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Old 03-18-2023, 03:12 PM   #15
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What is engine RPM at idle? Cummins setting is 700RPM. Your description sounds like air in fuel, and is listed under several issues on this trouble-shooting tree.

Inspect above the starter area for fuel leakage, if you see any it is most likely a leaking 12V lift pump, for which the 8.3L engine is well-known. If you see any sign of the lift pump leaking, tighten the 3 bolts on the top of the pump and hopefully it will temporarily stop the leak, but order a new replacement gasket ASAP. The actual pump is bolted on top of the electric motor with a gasket between them.
When you let off the throttle, the main injector pump sucks air through the leaking gasket, as the lift pump only runs for 30 seconds when the ignition key is turned on to prime/pressurize the fuel filters. From that time on the fuel system is under a slight vacuum -5psi.

This problem is accompanied by hard starting.
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Old 03-18-2023, 04:26 PM   #16
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Once engine shuts down on its own, are you able to start it right back up? Or does it need to crank a while before starting?
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Old 03-19-2023, 04:49 AM   #17
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Quote:
Originally Posted by Gallivant View Post
My 2000 Monaco Windsor Cummins ISC had an in-line one way check valve just before the primary fuel filter. Iíve had algae/crud get stuck in there and more recently rubber bits that acts like bubble gum. Both of these have eventually blocked fuel delivery when the filters where good. I didnít even know about this valve as it looks like regular fittings back there. New supply and return hoses and FASS pump have cured my issues.
Did you have the same issues i have ?
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Old 03-19-2023, 01:38 PM   #18
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Originally Posted by mackwrench View Post
Once engine shuts down on its own, are you able to start it right back up? Or does it need to crank a while before starting?
yes it starts right back up.
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Old 03-19-2023, 01:41 PM   #19
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Originally Posted by Ray,IN View Post
What is engine RPM at idle? Cummins setting is 700RPM. Your description sounds like air in fuel, and is listed under several issues on this trouble-shooting tree.

Inspect above the starter area for fuel leakage, if you see any it is most likely a leaking 12V lift pump, for which the 8.3L engine is well-known. If you see any sign of the lift pump leaking, tighten the 3 bolts on the top of the pump and hopefully it will temporarily stop the leak, but order a new replacement gasket ASAP. The actual pump is bolted on top of the electric motor with a gasket between them.
When you let off the throttle, the main injector pump sucks air through the leaking gasket, as the lift pump only runs for 30 seconds when the ignition key is turned on to prime/pressurize the fuel filters. From that time on the fuel system is under a slight vacuum -5psi.

This problem is accompanied by hard starting.
I will check tomorrow but I do know I have no puddles under the engine area.
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Old 03-19-2023, 01:55 PM   #20
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Your vintage of Cummins engine has an adjustable idle throttle stop ; that is prone to wear and allowing low idle speed ; particularly noticeable if the dash A/C compressor is cycling; that can cause a stall.

Replies with info about the newer ISC version of the 8.3L Cummins won't be of any use as the CAPS fuel system ( 1998 -2003 ) has computer idle speed control and your engine does not.

When you view your injector pump, from the top , is this what you see ?
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Old 03-19-2023, 02:05 PM   #21
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Originally Posted by Skip426 View Post
Your vintage of Cummins engine has an adjustable idle throttle stop ; that is prone to wear and allowing low idle speed ; particularly noticeable if the dash A/C compressor is cycling; that can cause a stall.

Replies with info about the newer ISC version of the 8.3L Cummins won't be of any use as the CAPS fuel system ( 1998 -2003 ) has computer idle speed control and your engine does not.

When you view your injector pump, from the top , is this what you see ?
Very similar yes
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Old 03-19-2023, 02:13 PM   #22
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Originally Posted by Skip426 View Post
Your vintage of Cummins engine has an adjustable idle throttle stop ; that is prone to wear and allowing low idle speed ; particularly noticeable if the dash A/C compressor is cycling; that can cause a stall.

Replies with info about the newer ISC version of the 8.3L Cummins won't be of any use as the CAPS fuel system ( 1998 -2003 ) has computer idle speed control and your engine does not.

When you view your injector pump, from the top , is this what you see ?
it is also idling at 550-600RPM while in drive.
the video is taking while it is in gear and holding there brake
https://youtube.com/shorts/blqc-qbBspQ?feature=share
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Old 03-20-2023, 08:29 AM   #23
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Interesting video.
If you touch the throttle pedal slightly to bring the RPM to 750 , will the RPM stabilize ; or does it continue to flare ?

Many U Tube videos on idle speed adjustment on the P7100 pump , both the 5.9 Cummins in Dodge trucks ( 94>98 1/2) and the mechanically injected 8.3 used the P7100 and adjustment method is the same .
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