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Thread: M1028 Fuel Issues

  1. #11
    4 Star General sandcobra164's Avatar
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    Sir,
    I have not tried clear fuel line to check for bubbles. The black particles were only observed when I removed the housing pressure regulator valve, they were holding the check ball closed. It was only 3 little specks but it doesn't take much to plug the valve. Cleaning the valve caused the truck to run great again, eliminating the check ball made the truck run well also. Going off the peer reviewed comments in this forum concerning symptoms for an injection pump failing is what drew me to the conclusion that the injection pump had failed. In concern of rubber lines, the only non-filtered rubber line leading to the injection pump is the 2 foot section from the fuel filter to the injection pump inlet. The rubber line appeared to be fine but I replaced it when I installed my spin on fuel filter assembly so I don't think that was where the rubber specks were coming from. I'm fairly certain the governor drive ring was coming apart which seems to be a common issue amongst the 1985 and earlier injection pumps.

    Joseph
    84 AM General M923 "General Non-Sense"
    85 Chevrolet M1028 CUCV "Sarge"
    05 Silver Eagle M1102 (Sarge's New 4 Wheeler Hauler)

    Gone but not forgotten....
    71 AM General M35A2 "Big Trucks"
    87 Pribbs Manufacturing M105A2

  2. #12
    4 Star General cucvrus's Avatar
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    DSCF5619.jpgDSCF5620.jpgDSCF5621.jpgYou are right on task. The injection pump is bad. Have it rebuilt or replaced. Don't bother putting a used or a NOS injection pump on. I had a few brand new ones fail a few months after installation. You will be happy with the results of a fresh rebuild injection pump. I would also drop the tank and replace the fuel strainer sock if you have NOT already done so. I replaced this sock 10 years ago. The truck M1009 sat wrecked the past 10 years. But continue on the path you are on and you will get it done. I don't think rubber particles from fuel line would get thru any filter. I always had the particles right before the injection pump went out. Good Luck. Have a Great Day.
    To argue with a person who has renounced the use of reason is like administering medicine to the dead. Thomas Paine: Founding Father Quote.

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  4. #13
    4 Star General Keith_J's Avatar
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    When the Pellethane damper ring breaks down, the particles clog the fuel return check valve, causing case pressure to rise which retards timing. Knocking the glass ball out causes timing issues as there is a cold start advance which holds the valve open when the engine is cold, causing case pressure to drop which advances timing. With the engine warm, the timing is still too advanced so the idle clatter is louder.

    Removing the check ball is just a stop gap measure, without the Pelletane ring, the governor cage wears on the input hub which can cause further wear from particles. The fuel for the hydraulic head comes from the transfer pump, fuel in the case is all return to tank. But because the fuel return is at the top, all metallic debris concentrates on the bottom where it can cause problems with the main shaft, advance mechanism and the cam ring/rollers.

    Replacing a pump before it bricks itself saves you the core charge. It isn't hard, just time consuming. Allocate 8 hours and lots of patience. If you aren't sure, read the TM and ask questions.
    1986 M1031 SECM.
    1985 MEP 002A
    1974 MEP 026C, eventually converting to electric start.

  5. #14
    4 Star General sandcobra164's Avatar
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    Sarge is running again. If you use a newer 6.5 injection pump you will have to find a solution to adapt the throttle shaft to the vacuum modulator for the transmission. My idea so far is to drill a hole for the roll pin to fit in, grind the flat tipped end of the shaft that would fit into a throttle position sensor and let it ride. The mounting boss is the exact same on the newer injection pump. I took it for a short drive and 1,200 rpm shifts occur if the modulator doesn't receive a throttle input to regulate the vacuum. As for my top cover concerns, the CUCV top cover works fine on a HMMWV Injection Pump and the HPCA works as it should as well.
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    84 AM General M923 "General Non-Sense"
    85 Chevrolet M1028 CUCV "Sarge"
    05 Silver Eagle M1102 (Sarge's New 4 Wheeler Hauler)

    Gone but not forgotten....
    71 AM General M35A2 "Big Trucks"
    87 Pribbs Manufacturing M105A2

  6. #15
    4 Star General sandcobra164's Avatar
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    Took if for another drive today. I zip-tied the rotating assembly on the vacuum modulator valve at about 1/2 of it's rotational travel. It's shifting at about 2,300-2,500 rpm judging by ear. This feels like a whole new truck. It accelerates much stronger than before and oddly enough sounds much less stressed going 55 mph. I'm sure that's likely due to advance curve differences between the two models. I do have some light puffs of black smoke if I stand on the throttle but no worse than I've seen out of HMMWV's before so I think this is a worthwhile upgrade over a pump with .290 bore plungers. It also did not lose prime overnight like the other pump was doing. Now to sort out the mounting of the vacuum modulator this weekend but his biggest task today is to go get ice cream for my little buddy. He wasn't too happy about Sarge being down for maintenance.
    Attached Images Attached Images
    84 AM General M923 "General Non-Sense"
    85 Chevrolet M1028 CUCV "Sarge"
    05 Silver Eagle M1102 (Sarge's New 4 Wheeler Hauler)

    Gone but not forgotten....
    71 AM General M35A2 "Big Trucks"
    87 Pribbs Manufacturing M105A2

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  8. #16
    4 Star General sandcobra164's Avatar
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    I used an old picture showing my little buddy getting icecream. Here is today's picture. The truck did fine and will be in the 1st Annual Leesburg Veterans Day Parade along with General Non-Sense (M923) and Welder1's Deuce. I'm glad I got it's issues figured out and back together in time.
    Attached Images Attached Images
    84 AM General M923 "General Non-Sense"
    85 Chevrolet M1028 CUCV "Sarge"
    05 Silver Eagle M1102 (Sarge's New 4 Wheeler Hauler)

    Gone but not forgotten....
    71 AM General M35A2 "Big Trucks"
    87 Pribbs Manufacturing M105A2

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  10. #17
    4 Star General sandcobra164's Avatar
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    Sarge made the Veterans Day Parade today with zero issues. I was driving my 5 ton and everytime we took off from a stop sign my wife would put about a 1/4 mile between us before I could get up to her speed. It's running very well with a 6.5 pump.
    Attached Images Attached Images
    84 AM General M923 "General Non-Sense"
    85 Chevrolet M1028 CUCV "Sarge"
    05 Silver Eagle M1102 (Sarge's New 4 Wheeler Hauler)

    Gone but not forgotten....
    71 AM General M35A2 "Big Trucks"
    87 Pribbs Manufacturing M105A2

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    1986 M1008

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    Those prices are crazy

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    4 Star General cucvrus's Avatar
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    No those prices are insane. And I know where that place it. Glad I never stopped to ask. I am OK with the $350. rebuilt injection pumps. They haven't failed me yet.
    To argue with a person who has renounced the use of reason is like administering medicine to the dead. Thomas Paine: Founding Father Quote.

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