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.

Bad fuel, plugging filters, bad lift/fuel pump, got cracked/rotten fuel lines causing air leaks, injection pump going bad, bad injectors.

Updates??

Please update. :pca1:

Sorry about that. Still working on this thing.
Some snow has held up progress but I am taking it all apart and cleaning everything out. Injectors were fine and so was the lift pump.
I ordered a new fuel return line as it was toast, I'll update again as soon as that comes in.

I want to say you got a short or dirty connection. But where is the big question. If you haven't already, chase em all with electrical contact cleaner, especially the PMD. Which might even be the problem.

Well. Replaced the line and replaced the PMD. Now the truck pours white smoke at an idle, just plain dies if driven more than 20 feet, and does not start unless the pedal is to the floor.
The only thing I found entertaining today is the truck makes perfect smoke rings. :nope:

White smoke is usually coolant or fuel. Check the coolant level in the radiator, and if it's low, you got a head gasket issue. If not coolant, you got a bad injector or two. To find out which one, crack the line at the injector. If the engine rpm doesn't change, you found the bad injector or injectors.

It is not coolant, and I know which injector to start with. It is the only one that is not a Bosch. Long story but in short I sent one back due to defect and they sent me a rebuilt replacement.


Again,
Thank you for helping out with this. I would have been scratching my arse and doing the shotgun routine without the help.

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I believe I just found the problem :jump:
However solving it is going to suck :dang:

Allright, I could pass fluid through my return line and I could blow on the end with my lips and it would flow air nicely. I plugged the end of my air compressor hose up to the end of it a couple hours ago and it flowed for about a half a second before it plugged big time.
Instead of going the full bore 260psi routine, I am going to take the rear (long) line out and see if I can get it cleared out without being a butcher.

Bunch of crap in the tank, plugging off the sock??

Updates??

Not fixed.
Pulled the return line off the top of the sending unit and blasted it out so now it runs like crap again.

I need to take a day off of work so I can check some of the things that take time like drop the tank to check the sock.

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Somewhat fixed now.
Runs smooth up to 2500, at that point it either starts coughing or the power just suddenly drops off. It used to pull great to 3500.

The lift pump is supposed to run when the ignition is on and the truck is not running, right? Only asking because this one does not.

It'll kick on till it pressures up, then it'll kick out. Turn the key on, and listen, it'll run for about 3-5 seconds. Bump the starter, and it should run continuously.

Updates??

Pump relay is junk. Ordering a new one.

I think the white smoke was three things working against me. PMD had some stability issues, filter housing had a small crack at the inlet, and there was a chunk of rust in the return line.

Updates??

Please update.

Have you checked the lift pump? PMD usually doesn't have anything to do with white smoke, just rough running and most stalling issues. Also, make sure your vent on the top of the filter housing is closed after you get it primed.

Lift pump runs fine when power is applied to it.
I don't have a dry place to work on the truck at the moment so it is parked and covered in snow.

It runs fine until 2500rpm in any gear higher than first in any other hear it starts running way too lean above 2500, it surges like hell.
Another thing that tells me it is too lean is if I put my foot to the floor, it does not put out black smoke above about 2200rpm. It does not put out any smoke at all above 2200.
We bought the truck with a bad lift pump so I replaced it, after that the truck had lots more power and put out black smoke well past 3500.

At this point, I am about to kill something.
I am going to have to attack the pump circuit and see if there is something that is getting disrupted because the pump runs when external power is applied but I don't hear it run on its own.

Give me a few days on this while I find time to work on it.

Updates??

Please update.

Have not worked on the truck but I have narrowed the current problem down to two possible things since I have fixed everything else that was broken or rotted on the truck.

The lift pump is not working and if the problem is not fixed after that my only option left is the injector pump.

I know I have not been updating on this thread as often as I probably should but I don't have much time these days.

I am freaking out at the part where I am going to have to find time to rebuild the old trans and stuff it in the truck since I don't like how the current one shifts. Yes, the truck is a 5-speed manual.


I really appreciate all the help with this. I found a few problems that needed to be fixed and learned a lot more about diesels in the process.
I am most likely not going to be near a computer for the next couple weeks so you may do what you like with this thread.

Once again I would like to thank everyone here for helping me out.

first of all this is a electronic injection pump. where excatly are you getting your pmds. a good reputable source will insure you that you are getting a god pmd. once you get a good pmd you need to relocate it to the bumper so it does not overheat like the last one did. any codes? have you cleaned all the grounds? and i mean all of them. replaced any old fuel hoses? it would be best to just take the sock off because they always get plugged eventually, just put another fuel filter in to do the job the sock was doing. check coolant, and oil for any of it burning in the engine. check for any airflow restrictions on air intake and intake manifold. if you have ever seen the inside of a 6.5 intake manifold you know how much carbon those things can build up.

check to make sure your oil pressure switch is working, i would just run keyed power to the sending side of the oil pressure switch and see how the truck does with the pump running. is the check engine light on? when you open the little drain valve on the front of the IP does fuel come out while its running or does the engine just die?

Updates???

Please update.

I drove the truck a few days ago after getting the wiring nightmare sorted out. Lift pump worked fine and the truck ran great.

Lift pump just locked up on sunday and will not allow any fluid to pass through in either direction...

All problems found and I am in the process of fixing the thing once my driveway thaws. I worked on it last night until I slipped on some ice that had a little fuel on it and knocked myself out cold on the brush guard (at least I think that is what I hit). :ouch:

You may lock this thread or do whatever. I know what the two problems are with the truck and will fix it once it is safe to do so. Fuel pump and clean the sock/ inlet lines.

I really appreciate the help a lot. Thank you To everyone that has helped.

Ok, I'll close the thread down. Remember, you can reopen it if you happen to get the issue fixed.