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truck is bucking bad pulling my trailor bad!


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I'm sitting on the side of the road waiting for somebody to fold me meantime I'll tell you my symptoms

The truck started bucking a few days ago so i shut off my tst and it seemed to help. Now coming home today from work doing 70 on the highway the truck started bucking? Worse when i went up hill. Fuel pressure is good yo the pump engine is not hot, checked the tranny its good. I dont know? Any suggestions? Could the vp be getting weak? No codes either?

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we are at the trailer and I drove it home. I don't get it something's wrong though?? It didn't even buck or nothing?? Anybody got any ideas

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Bucking could be the VP. What kind of fuel pressure are you seeing at idle and WOT?

--- Update to the previous post...

I had bucking issues with Mine several years ago. We detirmined fuel pressure was very low and I added a booster pump to the fuel system and got the pressure up ot a safe level. This really helped with the issue but did not copletely cure it. I also had some dead pedal issues also. I got by with this for 2.5 years and finnally replace both the VP and the fuel system. No problems since.

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I am not trying to tell you to run out and buy a new VP. Some more diagnotics need to be done before you spend that kind of money.

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It started doing it before I changed the fass to the 165 Airdog. That was why I changed it. I figured maybe the pum being 8 years old it waas getting weak because the pressure at wot was at 8-9.

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Mine did it underload especially pulling the fifth wheel. I dont remember it happening while I was empty. Do you know what kind of pressure the Fass is putting out?

What was wrong with yours
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It started doing it before I changed the fass to the 165 Airdog. That was why I changed it. I figured maybe the pum being 8 years old it waas getting weak because the pressure at wot was at 8-9.

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What was wrong with yours

Low fuel pressure. It had started the bucking and dead pedal. Thats when I found my pressure to woefully low, in the nieghborhood of 0.5 psi and wot. I installed a booster pump and got that pressure up to 13 or 14 psi at wot and 17 at idle and my problems greatly diminished but were still present. I am sure to low pressure damaged the pump, but ran it for another 2.5 to 3 years. I was very lucky to get that much out of it. some wont last a day withthose probems. The truck started acting up again so I bit the bullet and bought a new pump and before I could get it on the ECM crapped out. Thats another story though, but probably compounded the issue.

before it was over with I had replaced my VP, APPS sensor, ECM, and about 2months later an ADII 165 like you. And last but not least a fuel pressure gauge. Very important to keep an eye on that all the time. I am convinced the low pressure is what ruined the pump. Do you know what pressure your AD is putting out?

The 8 or 9 psi you had with the fass, was that checked under load or just fre revving?

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Under a load, towing my company trailor. I would se the readings like that when I was flooring it to pass someone. That is why i changed the system. I am waiting for my fuel pressure adapter to come in, but I doubt its the brand new AD 165. However you never know? I drove it around today and had no symtoms! This is a mystery for sure! Im losing faith in these Cummins really quick I hate to admit! It just gets the best of me when I see it sitting there not making me money.I really appreciatte any advise know matter what it is. Opinions count!!

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Some damage has already been done and the best pump in the world will not overcome it. The new pump will help and you can probably get some more life out of the vp. The new pump I put on mine helped and I got alot more life out of it, but it still acted up occasionaly and intermitantly. Might run grat for a month then act up a couple days in a row. No rhyme or reason to it. I finally changed it out so it would not leave me stranded.

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