I'll give you a little history on the Truck. And I am a Mechanic, just lost with this one, and so are the other local diesel shops.

It's a 95 Chev 2500 6.5. Bought the truck with blown engine, had it rebuilt. This summer put a set of injectors and glow plugs in it, lift pump/oil pressure switch/relay. Among other things. Everything has been working fantastic since. Starts at least to -20 as that's as cold as it's gotten here so far, not being plugged in.

What's been happening is when it's cold, sitting for about 3 or so hours (it's about -10 here right now) when I start it, she misses. Misses until it gets hot, even on the highway, it won't stop missing until I throw it in neutral and let the RPMs come down. Then it's good to go. No unusual smoking when starting or anything either. Caught it today when it stopped, hopped outta my truck, while letting it idle, hammered a couple times, then quit missing. Sounded like an ether type knock, when you use that crap, about that loud.

First time it started missing, it was missing on #1, so pulled the injector, looked like it was stuck open (soaked in fuel), put an old one back in and had that one rebuilt. They found nothing wrong with it. With the old injector it did the same thing anyway.

I know it cant be valves, as it's too quiet for that, and it goes away hot. Can't be injector, unless 3 have been bad in a row somehow. Injection pump I've never seen make miss on one cylinder before, and to my knowledge, not even possible.

Can anybody point me in another direction to look?

Thanks

 

Is it the electronic injection pump?

there is an optical sensor in there and it's possible the fuel being cold it's getting cloudy and causing an issue with the timing momentarily?

 

What is the micron rating of your filter? I don't feel comfortable unless the last filter in line is 2 micron. Maybe you got a bad batch of fuel and some of it's getting by your filters.

 

thing is if it was the optical sensor it would miss more than just on the one hole, and the same hole #1, everytime I've had one go, the truck is hard to start (mine fires right up) and when it does it runs terrible (mine runs well, as far as a missing engine goes).

It wasn't the fuel, I thought that as well, so ran that tank out, and got some fresh fuel in it. Same problem, misses cold, good hot. I don't know what the micron rating is, but I change the filter every oil change, and I only use Wix filters on everything I own.

I'm starting to think it's in the pump. There's not much else that could cause this. I may just pull it off and take it apart to check it out. I've never had one apart but can't be that complicated.

 

Do you have the fuel heater working on the truck? You may have fuel starting to gel.
What brand of injectors are you getting? There are a lot of cheap brands out there for the 6.5 that can cause problems. I would make sure they are Bosch or another good manufacture.
Taking the injection pump apart is fairly complex and unless you have the proper stuff to do it I would not attempt it.

 

Never checked the fuel heater, but even if that weren't working it wouldn't just miss on the one cylinder all the time.

Injectors are the marine ones, forget the brand. Pulled the one that's missing out and had it checked by a diesel shop and it tested good, also, put an old injector in so I could drive it around while they did that, and the old injector acts in the same way, changed that one too and did the same thing again.

I'm not afraid of taking it apart. I've taken apart way more complex things in my time than that. Just a matter of whether my information at our shop has has all the tolerances and clearances in it. Never looked into it. If I can find anything it'll save me 600 bones on a rebuilt pump so it's worth a shot imo. I'm just convinced it's in the pump. There's just nothing left I don't think...

 

Could be a delivery valve issue?

not sure if those are replaceable on that pump as a single piece or not it's been awhile since I looked at one.

 

I have no idea, but I did just remember this morning that I have a pump off another 6.5 at my shop, that I believe is mechanically sound (been sitting there for about 5 years) I may just pop that one one and test it that way. Even if it isnt, as long as it does something else I know where the problem lies then.