Engine: 87 6.9 idi, 176k miles

I almost got stuck at work today, because my truck was having a time starting. I let the glow plugs cycle normally (40 degrees outside), then when the light went off, I turned the key and the truck cranked and cranked but wouldn't start. Every now and then it would catch a little, but wouldn't start. I turned the key off, back on, let the plugs cycle, then tried again. Like before, it just cranked. After a little while, it caught enough to start, then idled for about 5 seconds then shutoff. Repeated the process again, and the next time it started it continued to run. The only problem, was the idle was rough. It was fluctuating between 900-1000 rpm, and was choppy.

I left for home, not wanting to get stuck at work. A little ways down the road and at a stop sign, the idle worsened. While driving after that for about a half mile, sometimes it would feel like the pedal stuck because the truck would take off faster than I was pushing the pedal down. By the time the truck had warmed up to operating temp, I didn't have any problems. Idle was smooth and 600 rpm, accelerating and decelerating was normal. When I got home, I started it up a few times, and all three times there were no problems.

I was thinking maybe it was a glow plug problem, so I pulled the no. 8 plug to start, and tested it for resistance. It was registering at just above 1 ohm. The stem was coated in a thick layer of soot, which I don't know if that is normal or not. I'm in the process of checking the other glow plugs for resistance. At the same time though, I'm not sure if bad gp's would be causing a rough idle.


Any ideas?
Thanks
Jameson

 

Update. Pulled all the plugs. Cleaned them with acetone, and they all tested good, going form .5 ohms to 3 ohms

 

Sounds like you had air in your lines, start it in the morning and report your findings to the forum sir.....I had issues like that when I needed a return line kit.

 

The next morning, the truck started fine, but about five minutes after starting the choppy idle came back. And once again, when it warmed up it went away. Still had the "catching" deal when accelerating, where it seemed like all of a sudden I floored it, when I didn't actually move the pedal. That night, when I left work the the truck was fluctuating between 500-900 rpm at rough idle while at a stoplight. Almost quit out on me, but I kept it running. Went to the gas station and got a full tank of fuel plus some diesel conditioner in the back and switched over to that (had been running on the front tank), and the issues seemed to have gone away. The fuel in the front tank isn't bad. I had just put it in. Rough idle came back this morning, but not nearly as bad as before.


Jameson

 

I second the air in your fuel lines, and you are correct, GPs do not affect idle.

 

Some type's of fuel fillters have water drains on the bottom, you can open this valve when the engine is runnig and push out water and debris ,(some idi's have a hose atached to this drain ) if you can catch the fuel comeing out on a paper towell, you may see darkish dirt looking stuff and water,,may be time to change fillter? ,,some times if shower head in tank(fuel pick up) will rott off and start sucking air below 1/4 tank...poss air intrution elsware..