Fuel Pressure 98 Vortec 454


tjwib
12-08-2005, 10:28 PM
Hi Everyone, this is my first post and I find this board very helpful but I still have a couple questions. I have an 83 Chevy Crew Cab with a 98 Vortec 454 and had a custom wiring harness built. It will not start. I sprayed some starting fluid in there and it tries to start but just a little. With as much fluid as I sprayed in there, you would think I would get a little more than a couple pops. I know the problem can be a number of things with so many variables, but I think it just needs fuel. It looks like the fuel pressure regulator causes very similar problems and I was wondering what behavior to expect.

I put the fuel pressure guage on and turn the key to the on position. The pump cycles for the normal 2-3 seconds and I have 60 psi. As soon as the pump is done cycling, it immediately drops to 40 and slowly reverts to about 22. Also, while cranking (while the pump is running) it is also at 60. I initially tried running the pump for 60 seconds to prime the lines and I heard something that sounded like an air leak under the hood. I made sure to vent the tank with the cap off also.

I also tried a suggestion to test the regualtor by pinching the return line and checking to see if pressure held. I got 80 psi and it still dropped off when the pump disengaged. I was told if pressure held, my regualtor was bad, but since it didn't, is it leaking through the injectors. I am a little confused at this point.

The motor has 56,000 miles on it and did sit in my garage for about 2 years. The fuel pump is brand new from GM. Fuel lines are all new except for the flexible hoses off the back of the motor. Fuel filter is new and of the stock variety for this motor.

Is there any other sensors that would prevent it from starting? What about vacuum leaks?

Please help!

Thanks

TJ

Scottman72
12-23-2005, 11:27 PM
those vortecs like a lot of fuel pressure , try blocking off your return line again only this time see if the engine will run. If it tries to run the regulator is probably bad.

Bob B
12-24-2005, 10:29 AM
[QUOTE=tjwib]Hi Everyone, this is my first post and I find this board very helpful but I still have a couple questions. I have an 83 Chevy Crew Cab with a 98 Vortec 454 and had a custom wiring harness built. It will not start. I sprayed some starting fluid in there and it tries to start but just a little. With as much fluid as I sprayed in there, you would think I would get a little more than a couple pops. I know the problem can be a number of things with so many variables, but I think it just needs fuel. It looks like the fuel pressure regulator causes very similar problems and I was wondering what behavior to expect.

I put the fuel pressure guage on and turn the key to the on position. The pump cycles for the normal 2-3 seconds and I have 60 psi. As soon as the pump is done cycling, it immediately drops to 40 and slowly reverts to about 22. Also, while cranking (while the pump is running) it is also at 60. I initially tried running the pump for 60 seconds to prime the lines and I heard something that sounded like an air leak under the hood. I made sure to vent the tank with the cap off also.

I also tried a suggestion to test the regualtor by pinching the return line and checking to see if pressure held. I got 80 psi and it still dropped off when the pump disengaged. I was told if pressure held, my regualtor was bad, but since it didn't, is it leaking through the injectors. I am a little confused at this point.

The motor has 56,000 miles on it and did sit in my garage for about 2 years. The fuel pump is brand new from GM. Fuel lines are all new except for the flexible hoses off the back of the motor. Fuel filter is new and of the stock variety for this motor.

Is there any other sensors that would prevent it from starting? What about vacuum leaks?

Please help!
-----------------------------------------------------------
Hi,
My 97 5.7 had all the same symptoms exactly.
I misread something and so I replaced the pressure regulator but it made no difference.
Reread the diagnostics chart and then replaced the less than six months old fuel pump which fixed it. The pump was Delphi which is the new factory supplier.(They now own Delco)
I believe there is a check valve in there that was failing.
With the bad pump, it would start but have no power. Or start and stall.

Bob B

MT-2500
12-24-2005, 10:50 AM
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 around 60-66 on most of them.
Cold start ond the 98 -454 should be 58-62 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 58-62 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.
Start looking for the leak.
Also after fuel pressure is built up pinch off the pressure line from fuel pump to check if pump is leaking back.
Post back fuel pressure readings.
MT :lol: :grinno: :lol2:

TEXAS-HOTROD
12-25-2005, 11:58 PM
60 psi cranking, 80 w/the return pinches sounds like a strong pump to me. All pumps/regulators bleed down over time, some faster than others. You need to find the problem before you start replacing parts.
Was it running before or is this the first attempt to start it? It sounds like you did a lot of modding to put it all together. Did you have the distributor out at any time? The cam sensor has to be in synch w/the crank sensor or it will cause some strange probs.

Sometimes it's the small things that kick your (and mine) ass. Pull the spark plugs and see how they look. Dry or shiney?

d804boy
09-22-2007, 10:48 PM
i have a 97 tahoe 5.7 and it wont start uless i spray starting fluid in the intake then it starts and run good ,but once and a while it wil bog like its not getting gas or something. i checked the ignition system and seem to belive everythings fine.i belive its to do with gas.i checked pressure from pump straight to the check valve is 50lbs. i know i heard it should be 60 to 66lbs.
but when i spray it it starts(im confussed) cause it start with only 50lbs pressure with a shot of starting fluid.it will leak down somewhat over 10 min.
could it be the fuel pump or fuel pressure regulator? or tell me what you belive it is....thanks

Add your comment to this topic!