fuel pressure regulator ?

[shanes76]

on a 94 jimmy 4.3 vortec Vin"W" if the regulator was faulty- is it possible for a regulator to let it start everytime, but give it a lopey idle and s urge while at low speeds and no power at high speeds? I mean like allowing to much fuel to return to the tank? I have replaced the nut kit due to leaking lines, and I just read a post from Old Master about fuel pressure and the regulator. It has no trouble starting, I thought I had amiss at idle but I dont think its a miss anymore, I think its a fuel problem like MT had said before but I never had any way to check the pressure and I finally can check my pressure which Im doing in the morning since we got the snow storm. I thought that if the regulator went bad it would dump gas into the intake and get into the oil, or is that if the diaphram ruptured? What should my pressure be when the key is on and engine not running? I have already replaced the filter too.

[Darren509]

try doing a search in this forum "fuel pressure" and you should be able to find the correct specs for your year. Old Master also has a nice pic of a home made shut off tool to find out where any fuel pressure drops are with a detailed part description and numbers. I used it and it works great...I just cant remember how to copy it from my messages in here to show you.

[Darren509]

I think you should be around 58-64 psi with key on, and stay above 53 psi for atleast 5 min after you turn key to off. "NOT POSITIVE THOUGH">>>>

[MT-2500]

Originally Posted by shanes76

on a 94 jimmy 4.3 vortec Vin"W" if the regulator was faulty- is it possible for a regulator to let it start everytime, but give it a lopey idle and s urge while at low speeds and no power at high speeds? I mean like allowing to much fuel to return to the tank? I have replaced the nut kit due to leaking lines, and I just read a post from Old Master about fuel pressure and the regulator. It has no trouble starting, I thought I had amiss at idle but I dont think its a miss anymore, I think its a fuel problem like MT had said before but I never had any way to check the pressure and I finally can check my pressure which Im doing in the morning since we got the snow storm. I thought that if the regulator went bad it would dump gas into the intake and get into the oil, or is that if the diaphram ruptured? What should my pressure be when the key is on and engine not running? I have already replaced the filter too.

Fuel pressure regulators can leak pressure several ways.
External or bypass back to tank.

When the upper platinum if off always prime up pressure and look for external leak.

And watch for fast leak down.
But beware tkat a check valve in tank can cause a fast leak down to.
Pressure specs are 55/61 lbs on yours.
First thing.
Run the full pressure test and post back readings.

If your pressure is low or leaking off.

If You fuel pressure is to low or leaking down .
Specs on it is 55/61 lbs of pressure
Here is some guide lines of fuel pressure checking.

Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 55-66 fuel pressure.
Cold start should be 60 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 55/61 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
If pressure does not come up with return line pinched or blocked off.
Go to fuel filter and hook a gauge direct to a line at fuel filter.
Pressure should come up to 75 or more and will hold after fuel pump is turned off.
If it leaks down there after fuel pump is turned off it is LEAKING BACK THREW PUMP CHECK VALVE OR PUMP MODULE LINES.
Post back your fuel pressure readings.
MT

[shanes76]

ok, do I leave the key on after the pump turns off? When I had the plenium off I did prime up the system and did not see any leaks. I just replaced the filter so I know the lines will come off easilyto test full pressure.

[MT-2500]

Flip the key on a couple of times to get full pressure or just jumper fuel pump to build up full pressure and turn pump off and watch for fast leak down.

[Simplefix]

dose the tail pipe shoot black smoke on start up?

does you oil have a stronge gas smell?

if so you may be close on the fuel issue. CFI spinder maybe a better thing to check. When the spider injection system gose bad what happens is the fuel lines in the mainifold crack allowing fuel to exscape into the oil witch will make the engine act like its missing. while driving it will not have the power it needs.

[shanes76]

no I dont have any black smoke, I have replaced the return lines in the plenium already and primed it up when I had it apart and didnt see any leaks inside

[Simplefix]

Then if it dosent leak i would look to other possibles like ign. from what you said about surging and lack of power at high speeds almost makes me think it would be a coil issue. Does the car stay running at idle or dose it struggle?

[shanes76]

it stays running, doesnt struggle to stay running, starts every time, has never died on me or anything

[shanes76]

it used to be after ir ran for about 2 minutes then it would start, now its as soon as it starts it does it,

[Simplefix]

have you replaced the fuel filter? dose it have a long start up time meaning how many sec dose it take to start the first time?

[shanes76]

I cleaned the cap and rotor, the rotor looked new, the cap had like a white corrosion on the tabs, I put new wires on it and new ac delco plugs about 2 weeks ago

[shanes76]

yes I have replaced the fuel filter in the last 2 weeks also- start up time is about 2-4 seconds and this is every time, every once in a while it will act like a dead battery then fire right up, but my volts are good- not very often though

[Simplefix]

Heres a long shot. I did some digging in my mechanic notes on your car. I would like you to try something. The wires from your injector go throught the intake. they should be a blue and red wire located infront on the right of the Throttlebody. have the car running and move the wires around. If I am right the car should either run better or show you a worse condition. If thats the fact then you need to replace you fuel injector harness. I ran into this 4 years ago when i was working in a shop.