Need help narrowing down low fuel pressure...

BOOM_FIST · Apr 27, 2018

M1Gunner said:
Also what grade fuel do you use and any record of o2 sensor maintenance?

I just run regular ol’87. I tried 89 recently, but it made zero difference except made my wallet lighter.

swathdiver said:
If the scan tool is good enough to see fuel trims, it should be good enough to read the commanded and actual fuel pressures, the manual gauge being redundant but still not a bad idea.

That’s my next step then. I’m going to have a shop run it with a scan tool to log some real-time data. I’m suspecting a defective fuel pump or a blockage in the fuel line.

swathdiver · Apr 27, 2018

One tank isn't enough to tell, especially since it was just 89. 87 is really crap fuel, you'll gain at least 2 mpg and probably more by switching to 91/93 from a top tier station like Exxon/Mobil or Chevron. By the 3rd tank you'll see the full extent of the gains made and realize that in most cases, it costs more money to run cheap gas both in loss of efficiency, mpg, and in fuel system repairs like you're having now. That's been my experience for the last thirty plus years anyway.

BOOM_FIST · Apr 27, 2018

swathdiver said:
One tank isn't enough to tell, especially since it was just 89. 87 is really crap fuel, you'll gain at least 2 mpg and probably more by switching to 91/93 from a top tier station like Exxon/Mobil or Chevron. By the 3rd tank you'll see the full extent of the gains made and realize that in most cases, it costs more money to run cheap gas both in loss of efficiency, mpg, and in fuel system repairs like you're having now. That's been my experience for the last thirty plus years anyway.

Hmm, interesting. I guess I'm willing to try anything at this point. Lol. Thanks James!

swathdiver · Apr 27, 2018

BOOM_FIST said:
Hmm, interesting. I guess I'm willing to try anything at this point. Lol. Thanks James!

I don't think switching to high test is going to solve this particular problem but stranger things have happened. If you get on it, go full throttle, does she fall on her face or keep pulling?

I reread your post about fuel pressures. I don't know much about mine either but the computer commands it and the pump delivers 43.5 psi all the time. Granted we have different engines but just saying. I see all this talk about my motor supposed to have 58 psi of fuel pressure too and it might be true with the key on and the engine off, but it's always been 43.5 psi.

BOOM_FIST · Apr 27, 2018

swathdiver said:
....If you get on it, go full throttle, does she fall on her face or keep pulling?

That's the weird part...she pulls hard as ever with no stumble or power decrease. It's just when sitting in Park and idling and when in Drive sitting at red lights. I'm going to try and take a good video of it to better explain my symptoms. Hearing the audible "strain/whine" sound is hard to explain.

swathdiver · Apr 27, 2018

And you said there was a vibration in synch with the strain/whine right? Maybe the mount for the pump is not as tight as it could be, something loose, maybe the pump bearings aren't the greatest. In my old Buick, when it was low on fuel the fuel pump was much louder as it was no longer submerged and muffled. So this happens with low and full tanks too then?

If you're getting low on fuel, put some high test in it and one or two of those little 6 oz bottles of Super-Tech from Walmart. I don't think the pump is bad in that its not performing as you have full power.

BOOM_FIST · Apr 27, 2018

I need to fill up today anyway, so I'll try that. Thanks man

BOOM_FIST · May 1, 2018

Filled up with 93 and added 2 different Fuel injector cleaners to this last tank. So far, nothing has changed.

I've been digging around online and saw that some 04+ 2500HD's came with a FPR similar to ours, but had a little T10H torx screw on the body of the regulator to adjust fuel pressure. I've been wondering if I could just source one of those and mess with my fuel pressure to see if that alleviates my symptoms???

Here's a pic of what I'm talking about...

BOOM_FIST · May 1, 2018

AHHH! I found a YouTube video of my EXACT same symptom. This is on a 5.3 Tahoe though...SKIP TO 0:30 to hear the sound.

It seems that people are reporting back with this symptom being AC Delco and Delphi brand related. The BWD brand from AutoZone/Advance Auto seem to work better for our trucks? Might give it a shot!

swathdiver · May 1, 2018

Now if you stick a long extension on the FPR and the other to your ear is that exactly where the sound is coming from? If so, then mystery solved!

Need help narrowing down low fuel pressure...

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