Fuel psi drop

[hex0rz]

Alright the other day, I noticed a drop in fuel pressure. Its been a continuous thing since then. It will now run at 15psi instead of 20 at idle. I did not mess with the pressure regulator or anything else of that nature. I have less than 10k miles on the fuel filter.I'm worried that if it is not the fuel filter, it could be the airdog pump going out, AGAIN...I will have to check the fuel pressure gauge and make sure the connections are still good and air is not getting into the system.I use permatex thread sealant, its really sticky stuff and says it wont be dissolved by fuels. If this is my problem, anyone have any suggestions about what sealant to use on the connections?Or is there another reason why my fuel psi is dropping?

[rickf]

Check your voltage at the pump and as far as the thread sealant that stuff should work but if you have any doubts just use Teflon tape. I know that when my grid heater comes on I drop 5 lbs. of pressure.

[Mopar1973Man]

Personally I don't use any thread sealants on any fuel fittings. Just to risky to have a gob of permatex or Teflon tape get sucked into the VP44 and it would most likely plug it up and ruin it. That what sealing washers and o-rings are for. As for tapping for fuel pressure gauge I use brass fittings because they are self-sealing to some degree.I would take the regulator out and inspect it. I'm not very fond of the newer adjustable regulators they never seem to be able to hold the pressure even like the old spring and check ball does.

 

Edited February 11, 2022 by Mopar1973Man

[oldbeek]

X2 , never use thread sealant on a fuel system. But the new adjustable regulators are just an adjustment on top of a spring and ball. No diffrent than adding shims. I added a line to my system from the fitting entering the final filter over to near the left fender. There I can EASILY add a test guage to measure filter drop.

[hex0rz]

Check your voltage at the pump and as far as the thread sealant that stuff should work but if you have any doubts just use Teflon tape. I know that when my grid heater comes on I drop 5 lbs. of pressure.

Where do I test at the pump specifically? I also see a drop in psi when the grid heaters cycle. I left the wiring harness stock length for the pump and just hooked it to the aux battery. But thats not the drop I'm speaking of. This is with the engine at idle when the grid heaters are not even cycling.

Personally I don't use any thread sealants on any fuel fittings. Just to risky to have a gob of permatex or Teflon tape get sucked into the VP44 and it would most likely plug it up and ruin it. That what sealing washers and o-rings are for. As for tapping for fuel pressure gauge I use brass fittings because they are self-sealing to some degree. [ATTACH=CONFIG]5059[/ATTACH][ATTACH=CONFIG]5060[/ATTACH] I would take the regulator out and inspect it. I'm not very fond of the newer adjustable regulators they never seem to be able to hold the pressure even like the old spring and check ball does.

I use brass fittings as well and they are leaking. I suspect the permatex was not allowed to sit long enough to "harden". What are these sealing washers and coul I use them on the brass fittings to seal them? Do you think my regulator spring could ALREADY be weakening? I was thinking about just upping the pressure, but I did not want to "band-aid" it. I tell ya, if this is not my fault, I'm getting tired of AD and may start looking at the Assassin more and more.

[rickf]

If you put Teflon tape ONLY on the threads you will have no issues with anything in the system. I have seen people get lazy and just slap it on and it overlaps the end and then you have a problem because that piece will get cut off as you thread it on. Also only use sealants on tapered threads, never seal any type of straight thread fitting. They should have a gasket or o-ring seal. I have seen brass fitting leak many times, they are usually sealed from the factory also.

[gassernomore]

Instead of teflon tape, I use Permatex spray. You use a pray to prep the surface, then use the sealant. Made specifically for diesels. My psi drops while the grid heaters are on. As soon as they stop turning on and off the psi is steady.

[Te300]

I put a fass one fifty in last summer and stretched the spring a little so it would idle at eighteen. Now it's idling at sixteen. I think it's time to stretch it some more. Also if the filters start clogging I noticed that there isn't much difference in idle and wot. Like when my filter is new it will visibly drop to fourteen no prob but when they get ten thousand on them it will stay at sixteen. You should change filter every two oil changes. (10000 seems like the max )

[Mopar1973Man]

Where do I test at the pump specifically? I also see a drop in psi when the grid heaters cycle. I left the wiring harness stock length for the pump and just hooked it to the aux battery. But thats not the drop I'm speaking of. This is with the engine at idle when the grid heaters are not even cycling. I use brass fittings as well and they are leaking. I suspect the permatex was not allowed to sit long enough to "harden". What are these sealing washers and coul I use them on the brass fittings to seal them? Do you think my regulator spring could ALREADY be weakening? I was thinking about just upping the pressure, but I did not want to "band-aid" it. I tell ya, if this is not my fault, I'm getting tired of AD and may start looking at the Assassin more and more.

I did not hook the fuel pump to the batteries. I hook mine to the PDC where the red heavy gauge comes in. This way there is no corrosion problems with the wiring. So the pressure drop after grid heater is going to be a regulator problem most likely or gauge issues if its a electric sender. The sealing washers are the stock washers used on the banjo bolts I'm talking about. If it was me I would pull the regulator out and inspect it and see if you can spot possibly issues of sicking or such.

[LiveOak]

Put an actual test guage on the fuel system to verify actual fuel pressure first and to eliminate the possibility of a bad or out of adjustment fuel isolator (if you are using one). How old is the fuel filter? I have never actually had to replace a fuel filter on my Air Dog 150 due to a pressure drop/contamination, they last a LONG time. I replaced one due to getting rusty. If your fuel pressure reading is low and your fuel filter is good, I agree with the above troubleshooting steps. On the wife's truck, I have to replace the fuel filter (OEM fuel cannister filter with Baldwin PF7977) about every 4,000 to 5,000 miles due to fuel pressure gradually dropping down to 12 psi.