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Need Opinions: adequate LP PSI, 95 C2500HD

GM Guy

GM Guy

Manual Trans. 2WD Enthusiast
Messages
4,838
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Location
NW Kansas and SC Idaho
hey all,

murphys law, I decided to check fuel PSI before I leave tonight or tomorrow with a gooseneck load to Idaho with the 95 GMC C2500HD. not even done loading yet unfortunately (running late as usual), and I am slightly worried.

I put the guage on the water drain, (the guage is a Kent moore J-28552-A IIRC) and with it idling, I have 5-6 psi on the guage.


So, my question is, is this adequate? am I harming the IP running it as is?


also, on a possibly related note, it has "stuttered" twice in the past 500 miles, usually accelerating hard. PMD or LP? fuel filter is around 1 year old, havent had bad fuel ever that I am aware of. spare filter is carried.

When I have time to change the LP, is it recommended to change the LP relay in the underhood electrical center, or is a new OPS all I need to do, or do I even need to do the OPS if the LP is still pumping? will it hurt the LP (low voltage) if I keep the current OPS?

I have a new 1993 spec EP158 AC Delco lift pump, and a new AC Delco OPS, and new GM o-rings for the hard lines in a box of parts I carry with me.

I also am carrying a used Heath 2wd PMD kit (the kind that can only be bumper mounted, and the guy I bought it from on ebay said he bought it new, put it in the bumper, drove for 2 years, got rear ended and totaled, and removed and sold me the PMD, so I will rate it as a trustworthy part. IIRC I test ran it on mom and dad's 98)

so I am thinking I may just pack the parts with me, and change parts when I get to Idaho and get the tires dropped off with the trucker to go to California (the time sensitive deadline we are working against), as we still need to load the second truck (full size semi trailer) and we havent made it very far on it, so I dont really want to be taking time to work on the pickup, but will if absolutely necessary.

any input greatly appreciated,

thanks!
 
You will make it but I suspect you are getting 0 or even a vacuum at WOT towing.

Do the relay mod, low voltage hurts the LP.
 
Take the parts with you, if it were devastating it would not have flow on fail. You really need to see pressure at wot to verify. Ds4 right? It is kinda low. If db2 it would be perfectly fine. Either way I would run it, if ds4 just put it on the "soon" list.
 
WOT not required. just snap it to max RPM and watch the pressure. Above 0 is ok - Better lift pump later.. Below 0 you have issues.
 
Just my 2 cents, but after reading your fuel bug thread and having that fp 4 5 pounds for a baseline, I used to have 12. I also had sputter at medium to heavy accel. I was unable to get rid of fuel sock or install walbro and filter from Leroy(back issues). I ended up using Hammonds boibor to kill the bugs and unplug the filters. The filtersock and ffm got back to 12 pounds after 400 miles. Thanks for the bug thread, you save my but. Safe travels as well.
 
I'd say you'll be fine. Stock LP's only put out 4-7psi at idle anyway. With DS4 though you will see an improvement in responsiveness by going up to 9-12PSI Its amazing what just that little bump in PSI makes
Def use a relay, it can save your pump and OPS.
 
leroy, I dont think Kennedy would mind you making something the same, or similar to his OPS relay harness, would he? I dont care for wiring too much. :)

as long as its USA made and uses OEM connectors like the PMD cables, I am sure I would be game for one ofr a reasonable price.

(PS I am still wishing and hoping that you will sell me a billet aluminum K47 intake silencer delete plug as well. ;) )

thanks for all the advice guys, I think I'll just pack the parts with me and try not to pin the throttle to the floor.

leaving for Idaho tonight! murphys law, a small snowstorm is going on in Wyoming right now, but it sounds like a small and weak one.
 
hookedup50 said:
Just my 2 cents, but after reading your fuel bug thread and having that fp 4 5 pounds for a baseline, I used to have 12. I also had sputter at medium to heavy accel. I was unable to get rid of fuel sock or install walbro and filter from Leroy(back issues). I ended up using Hammonds boibor to kill the bugs and unplug the filters. The filtersock and ffm got back to 12 pounds after 400 miles. Thanks for the bug thread, you save my but. Safe travels as well.
Click to expand...

You should add Hammonds boibor to that thread. I have been looking for alternative dual phase biocides to mix it up and kill anything that gets an immunity to the current stuff... Thx.
 
GM Guy said:
leroy, I dont think Kennedy would mind you making something the same, or similar to his OPS relay harness, would he? I dont care for wiring too much. :)

as long as its USA made and uses OEM connectors like the PMD cables, I am sure I would be game for one ofr a reasonable price.

(PS I am still wishing and hoping that you will sell me a billet aluminum K47 intake silencer delete plug as well. ;) )

thanks for all the advice guys, I think I'll just pack the parts with me and try not to pin the throttle to the floor.

leaving for Idaho tonight! murphys law, a small snowstorm is going on in Wyoming right now, but it sounds like a small and weak one.
Click to expand...

Never seen his harness. I have my prototype built though. It will be plug & Play and use weatherpack /sealed type componients. Heavy duty and no cutting original harness. Will have a additional switch in harness for turning on pump under hood.
 
Leroy does yours switch the ground? Kennedy's does and if you use the Walbro you have to either isolate the pump so the body isn't grounded or provide switched power to it.
 
Burning oil said:
Never seen his harness. I have my prototype built though. It will be plug & Play and use weatherpack /sealed type componients. Heavy duty and no cutting original harness. Will have a additional switch in harness for turning on pump under hood.
Click to expand...

I'll be a buyer, I was very satisfied with my last purchase from you!
 
Thanks guys,
AK, I have the Walbro on my truck. Its grounded to frame. Not sure what you mean about switching the ground? Do you mean to put the pump ground wire directly on frame? I ran the ground to the frame because to continue to run it though the stock harness will not allow the benefits of the relay (electrically) upgrade.
The relay takes the OPS as its input then it triggers the coil to run direct battery to the pump.
 
Stock wiring has a hot and a ground as the pump body is not grounded. With the Kennedy set up he had 2 wires as well but instead of switching the hot wire he switches the ground wire.

Sent from my Studio 5.0s using Tapatalk
 
Oh OK, Mine if using the stock type LP is going to require the ground wire from LP be run to the frame. I can provide for that very easy in the relay harness.
 
any rough idea how much a cable kit would cost? I think I would be game as long as the price is agreeable to my genetic cheapness. :)
 
Burning oil said:
Oh OK, Mine if using the stock type LP is going to require the ground wire from LP be run to the frame. I can provide for that very easy in the relay harness.
Click to expand...
Can you run a ground wire down there as well? Might be better than trying to get a good ground on a crusty frame.
 
My truck would stutter under a load at high RPM's too, I ran a hotwire right to the pump via a toggle and no more worries. If you don't feel like getting a Walbro, Raptor, etc, get a Delphi HFP905, stock lift pump for '93 6.5's. Flows a little more volume at high throttle.
 
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