97 454 L29 Long Crank

[Schurkey]

Fuel pressure test:
Key turned hits 50 PSI

Spec for 7.4L in '97 is 56--62 psi, key on, engine off. The difference between your reading and spec could easily be due to an inaccurate gauge. It'd be worth testing the gauge.

**did not purge line from air on test gauge**

Doesn't matter.

Key on started, cold, started immediately, 44 PSI exactly

No spec given in '97 C/K service manual for engine idling fuel pressure except that "high vacuum applied to the fuel pressure regulator diaphragm will result in lower fuel pressure." Seems reasonable to remove the vacuum hose from the regulator (if you can access it!) and see if the pressure is still lower than 56 psi on an accurate gauge.

If it is, they want you to check for restrictions in the fuel system including a partially-plugged filter, and if no restrictions are found, to gradually pinch-off the return plumbing to see if the pump is capable of producing adequate pressure (not more than 75 psi, or you could damage the regulator.) Depending on what you find, either replace the regulator or start investigating the pump. Best to follow the actual service manual procedure. In the '97 C/K manual, it starts on page 6E-854. Small-block and big-block are mixed together, be sure you're reading the correct steps 'n' specs.

 

[Spareparts]

Yeah, your FP is low for sure.
You can narrow it down to pump or regulator i think. Pinch off the return line and see what the pressure jumps to. Mine will hit 80psi. If yours will not get that i suspect your pump.
If it does hit 80 psi your regulator is probably bad.
My injectors are leaking 0. I don't believe injectors should leak at all.
Leaking injectors are the #1 cause of extended crank when hot.

 

[someotherguy]

Low pressure to be sure. I'm surprised you're not also complaining of low power or a bog when you mash on the pedal, but I guess that new pump is able to at least supply reasonably adequate volume. The big block Vortecs will run, albeit poorly, on low pressure since they have real injectors, where the small blocks with the original poppet valve setup won't even start.

Anyhow, you've given me all the info I need to know you have the wrong pump in there. If you chose it for a 1995 model you got a TBI pump meant for the 2 years of higher-pressure big block TBI's (1994-1995) but it's still not high enough for a Vortec. Get that 1996-1997 pump and drop it in your sender and go.

Richard

 

[Mangonesailor]

Check your ground at the tank for the pump and the relay to make sure it's getting full power to it. 45-ish PSI is weak.

This a Delphi pump? Is the vacuum hose for the FPR nice and supple n tight?

 

[someotherguy]

Check your ground at the tank for the pump and the relay to make sure it's getting full power to it. 45-ish PSI is weak.

This a Delphi pump? Is the vacuum hose for the FPR nice and supple n tight?

He bought a pump for a TBI 7.4 (Delphi HP10025) It's performing as designed. It's the incorrect pump for a Vortec.

Richard

 

[TN454K3500]

I've got the correct pump ordered. Should be here tomorrow. Gonna try to swap it out Friday. I'll report back.... first gotta get the fresh 22 gallons I just filled up last weekend :| SMH...

xc_hide_links_from_guests_guests_error_hide_media

Thanks everyone!!!

 

[TN454K3500]

He bought a pump for a TBI 7.4 (Delphi HP10025) It's performing as designed. It's the incorrect pump for a Vortec.

Richard

I got everything installed this evening and put about 5 gallons back in the front tank. I have the same fuel pressure readings....... Still key on ~50 PSI and then running around 44PSI

Here is the picture of the fuel pump box part # that I installed tonight:

You must be registered for see images attach

This is the FPR I installed a few weeks back:

More Information for ACDELCO 2173073

Is that the correct one?

Ross

 

[Spareparts]

Looks like its good for 85PSI. Look like a bad regulator or Clogged fuel filter if your gauge is correct.
I think this is the FPR you want. Napa lists it as being 57PSI.
Getting the proper FPR is a real PITA as the pressure is usually not listed.
The one you installed is listed to be 36PSI.

Delphi FP10021-11B1 Delphi Fuel Injection Pressure Regulators | Summit Racing

Free Shipping - Delphi Fuel Injection Pressure Regulators with qualifying orders of $109. Shop Fuel Pressure Regulators at Summit Racing.

www.summitracing.com

 

[TN454K3500]

Looks like its good for 85PSI. Look like a bad regulator or Clogged fuel filter if your gauge is correct.
I believe this is the FPR you want.

Delphi FP10021-11B1 Delphi Fuel Injection Pressure Regulators | Summit Racing

Free Shipping - Delphi Fuel Injection Pressure Regulators with qualifying orders of $109. Shop Fuel Pressure Regulators at Summit Racing.

www.summitracing.com

You mentioned, "Pinch off the return line". Where do you do this at? Can I do this back at the tank or do I need to do this up near the engine?

Also, that FPR is equivalent to what I installed:
Delphi interchanable: OEM / Interchange Numbers: 12499841, 12555909, 12574986, 17113517, 17113536, 17113555, 17113678, 19245530, 19245531, 8125749860, 8171135360, 8171136780, 8192455300, 8890604200, 89060420


AC Delco:
More Information for ACDELCO 2173073
{Alternate Inventory Numbers: 217-3073, 89060420, 19245530}

 

[Spareparts]

Im just listing the numbers i can find for pressure.
I did learn when going through the regulator dance you need to make sure of the pressure of the exact one you want.
They all fit and interchange but will have the wrong pressure.
Pinch off the soft return line under the driver door. Thats where i did it.