1996 RMW Hard start diagnosis

I'm trying to get to the bottom of the hard start problem with my 96 wagon.

I normally have to crank the engine for at least 5 seconds and usually I have to do that 2 to 4 times before it will start. Once it catches it will sputter for a few seconds then even out and run fine. I don't notice any drive-ability issues once I get it started. I always turn the key to run before starting to allow the pump to do its initial prime. This does not seem to have a positive effect.

So I went out and rented a fuel pressure test kit and here's what I've logged.

Fuel pressure specification is 41-47 psi.

Car sat overnight. I forgot to bleed the fuel system before attaching the fuel pressure gauge. The gauge registered 0 psi and no fuel spilled.

I cycled the key on a few times to build up pressure then purged the air from the gauge as per instructions.

Next I cycled the key on a few more times. While the pump was running I had 47 psi and once it stopped I had 40 psi. Just a tad below minimum spec.

At 1 minute after the pump stopped running I had 34 psi, within 2 minutes 27 psi and at 3 minutes I had 23 psi.

Next I started the car (key to run first) and it fired right up. Within 1-2 seconds.

With engine idling I had a constant 40 psi, at 1500 rpm I had 39 psi and at 2000 rpm I had 38 psi.

I turned off the engine and I registered 30 psi.

This is my first time doing this type of diagnosis. I am not sure what this is telling me but it's pretty clear that I have a problem. Do these results point to something specifically or must I do some additional testing. I want to get to a point where I'm not just throwing parts at it or replacing more parts than necessary, which its what I've always done because it is fairly inexpensive when DIY.

Thanks.

Fuel pump needs to be replace. Check valve is not functioning, allowing gas to drain back into the tank.

Tom

To throw in my 2-cents, I'm guessing you have a bad fuel pressure regulator (star/torx bolt faces DOWN on the backside of the intake/motor facing the firewall…nice design GM!!).

I had the EXACT same starting issue a while back, but once I replaced that regulator the car now starts at first turn of the key, cold or hot.  

I would do the regualtor before doing the pump.  The part is not expensive, and the hardest thing is just getting back there to swap the thing out.

-Mike

See if this video looks/sounds familier.

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I'm siding with Tom on this one. Have had to do it on 2 cars.

jasonlachapelle wrote:

I'm siding with Tom on this one.  Have had to do it on 2 cars.

I've also had it with two, one I changed, the other on the Caddy isn't quite bad enough to change. But I hope Mike is correct, as that would be a lot easier.

Tom

81X11 wrote:

See if this video looks/sounds familier.  

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That's exactly the same as what my car is doing.

I've been doing some reading about FPR problems but it is not clear to me if a bad FPR would cause the pressure to drop as in my case. I know if there was an external leak that could happen but I do not smell raw fuel inside the engine compartment. So I'm working under the premise that my fuel leak is internal as in the case of a bad check valve as mentioned by Tom. Would my 2 psi pressure drop under load (2000 rpm) indicate a bad FPR? Maybe I have 2 problems?

I decided to bite the bullet and replace the fuel pump/sending unit, fuel pressure regulator and the fuel filter. I have the tank down and the old pump/sending unit out. In the process I pulled out the insert tube that goes in the filler opening. The one with the ball inside it. I can't figure out how it is supposed to go back in. Below is a pic of my best guess. But taking it out required some force while it now comes out very easily. Does anyone know how this is supposed to mount?

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