87SS

Had some start up issues lately and noticed low fuel pressure. Since this was a modified SBC setup I have my A1000 pump wired to a switch, so I can hit the switch without the key on to test. I noticed with a fully charged battery a pressure around 30psi (motor not running).

Thought maybe the FPR (Aeromotive 13101 which has a -10 return to the cell connected) or the small pressure gauge mounted to the FPR was messed up so I connected my feed from the pump directly to the feed to the rail (have a L92 intake with single feed). When I connected a fuel pressure gauge to the fitting on the passenger fuel rail I had the same thing, 30 psi (motor not running). Our baby was sleeping in the next room, so did not have a chance to fire it up, but really did not want to without a FPR.

I have -10 from the cell to a filter, then A1000 then filter then FPR (or rail as connected right now for test). Thinking either a clogged filter (hoping), but possible pump issue? Any other ideas? I guess I could remove both filter medias and do a quick test to see if pressure rises or not. Do not see any kinked lines either. Since motor sat for almost 2 years I think the injectors need a good cleaning, but wouldn't think that would affect the pressure reading.

bayer-z28

iTrader: (14)

The regulator should be on the return side.... unless I mis-read.

87SS

You didn't misread. The L92 intake only has 1 connection feed, so I have the regular before the fuel rails. I know, not the best as I plan on ordering new rails soon so I can put the FPR post rails and regulate pressure that way.

bayer-z28

iTrader: (14)

^ I think that's where your problem is. I've been doing a lot of reading on this lately as I have to re-plumb my fuel system also.

87SS

I agree, needs to be post rails. But there is a problem regardless because the gauge is only showing 30psi without the FPR in the mix.

stevieturbo

Nonsense. The FPR can be anywhere on the pressurised side and it should maintain pressure within that section of rail. Whether at the start ( like many OEM dead end systems ) or as the last item in the chain before returning to the tank.

Running it the way he has does have some advantages, in that there will be far less hot fuel circulated back to the tank ( as the fuel normally gets heated in the hot fuel rails )

Injectors will have no impact on fuel pressure. it is either an FPR problem, or a fuel flow problem.

Whilst you shouldnt have to adjust the FPR, have you tried doing so to see if it is capable of making more pressure ?

Can you monitor the return back to the tank to see how much fuel is actually flowing ?

87SS

Thank you.

I have tried adjusting the FPR and it is maxed out. Between this and no effect on the FP when I removed the FPR I basically believe it is 1 or both of the filters on either side of the pump that are clogged, a bad pump or a pump that is not getting full voltage. Been a crazy week at work, will trying removing the filters and starting there.

This car had a different setup a few years ago and sat for at least 2 years before trying to start the LS. Though the gas was completely drained from the system and removed from the car I wonder if the filter got gunked up. Will see.

I had emailed Aeromotive as well and they suggested trying to run the return from the FPR into a gas can to see if it is flowing slowly or firing into the can to help diagnose the issue as you mentioned as well regarding the return.

stevieturbo

Checking the return would be the easiest and best thing to do at the minute, as it will give you the most information.

If the filters are easy to access, again it will do no harm to give them a visual. Does the pump sound normal when it is running ? Should be a smooth even noise

87SS

Thanks.

I have the cell, filter-pump-filter setup mounted in the trunk so it is easy to get to, not fun when you have a cell full of fuel. Thinking of springing for the newer fuel filter with a shutoff which would make this exercise less painful.

The pump sounds pretty smooth once pressure begins to build (takes a few seconds). I think I also need a check valve since the pressure drops right off once it is shut off.

Ollie8974

When you say maxed out what is the What is the fuel pressure.

87SS

30 psi

stevieturbo

I really dont see why people see this is a problem.

And not all FPR's will offer a total seal with no fuel flowing into them.

I'm quite happy to have mine sitting with no pressure built up when the engine isnt running.

87SS

Good point. I like that the pressure is relieved when I have to disconnect something, just needs a little longer to prime when starting is what I have noticed.

stevieturbo

When you key on the ecu primes the pumps for a few seconds anyway. And whilst the engine is rotating the pumps are running. TBH Ive never noticed any starting issues because of it.

Big Al

iTrader: (1)

It's the pump or the bypass spring. Should be easy to determine which. Take the bypass apart and see what you find.

Al 95 Z28

bayer-z28

iTrader: (14)

Same here.. I'd almost rather have the connections and hose relax. I don't need them under constant pressure (car off.)

87SS

Sounds like no check valve it is then

87SS

Ran the return to a gas can. Nothing came out the return and pressure was still 30 psi. I turned the adjuster way loose on the FPR and it dropped to 20psi before I noticed a little fuel dribbling out of the return. Voltage at pump was 12.9 volts

stevieturbo

Either the fuel pump is bolloxed, or there is a filter or line blockage.

87SS

Took out both filters. Paper filter looked a little dirty, so I tried running it for a few seconds without the filters in the cartridges. No difference. Don't see any kinks in the stainless lines so it must be the pump. I will email Aeromotive, I believe they will test their pumps for a charge if you send it to them.