Famous Fuel Pressure

[OBS_Trash]

I’m looking for someone with no problems to run a test or chime in.

1996 - 5.7 350

I know the documented GM Spec is (60-66psi). But it seems this is also Key on, Engine off. Everything I’m finding in forums are post with people having issues, some replacing pump and same pressure, same problems. (50’s)

I would like someone with zero issues, same engine do a FP Test with engine running and post results. I’ve replaced every GD thing aside from the Fuel pump,(EGR.FuelFilter.MAF, Plugs.Wires.Rotor.Cap.Ignition Coil.IAC.CrankShaftposition sensor.EngineCoolant Temp, New Fuel spider Injection assembly with new Fp Regulator and I swear I’m not spending another $20 without guaranteed results.

At this point I’m just going to LS Swap it. I don’t have a nice REAL mechanic scanner just an OBD2, and 2 local shops have been unsuccessful in diagnosis. I’m not even willing to pay a diagnostic fee, I’d rather just go get a LS. I live in Houston and they Dime a dozen round here. Never thought I’d end up at the Parts Cannon storyline but well it happened. Engine is good! I wanted to keep it OG 350 till I got a square body. Any way, any help much appreciated. Maybe this was more of a rant? Still curious in good running Fuel Pressure numbers though, if that’s it I have to replace anyway with LS swap

 

[HotWheelsBurban]

I’m looking for someone with no problems to run a test or chime in.

1996 - 5.7 350

I know the documented GM Spec is (60-66psi). But it seems this is also Key on, Engine off. Everything I’m finding in forums are post with people having issues, some replacing pump and same pressure, same problems. (50’s)

I would like someone with zero issues, same engine do a FP Test with engine running and post results. I’ve replaced every GD thing aside from the Fuel pump,(EGR.FuelFilter.MAF, Plugs.Wires.Rotor.Cap.Ignition Coil.IAC.CrankShaftposition sensor.EngineCoolant Temp, New Fuel spider Injection assembly with new Fp Regulator and I swear I’m not spending another $20 without guaranteed results.

At this point I’m just going to LS Swap it. I don’t have a nice REAL mechanic scanner just an OBD2, and 2 local shops have been unsuccessful in diagnosis. I’m not even willing to pay a diagnostic fee, I’d rather just go get a LS. I live in Houston and they Dime a dozen round here. Never thought I’d end up at the Parts Cannon storyline but well it happened. Engine is good! I wanted to keep it OG 350 till I got a square body. Any way, any help much appreciated. Maybe this was more of a rant? Still curious in good running Fuel Pressure numbers though, if that’s it I have to replace anyway with LS swap

Hey if you are looking for a 6.0 I still have the one in the '06 GMC Denali, comes with the truck.....

 

[Vikingdude]

what voltage is the fuel pump getting? Any corrosion in connectors or wires?

 

[Schurkey]

I’m looking for someone with no problems to run a test or chime in.

1996 - 5.7 350

I know the documented GM Spec is (60-66psi). But it seems this is also Key on, Engine off. Everything I’m finding in forums are post with people having issues, some replacing pump and same pressure, same problems. (50’s)

I would like someone with zero issues, same engine do a FP Test with engine running and post results.

1. Fuel pressure is going to be higher when there's NO MANIFOLD VACUUM acting on the pressure regulator. So 60+ with the pump priming, engine NOT running. May take more than one prime cycle to achieve max pressure. But low-50 psi when running because manifold vacuum is reducing the regulated pressure. TOTALLY NORMAL. GM does not even list a spec for fuel pressure with the engine running except to say that it'll be lower than the prime pressure.

2. Is your fuel pressure gauge accurate and repeatable? Lotsa gauges come from China, they're cheap junk. Or they've been abused in a shop environment and have lost whatever precision they once had.

3. WHAT PROBLEM ARE YOU TRYING TO FIX?

I’ve replaced every GD thing aside from the Fuel pump,(EGR.FuelFilter.MAF, Plugs.Wires.Rotor.Cap.Ignition Coil.IAC.CrankShaftposition sensor.EngineCoolant Temp, New Fuel spider Injection assembly with new Fp Regulator and I swear I’m not spending another $20 without guaranteed results.

WHAT PROBLEM ARE YOU TRYING TO FIX?

At this point I’m just going to LS Swap it.

If you can't fix the original system, making major modifications to that system will make it even harder to fix.

I don’t have a nice REAL mechanic scanner just an OBD2,

WHAT is an "OBD2"? Either you have a scan tool, or you have a "code reader" or you have nothing.

There's no substitute for a proper scan tool. Code-readers should be properly disposed of. "Codes" can be helpful, but the real diagnostic power is in the data stream, and the bi-directional control.

