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Cummins Stutter - Fuel lines

CHOP SHOP

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Joined
Sep 13, 2007
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11,498
Location
pierce county
I have a 98 Dodge Cummins 12v thats stock. It has a problem. It is a great running truck, most of the time.

It first happened a few weeks ago. I started it up after letting it sit for 4 days (never sat that long, daily driven usually) and it started right up and ran for about 30 seconds and started running very rough and losing RPMs. I brought the RPMs up for a little while till it cleared out. Then it was fine. Was fine for a week of daily driving, then it hit again after letting it sit for three days in a row. Same thing as before. Then it did it three times this weekend on three consecutive days in a row.

It never had ever done it after the first start of the day either. Only does it the first time its lit off in the morning. You can stop as many times and shut it off and restart it throughout the day and it wont do it, only the first start of the day.

I think its sucking air in somewhere on the fuel lines. This is getting worse. I have heard a few things about cracked fuel lines and an upgraded part form dodge too. Do I need this upgraded line or can I make it myself? What fittings/line size do I need? Is at the frame to engine area? or the frame to take region? or steel lines between? Could it be sucking air at any of the fuel filter junctions?

Whats the common problem I should look at first?

could this be an inj pump on the way out? Or will a bad inj pump just die?

Thanks for the input!
 
i had a similar problem on a 4bt cummins generator the other week, if you dont know gensets exercise once a week and sit the rest of the time. so its a similar situation. What happened is the stanadyne db4 (rotary pump not p pump style like your 6bt)
stopped putting out the correct pressure. it would stutter at first for a while then it would warm up, and the fuel would expand and run fine. what i determined is that the fuel was 12 years or so, it lost its lubricating propertys and wore out the pump. i threw on a new pump and it ran great. dont know if this will help you but what the hell:stirpot:
 
I havent had the truck for two months yet. Isnt there a prefilter too?

No prefilter on your truck, unless someone added one...Check the rubber lines going to the pump under the intake...but usually you'll see fuel leaking...it is entirely possible you have a pump going south. Just diagnosed one at work! Did alot of whitesh blue smoke come out tailpipe when the stumble is happening???
 
Definitely sounds like the fuel lines are cracked. These pumps don't go out very often. So I wouldn't jump to that conclusion quite yet....
 
no smoke that I noticed. When its cold it will have a little grayish black smoke floating around but nothing when its warm. And I mean a little, very faint.
 
Mine did something similar even after a new fuel pump and a new injector pump. It would just die even at some rpm's. It wouldn't start. I noticed fuel dripping from the fuel line on the driver's side just before the injector pump. There was still a factory hose clamp spring type thing on there. I put a regular hose clamp on and it has been fine for 2 years now.
 
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