24 Valve misfire? Help!
 

Towing my jeep (about 5.5k lbs with the trailer) to Rausch Creek this weekend I noticed the truck sucking a whole helluva lot more fuel than usual. I'm talking 8-9mpg. I also noticed 1100* or so EGTs on hills. FWIW, I tow on lvl 2 or 3 usually. Never have I had EGTs over 1000 towing to Rausch. I was on 2 to begin with, when I noticed the EGTs I dropped it to lvl 1. This helped some but I was still over 1000.

I also noticed on the way home, when I got stuck in traffic, the truck almost sounded like it was misfiring. If I lugged it into 3rd and 4th slighty it sounded like a jake brake. Cool and all, it's not normal.

Any idea whats wrong? There were no CELs. Boosts fine, 20-25 psi peak on the hills. Fuel pressure was maybe a little higher than usual, but I just put a new lift pump in.

I'm at a loss. Kinda thinking it's a clogged/toasted injector. I don't know how that would over fuel though.


Today I decided to try unplugging the Edge box to see if it was the problem. No change, but a CEL came on. I will run the codes when I get a chance.

Am I right to assume it's an injector issue? I don't mind upgrading, but I want to be sure it will cure my issues.

I need to move to Illinois in two weeks. I'd like to have this fixed before that.

From just the quick version of what your sayn here it sounds like a classic toasted VP44. But cosed should tell more.

Where you movin to here in this fine state of ours.

Peoria. The VP44 is new as of Thanksgiving. I'm still thinking it's a stuck injector but I can't be sure.

Just one bad injector wouldn't make nearly that big a difference. Matter of fact you really can't even feel one bad one in these mighty Cummins engines, they just keep chuggin like nothins wrong.

The other possibilty is that the APPS may be way out of adjustment or bad. Give me a minute and I'll find the directions for it.

Here's for the APPS: https://www.dieselbombers.com/5-9l-2...s-i-bored.html

Some of the best explanation of your fuel system your will find anyplace: https://www.dieselbombers.com/24-val...el-system.html

Wow, I totally forgot about that. Sometimes starting off at a light if i'm feathering the throttle (slow pokes in front of me) the APPS quits responding until I let off completely and get back on it. Sometimes it even stalls because I actuate the clutch normally.

Do you think that would make a loping sound though?

Mine did the same thing,only no lope till it was terrible.
It was a VP

This VP has 5k miles on it. If it's the problem i'll be pretty surprised. I think tomorrow i'm going to check the APPS voltage and adjust/reset it as necessery. We'll see where that puts me.

I'd be surprised too,just sayin's all:ouch:

The other possibilty here is the pressure valve on the outgoing fuel side of the VP44. It's the banjo bolt with the spring loaded ball bearing in it. When you replaced your pump did you also replace this check valve. When they go bad they do all kinds of bad things to the pump depending on how they hang up.

I can't seem to remember. I know the pump came with one banjo bolt and I had to reuse the other one. I'm assuming thats the check valve you are talking about. I remember it being much larger than the other one.

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That would suck wouldn't it?! I'm hoping it's something simple.