No compression in Cylinders 4, 5 and 6 Help

Most likely the OP isn't going to see this but here goes anyway

Did you have problems with the batteries in the EPU?

If not, why the hell did they even touch the EPU batteries? Did they actually test them and show you they were bad or just say they were?

I had a FL dealer replace 4 new batteries on a driver without even testing them, I told the shop manager to put them in the side box of the truck and I'll pay the core after dealing with a driver who refused to pay, NOT ONE OF THE BATTERIES WAS BAD when it arrived here, they were holding a great charge and I put two in my beater truck and they are still being used after three years.

They ran a relative compression test which is a "let's see if we have to run a mechanical compression test". IF they are a Detroit Diesel shop (meaning they represent DD) then the moron mechanic ignored DD explicit instructions to confirm each "below 85%" result from the relative test by doing a mechanical test on each cylinder.

This tells me that your valves may be too tight, did you do the overhead or did a shop do it? I was told (maybe they are wrong) but the back bank of 3 needs to be a little loose, especially 6.

That's good, hope nothing happens on the way back to chicago.

If it is YOUR truck, why are they doing anything to it?

Bring it to a Detroit Diesel shop with a good reputation.

Maybe, I would just Go Go Go (safely of course).

Dealers employ part changers, not mechanics. Mechanics troubleshoot problems, they know before hooking up the computer what a problem could be.

 

Good luck with the ride home. I understand wanting to get home where you can be comfortable with the mechanic and sit home, Not in a waiting room.

 

Man, you just got a bad tech. I would bet that batteries were weak, Truck cranked slow, ether helped it start for that and only that reason. 2019, runs great. Started fine this morning. Forget everything and run the Truck. There’s nothing wrong with it. Save your money. Don’t waste another dime trying to diagnose something that doesn’t exist. Reminds me of an old saying. If you go to a barber, you’re going to get a haircut. Be glad you didn’t let them start tearing apart your perfectly fine engine. No telling what the end results wound be. Probably a whole rebuild or reman engine, costing more than the Trucks value.

 

It’s your money. I would talk to your Mechanic that did the overhead, if worried about it. No need to try to buy peace of mind. You already paid that bill. Should be good for at least a year and 100k. If it’s running good, getting good mpg’s, I’d leave it alone,

 

The one time I had to use ether. It was because the fuel pump was sucking air. It was only a problem when the tanks were less then half full. It also had erratic idle. As long as the tanks were above half. Nothing was wrong.

Later on that same truck lost 2 cylinders and was adding fuel to the oil. An overhead cured that problem. But I had to limp it home on 4 cylinders. That was not fun with a load.

Ether I'd say you had a fuel problem. If 3 cylinders were indeed down. Even bad batteries would crank it over fast. Since there's no compression. If only 3 cylinders were firing. You won't be packing a load anywhere. The truck would be shaking also.

I don't know what kind of damage a semi motor would suffer packing a load on 3 cylinders. But I can't imagine it be pretty. Definitely won't do the dpf any favors. You could be looking at an expensive motor repair PLUS emissions repair.

When there's popping out the intake or exhaust. It's a valve problem. Your overhead might be too tight.

You said the truck started up. So it was probably high time for new batteries. And there's nothing wrong with the motor. I'd probably have the overhead rechecked. But those reports don't make sense. I don't think that mechanic was accurate in his diagnosis.