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Very hard starting 1994 Trans Am...Fuel pump failure? PLEASE HELP! Rate Topic: -----

#1 User is offline   BlackOut94 

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Posted 06 November 2010 - 05:06 PM

Hello everyone. Hoping I could get some assistance. Heres my problem:

--When starting the car for the first time, the car cranks over for a fairly long amount of time before the engine actually "fires". Once running, the car seems to run fine. I dont notice any signs of a rough idle, or anything of that nature. If you then shut the car off and let it for for about 5 minutes, and then come back to start it, it absolutely will not start for about an hour. It will crank over, but wont fire until you let it sit for some time and then try it again. Finally, after a good amount of time left without trying to start the engine, it will start, however its still very hard and appears to crank for way too long before it does.--

Im thinking it could possibly be a fuel pump failure, but im honestly not sure. I hope this description makes some sort of sense. I have a fair amount of mechanical knowledge, however, I would greatly appreciate some opinions as to what my problem could be before I start tearing into the underside of the car, removing exhaust and suspension components, only to find out that wasn't the problem. Thank you for any/all help and opinions.
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#2 User is offline   Injuneer 

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Posted 06 November 2010 - 06:16 PM

A couple possibilities.

When you turn the key to "on", the fuel pump runs for 2 seconds, then shuts off. If the fuel pressure leaks down quickly, the engine requires an extended cranking time. Check your fuel pressure by turning the key to on, and not starting the engine. Pressure should be at least 40psi when the pump shuts off, and should not drop rapidly. If it does drop rapidly, it could be:
-leaking check valve in the fuel pump assembly
-leaking diaphragm in the fuel pressure regulator
-leaking fuel injectors
-leaks in the fuel lines, including the line in the tank that connects the fuel pump to the pump support assembly

Try this, when the engine is cold - turn the key on until the fuel pump shuts off, then turn it off, and repeat the process 5 times. If it start quicker after that, its a problem with the fuel pump losing pressure.

If the fuel injectors are leaking, it may cause the fuel to puddle in the intake runners. If the above procedure did not improve starting, before attempting to start it, put the accel pedal on the floor and hold it there while trying to start the engine. That puts the PCM in "clear flood" mode.

An outside possibility is a problem with the coolant temp sensor. Hard starting when hot could be the result of a faulty coolant temp sensor telling the PCM the engine is colder than it really is. When the engine is hot, that could cause the PCM to richen the mixture for a cold start, and its going to be very difficult to start the engine.

I'd start by cycling the key, to see if it starts faster. Then proceed to the pressure test.
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381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC engine management - 8 LS1 coils - 58mm TB - 78# injectors - 300-shot dry nitrous - TH400 - Gear Vendor O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motor
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#3 User is offline   BlackOut94 

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Posted 09 November 2010 - 07:18 PM

Just hoping I could get some more positive feedback:
--Today, I went out and picked up a fuel pressure gauge at the local auto store. With the gauge hooked up, I turned the key on, let the pump prime until it shut off, turned the key off, then turned it back on and checked the pressure gauge reading. The fuel pressure was at around 35lbs. and falling slowly, but steady. I then started the car and checked the gauge and got a reading holding steady around 38lbs. Then, when I shut the car off, the pressure again fell steadly.--

The result of this seams af if it would definately be fuel pump failure, and that the check valve inside the pump has failed and fuel is leaking back into the tank, correct? Could there be any other possibilities?

Also, my other question still stands that if this is definately the problem, could this also be causing the "No Start" problem that I have after turning the car off and it not restarting for quite some time after running for a while? Or could that be another issue? One thing I would like to point out is the unusually strong gasoline smell from the exhaust. Is it possible that I maybe have leaking/stuck injectors? I would think that it would still remain hardstarting, but would at least start. No?

I appreciate any and all input on my issue. I am a college student now living alone so all of my car troubles are on my shoulders and Im just trying to learn as I go. :) Thanks all for your help.


