Hi --

I have an 84 f250 6.9 that I bought 3 years ago from an old farmer who had bought it new. He maintained it well, but wasn't easy on it. It had 144,000 miles.

First year it ran ok. The second year I had a lot of white smoke and was sluggish. I changed the glow plugs, injectors (rebuilt), fuel filter, return lines and replaced all the rubber portions of the fuel lines, but saw no improvement. Previous owner had bypassed the water separator.

I replaced the injection pump and took it to a diesel mechanic to time. I also had him test the compression. He said he timed the IP the best he could (a few degrees toward the drivers side), but the compression numbers were terrible and recommended an overhaul. He said the compression numbers ranged from 150-170 except for 1 cylinder which was 450 (don't remember which one). I didn't want to spend the money on an overhaul and took it home.

I tested the glow plugs and most of them were burnt out (my son mostly drove it, has manual switch), so I replaced them again. I changed the oil and added a can of Engine Restore. Since then it seems to have enough power and starts right up. White smoke is minimal except during hard acceleration when it is sometimes moderate. Now it has 147,000 miles.

For the past two years I've debated getting it overhauled. I would like to fix it up but not until I had the money to overhaul it. I'm mechanically inclined, but I have never done a complete overhaul.

From reading a lot recently I began to doubt the mechanic's diagnosis. It still runs good, idles ok, ok power, doesn't burn or leak oil, no oil in the coolant, starts right up. I bought a slightly used compression tester off Ebay (Mityvac mv5535) and tested the compression this morning. I did it on a cold engine (I know it should be warm) and here are the numbers:

1 345
2 365
3 368
4 346
5 356
6 380
7 367
8 347

These numbers could be higher, but they don't seem like time to overhaul numbers. The difference between the highest and lowest is 10%. They make more sense than the mechanic's numbers given how it runs.

So, you guys think it still needs to be overhauled? If not, what else should I check to explain the white smoke on acceleration?

Thanks!

 

For what its worth, Ford recommends if the lowest reading cylinder is within %75 of the highest reading cylinder, everything is normal.
In your case, you're less than halfway to that mark, so by their books you're A-OK

Also, the Ford table only goes as high as 440 for the maximum cylinder pressure, so the 450 may be a bit odd... also, unless you saw him do it, don't assume the mech timed it using the right equipment (and tables, if it was a lumy probe method) in my experience, this is usually not the case...

 

Thanks I was thinking of getting it re-timed

 

That compression looks good to me. Ive heard of some 6.9s being over 500, but so long as theyre all close it should be fine.

What you describe could be very possible, as far as the rings being gummed up and not sealing correctly. Search Engine Rx or something like that theres some guys that have done it with awesome results. Im planning to do it before i tear mine down for some minor refreshing. Planning on adding a bypass filter as well.

 

You mean Auto-Rx? I'll do some searching. Thanks.

 

Yarp thats the one

 

It sounds like your pump needs advanced or isn't working properly...and you say its only on accelleration...is it a solid stream of white smoke

 

Yes it is. It's a reman IP and I've wondered if maybe it's not that good. I'll try advancing it a bit. Thanks.

 

Just make sure you advance only a tiny bit at a time... you can burn your GPs if you go too far (and generally run too hot)

 

Thanks I advanced the timing a little at a time now more power and just a little smoke on hard acceleration, but now it's black so I think I'm good!