TIMSPEED

Just quick,
If the fuel pump is REALLY loud, it's bad right?
It's not loud ALL the time, at idle, in neutral, it's not loud, but in drive, above about 2000rpm, it's LOUD and increases with rpm, but at about 3000rpm it really basically stalls out.
Also, immediately after shutdown, I pushed the valve stem on the fuel pressure test port and there was like NO pressure there. (gas barely dribbled out)
So, new fuel pump time, right?
I think the key things are
1.) Loud
2.) No Fuel Pressure held between pump & regulator
I'm almost certain the regulator's not bleeding pressure off, because immediately after I kill it, I can start it right back up, without any sort of backfiring. (TBI motor)

AGENT 86

I had an electric fuel pump on my 68 Camaro and when it got loud it was because it was starving for fuel. Maybe you sock is dirty and your check valve is shot.

CFI-EFI

The fuel pump basically runs at a constant speed. At idle and neutral, the fuel demand is the least and the pump is pushing hardest to overcome the regulator pressure setting. First, I'd replace the filter and the sock, and than drive it with a pressure gauge attached. If, after the replacements, the pressure drops at the point of the greatest fuel demand, then the pump is probably bad.


That last quote has two sentences. They contradict one another. You can start it right back up? That proves the regulator isn't bleeding off pressure? BUT, there is no pressure between the pump and the regulator? If no pressure, why does it start right back up? If no pressure, why is it not the regulator? Your conclusions aren't supported by your evidence.

RACE ON!!!

TIMSPEED

I mean, it's not HARD to start back up. It cranks for about 15 seconds, then starts back up. My thinking is, if the regulator was leaking, gas would already been in the TB and it would momentarily backfire or pop or something.
BTW: I didn't know the pump ran at the same speed, no matter what, it's just the regulator that changes the flow. (I'm thinking mechanical pump, faster rpm = more flow.)
Hmm..I'll check actual pressure's today, and a few other things...

ittlfly

You could put a fp guage on it and try some trouble shooting by pinching off the pressure side at the fuel tank after priming the system. That will narrow it down some.

TIMSPEED

Doing that today..had the guage with me yesterday, but the fitting on the fuel line was too small, it's not 1/2" like normal, it's like 1/4" (GM High Side R12 A/C size)

Redeasysport

If you regulator is bad you can tell it by pulling the vacuum hose before shutting it down it will leak pretty good if it is bad.

A noisy pump can be bad and instead of just changing the sock the pump is cheap enough to do it with it.Peace of mind with a new pump that you won't get stranded.

Cranking for 15sec IS a hard start mine cranks for 2 sec at most and a bad regulator dumping into the intake takes about 15sec to crank up.Guess how I know that.I changed out my whole fuel delivery system when I got mine 9mo. ago chasing this down.No regrets that I did and it was not that much money except for injectors which I got stockers for $125( a great deal) with low miles on them(like new).My old ones looked like crap had corrosion all over the tops the original owner must have used a lot of watered down gas

TIMSPEED

No fuel sock in this system. Just a pickup from a fuel cell. I think just before the regulator, it has a mesh screen...but it also sounds to me that the pump is starving...interesting setup..filter before the pump, but i guess with EFI it really doesn't matter.

Redeasysport

The fuel sock should be in there I would look around in the tank for it it is about 4"X1" if stock it should be white I think. The screen is attached to the sock and clips on.The sock just keeps junk from getting into the filter. Oh I could be wrong what year is yours mine is LT1. There is another "Fuel" filter near the pass front wheel.That is another candidate if the fuel pressure in the rail is low and also can cause the pump to strain even if the pressure is OK if it is dirty.If you have not done it in the last 25k miles it might be good to change that too. Did you pull the FPR hose to check for leakage?


edit: I see you have an 87 so this may vary but I thought it had an intank pump like mine if so that is where the sock will be.You won't see it till it is out.

Great-White

your problem with fuel delivery and noisy pump happens a lot with a dirty fuel filter. g.m filters are notorious for this. when i worked at a g.m dealership i don't know how many vehicles came in with fuel problems and all we did was change the filter. take the filter off and try blowing through it if it is hard to blow through it is dirty. bad thing is a lot of times the fuel pump is bad because the filter should have been replaced as regular maintenance. recommend replace filters at least every tune-up. hope this helps.

USAsOnlyWay

Here is a pic of my stock 135k mile pump. Still worked when I took it out. Hell it might be newer.
Anyway, the fuel sock, fuel flow direction, and fuel pump are labeled.


You said you had a mechanical pump?
You also said it ran in a fuel cell?
So have you severly altered your fuel system?

AORoads

I can't offer much help, but I agree with Redeasy: if you're cranking for anything approaching 15 seconds, that is a hard start situation. Do you have a modified fuel system?

CFI-EFI

He hasn't been totally forthcoming on the vehicle involved. He has dropped hints but hasn't let the cat out of the bag. In his opening he mentioed that it was TBI. This being the C4 section, I immediatly thought of my Crossfire, but if that is what it is, why wouldn't he just say so? My guess is that he is being somewhat secretive to keep the thread from being closed for being off topic.

RACE ON!!!

TIMSPEED

Not even on a car...but if I put it in General Engine, NO one will respond.
I think we got it fixed pretty much, thanks for the replies guys.

USAsOnlyWay

So now you can let the cat out of the bag....what's it on?

TIMSPEED

02' 21' Larson boat. Freakin TBI on a damn 02! WTF?! MPFI, HELLLO! Hard to believe they're still putting CARB'S on boats, FROM THE FACTORY!

USAsOnlyWay

Wow, I wouldn't have exected that on an 02 either.....crazy!