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disable the cold advance

Discussion in '1982-Present GM Diesel' started by pavo, Nov 17, 2002.

  1. pavo

    pavo Registered Member

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    just wondering if you could disable the cold timing advance on a 6.2. every since i got my timeing checked (and advanced) my truck starts a little hard. i was hoing to try to disable the automatic advance to see if that solved the problem.
     
  2. BlueBlazer

    BlueBlazer 1/2 ton status

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    Are you talking about the HPCA (housing cold pressure advance)? If so, you can find it on the side of the pump and disconnect the wires going to it. Im sure someone will chime in with the exact color and location of the wires. If I were you however, I would put the pump back at stock timing. It will do nothing but hurt your engine by raising peak cylinder pressure. The DB2 has an internal advance mechanism, so advancing the base timing on it does not have as much of a gain as it does on a lot of inline fuel systems that dont have automatic advance since the pump will advance itself as RPMs rise just like a distibutor on a gas engine. Just my opinion though.
     
  3. DieselDan

    DieselDan 1/2 ton status

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    I've never seen the fuel curve mapped out on paper of the roosamaster pump, but I have seen the little bosch pump (VW)mapped out. IF it's similar the cold advance only works at low RPM and tapers off to the normal curve by about 2000 RPM.

    I had a similar problem with hard starts and it turned out the HPCA was not working. The thermo-switch (under the left exh manifold) went bad.

    IIRC the HPCA is wired in series with the high-idle plunger on a <font color="green"> green </font color> wire. It is possible that your truck wasn't fully warmed up when they adjusted the pump timing.
     
  4. BlueBlazer

    BlueBlazer 1/2 ton status

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    The automatic advance I am talking about has nothing to do with the HPCA. If youve ever disassembled a DB2, you would see a piston on the bottom that fits into the cam that actuates the plungers. As housing pressure increases (from lift transfer pump inside the main injector pump spinning faster) the piston moves, thus moving the cam and advancing timing.
     

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