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Medium Duty Trucks Discuss GM Kodiak/Topkicks, 4500/5500 & up medium duty engine & all associated components.

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Old 03-25-2020, 06:52 AM   #11 (permalink)
mr93wrangler
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Both feed and return hoses from the tanks to the frame are new I just replaced them. I know it's not on the lines from the tanks to the pump cause they'll hold air pressure. The injectors dont leak on the return side or in the cylinder or oil. I'm going to have it sent to the shop that remanufactured the injector pump to see what they can figure out.

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I currently own a 2003 c4500 Chevy truck looking for help and advice for repairs and believe this is the best place for the help and information

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Old 03-26-2020, 12:53 AM   #12 (permalink)
ScannerRavager
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your not testing for injectors to leak on the return side, you have to flow test them to see if they return to much fuel while in operation.

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Old 03-26-2020, 12:57 AM   #13 (permalink)
ScannerRavager
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the return test is near the end of the video, you measure the fuel going into the return rail and see if it meets spec.
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Last edited by OkDually; 03-26-2020 at 08:59 AM. Reason: repaired video link
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Old 03-26-2020, 07:03 AM   #14 (permalink)
mr93wrangler
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It runs good when it's running so I doubt it's an injector problem. To me if it was an injector problem it would leak into the oil, the cylinder or bleed back into the return system none of which it's doing. Like I said with the return line unhooked from the injectors it doesnt leak there when the feed side is pressurized.
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2006 c7500 with the 7.8 isuzu engine
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Old 03-26-2020, 09:03 PM   #15 (permalink)
ScannerRavager
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actually when the return is out of spec on injectors they can work perfectly fine when the engine is running, but return to much and make a no or hard start.
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Old 03-26-2020, 09:10 PM   #16 (permalink)
mr93wrangler
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I understand what you're saying but with the engine off it's not holding pressure. If I take shop air pressure to the feed line going to the engine and nothing but the return line hooked to just the injection pump the pressure feeds back to the tanks. Therefore it's not loosing pressure from the injectors fuel filter housing fuel rail or fuel lines. Its somehow bypassing it in the injection pump. I'm going to have it taken to the shop where the injection pump was rebuilt at to see what they say.
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I currently own a 2003 c4500 Chevy truck looking for help and advice for repairs and believe this is the best place for the help and information

2006 c7500 with the 7.8 isuzu engine
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Old 03-26-2020, 09:13 PM   #17 (permalink)
ScannerRavager
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Ive changed lots of injectors that have good balance rates but the return rate is way out of spec
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Old 03-26-2020, 09:14 PM   #18 (permalink)
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Best of luck man, youve heard what i have to say
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Old 03-27-2020, 08:35 PM   #19 (permalink)
mr93wrangler
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So if your right hows the pressure getting back to the return side of the pump with the return line not even hooked to the injectors??
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I currently own a 2003 c4500 Chevy truck looking for help and advice for repairs and believe this is the best place for the help and information

2006 c7500 with the 7.8 isuzu engine
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