Lift pump? IP? Other?

[Caver Dave]

I apologize for the "repeat" (for those of you on TDS), but thought I might possibly reach a new set of eyeballs here...

Recently, I pulled both tanks from my '92 F2504x4 w/ 7.3L & ZF5. After replacing them, I dumped about 3.5gals in each tank, drove to a local station (frequented by 99% of the independent truckers) and filled up. Drove about 100 miles without issue, then began suffering a power loss. Babied it home, and found quite a bit of water in the filter (the "water in fuel" light never pulled). I drained the water, dosed those tank fulls with DieselKleen and went on. Never have figured *where* the water came from... 10 local truckers using the same fuel swear they've had zero issues, so I'm guessing neighborhood hoodlums (potentially attempting to cover diesel theft by adding water?).

Last weekend, I pulled a 6k# load with it and all was great for 30-45 minutes (slight black smoke during WOT), then power went way down (unable to turn past 3K rpms & NO visible smoke)which turned into noticeable stumble & missing (whitish smoke at WOT) after an hour. Same symptoms on the return trip. Still no water in the oil, no oil in the water, and no additional water in the filter...

I was advised to check the lift pump *first* which I will do tomorrow, but was told it's likely the IP. I wondered if these symptoms lead you to think 1 over the other (lift vs IP)?

Also, why would it take so long to manifest? I can't see it taking 30-45 minutes for the entire block/IP to become completely "heat soaked" pulling a load in 90* temps for a heat/overheating issue (lift or inj. pump) to happen. I realize that internals will swell when hot, but the an mount of time seems to be too long?

As always, any insight you could give me is greatly appreciated!

 

[Agnem]

Sounds like a fuel stavation/air intrusion issue. The injection pump generally doesn't get very hot during operation, because the constant flow of fuel through it cools it. Given that you have been messing with your tanks, and you didn't give a time line on what you described, the water may have been condensation from having the tanks mostly empty for some period of time. If you are running the factory filter, and the WIF light didn't come on, I doubt you damaged the IP. If you didn't change the filter yet, I would do that, and don't rule out the possiblility that something is going on with your fuel pickups since you have done something with them and the fuel lines.

 

[Caver Dave]

Sounds like a fuel stavation/air intrusion issue. The injection pump generally doesn't get very hot during operation, because the constant flow of fuel through it cools it. Given that you have been messing with your tanks, and you didn't give a time line on what you described, the water may have been condensation from having the tanks mostly empty for some period of time. If you are running the factory filter, and the WIF light didn't come on, I doubt you damaged the IP. If you didn't change the filter yet, I would do that, and don't rule out the possiblility that something is going on with your fuel pickups since you have done something with them and the fuel lines.

Bless you Mel! (was hoping to you'd reply)

Time frame...
Early July found midship tank to be leaking (strap "isolator" gone, strap rubbing on tank). While I had the bed off to troubleshoot rear tank issues:
- both tanks were replaced (absolutely *nothing* in either tank)
- tank fittings were cleaned & lubed w/ white lithium grease before reconnection
- pressurized (10#si) & sprayed with soapy water (NO leaks detected)
- pickups checked & "strainers" hose clamped (just enough pressure to insure they won't fall off) in place
- installed tanks w/ filler necks harpooned
- 3.5 gals added per tank (later filled completely)
- and it fired up very nicely after purging air
All this over over a 2 week period (very busy)

Late July, drove to folks house 1 hour away, truck ran great until last 5 minutes of return trip, seemed to mimic early stage of power loss (noted in first post), & was scared to stop, so babied it home:
- Found lot's of water in filter... drained until only clean fuel came out
- added appropriate amount of DK for fuel in tank.
- Would idle, but not return to idle
- WIF light never lit, even though it does light with the others when key intially turned to run position.

Fired up several times each week to keep batteries up and check for leaks.

Last week:
- replaced filter and added more DK (4x normal dose)

Last Weekend:
-pulled load 30-45 minutes (of 1.5 hour trip) when the power loss began occuring, eventually degrading to mega power loss & several cylinders "missing".
- checked water, oil & filter before return & found everything in place

Today:
- checked filter again and drained about 3 drops of water before fuel ran clean/clear
- drove it to work so I can test the lift pump pressure/flow at a buds shop this afternoon. As always, ran absolutely GREAT from cold (didn't run it long enough to get "hot", as factory temp gauge stayed on "N"), which historically pretty decent representation of coolant temps based on load & grade.

I'm running the "factory" filter (new style WIX filters). Not sure about condensation as both tanks were clean & free of anything (were installed & filled with 2 days when weather was hot & dry = no rain) and the total qty. of water drained was about 1/2-3/4 of a pint...

Could the lines (tank to FSV & FSV to lift pump) be getting warm, expanding, causing a leak? (Seems more plausible given how it runs colds and time it take to happen)

Could the lift pump be breaking down when warm? I guess if the flow & pressure turns out to borderline/marginal when cold, it would tend to indicate it could drop even lower when "warmed"? Will let you know what I find tis afternoon...

In the meantime, I appreciate your response and welcome any additional thoughts you might have!

 

[Caver Dave]

Tested the lift pump today...

4-6# while cranking (pressure dropped immediately when cranking stopped) & 6oz. in 10 seconds of cranking...

I guess that means it isn't the cheap(er) fix?

 

[Caver Dave]

Sorry to bring this back up, but...

I got to thinking about it a bit more yesterday (pulled an "in parts" '64 CJ5 for a bud)...

- The fuel filter has only been changed once... *IF* the water (still clueless where it came from! ) was still present after filter change, possibly the new filter is *****'d also?

- What happens to a filter after water introduction? Seems the element could get coated with the "emulsion" and simply *STOP* passing enough fuel?

Given the results of the lift pump (fine according to spec...) and the long time running between symptom onset, does it stand to reason that filters ability to pass fuel to the IP could be cut as run time increases? IOW, the "emulsion" (water/diesel mix) settles when parked... the truck runs fine until the emulsion is "stirred" by the volume of fuel (after say 45 minutes) or warmed by engine hgeat, clogs the element & is simply cutting off the fuel as run time increases?

Or am I just in denial and really need an IP?

Also, I've heard there is a unitized filter that replaces the OEM bottom "cap" and has a built in drain valve. Any chance they're less expensive than my current $40 WIX filters?

 

[highest_vision]

Also, I've heard there is a unitized filter that replaces the OEM bottom "cap" and has a built in drain valve. Any chance they're less expensive than my current $40 WIX filters?

Hastings has one, unsure of # or $. Personally, I'd rather have the two piece for inspection purposes.
A quality filter shouldn't 'clog' from water or because of the introduction of water. If in doubt of something, change the filter and check for water every day.
James

 

[Agnem]

Sounds to me like the IP starting to go out on you. If your not having hard starts due to air, then you don't have any accumulating in the system, and it doesn't sound to me like there is any water to worry about. It is possible that because you found a lot of water in your system at one time, that it may have reached the IP and damaged it.