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noroots

1985 Dmm 300hp Maxidyne

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I recently bought my first Mack. It is an 85 dmm with 300hp. I think it had been sitting around for a few years but seemed to run pretty good without too much smoke. I jumped in the truck and drove it from iowa to ca. About nevada it started cutting out after being under throttle for a few minutes. I figured this was due to a clogged fuel filter so I changed it and it seemed to solve the problem. Somewhere around the same time it started to blow large amounts of black smoke when I hammer it. Now it seems to run pretty good but way too much black smoke. Where do I start?? turbo? a leak? settings on the pump? injectors? Everyone I ask points in a different direction.

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Change the air filter first and then take a look at the puff limiter to see if its working, a quick way to check it is to do a full throtle snap test once with the parking brake on and once with the brake off, if it's working you will see a lot more smoke with the brake on.The puff limiter is on the front of the pump and has an air line on it comeing from the intake manafold.

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MACKS is right but count me among the lovers of the black Mack clouds. If you've been around them long enough you can smell that smoke and pretty much tell the health of your motor.

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That black smoke cost me some money this year and a day in court,plus I had to have my truck re inspected before I went to court,no more black smoke for me.

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Macks and dog lover right.... puffer valve most likely. yes, DEC, re-inspection, smoke test, fines usally add up quick. Better of paying core and cost. Hopefully a little more helpful.

Edited by UNCLDAVE

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Yep, puff limiter, and just double check air filters and the intake plumbing for restrictions. If its been sitting for a while, who knows what could have nested in there.... :D You may laugh, but here in the country areas of Australia where some trucks sit parked for 6 months or more waiting for harvest, all sorts of nasties find intake pipes suitable accommodation.

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