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  1996 RMW Hard start diagnosis

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Haze5736



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Location : East Syracuse, NY

PostSubject: 1996 RMW Hard start diagnosis   Sun Apr 30, 2017 1:48 pm

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.
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silverfox103
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PostSubject: Re: 1996 RMW Hard start diagnosis   Mon May 01, 2017 9:42 am

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

Tom
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81X11

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PostSubject: Re: 1996 RMW Hard start diagnosis   Mon May 01, 2017 12:31 pm

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


Last edited by 81X11 on Mon May 01, 2017 12:34 pm; edited 1 time in total
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81X11

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PostSubject: Re: 1996 RMW Hard start diagnosis   Mon May 01, 2017 12:34 pm

See if this video looks/sounds familier. Wink

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jasonlachapelle

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PostSubject: Re: 1996 RMW Hard start diagnosis   Mon May 01, 2017 7:33 pm

I'm siding with Tom on this one. Have had to do it on 2 cars.
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silverfox103
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PostSubject: Re: 1996 RMW Hard start diagnosis   Mon May 01, 2017 7:43 pm

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
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Haze5736



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PostSubject: Re: 1996 RMW Hard start diagnosis   Tue May 02, 2017 11:04 am

81X11 wrote:
See if this video looks/sounds familier.  Wink

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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?
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Haze5736



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Join date : 2016-08-12
Age : 44
Location : East Syracuse, NY

PostSubject: Re: 1996 RMW Hard start diagnosis   Wed Jun 14, 2017 7:38 pm

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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