jakebrake86 Posted November 28, 2012 Share Posted November 28, 2012 Got another tech question for all you Mack professionals... I've got a '96 RD688S tri axle dump truck with the manual E7 350 and an 8LL. It just doesn't seem to have anywhere near the power it should. You've really got to run the tach up to get anything out of it. I was talking to a mechanic the other day and he told me there's a diaphragm in the back of the pump that could be blown. I believe he called it an ACF??? Anyway, I was looking at it today, and the housing has three flat head screws and what appears to be a rivet. Is this a tamper-proof set up? If so, how do you go about changing it, or am I just barking up the wrong tree all together? Quote Jake Link to comment Share on other sites More sharing options...
theakerstwo Posted November 28, 2012 Share Posted November 28, 2012 To check that diaphram use a hand air pump with a gauge on it and connect to the fitting on the housing. Pump up about 25 psi and it should hold the pressure. Also mash you throttle down and make sure it moves the pump lever all the way to go fast. Make sure the stop cable is not holding it in slow postion. Quote glenn akers Link to comment Share on other sites More sharing options...
jakebrake86 Posted November 28, 2012 Author Share Posted November 28, 2012 Ten four. I believe I'm getting all of the travel out of the throttle lever. I can get 2100 rpms, it just takes forever to get there. I'll try the hand pump trick and see where that gets me. If it doesn't hold, is changing the diaphragm possible? I already went to Mack and got it. Quote Jake Link to comment Share on other sites More sharing options...
theakerstwo Posted November 29, 2012 Share Posted November 29, 2012 Ten four. I believe I'm getting all of the travel out of the throttle lever. I can get 2100 rpms, it just takes forever to get there. I'll try the hand pump trick and see where that gets me. If it doesn't hold, is changing the diaphragm possible? I already went to Mack and got it. Just because it will turn full rpm dont mean its getting full rack or full throdle.To check it do so with dead engine and mash it down and have some one see if they can advance the throttle lever any more to go fast. glenn Quote glenn akers Link to comment Share on other sites More sharing options...
jakebrake86 Posted November 29, 2012 Author Share Posted November 29, 2012 I gotcha. I'll sure check it out. Thanks for the help! Quote Jake Link to comment Share on other sites More sharing options...
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