cobraboy

Okay, so I've been having some issues with this SE at high RPM/loaded conditions. She literally falls flat on her face within minutes of driving.
Originally thought it was something electrical, because I had ruled out fuel pressure at idle. Today, I checked the pressure again and, yes, at idle it is right at 38 PSI. However, as I increase throttle it drops progressively and eventually gets low enough that it stumbles and dies. Starts right back up and idles great until about 25-30% throttle and....Boom....same thing.
I checked voltage at the pump throughout this process, thinking maybe a voltage drop was at fault......no voltage drop...steady 13volts across the board.
The fuel filter is brand new, but the pump is a cheap O'Reilly universal that has had some (50-75 gallons) dirty fuel (rust, sediment) flow through it since installed.
The fuel lines after the pump have been blown out with compressed air prior to all of this trouble, and the fuel lines before the pump were boiled and bore brushed. Is it possible to have clogged fuel lines with only 75 gallons max of dirty fuel going through them?
If I test the pump outside of the fuel system ( from a gas can with no return line, it reads 100 psi.
Is there anyway to determine if the pump is dying out under load or if I've got a clog somewhere?
THanx
Cameron

misterstyx69

iTrader: (142)

Did you service your injectors when you did all this fuel system cleaning?

diabolical1

iTrader: (3)

do you happen to have any specs on the O'Reilly pump? even if pressure is fine, volume may not be.

cobraboy

I did have the injectors serviced. Car was running great for a few weeks and then slowly started into this problem. The tank was cleaned, pump new, filter new, lines cleaned, strainer new, prefilter replaced cone filter. The only thing on the fuel system I didn't do much with is the regulator because it seemed to hold 38psi at the time.
So I'm down to wondering if it's a faulty pump or a faulty regulator.
Thanx thus far...
Cameron

84SpecialEdition

I had issues with my SE for a while also. This thread help me a lot.. especially the fuel volume test.

https://www.rx7club.com/1st-generation-specific-1979-1985-18/84-gsl-se-fuel-issue-904173/

Good luck

diabolical1

iTrader: (3)

well, if the pump checks out fine for supply volume, the regulator was my next idea, so ....

Vicoor

If the injectors were clogged the pressure would not drop.

This does not sound like a typical fuel pressure regulator type of problem.

Try this...

Run the engine til the pressure starts to drop off. then pinch off the fuel return hose and see if the pressure goes up. if the pressure regulator is the problem the the pressure should go very high, 100psi or so.

if the pressure does not go up then look at the supply side. You've verified the power supply to the pump so really the pump or filter would be the issue.

I've seen problems like this on cars with a lot of rust contamination It's possible that your new filter (or even the filter sock on the pump) is already clogged. or that after running a bit the new pump is giving up.

Hope this helps.

Victor

cobraboy

Vicoor....Thanx for the tip. Pinched off return line and pressure went through the roof.....beyond what my meter would read 120+ psi. Already had in mind that regulator might be at fault and had ordered new one (should be here sometime this week). But that helped to confirm my thoughts.
Can't wait to get back to drivin her.....it's so much fun.
Cameron

cobraboy

replaced FPR idled great and started up the road fine. Once I got to 60mph though, it started to die off. Checked pressure, was down to 30psi. attempted to drive back into town....stumbled and died. waited 5 minutes started again and drove into town fine. pressure was back up to 45psi, but gauge was bouncing rapidly. went for another drive, same thing....after 60mph died off. pressure was all over the place... does this sound like fuel pump?
Thanx

gsl-se addict

iTrader: (3)

Do you have the regulator vacuum line connected correctly (to manifold vacuum)? Are you doing anything with the orange solenoid electrical or vacuum connections when testing? I ask because the pressure at idle should be ~37 psi, but this is with the vacuum line referencing atmospheric pressure (same as running the car at WOT). With the vacuum line referencing manifold vacuum, it should be around 28 psi or so.

Have you done a volume test (with the pump in the car) yet? Follow direction that I gave in that link on how to test. Usually, when it falls on its face with higher loads, it is usually a volume issue.

The fact that this pump is going to 120 psi deadheaded concerns me a bit. The stock pump deadheads around 70 psi. This may or may not be an issue. Whether it is or not depends on the capcaity of the pump versus the capacity of the regulator and return line. If the return/regulator can't handle the volume, the regulator can't regulate correctly (but this would normally only be an issue at idle/low loads).

A measured pressure that is too high (45 is too high) indicates a probelm with the FPR or the return line. If the return line is partially blocked, not enough fuel can flow back to the tank and this will result in a higher pressure. However, your symptoms don't point to high pressure being an issue (unless it is going VERY high and flooding it out).

A restriction on the supply side (anywhere between the pickup and the fuel rail) may show normal pressure at idle, but will fall when load is applied. A volume test will tell you if the pump is giving the amount of volume needed. If it isn't, it may be a pump issue or a blockage in the line.

Another thing that could give wacky readings is if that orange solenoid is going nuts. It will change the reference between manifold vacuum and atmospheric pressure and could cause a bounce in pressure of say 5 or 10 psi (difference dends on throttle, engine wear, elevation, etc.).

Anyway, start with the volume test and we will go from there.

Kent