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Hi I bought an old 1985 R model Mack truck last year and it ran good but recently it has started smoking blue smoke, it had a miss in it so I changed the number 1 injector spray nozzle but truck is still smoking but not as bad can it be my fuel injection pump or something else? Would really appreciate some advice!

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Hi I bought an old 1985 R model Mack truck last year and it ran good but recently it has started smoking blue smoke, it had a miss in it so I changed the number 1 injector spray nozzle but truck is still smoking but not as bad can it be my fuel injection pump or something else? Would really appreciate some advice!

Does it smoke all the time or just when it cold, does it have blowby it could be low compresion or more injectors.

yea smoke can be so many things. Is it low on power?

you can have bad valve guides, turbo seals, incorrect pump timing, bad injector(s), bad injection pump, worn rings, cracked piston, etc.... best way is to do some basic tests on the engine and pump and hopefully.... or not..... you will find the clue. If these tests dont give you any ideas and if you have time pull the exhaust manafold and see if any of the ports are wet with oil.

If it smokes all the time try doing a cylinder cutout test with truck running a idle crack each fuel line loose at injection pump one at a time to see which cylinder is causing the smoke and miss be careful fuel is under pressure and will make a mess, get the problem narrowed down to which cylinder and we will go from there,

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