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

low fuel pressure

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  #1  
Old 04-18-2014, 06:59 PM
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Default low fuel pressure

95 dodge all stock. I've had problems with this truck running rough and blowing white smoke when starting up cold. Put a new LP on awhile back and no change. I've pressurized the tank several times and looked for leaks...nothing.

Got a fuel pressure gauge put on today and pressure seems to be low. Holding 13 psi at idle. 20 at 2500rpm. On the highway it drops to 10 when I put my foot down.

Could something be restricting flow? (F
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Old 04-18-2014, 07:01 PM
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timing issue ..
 
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Old 04-18-2014, 08:28 PM
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^ What he said. A 1995, all stock, chances are extremely good that the pump timing has never been messed with and has probably slipped. It will do that, and it doesn't take two decades... so I bet you're probably 3-4 degrees low at this point. It can eventually slip so low that it'll barely run. It only takes a few minutes for someone who knows how to do it to check it and see if it's where it belongs. Not that it hurts to check the flow culprits yourself: how old is the fuel filter? The pre-filter screen in the fuel heater can also get pretty full of crap if it isn't popped out every now and then.
 
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Old 04-18-2014, 08:47 PM
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Seems pretty low fuel pressure wise. Overflow valve ok?

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Old 04-18-2014, 09:42 PM
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Originally Posted by mysterync
Seems pretty low fuel pressure wise. Overflow valve ok?

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I was kinda thinking the overflow valve too, especially if its the original.



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Old 04-19-2014, 08:23 AM
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ofv all the way.
 
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Old 04-19-2014, 11:36 AM
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Yea I pinched the return line this morning and my pressure jumped to 30. It has a tork tech adjustable valve on it. The plug seemed extremely loose. I could turn it with my fingers.

I turned it down a little bit now getting 20 psi at idle. Only 25 at 2500rpm. Didn't seem to help the cutting out and white smoke. I'm going to order a new valve and if I can find someone to check my timing.

Any recommendations on the ofv I should get? Brand? Adjustable?
 
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Old 04-19-2014, 11:58 AM
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Originally Posted by burnhedge
Yea I pinched the return line this morning and my pressure jumped to 30. It has a tork tech adjustable valve on it. The plug seemed extremely loose. I could turn it with my fingers.

I turned it down a little bit now getting 20 psi at idle. Only 25 at 2500rpm. Didn't seem to help the cutting out and white smoke. I'm going to order a new valve and if I can find someone to check my timing.

Any recommendations on the ofv I should get? Brand? Adjustable?
Truck still have a fuel heater?
I'd crank the fuel pressure on up and leave that ofv in place.
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Last edited by mysterync; 04-19-2014 at 12:10 PM.
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Old 04-19-2014, 12:40 PM
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[QUOTE=burnhedge;1058386]
I'm going to order a new valve and if I can find someone to check my timing.
QUOTE]

i will be in KS in about a month. you got tools? LOL
 
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Old 04-19-2014, 01:44 PM
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Don't crank the ofv to much ... You will damage the IP if the flow isn't enough to cool he pump ...
 


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