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

98 12 vavle miss. HELP!

Old Sep 20, 2011 | 06:18 PM
  #1  
douger0500's Avatar
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Default 98 12 vavle miss. HELP!

I own a 1998 dodge 12valve. It misses when it free revs around 2000 rpms and on up. And blows a boat load of the "lack of fuel smoke." I just bypassed fuel heater in hopes of fixing my problem. I know the lift pump works well due to the fact when the filter drain is open it pulsates a **** ton of fuel everwhere.

I turned up the afc housing in hopes of killing the miss. Now it doesn't miss when under a load. Just getttin there is the problem.

Is there a valve on the return that could be letting my fuel all go back to the tank?

please help!
,Doug
 
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Old Sep 20, 2011 | 08:57 PM
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how many miles are on your injectors? pump timing? fuel filter?
 

Last edited by turbo2332; Sep 20, 2011 at 09:03 PM.
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Old Sep 20, 2011 | 10:45 PM
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Maybe time to adjust the valves? but yes, we need more info on the truck like mileage? stock or modified?
 
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Old Sep 20, 2011 | 11:05 PM
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Just because it pumps fuel dosn't mean it has enough pressure, first I would get a fuel pressure guage on it and go from there. There is an overflow valve, it's on the engine side of the injection pump right where the return line is
 

Last edited by tiremann9669; Sep 20, 2011 at 11:07 PM.
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Old Sep 21, 2011 | 06:00 PM
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280,000 fresh fuel filter didn't make any change. completely stock besides me turning up the afc housing. It does clear up a little once it warms up. I also wouldn't tthink lift pump is the culprit due to the fact after it hit's boost it smokes black

---AutoMerged DoublePost---

bump for some more advice.
 

Last edited by douger0500; Sep 21, 2011 at 06:00 PM. Reason: Automerged Doublepost
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Old Sep 21, 2011 | 06:02 PM
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Default Re: 98 12 vavle miss. HELP!

Timing is my opinion.
 
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Old Sep 21, 2011 | 06:48 PM
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just a thought,i would check the fuel lines where the factory line clamps that hold the lines to the frame will in time rub a pin hole in the line this will cause a miss and then it will not run at all.I worked for two days thinking lift pump,injector pump,oring in the preheater.Trust me check the fuel lines loosen the clamps then try cranking the motor sometimes the leak is hard to spot cause the clamp seals the pin hole but you will draw air into the pump.cut the line splice with rubber hose and small clamps.This may not be your problem but youll be happy if it is.
 
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Old Sep 21, 2011 | 07:08 PM
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Default Re: 98 12 vavle miss. HELP!

After re-reading , I didn't see that you hadn't pressurized the tank. That's where I would start. Generally the fuel line and heater cause a hard start before other symptoms
 
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Old Sep 21, 2011 | 07:43 PM
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does the truck have less or the same power as before it started smoking? i think timing has slipped
 
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Old Sep 21, 2011 | 10:59 PM
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Originally Posted by mikej
just a thought,i would check the fuel lines where the factory line clamps that hold the lines to the frame will in time rub a pin hole in the line this will cause a miss and then it will not run at all.I worked for two days thinking lift pump,injector pump,oring in the preheater.Trust me check the fuel lines loosen the clamps then try cranking the motor sometimes the leak is hard to spot cause the clamp seals the pin hole but you will draw air into the pump.cut the line splice with rubber hose and small clamps.This may not be your problem but youll be happy if it is.
mine was doing the same thing, replaced the lines an fixed the prob.
 
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