Okay, I’ll admit it, I’m stumped and need some fresh minds!
My son and I have thrown his boat together with a bunch of spare parts I had in the shop and we're struggling with fuel pressure issues.
The motor is a mild 468” Chevy. The fuel system comprises of twin SS gunnel tanks.
The tanks are vented with separate vent lines and vented caps.
Coming out of the tanks are 2 3/8” NPT 90s with 3/8” hose barb out of the top of the tanks. I know, not ideal but this was a 4 week thrash to get it together.
From the tanks we have about 2 1/2' of 3/8” rubber fuel line to a tee.
Off the tee is -8 SS to a Holley HP150 electric pump that is mounted as low in the keel as possible and well below the tank bottoms.
From the pump we ran -8 to a standard Holley regulator.
From the regulator we ran -8 to the carb with an inline fuel pressure gauge.
Carb is a 1407 Edelbrock
This setup worked flawlessly for his maiden voyage and then again on the Friday of the Laborday weekend.
That Friday afternoon he ran the heck out of the boat to the point that he ran the boat out of gas.
We dumped some more gas in it and it got fuel pressure right away but it’s never been right since.
It’s gotten to the point that it won’t even allow the boat to get up much past 3000 rpm in the water with little to no fuel pressure.
We loaded it up and brought it home and we’ve been messing with it ever since.
The fuel pressure on the inline gauge up near the carb jumps all over the place. It’ll go 9lbs then 3lbs then 6lbs then 2lbs. It’s completely inconsistent.
*I’ve changed the fuel filters.
*Swapped out the regulator with a spare Holley regulator I had in the shop.
*Bypassed the relay (momentarily) to make sure the pump was getting sufficient voltage.
*Opened up the fill caps so I know it’s got enough venting.
*Pulled the pump apart and cleaned the inlet screen.
Still inconsistent and insufficient fuel pressure hovering around 3lbs but continues to bounce all over the place. I could probably turn the key right now and it’d show 9lbs for a second and then drop soon after to 3lbs.
One of our friends (thanks Glenn) mentioned that that the rubber hose might be culprit and so I disconnected the fuel line from the tee and put it in a coffee can of fuel and turned the key. The fuel pressure was 7.5 lbs and stayed consistent.
Figuring that I must indeed be collapsing the fuel hose, I replaced the little bit of rubber hose with new Goodyear 3/8” fuel line and put it all back together.
Nuthin, still does it. Seems to hang around 2 to 3lbs of fuel pressure but still jumps around.
So here I am, completely stumped and hoping that you guys can give me some ideas.
If it was the fuel pump taking a dump, I would have expected it to be consistently low and plunking the line in a coffee can of fuel shouldn’t have changed anything.
If the pickup tubes were too small, that should have shown that right away, not till after he ran it out of gas while boating.
Does anybody have any ideas or see something I’m missing?