Engine/Transmission (1998.5 - 2002) New Problem with L/P, filter and VP44

[Big_Bad_Dually]

I just started having some fuel related problems with my 98. 5 3/4 ton auto that i have had for just 3000 miles (145000 total).



Started with the problems on Monday.



Went to the dealer Monday to have the winter idle TSB performed. That went good. The next morning it was 18degrees out, the high idle worked. But i was crusing along, that morning to town at about 75-80mph @ 2050-2100 rpm when the motor cut out. Right away I thought it was fuel related. First I guessed gelling, but it was winterized diesel. So I got into town and bought some PS Diesel TReatment and added. When heading home that afternoon it did the same thing @ the same rpm/mph.

Wednesday it didn't ever do it.

Thursday it did. Went to the dealer and they said they could look at it tomorrow.



So i came home tonight and rigged up a temorary fuel psi guage. When i tapped into the psi tap on the inner side of the two the taps (post filter) it wouldn't spit out diesel when i was going to prime it, the motor just died. So i proceed to hook up the guage just to try it again. Cranked the motor over for ten seconds and it fired. Took her out for a drive and never got any psi to build. Could the VP44 be sucking its own fuel?



I didn't think that the pump could run without any pressure @ idle so i got on the 'ol TDR to get some help.



I guess this means the L/p is dead right? Or did the reprogram possibally mess something up? If i have zero psi at idle than there can't be more at WOT, right?



Any help would be great (Sorry for long post)

THIA

Brian



P. S. Fuel filter has 3000 mile on it, i have great hp but no mods, 13mpg, YEAH i've got guages just haven't had time to install

 

[B.G. Smith]

Fuel related problem

Sounds like the LP is dead. The truck will run with 0 pressure as long as it doesn't lose prime. bg

 

[TKemper]

Yeah, It'll run with 0 PSI. Today I went to change the fuel filter in my boss's 99, everything went fine until I tried to prime the truck. I got no fuel even with the bleeders removed. Hooked up a pressure gauge..... 0 PSI I got a new one, primed it, and now have 12 psi @ idle. I was surprised the truck ran as good as it did with a bad pump. Now I'm trying to convince him that he needs fuel pressure gauges in the rest of his trucks. Good luck. Todd

 

[JTeague]

I have seen several trucks that will suck up to 15 in. vaccuum at the post filter check port!:--) The VP will pull its own fuel without any help from the transfer pump, but not for very long.

 

[Big White Beast]

I checked one.......

That was zero at idle, then after you got moving it jumped up to 12 PSI. Guess the VP suck started it. Needless to say the LP was replaced and everything seems fine.



Cummins part# 3990105 is the latest for the lift pump.



Garrett

 

[Big_Bad_Dually]

Thanks guys. I just got one from cummins. Sure makes me want to install the guages right away this weekend. I just hope i didn't do much or any damage to the VP44.



Will the VP44 pump just enough to run the motor or some to cool it too?

Anyone have any good advice on installing a new lift pump? I had a hard time reaching down to test voltage.



Brian

 

[Big White Beast]

From up top.........

It's really not that bad. A few including myself have found that the studs come out of the pump instead of the nuts coming loose. One person retightened the stud and his pump worked fine after that. Seeings your replacing it I wouldn't worry too much about this. Once the stud is out you can usually get the nut off for re-use.



Garrett

 

[Gary - K7GLD]

Well, look on the bright side - yer pump may be dead - but those nice shiny guages sitting unused on the shelf are still good as new... :-laf :-laf :-laf

 

[Ncostello]

Probably out in left field on this...

I noticed the ISC on our fire truck has a transfer pump with the same electric motor as the ISB. Only difference I learned is that the ISC lift pump primes a dry filter (spin on type) and purges the air out... then lets the injector pull its own fuel without the need for the lift pump (info from posts in "General Diesel Topics" forum). The lift pump housing has a bypass valve that lets fuel flow right on through. And it has 1/2" (maybe larger) fuel lines. The injector pump is fuel lubed and oil lubed.



I wonder if the ISB VP-44, seeing as it pulls a good vacuum and is known to be able to pull some amount of fuel on its own, could do the job all on its own if the entire lift pump was out of the equation and the fuel line was much larger. Obviously the ISC injector pump was made to do this whereas the ISB VP-44 wasn't... but it would be an interesting experiment if you had the $$$ to blow on a ruined VP. I'd bet if a LP dies, coupled with the small diameter stock lines, its very hard for the VP to pull its own fuel through all that. But we see it happen all the time.



I know... I'm out in left field but I like looking at the impossible.

 

[Big White Beast]

Neil......

I'm wondering about the fuel tanks too. With the up and over that our fuel lines do it makes it even harder to suck the fuel. I would bet these larger trucks draw from near the bottom and have way more fuel to develop a head pressure. That coupled with the larger lines probably makes it easier all around to get fuel to an injection pump.



Garrett

 

[Pit Bull]

Re: Probably out in left field on this...

