Got a fun issue here.

Recently my original fuel pump gave out (Lasted 90000 miles...not bad!) and I had it replaced with a racetronix pump. Ever since the pump was swapped out I am having trouble starting the car. When I turn the key to the acc switch I hear the pump prime, but it takes a long time to turn over. The starter sounds good, and the car has a brand new optima red top. The starter does not sound slow, it just takes a while for the engine to start. After looking through some old threads I was starting to think that the fuel pressure regulator had gone bad on the car, so I hooked a gauge to the fuel rail. Sure enough, when the pump primes, the pressure gets up to about 45-50 and then drops off to 0 in a matter of seconds. If I prime the pump multiple times (by turning the keybetween off and acc in 3 second intervals) the car starts right up with no hesitation, and once started runs great.

So my two questions are:

1 - Do you guys agree that it is probably the FPR
2 - Most every post on the boards say that the LS1 FPR is located in the tank with the pump (Eventhe Hayes manual says this), but the Chevy dealer parts department shows the valve on the driver's side fuel rail ( I saw the part and the tech writeup...they were nice enough to print me a copy). Can anyone confirm where the FPR is on a 1998 Camaro Z28?

 

The only LS1 cars with external FPRs on the fuel rail are 97-98 'vettes. All LS1 f-bodies have the returnless fuel system with the regulator at the tank.

Your problem isn't necessarily the regulator.
What's the fuel pressure idling? what is it when you rev it up?
Could be a leaking injector bleeding off the fuel. You could check the plugs to find a rich cylinder.
Could be the check valve in the pump.

 

Ill have to check the idle pressure when I get home today. As for the leaking injector, I didnt think to pull the plugs and check for a rich cylinder since the fuel pressure drops so abruptly (Approx 5 seconds after the pump primes). In addition (and I know this is in no way an accurate test) trying to start the car with the throttle fully depressed to allow more air into the engine does not help the car start any faster.

It has been suggested that it could be the check valve at the pump, but I am really praying that it is not (I soooo dont want to drop the tank again). I was going to go after that once Ive eliminated the FPR (Though if it actually is in the tank, Ill be pulling it either way)

As for the external FPR, I am severly confused. You confirned what everyone else on the board has said before. That the LS1 F-Bodies have no external FPR, but the dealer's techs showed me the part, and where on my fuel rail it resides.

Just so I can get this straight once and for all, I snapped a picture of the drivers side fuel rail this morning to show you what the techs showed me yesterday. Im looking at the small silver object in the middle of the fuel rail. The part they showed me looked exactly like this, and it was identified as the Fuel Pressure Regulator. If it is not, I would love to know what it is so that I can go back to the dealer and get the right info on the FPR



Thanks for helping out with this...it's driving me nuts

 

I always thought that that part was a cushion to absorb the shock of extra fuel when you go from WOT to closed throttle.
If it was a regulator then there would be a fuel return line going from the fuel rail to the gas tank.

 

And that is why I was so confused yesterday when they pointed it out to me. There was no return line anywhere (as is expected on the LS1) The fuel hose feeds directly into that little silver thing on the fuel rail and then splits between the rails. It makes a lot more sense that it is a cushion rather than a pressure regulator.

SO it sounds like it is likely that I will be dropping the tank to replace either the pump (If it is a faulty check valve in the new pump) or the FPR.

Here is an interesting question though. When I initially asked the guy at the dealer about the FPR, and told him it was in the tank, he stated that they could not sell it to me if it was, since they only sell the pump assembly as one piece. Is this true? Does anybody have a part number or an image of the fuel pump that shows the FPR? I would like to go back with a bit of ammo and information so that I can get this mystery solved (Especially since the dealer wants 650 for the whole pump assembly)

Ill also scan the FPR replacement procedure they printed for my while I was there to show you what they say to do to replace the FPR (On the fuel rail for some reason)

 

Well...I now know why the dealer was confused!

It appearsthat they were not looking up the correct part number. Even though I told them that I hada z28, they still looked up the part for the V6 (Duh!). Only reason I found out was I looked up the procedure in the hayes manual, and there was the fuel pump regulator they showed me yesterday.

So Im back to pulling the tank again (*Sigh*)

Does anybody know the FPR part number? because the guy at the GM dealership insists that they can only sell the whole assembly. At this point Im pretty sure I got a pump with a bad check valve, or Ive got a bad regulator.

6 dozen one way, and a half dozen the other I suppose

 

Final piece of information to see if I cant tell what the problem is

I hooked up the fuel pressure gauge to the rail to see what the pressures were

First prime (Pump did not even get off 0)
Second prime (Pump got up to about 40
3rd prime (Pump got to about 60, and I was able to start the engine without issue)

Once the engine had started, the pressure held steady at about 56-57psi and never went down.

I wont be able to pull the plugs any time in the next few days. (And would prefer not to if I can avoid it...my luck it would be cylinder 7 or 8)

Any final ideas before I drop the tank next week, please let me know.

Thanks again

 

SS590 brought up a good point. You need to get the pressure values with the car running at idle and with throttle. This will point directly to the regulator if the pressures are not consistent with engine load.

 

Sorry...guess that was important information that I should have included

The pressure seemed to hold at 57 no matter what the throttle was at (Idle up to about 3K when I tested it. I didnt try WOT, but I figured that would have been pushing it.

 

Yeah it's not the regulator. As stated above it could an injector bleeding the pressure off, but with the diagnostics that you posted, it's probably the hose connection at the pump inside the tank leaking or the check valve in the pump is defective.

 

Re: Starting problem after fuel pump swap
I just finished a racetronix installation, including the delphi harness. Also replace fuel filter and dropped the tank and washed it out. Have a brand new AC Delco battery. Original reason for fuel pump replacement was that I had ran it out of fuel.
Now I crank it over, and can hear the pump kick in. No start. Fuel gauge at the rail shows no pressure at all. I noticed when I replaced the filter that it had fuel in the line on the tank side, but none foward of the filter.
Am I just having problems priming the pump? Or is it possible that I got trash in the line past the filter?
Any ideas would be appreciated. Will call the pump supplier on Monday as well.

Update 1/28/07. It seems that fuel is spewing from the fuel tank vent valve when I turn the ignition key on. GM Parts counter guy calls it an Evap Pressure Relief Valve. It is mounted to the rear brake hose bracket on the header wall just above the inline fuel filter. I am thinking I somehow cross connected the lines, because I had to wait for the correct filter sock to come. They sent a filter sock for the bottom of the pump assembly which didn't fit. Meanwhile my car is sitting torn apart, and I have to guess at where the lines (4 of them) get reattached, going from memory of when I disassembled all of them a month ago.
Got a little better diagram from the chevy parts counter. My factory manual really didn't help much in their diagram.
Sound like I am heading in the right direction?