88 Iroc 5.0 TPI

I recently put in a Delphi FE0110 pump from rock auto, it was listed as a MFI pump, unless I misunderstood the specs I thought it would be fine for TPI. Cant seem to get a fuel pressure reading above 20psi.. Ive tried testing at the FPR (adjustable) and at the hard line before the fuel rail, 20 psi when the key is on then immediately drops to 0. The reading is consistent, but occasionally the pump does not prime, unless I wait 10 or so seconds , is that normal?
Does this sound like a pump issue or electrical?

The car sat for years, I replaced the entire fuel system at this point, tank, pump, fuel lines, fuel filter, injectors, plugs, and fpr.. Even on 20 psi I can get it to start intermittently but its obviously rough.

 

Pulsator bypassed ?

 

Put the stock regulator back on.

 

I put in a new spectra sending unit, didn't mess with the pulsator..

I got 20psi when testing before the fpr/ fuel rail so I am assuming putting the stock fpr back on wouldnt be the solution.

 

You might have to pull the spark plugs looking for fouled plugs. Check the fp vacuum hose for evidence of fuel. Does pressure go up when rubber crossover return line is pinched ?

 

Which one is the rubber crossover line? Other than the vacuum line from the fpr they seem to be hard lines unless I am missing something?

 

The return line comes off the regulator. It’s a hardline until it crosses over at the front of the engine to the fender well.

 

gotcha. clamped the return line while running, no change in pressure. Swapped the relay just in case, still intermittently priming.. ? Still 20 psi then immediate bleed off to 0, almost like a tbi.

 

You can use a volt meter or test light at the relay and see if it’s getting 12v for 2 seconds for prime. If after you get it to prime several times and plugs arnt wet it sounds like a bad pump or hose above the pump. I’ve heard good things about racetronix pumps. Might see what they have to offer.

 

THe immediate dropoff is a ringer for a bad pulsator, other in-tank leak, or bad pump. Pull, hot wire it w the sender in a bucket and if no leaking noticeable, get a diff. pump.

 

I appreciate the help!

Ok I checked voltage at the pump connector. Got 11.6-11.8 during prime, 10.6 cranking.

back probed thick orange wire at fp relay, 12.4 constant, dips a little when cranking. It’s also a new relay..

so I’m getting power, and prime intermittently, immediate drop off of fuel pressure after prime.
anything else I should check before dropping the tank? It’s a brand new sending unit and pump but it seems like something must be off in there.

 

I had an almost exact same problem with my '92. Could never get the psi above the low 20's even after installing nearly every part in the fuel system. Ended up that the pump was the wrong one. A lot of places don't verify that the pump if for TPI or TBI. All they see is that it is a 5.0. Swapped the correct pump in and it has ran like a champ ever since.

 

Thanks. Weirdly, that is encouraging to hear. At this point it seems like it has to be the pump or something I did in-tank. I can't even be frustrated anymore I just want to get it sorted out. I was so close to getting the Walbro instead of the Delphi too.. Will see what things look like when I drop the tank again.

 

If you do get a Walbro get one from summit racing. To many fake out there

 

For my 5.0 TPI I've used Precision Fuel Pump E16030 (O'Reilly's). The first one I had lasted for about 3 years, though the car sat mostly awaiting a rebuild and only started every couple months. On this one I had removed the pulsator as the original appeared torn, and also the examples I saw out there it appeared that most people bypassed it with fuel hose, so I did the same thing. When I removed this fuel pump, I noticed that the section of fuel hose that replaced the pulsator had a hole blown in it! So I'm thinking that possibly the fuel pump was just dumping fuel through the hole while it was in operation making it seem like the pump was dead, however I didn't get the usual FP prime sound, so I still think it was dead (though perhaps that hole in the line caused an early FP death?).

After replacing the fuel pump with the same model, the next one died after only 2 starts!! On the second startup it idled perfect. I was going through each gear to flow oil through the transmission and when I got to Reverse the idle got rough and engine stalled and never started again and no FP prime noise. I have yet to get under and check the voltage at the pump connector to ensure I'm still getting 12V.

Should I replace the pulsator? What do they even do?

And how does a 42PSI fuel pump blow a hole through 50+PSI fuel hose??

One possibility is that some newer model FPs supply much higher PSI and may require a bigger power wire than the stock wiring provides. Just a theory. But I can attest that Precision Fuel Pump E16030 works with a stock 5.0 TPI setup. And perhaps it would be more reliable if car is ran regularly.