Compression check how to, 1994 Peterbilt w Cummins 855/n14

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Dwragon, Jan 20, 2022.

  1. Dwragon

    Dwragon Bobtail Member

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    Jan 20, 2022
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    Hi all, I just purchased a 1994 Peterbilt with an all original non electronic 855 N 14 Cummins engine that uses the PT system from a local shop.The problem with the truck is that the entire fi system left with the mechanic.no pump,lines, injectors. Since the injectors are already out, I want to do a compression check to see if there are any other problems before investing in the parts. What type of compression guage do l need to do this?
     
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  3. Lazer

    Lazer Heavy Load Member

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    Jan 22, 2017
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    Is there a way to contact the mechanic? It’s my understanding, that a compression test is most accurate when the engine is warm.
     
    jamespmack Thanks this.
  4. BoxCarKidd

    BoxCarKidd Road Train Member

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    Aug 26, 2014
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    That kind of test equipment is expensive. Compression test specs on many diesels are while running. You can call around but I doubt you will find much help even to pay someone with the equipment.
    If I were in your spot I thank I wound find a junk injector. Dump the plunger out. Braze the fuel inlet and outlet ports closed. Braze a fitting on top. Then install a 600 + psi gauge. Not real sure what psi would be acceptable but you are looking for odd ducks. It is unusual but possible that all cylinders went bad at the same time. On some smaller engines I made similar stuff. Knocked the guts out of a spark plug. Then brazed that on an injector or glow plug fitting. That allowed me used a regular gas engine tester that has a check valve in the hose. Just had to use a higher pressure gauge. JD engine about 1/3 that size runs in the 400 - 500 PSI range.
     
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