6.5 bucking at part throttle rough idle

[PhattDaddy94HD]

OK guys I need to know where to use my biggest hammer on my truck! I just relocated my pmd to behind the bumper with kit from Leroys Diesel (new pmd). It runs better down low but at hiway speeds it starts bucking when you level off and try to maintain a steady speed. It did this before I replaced pmd so apparently there is another problem. It did not kick any code while on test drive (about 10 miles city-hiway). When I got the truck the lift pump wasn't working, I replaced it with the Wallbro unit and found out my ground wire in the truck harness was bad so I grounded pump to the frame and seems to work fine. I changed the fuel filter in December so I'm not shure how often that should be done either. I've heard of excessive wear on the injector pump on Dodges (excessive timing fluctuation) when the lift pump isn't working. Truck runs good under pull but doesn't have good "manners" under normal driving conditions. Any ideas are greatly appreciated. Signed, LOST IN 6.5 LAND:nonod: PhattDaddy94HD

 

[Burning oil]

Had a 94 with simular issue. It was the tank sock on that one.

 

[hookedup50]

Clean the engine to frame to body grounds as well. They are on back of intake on passenger side.

 

[JiFaire]

Sounding like fuel delivery issue. Where is your fuel pressure gauge tapped in?

If not to the delivery line (from LP), then:

Step 1: get a fuel gauge and about 6' of rubber hose, a few small hose clamps (for the fuel gauge and the WIF Drain), and a zip tie or electrical tape (to tie the gauge to your wiper arm, so you can see it out the windshield)

Step 2: Assemble from WIF drain to gauge, put it all in place, open the WIF drain (Brass T-handle)

Step 3: go drivin'. Try not to drive into anybody while you're squinting at the gauge taped to your wiper.

What to look for:

Make sure that, whenever you have the 'bucking', you have fuel pressure. If you do, it ain't the cap, sock, lines, LP, filter, anything up to the FFM.

If you don't, it's one (or more) of those things.

If it ain't one of those things, then it means you look for grounds, APP, ECM, PMD, RF Filter (yeah, you have a 94, so it might be there), etc.

You might also make sure you don't have any catchy square dance music playin' :hihi:

 

[ak diesel driver]

if fuel pressure/supply is the issue you also may need to change the OPS on a 94

 

[SmithvilleD]

Just catching this issue started in this thread - responded to the other thread as well. If this behavior is happening very consistently, it might help to hook it to my GMTDScanTech & see if anything odd fueling-wise, etc., shows while it's doing it. I'm in Smithville, so fairly closeby. Won't have time away from work until Thursday next week (Aug 8th or 9th) but would be happy to try help then.