Engine/Transmission (1998.5 - 2002) Quick Fuel Pressure question...

[Rattlin_Ram]

JUST got my fuel pressure gauge installed and plumbed today. It came from Piers with a banjo bolt that I put into the VP-44, I ran a grease gun hose over to the isolator (thanks to TDR ideas), and then it runs into the cab.



Question is this. I am seeing about 11-12 psi at idle, around 10 driving around and down to as low as 3 psi WOT. Should I be concerned? Could it be my gauge is inacurate?



I've read normal is around 14-15psi idle, 10-12 or so driving around, and no less than 5-7 WOT, correct?. Just wondering if I should be concerned or not since I'm a lil lower than those numbers.



Thanks... .

 

[Sticks]

Your WOT is low. 5 is low. I would not want the PSI to ever drop below 10, but 8 at WOT is doable.



I would change your fuel filter first. Kind of odd that your idle and driving around is almost OK, then drops that low on WOT.



If you change your fuel filter and still get the same pressure readings, yo7u can either A: Relocate teh banjo to the bottopm of the fuel filter and put the schrader valve banjo back in and get a fuel pressure test gauge to verify the new one. Or B: Get yourself a new LP.

 

[darkhorse]

Sticks' advice is spot on! Your pressure at WOT is low but the real damage begins when pressure falls below zero & the vp has to suck the fuel for itself.

 

[Rattlin_Ram]

Ok since Piers sent me the wrong gauges, white needles instead of red/orange, they sent me a new set of gauges. So I decided to wait and try the new gauge. Still got the same readings. One question, I can't get the entire line from the isolator to the gauge full of antifreeze, is this a problem??? there is some air in that line. I bought a lil $10 gauge from pep boys, and I'm thinking of putting it on a long hose and running it up out the hood in front of the windshield to bypass the isolator to see if that is the problem... . Then if it isn't bite the bullet and get another LP. If that is the problem I'll keep mine around for backup in the glove box... ... Since it does work... . mostly... .



Anything else I should check???

 

[d.miner]

Rattlin,



My line from the isloator has air in it also (antifreeze), I still get very stable and consistent readings.

At idle - 15psi, crusing @ 70mph - 10 to 11psi, WOT @ 3000+ RPM and I can suck it down to 6psi.



I tow a 27ft 5th wheel trailer and I can easily keep it above 10psi all day long. I've got 10K on the fuel filter and will be changing it in the next week or two.



My truck is an HO and feels like it makes it's power up high in the RPM range, that's also where I see the highest fuel demand.



My readings have been consistent for almost a year now and I do not plan on changing anything (except the filter).



When I first got the gauges I saw fluctuating pressure readings but then read a post that talked about the lift pump electrical connection being suspect some of the time. I purchased some dielectric grease and applied it to the connection and have had steady pressure ever since.



Hope this helps,



Dan