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Em6 237 Skips Under Load


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Hi everyone, I am new to Macks and need some help. A friend has a 1987 Mack tractor. It was originally a concrete mixer. The power plant is an EM6-237. A couple days ago it started to skip/miss under load. I advised him to change the fuel filters and call me back. This did not help. I would like to check the fuel pressure but there is one part I am unsure of. On the right hand frame rail forward of the injection pump is some sort of manifold. It has a diaphragm on top with an air line. Looks like supply fuel passes through this thing. Could/would this cause fuel starvation under load if defective? Also what is the spec on supply pressure for this engine? Everything under the hood looks good, no fuel leaks and the air filter is new. Runs like a champ until you ask for some real power then the skipping starts. No excessive smoke is evident when this happens. I have not checked the puff limiter operation. I didnt think limiting rack travel would make it skip. Any ideas from the Mack gurus would surely be appreciated.


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The fuel preasure should not drop below 20 psi the engine requires at least that to run properly! 25- 30 is best!There is a tee at the front of the fuel pump on the return line check that the spring is not broken inside that!It sounds like a definate fuel starve problem your chasing!

The other manifold thing you speek of sounds like a fuel heater is there coolant lines running to it!?

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