Car Starts Weakly, After Time Doesn't Start at All

[olopezm]

I'll put my two cents here, and would like to say before anything that I might be wrong here, I'm far from being an expert more like a regular amateur .

If you can feel a noticeable difference in the air being sucked into the engine I would say you either have a problem with compression (piston rings, valves) or your cat converter is clogged which creates backpressure and will lower the ability of the engine to create vacuum. Both a compression test or a vacuum test should help on determining what's your exact problem. I would just do both... I'm not sure, but think I remember reading from other members in the forum that you can rent both compression and vacuum gauge testers at most autoparts stores (loan program).

You could try disconnecting and removing the pre-cat O2 sensor to see if the air flow changes.

I'm pretty sure someone else will chime in; in any case I hope this information helps.

Oscar.

[rickisrad]

I would have to agree with Oscar with both suggestions. a compression test is easy and you can get the tester cheap or Loan a tool it just basically like changing a spark plug. I was also going to suggest checking the exhaust flow. an obdII live data scan would be best to see if all of your values are in check.

[Brandybuck]

Update:

I took the vehicle to a shop, along with the other Grand Prix with which I had been comparing it. I was told that the louder "rumble" near the rear of the other car was due to an exhaust leak - a hole in the exhaust pipe!

So much for the lack of rumble; I suppose the exhaust leak would cause engine in the red car to suck in more air - or not?

The mechanic did a backflow pressure test to see if the catalytic converter was bad; it was only 2 psi of difference, so I don't need to replace the cat.

I still have to deal with the starting problem - the mechanic experienced it as well. He said it "started hard cold" and suggested that the check valve in my fuel pump was defective. I didn't know there was a check valve in the fuel pump - doesn't the FPR control the flow of gas back into the tank, or is there a check valve as well?

[olopezm]

If you had a fuel pressure gauge tester, you could quickly find out if you have a fuel delivery problem or not, I think you can rent them from most autoparts stores and get your money back when you return it .

There is a check valve on the fuel pump but if it was bad, your car should start easily after priming the fuel pump for several times (4-5) before cranking the engine. If I remember correctly, you already did that and didn't help with your problem, right?

Oscar.

[Brandybuck]

Thanks for the quick reply!

I did try that - and it worked like a charm the first time. (The first time I turned the key on/off a few times and then started the car.) It started up wonderfully.

But I wanted to repeat that, and so I immediately turned the engine off again, primed the pump by turning the key on and off several more times, and then tried to start the engine. It wouldn't start (without pressing the gas pedal).

I have realized that when I tested the car, I did not check the fuel pressure while the key was out - only during Run and Start. So I plan to redo my pressure check more thoroughly, watching for the pressure to drop with the key out. (I bought an Actron Professional Fuel Tester with a bleeder valve from Amazon for $45.)

If I need to replace my fuel pump... what do you think about an aftermarket fuel pump from CarPartsWholesale on ebay? http://www.ebay.com/itm/370604399958...ht_2106wt_1334 A one year warranty. What do you think? It's inexpensive enough.

[olopezm]

You're very welcome!

I wonder if your mechanic did the compression test?

I wasn't sure about it, but if the problem went away (even if it was only one time) then you're mechanic might be right about the check valve in the fuel pump, the fuel is draining back into the tank and the fuel lines have no pressure, that's why it takes some time to start the car. You might want to try it again just to see if it helps, along with the pressure test.

That fuel pump is pretty cheap for a complete assembly, when I replaced mine I pay around $60 just for a rebuild kit, not the entire assembly! But your 2000 year GT isn't listed though, I don't know if there will be any differences between years (??). Just for comparison purposes check the following link:

CLICK HERE

The GREAT thing about our GP's is how damn easy is to replace the fuel pump, you just remove the carpet in the trunk and work form the rear seat. There is an access cover right behind the access panel at the rear seat. You remove a few bolts, remove the plate and voila! You've reached the fuel pump!!! See? Piece of cake...

Oscar.