Occasional sudden mystery problem just keeps getting stranger

[gavio]

Hi Everybody:

I have been having an intermittent problem for about two months now, and still can't get my brain wrapped around what it could be......

On occasion, the engine just suddenly hits a wall - power drops to zero, mass clouds of white smoke out the back, as best I can tell, from both tailpipes. Pretty much no options but to stop, it won't idle so it shuts off. I wait a few minutes, make a phone call or something, and then it starts up and runs exactly as normal. It has happened about 5 times now over the last two months, under various conditions - usually at operating temperature, but once right when I started it up. Sometimes going downhill, sometimes uphill, sometimes when really cold out, sometimes at moderate outdoor temps.

Between occurrences, it runs fine, power as usual, occasional trouble with cold starts. My idle is set a bit low, so it smokes a bit when the engine's cold (been meaning to fix that.....) but otherwise.... It eats a little bit of oil (has about 230k on it), and has a minor antifreeze consumption issue - probably water pump which has weeped a teensy bit ever since new.
Injection pump was rebuilt in October, fuel filter is recent, fuel is diesel #2 for the last 4 months. It's a 6.2 NA - pretty much stock, except no EGR.

The last occurrence was yesterday, it happened three times in a row, a few minutes apart, each time I didn't stop for very long. Finally, I stopped a little longer (maybe 8 minutes) and then it started up fine, ran normally, and went another 3 hours worth of driving without mishap. That brings me to now.

I am leaving on about a 2500 mile trip in 10 days, so wouldn't I just love to have this wrapped up before I go?

Any help appreciated.

Thanks

Gavio

[EWC]

Water in the tank ?

[Robyn]

The 6.2 has a mechanical IP so there is not an electronic gremlin likely.
This sounds like a fuel flow issue as in a partially plugged tank sock or possibly a cap vent that is not allowing air into the tank.

If the IP runs out of fuel and starves the thing it will blow white smoke.

Run a length of clear fuel line from the filter to the IP.
If you can route this so it loops up by the wipers and in your view you can then observe the fuel flow. If the power loss and white smoke is accompanied by air bubbles in the clear line you have the cause.

Then its only a matter of tracing it back from the IP to the tank.
The lift pump is a mechanical unit too so no electrical stuff there either.

This has got to be a fairly simple issue as Ip troubles dont heal up in a couple minutes and then go again.

Check these things and let us know.

Robyn

[gavio]

Thanks for the input......

I had been joking with my friends that my van was "possessed by a computer" :)

Seriously, though, I agree that it's unlikely to be anything really big since it vanishes without a trace.

An idea I had was that maybe it was intermittent failure of the lift pump, which is an aftermarket electric unit (I forgot to mention that in my first post - so sorry for the oversight). Could that cause such symptoms under certain circumstances?

An idea I have gathered from another source is maybe a partially blocked return line, or a blockage that somehow shows up from time to time.

Comments?

I'll try some things..... the deal, of course, is that I'll not know for an awfully long time if I really have the problem fixed or if it is just in hiding again...... after the first time, it didn't show again for like three weeks.......

Meanwhile, if anyone else has ever had or heard of anything like it happening, I'd love to hear from you.

Thanks

Gavio

[Peter J. Bierman]

I kinda go for the sucktion pipe blockage.

Had a thing like this with a Wheel loader a few years back, out of the blue it stopped and would not start again. ater a wile it woud start and no problems what so ever.
A few hours later, same thing.
Switched the feed and return lines, it would be fine for two weeks and then acting up again.
Switched the line back, fine for another two weeks.
Finally took the tank from underneith and made it dry, found a peace of plastic. It matched perfectly to their fuel filler gun at the fuelpump:D.
It took the plastic two weeks to wander from one end of the tank to the other and block the feedline.

So maybe you should check your tank or at least check the fuelpressure between the liftpumpand IP for a wile, you might find a drastic :eek: pressuredrop just before it start to act weird.

Good luck, Peter

[gavio]

Thanks, Peter, that's an interesting angle.... would that it weren't such a PITA to drop the tank and have a look.....

[Peter J. Bierman]

Try to plum in a feedpressure gauge, it can give you a clue before you strart heavy tooling.

Peter