p7100 pump ofv? - Diesel Bombers



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

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Old 09-17-2010, 06:34 PM
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Default p7100 pump ofv?

how does getting a new ofv for the pump help? i thought it was just a banjo bolt? How do they help with fuel pressure?
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Old 09-17-2010, 08:40 PM
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The Overflow Valve is on the banjo fitting on the return line at the forward end of the the IP. Inside is a spring and a bearing that holds pressure in the pump. When working properly it maintains a balance between the injection system and fuel flow returning to the fuel tank. As the spring wears the flow can lose that balance. If you notice a loss of performance that is a good place to look. In a pinch the spring can be stretched to give some temporary improvement in performance , but replacing the valve is an easy and cheap fix.
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Old 09-17-2010, 08:41 PM
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The Over Flow Valve is a check ball type setup and when the spring gets weak the its lowers the fuel pressure in the pump because it is letting fuel past to easy so to speak.

A simple temporary fix is to stretch the spring this will get you to a parts store

They are typically around 60 or so but probably 90 or 100 from dodge.

Should read 22 PSI at idle and 25-30 PSI at 2500 RPM

You can test the OFV by pinching off the return line. If the pressure goes up then the OFV is bad if it doesn't the LP is bad. You can pinch the return line with some vice grips on the rubber part of the line by the firewall

Symptoms of worn out OFV

Low RPM miss / instability
Hard starting
Engine dies at idle (especially when hot)
LOW POWER
Fuel Filter cracking
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Old 09-17-2010, 09:17 PM
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well if a rig has 100,000 miles or more on it should you just replace it as a maintenance thing to know your good for another 100,000?
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Old 09-17-2010, 11:13 PM
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So if i take that bolt out the spring is just loose and i can stretch it out and put it back in and see if thats the problem? when i says fuel filter cracking what that mean like literally it cracks? how would it do that?
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Old 09-18-2010, 07:49 AM
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That helped in my case.

Best to take off the entire valve assembly and take it to a bench to take apart or you may lose the spring or bearing. Also make sure to grab the plastic bushing/ gasket under the banjo fitting.


Check Ebay- I got mine for $25.00

Last edited by ktfroy; 09-18-2010 at 07:51 AM.
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Old 09-18-2010, 09:07 AM
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Only buy a Bosch don't buy aftermarket crap
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Old 09-18-2010, 09:45 AM
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All aftermarket isnt bad, I have one from tork technologies and it is a high quality item and solved my ofv issues without a doubt.
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Old 09-18-2010, 10:54 AM
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Default p7100 pump ofv?

You guys just made my day. Was getting ready to change my pump due to what was like dead pedal, but more of a power loss and seriously eratic idle, popped the banjo bolt out of another pump laying in the shop and is purrin. Thanks.
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Old 09-18-2010, 01:56 PM
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when you take out your bolt you screw it out and pull it up to get it out bc it hits on the metal?
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