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#4 User is offline   Black Widow 

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Posted 09 November 2010 - 08:10 PM

this may sound stupid but I would check out your cat if you have one. i have a mazda truck and the exact same thing happened to it. but the times were somewhat different.

cats can basically destruct your car. they clog up, heat up exhaust manifold and possibly burn your car down. if not that then they can melt underhood wires and ground them out which will then fry your computer. bad deal.

Also.. try taking off your gas cap and starting and killing your car. You could have a faulty gas cap which means it canot allow air in the tank to replace the fuel removed from the tank which then creates a vaccum in your gas tank which makes it hard to pump fuel. I think it may be this die to the fact that it will not start for a hour after shutting it off which resembles the time in which the vaccum in the gas tank is replaced by air..

check cat

remove gas cap.


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#5 User is offline   BlackOut94 

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Posted 10 November 2010 - 07:42 AM

Interesting point. I will say that everytime I remove the gas cap at a gas station, it lets off a big amount of pressure, almost like there was an air pressure build up inside the tank. I will look more into that. Thank You for the response.

This post has been edited by BlackOut94: 10 November 2010 - 07:44 AM

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#6 User is offline   Injuneer 

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Posted 10 November 2010 - 02:33 PM

View PostInjuneer, on 06 November 2010 - 06:16 PM, said:

................. Check your fuel pressure by turning the key to on, and not starting the engine. Pressure should be at least 40psi when the pump shuts off, and should not drop rapidly. If it does drop rapidly, it could be:
-leaking check valve in the fuel pump assembly
-leaking diaphragm in the fuel pressure regulator
-leaking fuel injectors
-leaks in the fuel lines, including the line in the tank that connects the fuel pump to the pump support assembly


Try this, when the engine is cold - turn the key on until the fuel pump shuts off, then turn it off, and repeat the process 5 times. If it start quicker after that, its a problem with the fuel pump losing pressure.

................

I'd start by cycling the key, to see if it starts faster. Then proceed to the pressure test.

View PostBlackOut94, on 09 November 2010 - 07:18 PM, said:

Just hoping I could get some more positive feedback:

..............
The result of this seams af if it would definately be fuel pump failure, and that the check valve inside the pump has failed and fuel is leaking back into the tank, correct? Could there be any other possibilities?

Also, my other question still stands that if this is definately the problem, could this also be causing the "No Start" problem that I have after turning the car off and it not restarting for quite some time after running for a while? Or could that be another issue? One thing I would like to point out is the unusually strong gasoline smell from the exhaust. Is it possible that I maybe have leaking/stuck injectors? I would think that it would still remain hardstarting, but would at least start. No?

I appreciate any and all input on my issue. I am a college student now living alone so all of my car troubles are on my shoulders and Im just trying to learn as I go. :) Thanks all for your help.


Why do you want more input. I don't think you read any of the info I gave you.

"Could there be any other possibilities" - There's a list of 4 possibilities in my previous response.

"Is it possible that I maybe have leaking/stuck injectors?" - Look at the third item in my previous list.

I'm really disappointed that I have spent my time trying to help you, and you didn't even read what I posted. Hopefully someone with more patience than this tired, grumpy old man can help you, because I really hate wasting my time, when it could have been spent helping someone who really wanted the help.

View PostBlack Widow, on 09 November 2010 - 08:10 PM, said:



Also.. try taking off your gas cap and starting and killing your car. You could have a faulty gas cap which means it canot allow air in the tank to replace the fuel removed from the tank which then creates a vaccum in your gas tank which makes it hard to pump fuel. I think it may be this die to the fact that it will not start for a hour after shutting it off which resembles the time in which the vaccum in the gas tank is replaced by air..

check cat

remove gas cap.

The 4th Gen gas caps are UNVENTED. They are sealed, and if they are not effectively sealed, in the OBD-II cars, you will get an SES light and a trouble code. A "faulty gas cap" is a cap that allows air in and fuel vapor out. The tank "breathes" through the EVAP system, and a pressure control valve that maintains a slight positive pressure in the tank.
1994 FIREBIRD FORMULA

FRED

Posted Image

381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC engine management - 8 LS1 coils - 58mm TB - 78# injectors - 300-shot dry nitrous - TH400 - Gear Vendor O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motor
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