Just picked up a new tow rig (93 f250 7.3 IDI turbo 200K miles). As stated in the title it smokes badly (white, heavy fuel smell), and skips at idle to mid throttle (clears up some at higher engine speed). I have done cylinder balance (crack each injector line and see if idle worsens), and was unable to find any dead cylinder. I also checked for air in the return line to the filter housing. Any ideas what to try next ? (trying to borrow compression tester+ adapter today, already checked for worn thru rockers) although both of those would show a weak/ dead cyl not a roaming skip. I also used a IR thermoometer to try to find a cold exh port but all were pretty consistent.
Any help would be greatly appriciated.

White smoke makes me think headgasket- any signs of coolant loss/overheating? Maybe a compression test will tell you more.

Check the IP timing- these motors are very responsive to timing changes. You'll probably need to have a shop do it unless you have the special tools.

Maybe run a search over at oilburners.net. Pretty good info for these trucks

i would change the fuel filter and fill up the new one with power service, then put the rest of the bottle in the tank. maybe you have older gummed up nozzles.

The bad idle happened to a friends Cummins. It ended up being the crank position sensor. He didnt have the smoke though.

The bad idle happened to a friends Cummins. It ended up being the crank position sensor. He didnt have the smoke though.

No electronics on the IDI trucks. One wire to the IP and thats it

Concerning overheating, Ran cool for the 120 miles back from the auction I picked it up at (going by factory guage), no signs of coolant loss (rad/ overflow was full when I left and still full when I got it home. The reciepts that came with the truck indicated new fuel filter and a few hours labor > 20 miles before I bought it (filter looks new too). I noticed today that the ramp on the throttle that actuates the advance (? going by some exploded views from intelidog.com) is severely worn (especially at low throttle where the skip is worst). Not sure if this is in any way related to the problem at all, just an observation. Hopefully I will be able to get the guage and adapters tomorrow. Thanks again

White smoke is unburned fuel most times. Thermostat stuck open? Timing off due to worn out IP pump? Back with good diesel the pumps were usually only good for about 100K miles, then they started doing all kinds of weird things.

White smoke is coolant getting burned - IE head gasket

Blue smoke is oil getting burned - IE blow by due to bad rings

Black smoke is unburnt fuel - IE to much fuel pressure or a bad turbo (even though you don't have a turbo on your IDI)

White smoke is coolant getting burned - IE head gasket

Blue smoke is oil getting burned - IE blow by due to bad rings



yea... wrong on both accounts. partially clogged injector with low pop pressure = thick clouds of white smoke.....

bad ksb, cold starts, large injectors with bad spray pattern = blue smoke/ hazing at idle/cruising.

If the advance isn't sticking, and the timing isn't out of whack, I'd vote for a dying pump.
Does it run like this?
http://www.bigblocksix.com/f100swb/81f100/oct05/MVI_2391.avi
http://www.bigblocksix.com/f100swb/81f100/oct05/MVI_2392.avi
That's a pretty much dead IP.....