Ok.. I am not sure but I am pretty sure that my fuel pump is on the way out.... here is my story.

Drove my car today and everything was running fine.... came home and shut the car off....go back a few minutes later to start it up and she started then cut out on me.... I popped the hood and couldn't see nothing out of the ordinary...so with the hood up I sit back down and try to start it again... this time it would just crank and crank... as I was cranking it I noticed that my fuel pressure guage was sitting at about 10 psi (I have one mounted to the Shrader valve on the rail). So I let everything sit for a few seconds and turn the key forward and this time I am listening for the fuel pump... nope she wasn't spinning up...

So with the fact that my fuel pump wasn't spinning up I start diagnosing (sp?) the problem...

1st I check the fuses under the dash... they all appear to be fine, but on the side of caution I replace the 10Amp fuel pump fuse.

Try and start it...nadda .. no fuel pump spinning

2nd I check the 20Amp fuse located over by the battery... this one is fine as well...

Try and start it... nadda.. no fuel pump spinning

3rd I check the fuel pump relay... I changed this relay a couple of weeks ago with a new one... no real reason, the old one was fine but a new one was given to me so I put it in... thinking that maybe the relay was shot I popped my old relay back in...

Try and start it... nadda.. no fuel pump spinning...

After all of this I decided to leave it alone and I came in the house...

About 45 minutes later I decided that just for the heck of it I would go and try it one last time...

This time I here the fuel pump spin up and I have fuel pressure back on the rail... turned the key and she fired right up.

I am baffled...

I am thinking that it could be the fuel pump on it's way out and after about an hour sitting it cooled off or something....I dunno...

So I backed my car into my garage and now every time I turn the key the pump spins up...

Now for some pertinant information..

1. I have an AFPR, the fuel pressure is set to approximately 42 psi.

2. I have noticed that my fuel pressure drops off siginificantly after I shut down the car....about a month ago I could leave her sit for hours and she would hold the fuel pressure on the guage to about 30 psi and overnight it would rarely drop below 20 psi... Now after I shut off the car I notice the fuel pressure drops off to below 10 psi in about 30 minutes... I know it isn't my injectors because they are all new and I don't get a hard start problem which would be caused by an injector leaking into the plenum..

3. There is approximately 1/2 tank of gas in the tank so the fuel pump should be sitting in the gas for cooling....

I don't wanna risk driving the car now because my luck it will be the fuel pump going south and it will die on me completely somewhere and I would have to get towed home....I would rather diagnose and fix the problem while it sits in my garage than take that risk.

Any suggestions? What is a stock fuel pump rated at? I am thinking that maybe my AFPR has put strain on the stock pump thus shortening it's life...

What's a good replacement pump which can handle higher PSI's

And finally.. I know replacing the fuel is going to be a HUGE PITA.. any tips/tricks to make this go easier?

TIA!!

 

As of today my car is exhibiting the same problem. Your diagnosis was corect. Did you replace it?

 

I scrapped the rear end... LOL.. dropped the tank, and put in a brand new Walbro 255 LPH fuel pump...

Here is a key step in all of this ... if you have an adjustable fuel pressure regulator check your fuel pressure after you install a new pump!!!

I wanted to set my fuel pressure properly but after I installed the fuel pump my guage was messed up (not due to the pump install just me being stupid and screwing it onto the schrader valve wrong)... Anyway, I never drove the car right after I installed the fuel pump cuz I wanted to make sure the fuel pressure was right...

Once I got my guage working again and fired up my car my fuel pressure was at 60 psi at idle!!! That will tell you how much I had to bump the pressure up on the old pump to get it to 38 psi at idle!!

So I shut the car down, adjusted the pressure properly and I was good to go....

No problems since... pump primes up every time.

Another thing I noticed after I installed the new pump was that my fuel pressure on my guage is now rock solid...needle wouldn't bounce around or nothing.. with the old pump the fuel pressure guage needle would bounce around wildly!! I am chalking that up to the old, failing pump not delivering a constant pressure. It would have been a matter of time before it died completely.

