kimmer

A Little background, my car started running bad.
put the pedal down and the power is not there like its not getting gas. I just put a pressure gage on it and at key on it went to 45lbs as soon as I turn the key off the pressure drops to zero like a rock. It idles at 35lbs with some surging now and then so Im thinking injectors, can I get a second on that.

antfarmer2

but would check the fpr and the pulsater first .

kimmer

Fpr is ok, pulsator, where is that?

Klondike

Mine did the same thing and it drove me nuts till a shop FINALLY found ONE intermittently sticking injector! It ohm'ed out OK and I could hear it click when I tested them all. If I let the car sit a couple of days, it would re-seat and I could drive around the neighborhood as long as I didn't press it too much. As soon as I would get out on a main road or the highway everything would go to crap again. Changed the FP Reg and the pump and still had the problem. Local Fuel Injector Specialties Shop took the injectors out and bench flow tested them and I had One injector that would stick wide open and flood the crap out of the car. The computer would go bonkers trying to adjust for the misfires and richness and the car would barely run. They put in new injectors, and now all is well.
Wouldn't have believed that just ONE injector would cause so much hell, but that's what is was in my case.

antfarmer2

It connects the fuel pump to the fuel line most just replace it with submersible fuel line. It will make a fountain in the tank and will not hold pressure. just take off the fuel door than the bib and pull it out easy fix. Smell your oil for fuel if there I would look at the injectors first.

Klondike

When I replaced my Fuel pump, the new pump said the pulsator gadget was not needed on the new Turbine style pumps because they don't pulse like the old gear displacement type pumps do. I think most new pumps are that type now. The only hassle was trying to fit a filter sock on the pickup end of the new pump.

aklim

IF you are sure the FPR is ok and so is the pump, lets try this. Do a WOT run and see what happens with the fuel pressure. Maybe take the FPR hose off and cap off the nipple it attaches to and that will force it into a WOT mode for the regulator and when you make the run, see the pressure? That will test if it can supply pressure. If not, your pump might be defective.

Next thing you can do is clamp off the return line and pressurize it by turning the key to run mode but don't crank. It should jump up and stay up.

John A. Marker

Kimmer here is GM standard test..

••••• TESTING FOR LOSS OF FUEL PRESSURE

... Here are the sure fail tests for the fuel system to save you time and money.. Take a fuel pressure gauge attach it to the Schrader valve.. Turn the key on and off a few times to build up the pressure in the system... If you are having starting trouble the pressure will probably drop as soon as it hits 38 or 40 and the pump turns off it will probably leak back to zero within a few minutes. Okay now right after you prime the system pinch off the return line near the tank if the pressure drop stops it is a bad fuel pressure regulator.... Next pinch off the feed line if the pressure holds then the leak is before the point where you pinched the line IE fuel pump check valve..hole in the metal line on the sending unit caused by it rubbing on the inside of the tank you should visibly be able to see this if you pull the pump and the sending unit...(this was my problem) or the pulse dampener which is the piece between the pump and metal line on the sending unit.. the diaphragm tears.. and last if you pinch both the feed and return line near the tank and the leak down of the pressure continues then a fuel injector is your problem.. This is the GM test.. saves time and money..
•• disconnect the vacuum line from fuel pressure regulator

bob arrowsmith

I have a similer problem, when first turned on fuel pressure pops to 40 and settles around 36 37 when running and will increase with throttle so fuel pressure seems ok, but drops steadily and after about a minute will drop to 0 with engine off key on. can a fuel pressure reulator
be bad and still show know signs of leakage, meaning when you remove the vacuum line and there is no sign of fuel smell.?

canuck buick

Mine is exactly the same.

cv67

It shouldnt drop fast when you shut it off
Can slowly bleed down over time

DanielRicany

A good test to see if the injectors are leaking is to use pinch style pliers and pinch off the return hose first (the rubber hose portion is in front near the water pump), turn the key on for 2 seconds and have someone immediately pinch off the supply line. After you do that, it means that the pressure is locked up within the front part of the fuel system. If there is any leaking now it can only be leaking externally or past the injectors. So if it still leaks down and you don't see visible fuel at the connections, then one or multiple injectors are leaking.

bob arrowsmith

i have replaced the fuel pump motor, gasket and a gas line hose that connects the pump to the fuel line and it still leaks down. i have a guage attached to my window to watch fuel pressure as i drive , all seems normal pressure is steady as i said but it still leaks down to 0 when engine is off key on, it does not seem to effect the running of the car so i am not to worried about it, on another note though what causes chugging motion at light throttle or when coasting, now this is annoying . Its like just touching the throttle on and off and sometimes i can even hear the slop in the drive line it get that bad.

antfarmer2

How old are the o2s?

bob arrowsmith

when i bought the car a few years ago the po said that he had replaced them do not know how many he replaced, i know there a re 2 ahead of the cat and i believe 2 in back..I want to get a data log of the engine running sometime soon, hopefully that will tell me if they are functioning properly..by the way this is a 96 auto. also i am getting very bad mileage and rough idol.

Cliff Harris

I had that symptom when one of my spark plug wires was bad.

1stVetteFinally

I wouldn't worry too much about fuel pressure dropping like a rock once you turn off the ignition. My '92 does that also, and it was just timed at 14.02 in the 1/4 mile and runs perfectly fine on the street. I'd look for another issue before I spent too much time on the fuel pressure drop off (I spent way too much time and money trying to stop the fast bleed off on my car because people were telling me it shouldn't bleed off as fast as it was).

bob arrowsmith

Thanks , i agree it does not effect the running of the car.

antfarmer2

The original fuel pump would hold all night. This was done for the EPA replacement pumps some hold better than others. If it gets worse look at your pulsater.

aklim

I think he has already tossed the pulsator.