Engine is running poor, backfiring through the plenum.
Fuel pressure test goes close to 60 at key on, drops to zero.
Pull the plenum and find poppets out of place (I assume from the backfiring).

I change the FPR. Key on she goes to close to 60, holds between 50-55. Looks good. Stays for about 1/2 hour, as long as I wait to put the plenum back on.

I run it up to get a little more gas. Same symptoms, coughing and no power.

I get it home and put the fuel pressure gage back on it.
Key on goes to 55, immediately drops to zero!?!?
Running at 45 now. WTF?

It holds fuel pressure one minute and 10 minutes later it doesn't? If changing the FPR did nothing I'd assume it was the spider, but why did changing the FPR solve the problem ever so briefly?


Spider and nut kit are a year and a half old.
Fuel pump number…3? 4? is a couple years old.

 

May be you have a leakage between pump and pressure regulator. Normally pumps had a internal check valve that holds pressure. So you could had a leakage at feeding line. If not, bad pump (i thing there is a kit that contains only fuel pump, not the entire assembly)

 

what did the intake look like when you took the plenum off? what side was clean, which was black? all one color? black is good, clean means fuel leak. Could still be the nut kit, could be the injector, could be pump itself.

 

There was no obvious signs of washing but there was gas inside the plenum (and I'm pretty sure in the oil too). But one of the poppets was blown out of it's hole, so the gas could be from that.

My plan is to isolate the pump at the fuel filter and check it there for pressure and hold, I assume that will tell me if it's the spider or the pump assembly.

I'd being doing it now… but there seems to be a bit of a hurricane outside.

 

If a poppet was out then that could cause some fuel going where it shouldnt. And isolating the fuel pump will let you know if the pump is bad or not.

 

Craziness.

Isolated the fuel pump and tested cold, hits 80-90ish (I shut it off) and holds.

Back up top at the intake she goes to 60 on key and is holding again. (???)
Still running at 45 though. (seems to have climbed to 50 as it ran a while)

I'm running it now hoping things heat up and will isolate the pump again.

Sucks with no electricity, sporadic cell, and mile long gasoline lines (literally).

 

This is so screwy I can't even ask questions right.
I noticed:

Key on the pressure goes up and drops.
If its running and I shut it off it holds.
If its running and stalls it drops.

I thought I was on to something... then it held key on.
Grrr....

 

Check pressure at the fuel filter, (the way you got the 80-90psi). Activate & deactivate the pump several times and watch for immediate pressure when you activate it. Could be a poor connection somewhere or a dead spot in the pump motor armature.

When deactivating, pressure must remain above 50psi for at least 10 minutes, (try it several times). If it drops, the check valve might not be sealing every time and if that's the case, it will drop rather quickly. Post your results.

 

I got pissed and dropped the tank. Changing the pump now (took a break for lunch). I'm either going to be right, or have a spare fuel pump.

 

Well the good news is... I'm getting good at dropping the gas tank.

New pump isn't any different.
Still running like crap, popping through the plenum now and then,
still running at 46 pounds. (of course now I'm starting to wonder if my pressure gauge took a crap or something).

Barely have enough gas for the pump to pick it up. Don't know what else I can do at the moment considering the local situation.