6.9 IDI White Smoke

Hi all,

Picked up a 1986 F350 with the 6.9 IDI as a project to mess with. First diesel, but not new to working on cars. Truck specs as I know them: 140k miles, used as a farm truck it's whole life. The engine area is caked in dirt, so I mostly believe it.

The immediate engine issues I have are these:

1. Intermittent stumble. Every like 3-4 seconds, the engine will quickly stumble and recover. I've tried to capture this on camera, but it doesn't work out well.

2. White smoke under load and now when revving. The smoke used to have a strong diesel smell, now it's kind of sour/burnt. Videos -

While revving -
Under load -
3. I recently replaced the CDR valve, but I ran the truck without the valve just to see. Zero blow-by with the valve installed. Some smoke with the valve off. Not too sure how that makes sense.

CDR valve off (sunlight) -
CDR valve off with oil cap flipped -
4. Hard to start when cold. The return lines look terrible, so I need to replace them.


I think the truck needs new injectors and glow plugs, but I'm hoping the rings aren't fried...

The rings should be fine with 140K miles.

"Shouldn't" lol could be if someone used ether all the time.
I would say you have a fuel supply issue. Could be drawing in air, could be the injectors, could be pump. (In that order)
Either of which can cause your smoke and stumbling. But check for air first.

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DaveBen said:

The rings should be fine with 140K miles.

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I generally agree, but with unknown maintenance history, the smoke is a little concerning. On my to do list is checking cylinder pressure.

79jasper said:

"Shouldn't" lol could be if someone used ether all the time.

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This is my main concern. She doesn't like to start when cold, but when warm she'll go instantly. It's easy to imagine the prior owner getting tired of cranking and just shooting starter fluid in there every time.

I wouldn't worry too much. It's running on the original pump from 86. I'd get a new fuel filter, add some diesel fuel treatment to it, order some new injectors, and then look at advancing the injector pump a tiny bit. My IDI never used ether and I couldn't tell what the problem was... until I found the cold idle advance and high idle prongs not attached. Check for fuel leaks and I wouldn't worry about the blowby, that's normal on these.

Good luck!

And mine surged intermittently when I first got it, after injectors and a new pump it was fine.

Change the glow plugs, then see how she starts cold. Replace GP's with Motorcraft/Beru only.

Put a full can of SeaFoam in a low tank of fuel.

Fill the filter in the outer holes with SeaFoam, run for 4-5 minutes, let it set overnight, start her up, after getting up to temp, how's it look then.

That little bit of smoke your getting is kinda normal on a cold engine.
What do you get when it's up to temp 180 190 degrees ?

OLDBULL8 said:

That little bit of smoke your getting is kinda normal on a cold engine.
What do you get when it's up to temp 180 190 degrees ?

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I'll try the seafoam trick. I let her get warm, but the temp gauge just barely crept into the low side of the normal range (she was about 150-160, checking with temp gun. Still got a puff of smoke when I gave her gas, but if I held her at 2500 rpm under no load, no smoke.

This also is a new development. I recently changed the oil and filter with motorcraft 15-40 diesel oil and a motorcraft brand filter, and the oil pressure gauge is pegged at the lower side of normal (even when revving the engine). Not sure what oil was in there before.

That gauge really doesn't mean much either. You need to have a real gauge in order to see what your oil pressure is.

Rossroams said:

I wouldn't worry too much. It's running on the original pump from 86. I'd get a new fuel filter, add some diesel fuel treatment to it, order some new injectors, and then look at advancing the injector pump a tiny bit. My IDI never used ether and I couldn't tell what the problem was... until I found the cold idle advance and high idle prongs not attached. Check for fuel leaks and I wouldn't worry about the blowby, that's normal on these.

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That blowby is normal? My Dad's '86 6.9L Doesn't have any at all, at 377k miles.

Yes, idis always have a ton of blowby which goes through the cdr and is burned. As long as the cdr is in place, you won't see it.

The small amount of smoke looks to me like blue smoke.Not white. White smoke means we have a new pope...... For the miles on the engine my best guess is the pump and for sure the injectors are worn out. Might try changing the injectors for a new set. Also this is a great time to replace the return line kit too. Just be sure to clean off all the dirt. No telling what glow plugs are in the engine. NEVER use champion or autolites.. Or for that matter use only the Beru Motorcraft plugs. Being an 86 engine you could have spade or bullit connectors. Best to check before you buy. Just remove a connector to any easy to reach glowplug and see if its bullit or spade connector.

Now that I'm on my computer(vs my phone), this is just plain retarded timing due to IP/injector wear.

The 'right' thing do do is replace both.

The 'workaround' is to just advance the IP a good 1/16"-1/8" and hope it's enough. Last time I had smoke issues on an IP, I basically had to crank it all the way as far as I could towards the passenger's side to get enough advance out of it.

I've also "skipped" the IP gear a tooth forward(clockwise) compared to the cam gear that drives it, which gives about 6 degrees of advance.