Originally posted by Ncostello



I wonder if the ISB VP-44, seeing as it pulls a good vacuum and is known to be able to pull some amount of fuel on its own, could do the job all on its own if the entire lift pump was out of the equation and the fuel line was much larger.

.

I remember reading some where that the VP44 was not designed needing a lift pump (read it on a bosch site). You could be right about it not needing one. I know my 2000 went for many KKK miles with a dead lift pump. Just wonder how many owners that don't belong to the TDR drive CTD's with dead lift pumps for 100,000+ miles and never know it?

 

[Gary - K7GLD]

"With the up and over that our fuel lines do it makes it even harder to suck the fuel"



This chestnut keeps returning like an urban legend...



Step back from your truck, and visualize the MAXIMUM vertical distance between the lowest likely fuel level in your fuel tank, and the point of entrance into the VP-44 - maybe 2 feet - 24 inches max?



THAT, and THAT alone determines how much physical suction is required to move fuel from the tank to the LP... Raising or lowering the SURFACE of the source in relation to the destination is the determining factor, NOT whether fluid is drawn off the top or bottom of the source!



Any of you ever siphoned fuel from one container into another? As LONG AS you keep the level of the container you are flowing fuel TOO lower than the source, fuel will flow - and IF you were to take those same 2 containers, and drew liquid from the BOTTOM , *or top* of the source container, the DIFFERENCE in actual physical fuel level will determine the flow pressure - drawing fuel from the BOTTOM of the tank as opposed to "pulling it over the TOP", *once flow has started*, GAINS YOU ABSOLUTELY NOTHING, all other factors being equal!



The difference in relative liquid/fuel LEVELS is the important factor, NOT whether you draw off the bottom or top of the source! Shucks, you can even take a siphon hose while liquid is flowing, and as long as you don't change the relative positions of the 2 containers, carefully raise or lower the siphon (or bottom) intake hose, and fluid flow won't change a bit!



Common high school physics...

 

[Ncostello]

I was typing a similar response to yours Gary when I read yours. Its true. Once that initial suction is started in a up and over line, the only portion of the line that sees negative pressure (vacuum) is the portion above the free liquid surface inside the tank. The free end of a siphon tube will basically flow just as good as the free end of a bottom discharge tube if they both end up at the same point.



If you can mount your lift pump in a position at the same basic elevation as your tank your doing it a favor. All you need to eliminate is the distance between the top of the tank and the OEM lift pump position... which is only a few inches. I dont think theres much advantage to getting all the way back to the tank either. I'm shooting to get my pump inlet at the centerline of the tank... when I'm above half I'll have positive head at the inlet. Below that I'll have just a slight bit of suction... not enough to worry about for any pump. And I'm going for 1/2" diameter feed lines to the lift pump.



Either that or I'm going 1/2" all the way to the VP44 and using a hand primer/bypass valve... who knows maybe eliminating the dang lift pump completely is the best solution yet .

 

[Texas Diesel]

Originally posted by Gary - KJ6Q

"

Common high school physics...

Gary, I would never have guessed you went to high shcool

you must have been asleep during "how to win friends and influence people" class, I know I was

 

[Gary - K7GLD]

"Gary, I would never have guessed you went to high shcool

you must have been asleep during "how to win friends and influence people" class, I know I was "





HEY! I represent that remark!



I think I've just been insulted (again)... . :-laf :-laf

 

[Ncostello]

Gary, I think Tejas set himself up. He must have also been asleep during English... high shcool???



Just kiddin Tejas... I usually dont get into the various forms of humor on the TDR .

 

[B.G. Smith]

Siphoning technology

Hey, are you guys really from California or transplants, never heard anyone so versed in siphoning since I left Oklahoma, they used to call a siphon hose an "Arkensaw credit card". bg

 

[Gary - K7GLD]

Can't speak for Nick or Tejas - but *I* am a "transplant wannabe!"



Sure would like to be FROM this state, instead of IN it!



The FARTHER "from", the better...

 

[Big White Beast]

Gary......

Ya caught me sleeping. And I am a High School drop out so there!! The up and over was only half off.



Anyway, I wasn't thinking of the siphon effect. The lift pump is higher than the tank and the lower the tank gets the higher it has to pull. The stock fuel lines are in the upper 2/3's of the tank so at a half tank your beyond siphon anyway.



With a bottom bung you would have positive head pressure at all times, granted not much but any positive is less work on the LP. I noticed on a really low tank that after fill up I gained 1 PSI so there has to be something to it.



Garrett

 

[Texas Diesel]

Transplant? Me? I am from La, moved to Texas City at 3 weeks.



I've been to Ca twice (that was enough for me), there are some nice people in/from Ca but the State Government needs to be overthrown.



Arkansas credit card, thats great.



And I DID fall asleep reading Dale's book on how to win friends and influence people. Does it show?



Cant remember much about High School for various reasons, some legal, some not, some female.



Glad you can take a joke Gary!