Car ALMOST doesn't start

edprush

Platinum Member
Sep 18, 2000
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When I turn the key I have to turn it 3 or 4 times or depress the accelerator to get it to start nowadays.

I have a 1991 Chevy Caprice Classic. I think it is EFI.

What the diagnosis doctors?
 

Demon-Xanth

Lifer
Feb 15, 2000
20,551
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If it turns over easily, it's not the alternator or starter. If it's not turning over easily, that's where to start looking.
 

NTB

Diamond Member
Mar 26, 2001
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could be the fuel injectors also. A can of fuel injector cleaner in the gas tank on the next trip to the gas station might help, but the vehicle is old enough that the injectors may have to be phisically cleaned or replaced; I had to do something similar on a '95 Blazer a few years ago before it would start running right again.

Nathan
 

Gillbot

Lifer
Jan 11, 2001
28,830
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Originally posted by: nakedfrog
Yep, need more info. Describe the sound?

More info needed. Does it act like it's labored to turn over? Like it's not getting gas?
 

edprush

Platinum Member
Sep 18, 2000
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Originally posted by: Gillbot
Originally posted by: nakedfrog
Yep, need more info. Describe the sound?

More info needed. Does it act like it's labored to turn over? Like it's not getting gas?

Tonight I had to crank the key 3 times. Each time I held the key turned about 3 seconds.

On the last turn of the key I depressed the accelerator all the way to the floor. It didn't do a thing until about 5 seconds. Then the engine started getting power and it finally revved up.

Then as I pulled away, the car almost died 3 or 4 times.

It does seem like this is gas related. Too much or too little? Or wrong air/fuel ratio?
 

nakedfrog

No Lifer
Apr 3, 2001
58,119
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Can you have somebody check for smoke at the exhaust, or are you aware of any?
Change the fuel filter?
 

jagec

Lifer
Apr 30, 2004
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Well, you could try the Seafoam method and see if it helps. Get the engine warm first. Pour half a can into your gas tank (half-full or below to increase the effect), and suck the other half up a vacuum hose bit by bit, and once you get near the end suck up enough to stall the motor. Then drive it hard for a while, until you stop filling the neighborhood with billowing smoke. See if it starts/runs any better.
 

YetioDoom

Platinum Member
Dec 12, 2001
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My car was doing something similar - I took it to the dealer, they replaced the fuel pressure regulator and all is well.
 

edprush

Platinum Member
Sep 18, 2000
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Originally posted by: nakedfrog
Can you have somebody check for smoke at the exhaust, or are you aware of any?
Change the fuel filter?

I plan to change the fuel filter this weekend.

There is white smoke that comes out of the exhaust when the car is started. It clears up quickly.
 

edprush

Platinum Member
Sep 18, 2000
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Originally posted by: YetioDoom
My car was doing something similar - I took it to the dealer, they replaced the fuel pressure regulator and all is well.
What kind of car was this?

I haven't even heard of a fuel pressure regulator.:eek:
 

exdeath

Lifer
Jan 29, 2004
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Regulator is a diaphragm that is connected to the fuel rail that either allows fuel to return to the tank or block the return flow in order to regulate fuel pressure.

First thing I do with any suspected fuel problems is check fuel pressure, with key on, cranking but not starting, and then running idle and revving. It's quick and simple, provides much info, and a fuel pressure gauge is cheap, should be able to get one for a few bucks or rent one. It attaches to the fuel rail on a fitting that looks like a valve stem on a tire. This will show problems with injectors, pump, filter, regulator, etc. Refer to maintenance manual for the factory fuel pressure requirements for your car in various modes of operation.

Fuel filter is also a quick easy fix and is regular often overlooked maintenance anyway.

Low pressure could mean an obstruction, pump/regulator problem, or even faulty injectors or injector driver module (would have to check this on a scope) Having to hold the throttle open to start the car, then having it stumble on load *sounds* like its running too rich on cold start.

