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Old 05-17-2023, 07:56 AM   #1
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Intermittent Starting

I have a 2002 Cat 3126 installed in a Winnebago Journey on a Freightliner Chassis. For the last several months I have been having an intermittent starting issue. On most occasions the engine will fire right up on the first start attempt. On some occasions it may take 3 or 4 attempts. Outside temperature, warm or cold engine, time sitting idle (shutdown) doesn't seem to have any pattern. I've recently replaced the fuel filter with no change. Seems fuel related like it may be losing prime but it has happened after only being shut down for a few minutes. There is definitely no pattern. Any suggestions team?
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Old 05-17-2023, 06:56 PM   #2
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There is a fuel pressure regulator in the return fuel line at the rear of the cylinder head , it should maintain 65 psi in the cylinder head fuel passage , if it doesn't you end up with repeated start attempts and long crank times .
Yellow oval ; red oval is a heater hose.
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Old 05-18-2023, 08:55 PM   #3
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Change the IAP sensor
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Old 05-21-2023, 04:05 AM   #4
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Thank you for your feedback and suggestions! I have a Fuel Pressure Regulator coming. If that doesn't do it I will look at the IAP Sensor.
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Old 05-29-2023, 08:08 AM   #5
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I received the new regulator, and removed the old one. There is a small pin that was just sitting in the regulator outlet when removed from the cylinder head (see pics). The new one does not have this pin. I installed the new one without the pin and started the engine several times with no issue. Any idea where this pin could be from or if necessary?
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Old 05-29-2023, 08:50 AM   #6
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Quote:
Originally Posted by wfrazier View Post
Any idea where this pin could be from or if necessary?

I've never had to change a fuel pressure regulator , but if your starting issue appears to be fixed , I'd guess it's unnecessary , particularly if the new regulator didn't come with one .
I can't think of anywhere in the fuel system that a piece that shape would come from .

I do have a repair manual for a 3126E , I'll look through for any clues to it's origin .

EDIT: BTW , the regulator is in the fuel return line from the head to the fuel tank , so the pin is in the regulator inlet .
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Old 05-30-2023, 12:11 PM   #7
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Thanks for the reply and explanation on the direction of flow. Seems to me that the pin setting in the inlet of the regulator could have intermittently prevented the poppet inside the regulator from closing off and allowing the fuel pressure to leak down to the tank causing my starting issue?? I'll keep my fingers crossed and let you know if I have any more starting issues. Thanks again!
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Old 05-30-2023, 12:47 PM   #8
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The manual I have shows nothing like the pin you found or mention of it .
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