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Old 03-13-2011, 06:10 AM
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Default Dodge Cummins P 7100 12V Starting Issue

I had a guy PM me on my youtube channel and he has an interesting problem that you guys might be able to help me out with.

hey man, I bought a truck awhile back , 96 dodge dually with the 12v, Bosch P7100 injection pump and the 5 speed NV4500,

I had noticed when you turn it off from being hot, you had to push on the pedal to get it started, if you didnt, it sounded as if the batteries were dead... both batteries were replaced with a bigger size, and I replaced the main power cable to the starter with something bigger along with a new starter.

why is this? somebody said vapor lock... but i personally dont know a great deal about these engines other than they are badass lol.

the guy never mentioned anything about mods, but It had dual 7" smoke stacks that are perfect size for the amount of smoke that comes from em, the pump looks stock, probably had a fuel plate, bigger injectors and the start wheel cranked all the way..

any idea on the starting issue?
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1997-12V-NV4500-Dana 80/3.54/2wd-350k---21-27mpg
Removed AFC--No Plate--13.5* timing--BHAF--5" Exhaust--Valair Clutch
1994-Jeep Cherokee-5spd-3.07-4wd-202k---16-19mpg

Last edited by stodg73; 09-15-2012 at 10:00 AM.
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Old 03-13-2011, 10:51 AM
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That is a new one on me. It spins over faster with light pressure on the throttle? If that is the case then someone needs to look at the ground to the engine. It sounds like the throttle cable is acting like a ground. It is also possible that without stepping on the throttle the engine has to spin more to start (typical 12V) and the starter is in need of some TLC like maybe starter contacts or even complete replacement. Oh, also mention that vapor lock is almost impossible with the fuel system on his truck.
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1996 RAM "Custom Ground" 100 plate 3/4 forward, 300 injectors, 16.5 timing, Goerends Auto = 365HP, 833TQ Third Gen Rims, Aluminum Headache Rack
Duct Tape can't fix stupid, BUT it can muffle the sound
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Old 03-13-2011, 11:24 AM
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If you read that again it says he replaced the starter. I actually have a youtube of my truck starting with and without pedal so I sent that to him to see if that's what it's doing. Also told him about the vapor lock thing. I asked if it did it cold as well, waiting on a response.
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1997-12V-NV4500-Dana 80/3.54/2wd-350k---21-27mpg
Removed AFC--No Plate--13.5* timing--BHAF--5" Exhaust--Valair Clutch
1994-Jeep Cherokee-5spd-3.07-4wd-202k---16-19mpg
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Old 03-13-2011, 03:46 PM
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Yep, hot and cold, needs throttle, same as most of us have to do.
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1997-12V-NV4500-Dana 80/3.54/2wd-350k---21-27mpg
Removed AFC--No Plate--13.5* timing--BHAF--5" Exhaust--Valair Clutch
1994-Jeep Cherokee-5spd-3.07-4wd-202k---16-19mpg
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Old 03-13-2011, 04:35 PM
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Musta missed the starter replacement, but it is possible that he got a bad one out of the box. Sounds a lot like he just needs to remember to give it a little throttle to start it.
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1996 RAM "Custom Ground" 100 plate 3/4 forward, 300 injectors, 16.5 timing, Goerends Auto = 365HP, 833TQ Third Gen Rims, Aluminum Headache Rack
Duct Tape can't fix stupid, BUT it can muffle the sound

Last edited by MnTom; 03-13-2011 at 09:06 PM.
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Old 03-13-2011, 05:57 PM
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You know, this problem plagues these trucks. I know they didn't do that off the lot. I wonder if the shutoff solenoid doesn't pull it in enough so it needs an extra kick in the rear.
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1997-12V-NV4500-Dana 80/3.54/2wd-350k---21-27mpg
Removed AFC--No Plate--13.5* timing--BHAF--5" Exhaust--Valair Clutch
1994-Jeep Cherokee-5spd-3.07-4wd-202k---16-19mpg
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Old 03-13-2011, 09:13 PM
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You can feel the throttle move when the solenoid pulls up so I don't think moving the throttle will help the solenoid pull up. I don't know why it helps to step on the throttle.
But, back to original issue, this sentence is the confusing one:
Quote:
I had noticed when you turn it off from being hot, you had to push on the pedal to get it started, if you didnt, it sounded as if the batteries were dead...
Does it pull the batteries down or turn over hard? Could it be that the positive cable between the batteries has a lot of resistance and it is drawing the one battery down?
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1996 RAM "Custom Ground" 100 plate 3/4 forward, 300 injectors, 16.5 timing, Goerends Auto = 365HP, 833TQ Third Gen Rims, Aluminum Headache Rack
Duct Tape can't fix stupid, BUT it can muffle the sound
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Old 03-13-2011, 10:03 PM
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I'm thinking he just assumed it was going slower and thats why it took longer to start. I showed him a vid of mine and he seemed to act like it was the same.
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1997-12V-NV4500-Dana 80/3.54/2wd-350k---21-27mpg
Removed AFC--No Plate--13.5* timing--BHAF--5" Exhaust--Valair Clutch
1994-Jeep Cherokee-5spd-3.07-4wd-202k---16-19mpg
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Old 03-14-2011, 07:37 AM
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That sounds like a reasonable explanation. Maybe he just needs be like the rest of us and just step on the throttle every time he starts it. I don't even think about it, I just automatically do it.
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1996 RAM "Custom Ground" 100 plate 3/4 forward, 300 injectors, 16.5 timing, Goerends Auto = 365HP, 833TQ Third Gen Rims, Aluminum Headache Rack
Duct Tape can't fix stupid, BUT it can muffle the sound
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Old 03-14-2011, 10:35 AM
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I just don't get why we have to do it. The rack moves forward when we hit the key because the solenoid gets out of the way, so stepping on it pushes the rack forward more. I am thinking the spring that pushes the rack forward or something gets a little weaker, because it will start eventually after 3 seconds or so. By stepping on it, it gives the rack a kick to get in the proper place. Hmm, that would mean you could tap the key so the solenoid would move, step on the pedal and let off, then start it and it would start right up. Only one way to know, but my truck is apart lol.
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1997-12V-NV4500-Dana 80/3.54/2wd-350k---21-27mpg
Removed AFC--No Plate--13.5* timing--BHAF--5" Exhaust--Valair Clutch
1994-Jeep Cherokee-5spd-3.07-4wd-202k---16-19mpg
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