Took me and a buddy about 4 hours to do the job in my backyard garage (but that included us replacing a broken brake line which decided to break, better then than in an emergency stop..)... but we had air tools, a huge car jack, and he is a AST Certified GM mechanic But this job can be tackled by anyone that has some mechanical ability and has patience...air tools makes things go sooo much easier though, especially on those tough panhard bolts (one of which I snapped off, hehe)

 

Glad it worked out. I ordered that exact same pump today. Glad to see it is working well for others. I just did a 4th gen rear swap so the bolts should not be much of a problem (I hope.) What really sucks is that it looks like I may ruin my new exhaust (welded in) to get this done.

Did you have to crack the brake line open when you lowered the rear end?

 

My exhaust is welded all the way from the headers (not what I wanted done but the shop did it before I could talk to them) right back to the muffler...we never had to cut the exhaust, there was enough clearance to get the tank out and in by just letting the muffler hangers go....

Umm.. not sure on the other thing... did you mean " did we crack the brake line when we dropped the rear?" ... if that is what you mean, nope, the brake line had a small pin hole in it that was ready to break on me anyway.... and by us moving stuff around I guess it just went, I was glad it went then as it was the best time to change it (seeing the rear end was down and everything was out of the way )... if your brake lines are solid and not rusty you will have no problems... all you have to do is obviously let go the bolt that bolts the brake line to the rear end...

 

And if you meant how it's written "did you have to crack the brake line open when you lowered the rear' ...LOL (sometimes I have to read things 10 times!!)...

No... you do not have to touch your brakes...all you need to do is let the bolt that bolts the lines to the rear go...

Just watch the brake lines as you lower the rear axle slowly, make sure that nothing binds or breaks on ya.. although I am pretty sure nothing will...

 

Thanks again. Hopefully I will not have to cut the exhaust. That is good news that you did not have to. Sorry I was not clear with my question.

Regards,
BILL

 

Make sure you don't re-use the original pulsator... it sits between the pump and the tank outlet pipe. It uses o-rings to seal the connection, and o-rings get old and crack and leak.

Either use a new pulsator ($40) or use a little piece of high-pressure fuel hose (usually comes with new pumps) and some clamps.

This is also a great time to replace all the old hoses up there. You can use regular fuel hose for the return line, tank vent, and charcoal canister line. The feed line uses a high-pressure hose with fittings; give your GM dealer a call; they're usually a special order part.

If your exhaust isn't welded to the rear of the cat, as soon as you drop the axle down, you'll be able to unbolt the intermediate pipe from teh rear of the cat and pull the whole system out of the car from behind. Very cool. In fact, by dropping the rear down to the floor, that's the easiest "shade tree mechanic" way to install a cat-back exhaust. It sure as hell beats trying to raise the car dangerously high in the air with floorjacks just to fit a new intermediate pipe underneath!

 

I left my pulsator in place... never mucked with it.. the new pump did have a short piece of hose but we never bothered messing around with it...my bud said I didn't need to do it so I never... no ill effects "so far"

What would happen if the pulsator when south on me? What symptoms would I have?

 

Thanks for the tip Tom. It's kind of hard for me to envision the exhaust system coming out in once piece as you described.

Unfortunately, mine is weleded in behind the cat. So I should only have to cut this weld and undo the rear mounting brackets. No loosening flange clamps, etc?

 

Well if the o-rings of the old pulsator aren't sealing well anymore, you'll get a leak, and lose pressure...

Yep, that's the only weld you'd need to cut. In fact you could probably cut your intermediate pipe in an "easier" spot, and rig it back together with a cut-open soda can and two regular 'ol muffler clamps so you could drive to an exhaust or body shop to have the pipe welded.

 

I had to use the little piece of hose when I changed my fuel pump because the existing piece of hose had a hole in the side of it. The pump was fine, but all of the fuel was blown right back into the tank.

 

The same thing happened to my Z in may.....RIGHT AFTER KNEE SURGERY! I had to remove my tank/replace pump 2 weeks after my #$%ing knee surgery! IT was a sight! I'm sure the neighbors were laughing or praying for me cuz of all of my swearing!