12 Valve 2nd Gen Dodge Cummins 94-98 Discussion of 12 Valve 5.9 Liter Dodge Cummins Diesels with P7100 Injection Pumps

truck keeps losing prime! where to start?

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Old 10-10-2010, 04:34 PM
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Default truck keeps losing prime! where to start?

1996 12valve air dog system on it 370 injectors no plate....

ok just changed the fuel filter(such a pain btw)
soo where do i look next it still starts just have to bump the starter a couple times to get the fuel up there... is the lift pump on my truck not there anymore since i have the air dog? and what else could it be
 
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Old 10-10-2010, 06:13 PM
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Go over all the lines and fittings to check for air leaks
 
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Old 10-10-2010, 06:13 PM
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check to make sure every inch of the the supply and return lines have no holes in them what so ever.. espically when it switches to rubber line which is under the driver seat along the frame. see if your injectors are leaking and also check the over flow vavle, which is the banjo bolt that comes off the side of the injection pump on the side closest to the motor... towards the front of the pump. and as a last resort. your injectors could be leaking fuel into the cylinder after it sits for a while. (like mine was) so have your injectors pop tested. that should give you a pretty good start
 
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Old 10-10-2010, 09:05 PM
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that is alot of good info thank you both! another question is if i had an air leak in a fuel line wouldnt it have some white smoke when my truck is roalin coal? im kinda new to my own diesel but ive worked on other peoples before...so forgive me if i have no idea what im talking about haha
 
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Old 10-10-2010, 11:33 PM
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If you got your fuel turn up, you wont notice it. but your'll feel a loose of power.
 
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Old 10-11-2010, 10:03 AM
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what mine did was when it sat for more than a few hours it would turn over for 10 seconds before it got enough fuel to fire, and when it did it blew a bunch of white smoke and popped. one more thing about those rubber lines, they might not be leaking fuel, but could be sucking air, so if they look old and rotted, replace them
 
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Old 10-11-2010, 12:50 PM
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ok quick question i have the air dog system so arent the old lines not even being used can someone explain to me how those are routed or which is pulling fuel...and do i still have the stock lift pump working also?? soo confused
 
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Old 10-11-2010, 12:56 PM
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the rubber lines just run on the driver side of the frame in the c-channel. no the stock lift pump is not used IIRC. theres 2 fuel lines, return and supply, the supply is bigger then the return but i cant remember the sizes.
 
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Old 10-12-2010, 07:52 AM
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so does it matter if there is holes in the stock fuel lines...cause im guessing they arent used as a fuel supply anymore i should just be checking the air dog and the overflow valvE?
 
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Old 10-12-2010, 09:19 AM
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yeh you wont be using the stock fuel lines anymore, all your fuel lines are rubber now, i'd check just to make sure they arent rotting but they shouldnt be. replace the ofv which you can get off ebay for like 30 bucks... and pop test the injectors
 


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