Not familiar with your car to know the extent of on board computer diagnostics, but a scan tool to check the problem logs on a EFI car is also invaluable.
 

edprush

Platinum Member
Sep 18, 2000
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Does this symptom mean anything additonal:

After I get the car started and the dying and near-dying of the engine are over and the car is running (about 2 or 3 minutes) it runs fine. It just struggles/dies when I'm starting it for the next couple of minutes then it seems to run okay.



 

exdeath

Lifer
Jan 29, 2004
13,679
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Sounds like flooding. Does it not start at all without throttle application? What if you shut it off while its hot, then start it up again a minute later? Do you have trouble first starting it for the first time, then after it's been running fine, can you park, run into a store, come back out and it starts right up, etc?

Another possibility besides stuck/leaky injectors is a temperature sending unit that the computer uses to decide enrichment mode. This may or may not effect the temperature gauge depending if it's fed by a different unit.

If it's an injector, fuel pressure will decay fairly rapidly when you turn the key off and you can find out which ones by looking for heavy black (dry) buildup on the spark plugs and strong fuel smell from the corresponding cylinders when you pull those plugs.

If you can start it without throttle application, but it just takes a while, it may be the check valve on the fuel pump or the regulator, which would drop fuel pressure on key off while being exposed to engine heat and vapor lock the fuel system. It would then take a while to start up and clear the lines/rails and rebuild fuel pressure, with or without throttling it.
 

edprush

Platinum Member
Sep 18, 2000
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60% of the time it will start without throttle application BUT I have to turn the key 3 + time (and hold it turned for a few seconds)--doesn't each turn of the key give a 'shot' of fuel?

After it starts it sputters and dies.

If I do just a little throttle application it starts to die too but if I let off it sputters and often dies.

What seems to work is to push the throttle all the way to the floor and keep it there until the engine starts to speed up.

It starts up fine if the engine is still hot, I believe.



 

exdeath

Lifer
Jan 29, 2004
13,679
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Turning the key doesn't have any effect on the fuel system other than turning the pump on. The computer controls fuel supply to the engine based on engine conditions.

60% success rate without throttle would indicate open throttle position doesn't really effect startup.

It's gotta be one of the things I covered. My bet's on the temperature sending unit that the computer uses to determine cold start enrichment conditions if you are only having the problem on cold start and don't have any problems otherwise. It may not be rich enough for cold start if it thinks the engine is hot all the time due to a faulty sensor. A meter or scope could quickly determine if the sensor signal is out of range. (the cold reading the same as the hot reading 10 minutes later for example)

Having to crank the key numerous times could mean it's not cold start enriching, and after trying long enough to start it enough fuel has accumulated in the intake tracts to provide the needed start up enrichment until it finally 'catches' and starts up.
 

edprush

Platinum Member
Sep 18, 2000
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I hurt my back a few days ago and wasn't able to replace the fuel filter. I did get as far a looking under the hood and I, embarrassingly, can't even find the fuel filter.
 

exdeath

Lifer
Jan 29, 2004
13,679
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Usually the main larger filter is near the tank, and sometimes there is a smaller one inside the engine bay on the firewall or inline on the hose just before the rails.

I'm doubting it's a fuel problem now or you would have hesitation and stuttering all the time, not just when cold starting. From what you said, your problem is exclusively when starting and driving with a cold engine and it's normal any other time. Get the temperature sensor feeding the ECU checked when it's cold (there may be aux sensors that control fan relays or feed the gauge or it may all just be one, but you want the one the ECU uses to determine cold start condition)


Fuel doesn't atomize well in a cold engine and the computer has to compensate by running a very rich mixture. If the temp sensor is bad the computer wont know the engine is cold and will think its hot and run a mixture that is way too lean for starting/running cold.
 

edprush

Platinum Member
Sep 18, 2000
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I forgot to mention that about 2 months ago the "Check engine light" came on for a trip (this was before the problems that I've been describing started).

Also, what is the ECU?