I just got done with the 350 swap. Now I am having fuel pressure issues. At an idle and reviing it when first started for about 20 min. the pressure is rock solid at 26#'s where I have the AFPR set. Then after a half hour or so the pressure droppes to 0 when I give it gas, but maintains 26 at an idle. Making it real hard to drive.

Any ideas? Everything is new which we all know doesn't meen a thing. I don't want to drop the tank if I don't have to.

Help me out.

 

Pinch off the return side if you can, the pressure should go up to 50psi or higher.

 

TBI car right? Your pressure should be about 13 psi. I would say 17psi is on the high side and anything past that then you need the proper injectors for a 350. You need 65lb injectors(cop car injectors). However, the 55lb injectors may be ok with fuel pressure bumped up a LITTLE bit.

 

I tried clamping the return line but it isn't doing anything. The pressure is staying the same. I will try clamping it better. There must be enough getting by still although I don't see how. I am using pump AC Delco #ep385 or 4 if I remember the number rite.

I had it just idleing last nite and it didn't do it's trick. I will take it on the road tonite and check it again.

I am hoping it's the AFPR although it is new too. The whole TBI is a custom built from Sean @ SPR Performance and it cost a lot of money.

 

1. Do you have proper voltage going to the fuel pump via the fuel pump relay? Test the voltage as close to the fuel pump as you have access to the wires. (typically there's a four-wire connector near the gas tank you can pop apart, and then install a four-wire test jumper.

You MUST test the voltage with the fuel pump RUNNING.

2. If you can clamp off the return hose, and the fuel pressure does not increase to 40+ psi with that fuel pump...the fuel pump may be toast. (I'm thinking that an EP385 pump is much higher-pressure than the typical TBI pump.)

 

The pressure does go up. I took it for a drive and as it was acting up I pulled over and checked the pressure and it was fine at an idle and as I gave it gas it went down. I pinched off the return line and the pressure spiked up.

I thought it may be the AFPR but how? It is just a spring and a bolt. No holes in the diaphram.

I will check the voltage tonite.

 

There may be debris in the FPR. It gets between the seat and the plunger and allows fuel to leak past.

RBob.

 

A wounded fuel pump that produces low volume; or a clogged fuel filter can have similar symptoms to what you've got.

Low-demand situations have adequate fuel volume and pressure, high-demand situations have low volume and therefore low pressure.

 

Changed the fuel filter, took apert and cleaned AFPR, pressure doesn't go to 0 it stays at 10#'s when I rev and hold it at about 3500. Haven't checked the voltage yet. I'll do that today.
It sure acts like something is plugging the suction. I sould just drop the tank and inspect it. The car is worthless as it is. Can't I just cut a hole in the floor? or push it off a cliff.

 

Gave up dropped the tank., The pump suction is clogged and my machanic didn't install the strainer or it is in the tank. Putting in a TPI pump and strainer from Napa for a Corvette. It wasn't cheep but it is made in the USA unlike my A/C Delco. ! year warrentee to boot.

 

damn. same thing happened to me not too long ago. glad you figured it out buddy.

 

On the road now it's time to tune. While it was down got a chance to put the suspension stuff on. I went a little cheap and didn't buy the Koni's. Now I just want it to run rite.

What do I do besides VE learns what do I tweek. Going for a cruise, one more learn.