Never thought I’d end up at the Parts Cannon storyline but well it happened.

That is what happens when you shortcut the diagnostic procedure.

Engine is good!

So why swap an LS?

 

[Komet]

Well I got 99 problems but fuel pressure ain't one. If you take vacuum off the regulator, that's your full pressure. So, what pressure are you getting?

 

[OBS_Trash]

1. Fuel pressure is going to be higher when there's NO MANIFOLD VACUUM acting on the pressure regulator. So 60+ with the pump priming, engine NOT running. May take more than one prime cycle to achieve max pressure. But low-50 psi when running because manifold vacuum is reducing the regulated pressure. TOTALLY NORMAL. GM does not even list a spec for fuel pressure with the engine running except to say that it'll be lower than the prime pressure.

2. Is your fuel pressure gauge accurate and repeatable? Lotsa gauges come from China, they're cheap junk. Or they've been abused in a shop environment and have lost whatever precision they once had.

3. WHAT PROBLEM ARE YOU TRYING TO FIX?


WHAT PROBLEM ARE YOU TRYING TO FIX?


If you can't fix the original system, making major modifications to that system will make it even harder to fix.


WHAT is an "OBD2"? Either you have a scan tool, or you have a "code reader" or you have nothing.

There's no substitute for a proper scan tool. Code-readers should be properly disposed of. "Codes" can be helpful, but the real diagnostic power is in the data stream, and the bi-directional control.



That is what happens when you shortcut the diagnostic procedure.


So why swap an LS?

 

[OBS_Trash]

1- low-50 psi when running because manifold vacuum is reducing the regulated pressure. TOTALLY NORMAL.**** Appreciate this Feedback, this is what I’m looking for, I’m curious what does yours run?

2- YES

3- (at times, worse in warm weather) Rough idle sometimes, backfires around 50-60mph, coke fines shoot out tailpipe on cold start leaves skid mark sometimes.

4- “If you can't fix the original system, making major modifications to that system will make it even harder to fix” - Wouldn’t say anything I replaced was considered major modification

5- OBD2 cheap ass Code reader (my bad)
“There's no substitute for a proper scan tool” I Couldn’t agree more, what I would give for a nice diagn.scanner

6- “That is what happens when you shortcut the diagnostic procedure”. - More to my point

7- why LS Swap? I mean why not, 330,000 , she paid her dues. Always wanted to anyway, this would be my first engine swap, mild Cam

1.1 - I’m still curious what anyone’s Fuel Pressure is when running.

 

[OBS_Trash]

Well I got 99 problems but fuel pressure ain't one. If you take vacuum off the regulator, that's your full pressure. So, what pressure are you getting?

I’ll check, and would like to compare

 

[OBS_Trash]

what voltage is the fuel pump getting? Any corrosion in connectors or wires?

At 330,000 miles the wiring is pretty crusty throughout, just heat rot making everything brittle, I’ll take a look at voltage. My meter is Harbor Frieght top notch quality, but I’m sure it will do the job

 

[Schurkey]

3- (at times, worse in warm weather) Rough idle sometimes, backfires around 50-60mph, coke fines shoot out tailpipe on cold start leaves skid mark sometimes.

I'd verify EVERY sensor, and computer output using a scan tool, which checks the sensor AND the wire harness connecting the sensor to the computer. Your fuel pressure seems OK, 50+ when running, more during the prime cycle, and you've replaced all the typical "tune-up" stuff.

Overall, wouldn't surprise me to find that this is a coolant temp sensor, MAP, MAF, or TPS (or the wire harness connected to them.) The injection spider is also suspect, but you've also replaced that, too.

4- “If you can't fix the original system, making major modifications to that system will make it even harder to fix” - Wouldn’t say anything I replaced was considered major modification

No, but an LS swap will be.

5- OBD2 cheap ass Code reader (my bad)
“There's no substitute for a proper scan tool” I Couldn’t agree more, what I would give for a nice diagn.scanner

$400--$500 would do it. I paid less than that, ($350 delivered to my door) but it was ~2 years ago, and Bideninflation has taken hold. Less for a software/laptop/connector cable/dongle, but I don't trust 'em. Others have had reasonable luck with them.

7- why LS Swap? I mean why not, 330,000 , she paid her dues. Always wanted to anyway, this would be my first engine swap, mild Cam

A replacement Vortec small-block will be easier, cheaper, and enormously less headache, ESPECIALLY for someone who hasn't swapped an engine with wire harness, computer, and aftermarket tune before.




Not that you're having problems, but there's a bulletin regarding transmission problems on '96 model-year trucks that recommends moving some wires around on the computer. Might be worth looking-up. Details are on this web site...somewhere.