charged and it would turnover okay, but it wouldn't catch (although it would restart well when still warm from the last run, and it used to start well when run once a month prior to sitting unused).
The only effective 'hack' to get it running from cold was a hot air blower into the air intake to warm things up prior to starting, and then often some ethanol spray into the air intake as it was turning over too. That was about enough to help it splutter into action.
But replacing all the engine oil, and replaced both the oil & fuel filters. It was back to starting first time again even from cold, consistently.
posted by many-things at 10:42 AM on October 7, 2023
Generally speaking "hard start when cold" comes down to two things: lack of fuel, and lack of spark.
First thing you should try: turn on the vehicle, but do NOT crank it. Listen to the fuel pump "priming" the engine. You can even give the throttle 2 pumps (all the way down, let it up, do it one more time). This usually tells the ECU (engine control unit) to get the engine ready to crank. Give it ANOTHER 5 seconds, THEN crank the car.
A search of Kia forum shows that your fuel pump may be bad with an air leak and thus causing fuel starvation issue, and repeated crank eventually purges the air from the lines and let you start normally.
posted by kschang at 10:44 AM on October 7, 2023 [5 favorites]
First thing you should try: turn on the vehicle, but do NOT crank it. Listen to the fuel pump "priming" the engine. You can even give the throttle 2 pumps (all the way down, let it up, do it one more time). This usually tells the ECU (engine control unit) to get the engine ready to crank. Give it ANOTHER 5 seconds, THEN crank the car.
A search of Kia forum shows that your fuel pump may be bad with an air leak and thus causing fuel starvation issue, and repeated crank eventually purges the air from the lines and let you start normally.
posted by kschang at 10:44 AM on October 7, 2023 [5 favorites]
You will probably need to leave it overnight with your mechanic. They should definitely test the fuel pressure when it's cold. Part of this test is to pressurize the fuel rail, and then after recording this reading, to turn off the car and see if the pressure remains, or if it leaks away, and how quickly. If any of the results are abnormal, they give clues as to what part is defective.
It looks like this car may not have the usual schrader valve (looks like a tire valve) on the fuel rail to make it simple to connect a fuel pressure gauge. That is unfortunate and it means to do the test you'd have to disconnect the high pressure fuel line somewhere and tap in to connect the gauge.
posted by fritley at 11:22 AM on October 7, 2023 [1 favorite]
It looks like this car may not have the usual schrader valve (looks like a tire valve) on the fuel rail to make it simple to connect a fuel pressure gauge. That is unfortunate and it means to do the test you'd have to disconnect the high pressure fuel line somewhere and tap in to connect the gauge.
posted by fritley at 11:22 AM on October 7, 2023 [1 favorite]
Ideas: Replace key fob battery or fob itself; clear clogged fuel line; replace failing crankshaft sensor.
posted by Iris Gambol at 4:38 PM on October 7, 2023
posted by Iris Gambol at 4:38 PM on October 7, 2023
Response by poster: I think @Larry David Syndrome has it. I tried his trick this morning (I turned the key a few times without cranking the engine). The engine started right up. So... my next question is this: Now that I know about this workaround, do I still need to get the car fixed? Will the problem get worse if I don't address it somehow?
posted by akk2014 at 5:42 PM on October 8, 2023
posted by akk2014 at 5:42 PM on October 8, 2023
The leak can always get worse... as fuel get into places where they have no business being...
posted by kschang at 7:29 PM on October 8, 2023
posted by kschang at 7:29 PM on October 8, 2023
It sounds like you have a leak in the fuel system somewhere and the fuel is draining back out of the feed line overnight. That's why Larry David Syndrome's trick worked - you are priming the fuel system back up by doing that, the same as you are priming it when you try a few times to start it. When you first turn the key, the fuel pump starts up but quickly shuts off if there's no ignition signal from a running engine (it's a safety feature to ensure the fuel pump shuts off if the engine stops eg in an accident), so it takes a few cycles to get the fuel pressure back up.
Your mechanic friend can probably track it down (or you can) by following the fuel line back from the fuel rail and looking for wet patches or other signs of leaking. If there's nothing there, it may be a stuck injector - the best way to diagnose that would likely be a scan tool, so that might be when you take it to a mechanic with a scan tool if your friend doesn't have one.
Will it get worse? Probably. If there's a leak in the fuel line, it will almost certainly get worse over time until it ruptures and you're standing on the side of the road with all your precious go-juice running down the gutter. If there's a stuck injector, it may just get better by itself, although that's not likely. Some injector cleaner fuel additive may fix it. There's a very slim chance that it gets worse and you end up with the injector stuck wide open, dumping fuel into that cylinder after you stop the engine to the extent it hydro-locks next time you try to start it and that would be very bad.
posted by dg at 9:37 PM on October 8, 2023
Your mechanic friend can probably track it down (or you can) by following the fuel line back from the fuel rail and looking for wet patches or other signs of leaking. If there's nothing there, it may be a stuck injector - the best way to diagnose that would likely be a scan tool, so that might be when you take it to a mechanic with a scan tool if your friend doesn't have one.
Will it get worse? Probably. If there's a leak in the fuel line, it will almost certainly get worse over time until it ruptures and you're standing on the side of the road with all your precious go-juice running down the gutter. If there's a stuck injector, it may just get better by itself, although that's not likely. Some injector cleaner fuel additive may fix it. There's a very slim chance that it gets worse and you end up with the injector stuck wide open, dumping fuel into that cylinder after you stop the engine to the extent it hydro-locks next time you try to start it and that would be very bad.
posted by dg at 9:37 PM on October 8, 2023
+1 on dg's comment. although I would lean more in the "it depends" direction- if it's an actual leak (whether injectors, fuel lines, etc) it needs to be fixed or there may Be Consequences. If it's something like a bad check valve in the fuel pump (fuel pressure bleeds back inside the fuel tank) not fixing it right away would be fine. I think getting it diagnosed so you know exactly what you're dealing with would be the smart thing to do.
posted by Larry David Syndrome at 5:16 AM on October 11, 2023 [1 favorite]
posted by Larry David Syndrome at 5:16 AM on October 11, 2023 [1 favorite]
Response by poster: Just wanted to update this question and then mark it as "resolved". Bizarrely, the problem has fixed itself. The car is now starting up normally, so I don't have to prime the pump anymore. I can't explain it. Anyway, thanks go out to everyone for your help.
posted by akk2014 at 10:00 AM on October 19, 2023
posted by akk2014 at 10:00 AM on October 19, 2023
Transient problems like this may be temperature related. But without it occuring it's going to be difficult to diagnose. The sucky part is by Murphy's law, it'll probably return when it's the worst time for you. Good luck.
posted by kschang at 4:48 PM on October 19, 2023
posted by kschang at 4:48 PM on October 19, 2023
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posted by Mitheral at 8:25 AM on October 7, 2023