oliver foster

That is right!

I was thinking the same!

It may be a week before I have the time to mess with it much , but I plan to figure this out.

I am going to get some clear hose for the return line and also check cylinder temps from a cold start to check for bad injectors…
Then swap in some used spare injectors if that seems like a likely culprit.

I will report back with any more info.

etn550

Okay, since we now know this is a pre-existing problem not fixed by other owners I think we should step back and start from square one. Either the other owners could not figure it out or they took it somewhere to be checked and found a problem too expensive to tackle.

Start with the easier things to check and go from there.

How is the blowby?

If you want to swap injectors that is fine but first get the spare set pop tested and record their opening pressure, check spray and spray pattern, leakdown, and leakage under holding pressure. Even if they seemed fine in another truck previously.

Checking the return line for bubbles needs to be done. Its low pressure just use some clear vinyl tubing from Home Depot and take it off after the test is complete.

When you crank the engine verify fuel is flowing in the return line. I know you are getting good pressure at the pump, but is it returning?

Blow through the return line from the pump to the tank to be sure the return line is not plugged. The inside layer of a hose can delaminate and block the ID of the hose.

While you are swapping injectors take a compression check on all cylinders.

If everything pans out so far then I would suggest checking the timing using an indicator on #1 plunger.

Still okay then I would pull the pump and get a thourough check on a pump test bench at the local diesel shop. If it has a worn cam, bad delivery valves etc. they will find it. I believe, but not 100% sure, that they can balance the outputs as well. If the pump is okay this is still money well spent and should not cost too much to test. It is not that hard to get it off the engine.

Again, don't worry about the boost at idle for now as when warm it should not white smoke. Address the white smoke first.

#1 priority is to change the oil if there is any indication it has been run for any length of time in this condition or if the oil smells at all like fuel. You do not want a much much bigger problem with excess fuel dillution in the oil.

And finally, I agree to persevere to get to the bottom of the problem. There is plenty of experience on this board to make good suggestions. I myself was a diesel engine design and test engineer for CAT, Cummins, and others and also managed a CAT truck shop. 1981-2001.

oliver foster

I was told from a friend of an old owner of the truck, a dealer told him he needed a new injection pump.
I would expect such a move from the dealer...
Then quoted him a price.

It was then sold from NH to Maine.
Where a guy had the same problems, it was then sold to a guy in Boston , where I bought it from and brought it back to VT.
I drove it for a few hundred miles this summer trying to figure out the issue, then blew a brake line and had no time to work on it, so took it off the road.
I just recently had the time to throw all the new fuel delivery parts at it, and get back on the problem.

Thanks for all the help.

I did try to blow the line out backwards into the tank from the lift pump and it seemed to flow easily.

Swapping the return line for a clear one, will be my first move.

etn550

I was meaning blow out the line from the overflow valve to the return in the tank, not the feed line from the tank to the lift pump. A plugged return line will allow fuel pressure to be made in the injection pump but if the return is plugged then air cannot be purged out to the injection pump fuel header.

What part of VT are you in. I grew up in Essex Junction through HS. Although the dealer might be right about the pump there is a greater chance they were just throwing the owners money at it. Dealers are not a good source for diesel truck repairs, generally speaking.

Report back after you have had the chance to check a few things out.

oliver foster

AHHH! a plugged return line.
That, I had not thought of, but if it is dead heading any trapped air...
I am 30 min north of Stowe VT, so Essex Junction is very close by.
Thanks for helping me sort this out.
I am tempted to just run the motor hooked to a 5 gallon jug on the floor with fresh fuel lines, the return line being clear tubing.
Just to eliminate fuel line leaks from the tank to the lift pump.

etn550

Yes, excellent idea. That might take a little work with fittings and hoses and such but once running it will either confirm or eliminate a lot of possible things to look at.

Has the fuel heater and or sediment bowl been bypassed at the lift pump? These are known to suck air. If not bypassed already I would recommend bypassing the sediment bowl and the fuel heater for the test.

infidel

The governor diaphragm could have a crack and be leaking.
Cheap to replace.
Also make sure the boost reference tubing to the AFC and wastegate isn't leaking.

kawi600

I run a boiler sight glass in the fuel line ahead of the lift pump so I can see any air being pulled in. Works pretty good.
Theres a ton of places that air can get in on the stock fuel system. Best to upgrade to all good quality fuel hose if you havent already.
I also removed the fittings on the top of the fuel pickup and used vulcan's draw straw 2 on it instead.

6cylinders

Oliver, what ever happened with this ?

oliver foster

Around Christmas time, a kid on the wrong side of the double yellow line hit my Daily driver ['01].
My insurance company totaled it.
I bought it back and parted the much rougher '97 [with the engine / fuel problem] for some of the needed parts to repair my daily driver.
The motor still sits in my shop.