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96 - 98 Fuel Pressure spec 5.7 VORTEC

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2018GMC Senior Enthusiast

2018GMC

Posted
Posted (edited)

Searching the net brings up all sorts of fuel pressure guesses and minimums.

 

I just ordered a Delphi HP10001 from rock auto for $138 shipped. Same pump is $250 at local auto part stores.

 

My 97 runs good but some hard cold weather starts. I just changed my fuel filter last year and the old filter seemed fine (was able to blow air though)

 

I checked my fuel pressure and its 59-60 key on engine off and 52 at idle, jumps to 60-62 after blipping throttle.

 

I could probably run pump longer but my fuel gauge has been all over place for years and hell maybe I will pick up a bit of performance.

 

Post your thoughts on proper fuel pressure spec for 1996 - 1998 and some 1999 VORTEC with poppet SFI or electronic MPFI conversion here

Edited by 2009 GMC
sputtle Enthusiast

sputtle

Posted
Posted (edited)

60+ is needed for a strong and reliable engine. I'm surprised it's even running at 52, because the injectors are designed to shut down at around 55.

 

But you're on the right track. Throw a new pump in there and I doubt you'll have any more issues.

Edited by smalltowngarage
2018GMC Senior Enthusiast

2018GMC

Posted
  • Author
Posted (edited)

Pressures with current pump...

 

post-50150-0-40151400-1432829585_thumb.jpg

 

Key on Engine Off

post-50150-0-84584400-1432829642_thumb.jpg

 

Idle

 

I will post new pics after installing new Delphi HP10001 Fuel Pump.

 

Truck starts and runs fine. Only issue is wacky fuel gauge and have to crank awhile when in cold weather (below freezing)

post-50150-0-40151400-1432829585_thumb.jpg

post-50150-0-84584400-1432829642_thumb.jpg

post-50150-0-40151400-1432829585_thumb.jpg

post-50150-0-84584400-1432829642_thumb.jpg

post-50150-0-40151400-1432829585_thumb.jpg

post-50150-0-84584400-1432829642_thumb.jpg

Edited by 2009 GMC
sputtle Enthusiast

sputtle

Posted
Posted

Yep, I think that's your problem. Electric motors slow down a bit in cold weather and can cause tough starts.

2018GMC Senior Enthusiast

2018GMC

Posted
  • Author
Posted (edited)

Replaced fuel pump. Only took 2 hours with lifting the bed method (first time) last pump I dropped the tank. I guess it was a little easier. I didn't have to disconnect any filler hoses, just removed 2 Torix screws to disconnect gas cap housing from body.

 

The $120 fuel gauge I rented from oreilly fell apart at the connection so I didn't get to test fuel pressure with new pump. And who knows how accurate tests were on old pump. I did need a new sending unit anyway so was worth replacing.

 

I will post some pics of my bed with topper jacked up. Only complaint is it was crampt getting lock ring back on. I guess I could have raised the bed a bit more but I thought I was pushing things at the angle I was already at.

Edited by 2009 GMC
2018GMC Senior Enthusiast

2018GMC

Posted
  • Author
Posted

post-50150-0-00894700-1433042109_thumb.jpg

 

Pulled 3 driver side bed bolts. Loosened 3 passenger bed bolts about half way.

 

post-50150-0-48197000-1433042173_thumb.jpg

 

A little tight but removal of old pump and insertion of new pump was easy. Getting the lock ring off and back on was the hardest part.

 

post-50150-0-59220900-1433042258_thumb.jpg

 

Removed old Carter fuel pump. Pic is of new Delphi Hp1001 pump installed!

 

 

post-50150-0-00894700-1433042109_thumb.jpg

post-50150-0-48197000-1433042173_thumb.jpg

post-50150-0-59220900-1433042258_thumb.jpg

post-50150-0-00894700-1433042109_thumb.jpg

post-50150-0-48197000-1433042173_thumb.jpg

post-50150-0-59220900-1433042258_thumb.jpg

post-50150-0-00894700-1433042109_thumb.jpg

post-50150-0-48197000-1433042173_thumb.jpg

post-50150-0-59220900-1433042258_thumb.jpg

sputtle Enthusiast

sputtle

Posted
Posted (edited)

Nice pics. Seems to be the way to do this. Definitely something I'll keep in mind.

 

How did the battle with rusty bolts on the bed go? These usually are never touched after the truck is built. Just curious. I'm from Minnesota, so every car I work on requires WD-40 Haha

 

And did changing the pump solve the problem?

Edited by smalltowngarage
2018GMC Senior Enthusiast

2018GMC

Posted
  • Author
Posted

I will have to wait for cold weather to test hard cold starting. Truck seems to run the same as before. It did fix my wacky all over the place fuel gauge. If I have to run to parts store in the future I will rent another gauge and see if pressure is up.

 

Bolts came out no problem with impact wrench at 110 psi. But then again I don't live in the rust belt.

  • 3 years later...
BigRalph New Member

BigRalph

Posted
Posted

So I'm curious as to what was the psi after the change? I'm having the same thing happen on my truck. 1998 c1500 Cheyenne 5.0 v8 automatic same pressure reading as above photos.

Please respond and thanks in advance for your time and help.

SILVER SLED Senior Enthusiast

SILVER SLED

Posted
Posted

These pumps also have a check valve that can go bad and allow fuel in line to drain back away from engine causing excessive cranking to start after sitting a while.   I would key up the ignition, without cranking the engine,  a couple times for a few seconds to get fuel to engine, then crank it and it would usually start quickly.  

BigRalph New Member

BigRalph

Posted
Posted

So I just replaced my fuel pump with a Delphi and filter and after this I'm getting 62 with key turned Engine off and after starting it while idling I get 52-53psi?

  • 2 weeks later...
jlcms2007 Enthusiast

jlcms2007

Posted
Posted
So I just replaced my fuel pump with a Delphi and filter and after this I'm getting 62 with key turned Engine off and after starting it while idling I get 52-53psi?

That’s perfect as long as it keeps under no vacuum about 56-59. No vacuum meaning open throttle.


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  • 2 years later...
Cole Foree New Member

Cole Foree

Posted
Posted

I have a 98 K1500 5.7. Recently started having extended and hard starts mainly after sitting awhile and during cold weather but after running a short while and while the engine still warm it would start no problem. Checking online I find that the 5.7 should 60psi with key on engine off and 60-66 with engine idling. I was getting 60 key on engine off and right about 51-52 with engine idling. So I went ahead and replaced the fuel pump and after replacing I checked the pressure again and sure enough 60key on engine off and right around 51-52 with engine idling. Now though the truck starts instantly everytime with no drama. I think silver sled is right about the check valve. In that case you may be reading the right pressure but is still the fuel pump causing hard and extended starts. Im not sure where the 60-66 psi spec comes from but even videos Ive seen of people checking fuel pressure on these trucks they get about the same as I did. Unless there is some other problem with my truck and others that I don’t know about. Either way it runs great now.

asilverblazer Senior Enthusiast

asilverblazer

Posted
Posted
On 11/28/2021 at 7:27 AM, Cole Foree said:

Now though the truck starts instantly everytime with no drama. I think silver sled is right about the check valve. In that case you may be reading the right pressure but is still the fuel pump causing hard and extended starts.

 

This...

 

And a way to confirm, install a fuel pressure gauge on the test port, shut the engine off and watch if it bleeds off pressure.

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