alex-z28

I have really hard time starting the car when the engine is warm. In the mourning it would fire up right away everytime. If I shut off the car and let it sit for 5-10 mins it would fire up right away but if I let it sit for anywhere from 10 mins-to 8 hours after shutting off the car it will crank for 5-10 secounds before firing up.

I had this problem ever since I got the car which was years and years ago. I have tried number of things and nothing helped, so I would give up for a while and then try again, its gotten to the point where I would have take it to the shop and get taken to the cleaners to get it fixed or this car its just supposed to work like that from factory. Here is everything I tried to fix this problem.


This sounds like leaking injectors right?

Well I just installed rebuilt stock injectors which were tested for leaks and flow and all that stuff and the problem is still there.


Fuel pump going bad or its bad?

Well I had this problem for years like I said and if its going bad it would be dead by now. I've started the car with the fuel pressure gauge on when the car is cold and the pressure was 0, as soon as I prime the fuel pump the pressure jumps to 40 psi and the car would start right away. So I don't thing its the fuel pump or anything dealing with fuel pressure.

Over the years I've replaced all this and nothing has worked.

Injectors
plugs and plug wires
fuel filter
ignition module

Can anyone shed some light on what's going on. Thanks.

Injuneer

Have you checked the coolant temp sensor in the water pump housing for accuracy?

alex-z28

No, I have never heard anything about coolant temp sensor causing hard starting. How do I go about checking that? Also can you explain why this would cause the problem I am having? Remember I can start the car right away 10 mins after shutting it off, if its sits longer after that that's when the my problem starts.

shoebox

You can do some testing with information here or you can use a scanner to read the temp.

The temp sensor reading is important because the PCM uses it to determine fueling. Fuel is added when the engine is cold. If the sensor read like it was cold all the time, it could cause excess fueling when it is not needed and perhaps causing a slightly flooded condition for warm start-up.

alex-z28

Thanks shoebox, that explains why I would hard starting when engine is warm and not when the engine is cold. I really hope that's it cause its simple and cheap fix but with my luck so far I am not holding my breath, LOL.

After Freds post I did some research and I ran accross your page the same one you posted. So now I know what to do, and I will check it out as soon as possible. I will look into investing into a scanner too as I don't have any plans of selling my car any time soon.

alex-z28

So today I worked on the car and I found out that its not the coolant temp sensor. So I went back to checking fuel pressure and I found out that the pressure drops fast after shutting that car off. It went from 40 psi to 10 in like maybe one hour. I am pretty sure I was aware of this problem before but I just thought it was due to leaking injectors, but now I know for sure that's not the case.

So that means that its the fuel pump or fuel pressure regulator that's causing the pressure to bleed out so fast, right? I don't know why this would cause the hard starting when the pressure is fine as soon as the fuel pump primes. Where do I go from here?

alex-z28

Ttt

Injuneer

May not be the problem - how fast does it drop in the first 5 minutes?

alex-z28

With engine on the pressure is 39 psi , as soon as shut off the engine the pressure drops to 35 psi. After 5 mins the pressure is at 31 psi, after 10 mins the pressure is still at 30 psi. After 30 mins the pressure went up to 34 psi , after 1 hour its at 20 psi. I haven't check the pressure with vacuum line off yet.

Also I should mention that I have a small stumble in 1st and 2nd gear only between 1500-2000 rpm. The car runs fine at WOT.

Fred, if you think its not the fuel pump could it be opti or coil? I mean what else is left. LOL.

alex-z28

bump

Injuneer

You are losing pressure a bit faster than you should be. That can be the check valve in the fuel pump, the fuel pressure regulator or leaking injectors. Leaking injectors can cause a flooded condition. When you go to start it, put the accel pedal on the floor, then turn the key to start, continuing to hold your foot on the floor until the engine starts. Doing that puts the computer in "clear flood" mode. If that shortens the start time, it could be pointing to flooding.

How did you verify the coolant temp sensor in the water pump is OK?

alex-z28

[QUOTE=Injuneer;6785270]You are losing pressure a bit faster than you should be. That can be the check valve in the fuel pump, the fuel pressure regulator or leaking injectors. Leaking injectors can cause a flooded condition. When you go to start it, put the accel pedal on the floor, then turn the key to start, continuing to hold your foot on the floor until the engine starts. Doing that puts the computer in "clear flood" mode. If that shortens the start time, it could be pointing to flooding.

How did you verify the coolant temp sensor in the water pump is OK?[/QUOTE]

I tried checking the resistance with voltmeter but I hard time getting any reading. So I just replaced it.

Also I don't think its the leaking injectors because like I said eariler I replaced the injectors.

I know you said that I am losing fuel pressure a bit faster then I should, but as soon as I prime the fuel pump the pressure is fine its at 40psi, so why would that cause long cranking? Also that does not explain when the engine is cold and pressure is at 0 it fires up right away.

I know that this sounds like injectors leaking but what are the odds that the new injectors that I put in are leaking as well, when they have been tested for leaks?