Lift pump????

[d.h.]

Hello! My 98 6.5 sputters evey now an then. Seems to do it under slight load and very rarely,maybe 1or2 times a week.It,s like the fuel cuts off then comes back.It somtimes is hardly noticable but other times it,s like you turned the key off and on again.Any comments would be appreciated.(it also does it more when the wife is driving!!! :eek: ) Thanks

[Turbine Doc]

Could be a lift pump or a clogged filter, use search feature above numerous posts on pump trouble shooting. Also look for posts on fish biting when the trucks acts up does it buck sort of like a line tug when a fish sets a hook on a line trying to get off, same on mine was partially clogged fuel filt.

[ucdavis]

Could be an FSD going out, initial symptoms of IP failure, bad grounds causing an intermittent, or other things. Time to go thru the Stalling,... checklist @ http://www.thedieselpage.com/members/tt99-9.htm
Real simple process, & should isolate the trouble.

[d.h.]

Thanks,I can pretty much rule out filter as I just changed it.The truck runs great full boost just every now and then it stumbles.I,ll check that link you refered to and hopefully find somthing.I have gone through 3pumps already and the thought of 4 doesn,t sit well.The truck always stalled or completly died with previous pumps.Maybe I,ll get lucky smile.gif and it,s something simple.Thanks

[dslpwr]

Make sure to check oil presure switch also.

Best way to check is with truck running open water drain valve. If truck dies you have bad switch or lift pump

[C.K. Piquup]

The fuel filter should be double checked.It`s not unusual to have to do it twice.Mine has mysteriously needed it before.Almost paid for new pump & injectors.

[d.h.]

Pulled filter out today.Reinstalled &so far so good.Truck actually stalled yesterday forcing me to drive my old 6.9f$%d. I,m not 100% convinced this was problem but it didn,t skip a beat today :D

[AndyL]

I had the exact same problem, bad FSD was the cause.

[Turbine Doc]

DH
Where is your FSD mounted still on the IP, if stumbling comes back remove it and get a good (" inch) lb torque wrench and retorque transistor mounting nuts to 10 " lb. Your call to relocate it back on IP or remote mounted on cooler plate, most here experiencing FSD problems remote mount it, lot of debate if remote mount is cure for FSD fail I'll not delve into that one, one thing for sure it's lots easier to swap one that is having problems on a cooler.

1-24-04 I had a remote mounted FSD that stopped the truck in it's tracks, OAT was 55F and FSD was cool to the touch, under hood heat was not very hot if I had to guess maybe 200F max I ran home 40 mi on glove box spare hanging on a tie wrap in the air under the hood off a bracket, as luck would have it I had every allen wrench with me except the one that fit the FSD to cool plate allen screws. The FSD has been on the drivers side fender for 2.5 years just aft of the drivers batt where old style washer tank sits.

When I got home I found that the nuts on the "Bad" FSD that had been previously torqued to 10" lb. 6 mos. ago, had loosened to 4-5" lb. break away torque. Retorquing back to 10" has resurrected the FSD from the dead, I will be keeping an eye on it to see how long it lasts.

On the fuel filter I had a recently changed one cause me some problems last summer. I was on a road trip away from home and got a load of "bad" fuel I guess, after returning home my truck would not pull my empty 5500lb GN trailer faster than 40 mph without stumbling, truck ran good without the trailer 75+ mph but occasional stagger.

I changed the "new" fuel filt that had only 5K miles on it truck was able to pull truck, trailer & load 18,700 lbs no problem. 75+ mph on flat road, 60-65 mph up steep hill. As a result of that experience, I'm now running a frame mounted 20 mic primary filter as well as OEM 10 mic on engine filt.

Next time staggers happen put a gauge on the filter drain line to see if you are getting full delivery to IP at load should be 2-6 psi steady depending on lift pump health, may drop to 1-1.5 at hard acceleration bad to 2-6 at final cruise speed, starving IP may cause performance problems at top end, either bad lift pump or bad filt. same result.

FSD could be in fact real problem but rule out IP delivery before plopping $$$ down for new FSD.

[d.h.]

Thank for the info.I haven,t had a chance to drive it today but wife said it was good.As far as remote mounting fsd I agree if nothing else its a lot easier to acess.I will check torqe on bolts to be sure there up to snuff other than that I,ll keep my fingers crossed.I still don,t think its i/p as previous 3 had all the same symptoms unlike i,m having now. Stranger things have happened mind you.Thanks for the input ;)

[d.h.]

truck is stalling every time you shut off and leave for a short time.Between that and it,s stumbling i,m taking to dealer to check over.I,m curious as to the cause.I don,t have time to do the step by step checkover.I wish i did...