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Phil Bennett

ENDT864 low on power Update

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Hello to all,

Update on trying to improve on low engine power output on 1970 R719  ENDT864 V8.

Thanks for the many replies and suggestions.

So far;

New filters, fuel lines and fresh diesel.

As advised, I've adjusted the pump stud by 1/4 turn clockwise (screwed 'in'), but no change.

**Even after reading manual, I'm really not quite sure what this 'stud' adjustment does (see image) - any advice ? **

Fuel pump readings (no load) are from 15psi @ 600rpm to 31psi @ 2000rpm.

Might go back to basic checks such as re-torque head nuts (weak point) rechecking cylinder compressions, valve clearances and injector spray.

Plus check fuel pressure 'under load'.

Other comments welcomed.



ENDT864 adjustment stud.jpg

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Your fuel or lift pump pressures sound fine and this means you are pressurizing the fuel gallery within the pump adequately. With pump wear, (which I suspect) the high pressure for fuel injection is suffering internal to the injection pump. No real way to check this without removing the injection pump from the engine and sending in to a fuel shop for evaluation. They will need to mount it into a test stand to check for output pressure and volume. 

What the fastener in your circle does is adjust fuel delivery to be injected per engine demands. This is what a fuel shop will adjust once they have all eight fuel injectors balanced as far as fueling rate and cracking pressure, (opening pressure). If the pump will not make adequate pressure to inject the fuel, adjusting this screw will gain you nothing. The lower screw in your photo adjusts the maximum engine speed. I do not recommend adjusting either without experience to what is affected. Both are precise in calibration settings.

With Mack engines it is always best to send both the injection pump, and injection nozzles into a fuel shop together to be calibrated together. These will be numbered as to which cylinder each is to be reinstalled into when all is done.

Dog.jpg.487f03da076af0150d2376dbd16843ed.jpgPlodding along with no job nor practical application for my existence, but still trying to fix what's broke.



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That is the rack stop adjustment ig you need to try give it more juice loosen the jam nut and turn the screw back 1/2 turn and lock the nut and try it! That is the old style adjustment I don’t recall the direction to turn it clearly. However if you feel a power increase you have gone the right direction/if it decreased the power turn the screw forwards one turn from that point and try it!  As I mentioned it’s been 25 years since I messed with one of those however I remember it being opposite to the newer two jam nut style.! Once you establish the direction do not surpass plus 1 1/2 turn from stock set unless you want to wreck something!

Edited by fjh

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