Post #1 - Fuel filter already replaced.
Post #1 - Fuel filter already replaced.
Could a failed seal at the gas cap cause pressure issues?
The pump is pushing some gas. Never heard of a weak pump, weird I thought they either work or they donít.
A new filter was first on my list. The last time it was replaced was about 5 or 6 years ago when the spark plugs were changed out. My had daughter accidentally put diesel in the tank prompting replacement of a few items, ie all 8 injectors, fuel pump, fuel filter, plugs and an oil/filter change. The car ran great up until recently.
I gona fight it out with the 4 rear spark plugs today.
The only way the seal at the tank could possibly affect fuel pressure is if the tank vent line(part of the EVAP system) is blocked AND you have a perfect seal at the gas cap. This condition over time will create a vacuum inside the tank due to the pump sucking the fuel out of it. It takes a long time for this to occur and even longer for the vacuum to start affecting fuel delivery. So a bad seal at the filler neck will actually prevent this from occurring at all. Just unscrew the gas cap and check pressure if you want.
Blocking the return line at the rail will rule out the FPR and ensure that the fuel is not bypassing directly back to the tank. I have done this before with a 3/8" brass plug and some teflon tape. It's not perfect but it will get you an answer. (dont run the engine this way)
With the return blocked, there's no other place for the fuel to go except out of the FPR vacuum nipple in which case it would be shooting out profusely. :flame:
Even with a partially blocked line or filter, a healthy pump will still be able to generate good numbers on static pressure. It's the volume that will be cut short. So in that case it should make good psi with the engine off. Once you start the engine and the fuel starts moving, the pressure will then drop due to the volume demand. What I'm trying to say is, if the pump cant make more than 30 psi static then it's toast. Just for shits, turn the key on and off a few times with the gauge hooked up and see what you can get it up to.
The 1990 and later engines use port injection (PFI) with eight small injectors located near each cylinder. PFI systems typically have fuel pressure in the 30-50 range
Look at the front valve cover, does it say V8 PFI in big red letters?
SOB! I finally got those bastards out! I see what you guys are talking about working blind. Good thing Iím long and thin, I wuz able to contort back and around but just barely.
Upon inspection the back four were fouled and burnt and looked very very old compared to the front four. Think I got took for a hundred bucks and four new plugs last time around, damit. Still puzzeling over the fuel pressure problem. Thanks ehall. Post #17 all 8 injectors were replaced. I think Sevillian273 is right "30 psi on the ready or the pump is toast. The pump I installed back when was an aftermarket from NAPA. Go figure. This time its GM.
Gota take a break before tackling the compression test.
Assuming that the pump is in fact what failed, do you remember what brand it was(bosch, airtex, wells, etc)? And how many miles on it?
I struggled for about 45 min trying to thread in my compression gauge hose before I decided the compression was OK, (the thing ran strong prior to this last mishap). Managed to get the new plugs installed.
Sevillian273, kudos to you. I re-tested the fuel pressure at the test port like you suggested;
8 gals in the tank.
YEP! I’m convinced. I'll check what brand the old one is when it comes out of the tank and let you know.
Dropped the tank this morning. When I removed the pump/sending unit carriage from the tank the strainer attached to it was plugged. This was probably the problem all along. No point putting the old pump back in through, no way to test it on the bench.
Priced out replacements:
GM: $125 / $30, pump/strainer
Napa: $85 / $7, pump/strainer “DEP & BOSCH”
$77 / $7, pump/strainer “NAPA”
This car has 330,000 miles on it; so on second thought, considering the cost difference, I think I’ll go cheap. The last pump did last 7 years and you just never know what will be next, whether or not it’ll junk the car.
Sure do give a shout out to all who contributed to this thread.
Bosch makes top-of-the-line fuel pumps, I would buy that first
Good you found the problem. Even though you found a clogged intake filter, you will be better off replacing the pump rather than just replacing the intake filter. A plugged intake filter is much harder on the pump than a plugged line filter. The Fuel Pump is cooled and lubricated by the fuel moving through the pump. When it is blocked at the intake, The pump runs hot and dry. I am sure that even if the pump was Ok now, It is probably not long for this world.
I have no idea who makes the best pump. I am sure others on the board can answer that. I have had good luck with every pump i have replaced except for a AC Delco installed at a dealer due to a failure on a long trip. (Not even sure it was an AcDelco but that is what i was billed for). That pump lasted only a month!