94 6.5 Chevy misfire and smoke
 

I am almost at a total loss with this truck.
It has 181,000 miles on it and it has been running great until two days ago.
Everything is original on the truck except the short block was replaced about 80,000 miles ago.

The truck had a bit of a power loss a couple months ago and I really never thought anything of it.

I went to change the fuel filter and ended up pulling the housing out due to a lot of debris at the bottom of it. I changed all the fuel lines while I was there as they were all split.
Put the new filter in, bled the whole system and fired it right up and drove it around for about 45 minutes, went home and parked it.

The next morning it started up and was idling smooth, went inside for a few minutes and when I came out it was off. The second time it did not want to start easily but it did and ran fine for about a minute and a half then ran like hell (Misfiring, smoking, whole truck shaking).
It does not matter if it is started blistering hot or cold and it runs just as rough no matter what RPM.

Here is a video of the problem. It runs smooth until 1:35.
http://videos.streetfire.net/video/1994-Chevy-65-Turbo_718636.htm
I am quite new to diesels so I really don't have much of an idea other than it may be the PMD but that sucker is $300 and I wanted a second opinion first.

I like this truck a lot and any information to help me get it fixed would be greatly appreciated!


This site has helped me out a lot in the past when I did a water pump on a 2001 Duramax 6.6, so you guys were my first thought when I ran across this problem :U:

We don't see very many of these, but lets see if we can help.

Is this an electronic or mechanical pump?

If its mechanical, what changed at 1:35 that could have caused it to run rough? My speakers aren't so good, did it kick down off a high idle?

The last time we saw a truck run rough and white smoke the injection pump was shot and the injectors were sloppy. According to our injection shop, 6.5 injectors get sloppy after about 60k miles.

By the looks of things, it is a mechanical pump.
I changed all the injectors about 20k miles ago when I changed the fuel pump.

The only thing that changed was the idle sped up for a second then it started running rough. Before that it idles at 500rpm smooth as can be.
After it starts running rough I can shut it off and start it up again and it runs smooth for another minute and a half before the process starts all over again.

sounds like a fuel pressure issue

One problem the 6.2 and 6.5 engines have is the return line check valve plugging up. The older 5.7 engine did also. The check valve has a glass ball in it and if it plugs it will run rough at idle and sometimes stall altogether. Take the return line off the IP, pull the check valve out and clean it to see if it helps.

Thank you! I will try this today.
This makes sense as There was a lot of junk in the filter housing and I just replaced the lines. My guess is there is a little rubber and probably a load of debris in there. I am really careful about keeping things clean but you know how that sometimes goes.

I'll let you know if this solves the problem.

Don't remove the ball all together. Fuel will siphon back into the tank from the return line, and end up sucking the injection pump dry. You'll end up running the pump dry starting up, and really shorten the life of it.

When you do remove the return line, you can blow through it into the tank to help clear any crap in it. If the check is full of crap, clean it and see what happens. If it keeps plugging up, the nylon disc is breaking apart in the injection pump and it's not long before your replacing the entire pump. :ouch:

Well, it wasn't the check valve and the return line flowed freely.
I drove the truck around for a little bit today. It revs freely and quite quick if I hit it to the floor for a moment and it gives out a healthy black cloud.
Sometimes I can drive it around in one gear perfectly smooth but when I lay into it a little it starts bucking and if I floor it and look back in the mirror, there is a white (well, kind of tan) haze behind me.

Sounds like the fuel pump isn't holding, causing fuel to leak back.

Any other ideas for me to try out tomorrow?
Just throw a list of things that could make the truck run rough and I will go from there.
The truck is about 40 miles from home so it takes me a while to get there and back.

I will take the pump off and see if it is working right. That only takes about 5 minutes.