tims red 1991 vette

I have used your advice and have tested and changed out the injectors, 4 had low readings. I put in Accel 22.5 lb injectors. I also put in a holley adjustable fuel pressure regulator and have it set to 50 psi with the vacum hose connected and it stays there with the engine off. It was originnally thought to have a clogged cat but it is new, and so are the series 50 borla mufflers, and this is now definetley not the problem as we thought it might be. The engine idles nicely and at low rpm's. It when i give it gas, say 1/2 throttle it will hesitate, sometimes fall on its face and at WOT it just bogs and sometimes takes a moment to recover. I am perplexed with this and frustrated. I was told that my TPS was to measure.54 volts but I am not sure how to measure this. What other things should I be looking at. I would really like to have my vet perform like a vet. Thanks,

Tim Hollowell

vinnies87

First thing, is you should fill out your profile so members know who, and what your talking about... esp your vette.

tims red 1991 vette

I just filled out my profile, thanks for the reminder. It is a 1991 L98 6 speed. Any help will be appreciated

JOHN89

Tim,
50 psi with the vacuum connected is way too high. When you disconnect the vacuum line it will increase atleast 5-8psi more. That means you are somewhere above 55psi. Thats too much!

You want to set the fuel pressure with the vacuum line disconnected to around 43-45psi. Then when you reinstall vacuum line it should drop down to 36-38psi or so. The stock injectors were rated for 22lb/hr @ 43.5 psi. That is plenty of fuel for your 91 350 TPI.

John

5abivt

tims red 1991 vette

so I adjusted my fuel pressure down to 34, 36 38 with the vacum hose connected and still got the same response. Two things did happen that seem like they shouldnt. One when giving it WOT the fuel pressure drops down to 15 or so and it pops through the throttle body sometimes. The other thing is when I let the pressure off of the guage I get a lot of air and when I release it the pressure goes back up and I get more air. The fuel pump is new and I am perplexed on what is going on. Thanks for any help.

Tim Hollowell

JOHN89

If its dropping down to 15 psi at wot then something is wrong.
1. clogged fuel filter
2. kinked/crimped line
3. bad fuel pump
4. clogged sock filter
5. pulsator line on fuel pump has a hole, is loose or disconnected in the tank.

I would change the filter first.
You can do a fuel pump volume check when you have it disconnected.
measure the liters/gallons per minute per the repair manual.
You say its new. Who installed it?

You definately have a fuel supply issue that should be relatively easy to find.

John

BLWN BUX

Certanly sounds like your new fuel pump is air-ating the gas.
Could be the pomp itself or the seal conections that enter it.
I am assuming it in-tank.

Who changed the pump?
Why was it changed?
Did you change the fuel filter?
Was anything else changed reciently?

Good luck,

Chad

yellow dragon

TPS voltage on the '91 is not adjustable, the computer uses the sensor's voltage as a base zero when you start the car