Engine/Transmission (1998.5 - 2002) Fuel pressure ?

[PLaFrombois]

O. k. , here's what's happening with my FP guage. I left on a trip to NC, and didn't have time to change my fuel filter. Only about 9,000 miles on filter. Left home and half way through IL the needle on the guage started to move from a steady 13psi, to 9-10, and back to 13. Sometimes it would drop down to 7-8 psi, and stay there for a while, then all of a sudden it's back to 13. This went on through the whole trip.



Changed the filter, and cleaned the grounds on the sender, and firewall as best that I could. The needle was moving around but not as frequently. Filled up with fuel before leaving today, and the needle stayed rock solid @ 13psi. Once I hit 3/4 in the tank, the needle starts to move around and staying at 7 psi. This would happen with no throttle, or wot. After a while, once it stayed at 7 psi cruising along at 70 mph, I could bring the needle up to 13 psi if I increased the rpm's by 150 or so.



Any thoughts/suggestions I should look at?



Thanks

Paul

 

[Cummins724]

Mine did that, get a isolator inline of fuel pressure gauge, it should take care of it.

 

[PLaFrombois]

Thanks for the reply 724. I should have mentioned that it's a Westach 16 from Genos.

 

[DieselRam30]

There might be an air bubble in the line. Mine did similar things before I purged the line.

 

[JKinney]

The stock fuel pumps will fluctuate like your describing

 

[Texas Diesel]

Been there.



I had that on one truck and I changed the overflow valve on the Vp and that fixed that truck. This happened on aother truck with slightly different symptoms and nothing will stop it. Tried 3 different LP's. Finally put a snubber in the FP line and now the gauge is steady, not sure if the FP is steady though.

 

[RCrosby]

mine did this also with the westach 16 psi gauge, bleed the fuel line near the sender. with engine at idle, it been doing good for last 6 months.

 

[rweis]

I put a needle valve in before the fuel psi sensor, and turn the needle valve all the way off. Enough psi gets through to indicate for the fuel pressure just fine.



Before I did this I beat up a couple of fuel pressure sensors.



Bob Weis

 

[RAJohnson]

Mine did the same thing until I relocated the sender farther from the VP. Originally it was tapped at the schrader valve. Now its att the bottom of the OEM FF and rock solid.

 

[BDudley]

My truck has started doing the same thing last month w/ a westach electronic gauge. Gauge has been steady for last three months since installation. It happens more often w/ 1/2 tank or less of fuel and if I stop suddenly or bounce across railroad tracks. I think I have a hole or something in the pickup tube and the sloshing fuel lets air get in. When I have full tank it hardly ever happens. With 1/2 tank or less I can sometimes make it happen while sitting in my driveway by rocking the truck w/ my hands. Thens a few seconds later the pressure goes right back to normal. Got delphi oem replacement pump on my 98. 5 24v fuel filter has less than 4k miles. Vacuum port on top of tank is clear. Been getting fuel from the same place for a long time. No other problems.

 

[Texas Diesel]

I thought the same thing so I added a clear line between the FF and VP. No bubbles, so atleast mine wasnt sucking any air.



You might try the clear line and see if you have any bubbles.

 

[ox1]

Bringing an old thread BTTT rather than starting a new one as this thread seems to be on track...



I just ordered up a new LP and IP and the <5# idiot light. Not real keen on the idiot light as they are generally for . . well you know...



I have ran a few mechanical guages on this in the past and between the vib of the motor and the pulsing of the pump - it just beat them to death - and the newer ones die quicker than the old ones. (Import guages?)



Anyhow - I have seen the Genos elect sending unit style and like that plan - but when talking to a feller this morning he says that the electric ones don't last but 6 months either as vib kills them.



How many miles doo you have on your Genos setups and what doo you think is causing the problems?



If it is engine vib - then a feller could easy enough runa length of hose to the sending unit to isolate it from engine vib 0 but if it's the pulsing of the pump - well then...



I was reading further up this thread aboot installing a "needle valve". ??? Like a flow control valve for an air or hyd cyl maybe?



I sounds like air is what is causiing the guages to flucuate - but that has to be air in the pump - not air in the sending unit line. Once the air is through the pump - it will compress to the line pressure too. Inline bubbles won't effect the reading. This was very common to see air bubbles in mech oil pressure guages on older Chevys. Nothing to be allarmed aboot there.



Should I still consider adding the guages to add to my idiot light?

 

[Texas Diesel]

See this:



http://turbodieselregister.com/forums/showthread.php?t=118389&highlight=westech+carry+plug



My mechanical gauge (Isspro) has lasted years. I use a fine hydraulic snubber in the line, it smooths out all the pulsations and doesnt need replacement like the Westach's did. I used the same snubber on all the Westach's too.



Hve no idea if they are any better now but I doubt it.

 

[ox1]

Hmmm - interesting thread. I would like to think that they have improved them since then - or they are still selling junk 2 yrs after the fact yet you think?





So you are runnin' mechs eh? In the cab? I don't think I'm up fer that. Don't you think that these "snubbers" would help to not destroy the elec units too - just as they doo your mechs?



I got aboot 200K on my original IP, I think I would rather run no guage and take my chances as to know that one day (possibly soon) that I will have an underhood full'a fuel. Good grief - that's gotta stink for months! And also - my wifey puts on a LOT of miles on this truck - and far from home sometimes too. I don't think I need to be sendin' her out with forty-levin pipe plugs and a wrench. LOL! (BOY - I'd be a gonner when she got home after that run!)



Can I get more info on the snubbers? (Maybe I should slip that wurd in the search eh?)



Thanks!

 

[Texas Diesel]

I dont know if they are better now or not but based on the design, I'll pass.



They make two grages of snubbers, one for liquid and one for air, I think. I got the one with the smallest pores.



Even back then some people had good luck and lots of people had the same problem I did. If you read the thread, WesTech admitted a design flaw. I got one of the 'improved' models, it lasted about 4 months.



I had a snabber on all of them.



The isolator type have had problems too and I dont want antifreeze&water in the fuel line.



Not many choices, electric, isolator, and steel braded fuel in the cab type.



Take your pick and take your chances.