I need to know what fuel pressure I should be seeing on a stock fuel pump on the LT1 during startup.

Problem was, the car would start, run for a minute then just shut off, could get it to start, go about 100 yds then cut off again. Changed the opti because it was going too. So now it will start sometimes, runs like it is really really lean and stumbles through rpms, the car died on me then wouldnt start and the batt died. Just put fuel in it. I havent checked the fuel pressue yet but I think the fuel pump is going, prob a 2 yr old pump I had put in and its stock on a stroker, its too small for my engine and probably why I think its going. What does anyone else think?

 

With the vacuum line connected to the regulator, you should see about 35-40 lbs, with the line off you should see around 40-45#.
The stock pump will supply enough fuel to run the 383 at idle and regular driving...will go lean at WOT..but other than that it should be fine....not saying that you shouldn't change it to a better fp...just that if the stocker is working ok, thats not your problem with it dying.
Hook up a manual gauge and see if the pressure is in fact dropping after startup for whatever reason...every fuel pump I've seen just quit...was not on and off unless its a short somewhere.

Was this a new motor build and has it ever ran ok since the build?
Were the injectors changed and if so was the PCM reflashed for the new size inj? Need to get a scan tool and hook up to it in order to diagose better.

 

Put a fuel pressure gauge on it, sure way of knowing if your pump is keeping up with the demand of the engine.

 

Well the last time my pump went out, it just went without warning. This motor has been running and has about 12k on it since the build. I was just having probs out of it, stock injectors, not tuned, use to start and run fine, and I know its lean during WOT. Now the problem I was having was the opti, (I Thought), so I changed the bottom piece and the cap and rotor. Then I get it together and does the same thing. I just think the fuel pump is finally giving out, It isnt load like it use to be when I turn the key on, I have to pump the key a couple times to get the pressure up to get it started and still takes some seconds to start. I have MSD Coil, and I have the factory ignition control module but dont think that could be the problem.

OKAY! I start i up.........runs, revs to high rpms, but it stumbles really bad. So I drove it off, up the street to get gas, dies at the light, then I start it up and drive off. Two seconds later I turn a corner and the thing dies, wont start so the batt died from it being drained.

The whole thing started when I left work, turned a corner doing about 60-70 MPH, really sharp and the damn thing just died, kinda like when your low on fuel. Dont know, I think its the pump, throwing a code but the code was there when it was running fine.

 

So tested the fuel pressure.

Key On: 8-10psi
Pump Key x10: Up to 30psi then drops to 0 in about 1/4 of a sec
Starting: Stays at about 30psi then it drops when key is off

I know the anti-bleed valve is bad on it but this is a stock fuel pump on a 388 stroker so I know its LEAN on WOT. The car started earlier and was stumbling really bad. T

The car will not start now and im getting plenty of spark. Anyone else agree?

I think its the fuel pump from the test, just wanna verify.

 

Sounds most likely like the pump then, but it could possibly be the regulator not holding any pressure... From what I remember the only rubber lines are right over the tank and not exposed, otherwise to rule out the regulator you could pinch off the return line with a pair of vice-grips and then turn the key on a few times to see if it produces 40# or so..so get 35-40# easy with one turn of the key and the pump run for about 3 secs.

I suppose you could disconnect the return line right there under the cowl and cram a piece of rubber hose on it and clamp it then pinch it off...just be sure not to spill away gas in the process and then turn the key on and have a spark

 

WOuld the car still run?

 

On the fuel rail, which line is the return line? The bigger one or the smaller one? I could disconnect the return line from the fuel rail and test it that way right?

 

From what I undestand, if it was the regulator, when I turned the key on the first time it wouldve shown 30psi then went down but only said 10psi and held until I pumped the key then it bled out.

 

anyone else?

 

The return line is the smaller line. I wouldn't try starting the car as the fp MAY be sky high.
1) Disconnect the return line, and connect a 6-12" piece of 3/8 fuel line hose to the steel return line coming off the plenum and clamp it with a hose clamp so it cannot come off at high psi.
2) Then, take a pair of vice-grips and clamp off a section of the rubber hose...this will prevent any pressure from escaping on that end.
3) Wrap a towel around the end of the hose in case any fuel escapes from the vice grip pinch and exits hose end.
4) Turn key on but do not start the car, after the pump runs a couple of secs and cuts off, there should be more than 40# of fp, if not, wait a few secs and turn key on again....if still not 40# then there's a pump problem....

Watch the gauge while the pump is running as the check valve could be bad in the pump, depending on how bad it is..if it never hits 40# the pump is toast. If it hits 40 and very quickly drops back, the check valve is toast and the pump should be replaced.
If it holds pressure after pump is off, then the regulator was bad.....if pressure drops slowly..then either back check valve or leaking injector.

 

Thanks

 

So I pulled off the fuel line, put on some hose, didnt even clamp it, used some ****ty zip ties but the held really tight. Clamped it off with Vice Grips then I turn the key and................ (i dont have the guage) the car wouldnt start, tried, and tried, and tried. Finally got to take the hose off, there was a drop of gas on the hose but no pressure at all when I took it off. Gotta be the fuel pump.

 

Sounds like it, may hook a long hose up to that line and run it to a can or something and see if any fuel will pump out of it...remember the regulator is still on there..so most likely the pump isn't generating enough fuel pressure to even make it past the regulator..thats why none is coming out the return....this test at least verifys the regulator isn't bad since nothing is getting past it.

 

So I know the regulator is good. But still gonna get a tunable one.