Famous Fuel Pressure

[OBS_Trash]

Alrighty Then. I appreciate all the good responses and partial ass chew-in’s. New pump went in, drumroll……

She idles at 50#’s (you heard it here folks)

Did not fix my air/fuel issue.

So taking very much needed advise and stepping back before I replace the distributor. Going to start a new thread with renewed title if need be.

My starting point will be the 2 codes (after clearing the previous codes)
P0102 (MAF A Circuit Low)
P0151 (O2 Circuit low voltage B2S1)

Both previously replaced, then brought to shop because still had issues, they replaced the MAF Again and said the truck was good to go.
That sent me on the downward spiral that left me replacing 1 thing at a time.

So starting over, I’m starting with the MAF

MAF Plug - 5v at signal, 12v Power, 0.3 Ground…..will pick this up on new thread.

Thanks again

 

[east302]

The 96 manual will have the diagnostic procedures for both of the codes. It can be downloaded here…

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

 

[Erik the Awful]

New pump went in, drumroll…… She idles at 50#’s (you heard it here folks)

If you hadn't already replaced the FPR, that would be my guess. Do you have another gauge you can verify the pressure with? Maybe the gauge is wonky, but that still doesn't address the problem, it just helps ensure your diagnoses are more accurate.

 

[tinfoil_hat]

If you hadn't already replaced the FPR, that would be my guess. Do you have another gauge you can verify the pressure with? Maybe the gauge is wonky, but that still doesn't address the problem, it just helps ensure your diagnoses are more accurate.

Another gauge won't help if he insists on using it incorrectly.

 

[OBS_Trash]

The 96 manual will have the diagnostic for both of the codes. It can be downloaded here…

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

Yes sir, thanks much I downloaded both files , great info. Using it now

Another gauge won't help if he insists on using it incorrectly.

Why Ike, whatever do you mean? (Tombstone) How would I USE a fuel pressure gauge incorrectly more over insist on it. I’m thinking you didn’t read the comments.(from your previous response)
My first post stated I ran the GM documented test key on engine off and yes passed the 60# with minimal leak down. Also pointed out that there is no other documented Driving pressure. I explained that because the whole post was about finding out what people’s # is when driving down the road.

 

[OBS_Trash]

If you hadn't already replaced the FPR, that would be my guess. Do you have another gauge you can verify the pressure with? Maybe the gauge is wonky, but that still doesn't address the problem, it just helps ensure your diagnoses are more accurate.

Appreciate the feedback brother. Yeah she has a whole new Spider FI module, includes FPR. mistake was not upgrading to the improved style, I stuck with the poppet unknowingly. Shurkey learnt me on that one. But like I said, I’m taking a step back and starting with the current codes. Looking into scantools (leaning toward Bluetooth OBDlinkMX+ , and the Torque App) need to post and get feedback on if folks have issues or like it, etc.

 

[tinfoil_hat]

Why Ike, whatever do you mean?

I'll give you points on the Tombstone reference.
As for the "driving down the road" pressure I think it would be variable based on fuel consumption which would be impossible to quantify from one truck to another.

 

[L31MaxExpress]

OE style spider should hold 66 psi at heavy to wide open throttle. MPFI upgrade 58 psi. Wrong or bad regulator could result in lower pressure, even if it is new. At 2,000-3,000 rpm with no load in Park or Neutral with the OE poppet design, lowest pressure I am looking for is 57-58 psi. Any lower is guranteed to cause issues.

 

[Schurkey]

As for the "driving down the road" pressure I think it would be variable based on fuel consumption

Not so much a matter of fuel consumption--the pump should have the capacity to maintain pressure at maximum fuel demand--but rather manifold vacuum.

The regulator is vacuum-referenced, changes in vacuum result in changes in pressure.

 

[tinfoil_hat]

Not so much a matter of fuel consumption--the pump should have the capacity to maintain pressure at maximum fuel demand--but rather manifold vacuum.

The regulator is vacuum-referenced, changes in vacuum result in changes in pressure.

Well the pump output is constant while consumption is variable, correct?