xdudebrahx Posted June 10, 2015 Share Posted June 10, 2015 Can someone tell me where the wiring for the engine brake runs on an 86 R? I'm trying to chase down a loose wire. It worked for a while and then started cutting out and now it doesn't work at all. I just don't really know where the wires lead to on the other side of the firewall. Quote Link to comment https://www.bigmacktrucks.com/topic/40411-86-r-engine-brake/ Share on other sites More sharing options...
fxfymn Posted June 10, 2015 Share Posted June 10, 2015 Not really familiar with the Mack engine brakes,but the number one problem we had with the DD brakes was a sticky activation switch located under the fuel pedal. The cure was to clean and lube it with a little WD-40 type of oil.The problem usually showed up as an intermittent failure like you described. Quote Money, sex, and fire; everybody thinks everyone else is getting more than they are! Link to comment https://www.bigmacktrucks.com/topic/40411-86-r-engine-brake/#findComment-292830 Share on other sites More sharing options...
xdudebrahx Posted June 10, 2015 Author Share Posted June 10, 2015 Not really familiar with the Mack engine brakes,but the number one problem we had with the DD brakes was a sticky activation switch located under the fuel pedal. The cure was to clean and lube it with a little WD-40 type of oil.The problem usually showed up as an intermittent failure like you described.This truck doesn't have a switch under the pedal. It just has the throttle linkage going through the floor. Quote Link to comment https://www.bigmacktrucks.com/topic/40411-86-r-engine-brake/#findComment-292839 Share on other sites More sharing options...
gearhead204 Posted June 10, 2015 Share Posted June 10, 2015 Follow the linkage to the fuel pump, there you will find the switch. quite often the sw. or lever is out of adjustment. the curcit is eng.brake sw. to clutch ped. to injection pump sw. to front and rear cyl. head Quote Link to comment https://www.bigmacktrucks.com/topic/40411-86-r-engine-brake/#findComment-292841 Share on other sites More sharing options...
xdudebrahx Posted June 10, 2015 Author Share Posted June 10, 2015 There's no switch on the clutch pedal. You can operate the clutch pedal with the engine brake on. The switch doesn't say Jacobs so I assume it's just a Mack retarder? Still the same setup with the switch on the fuel pump? Quote Link to comment https://www.bigmacktrucks.com/topic/40411-86-r-engine-brake/#findComment-292844 Share on other sites More sharing options...
keg1 Posted June 10, 2015 Share Posted June 10, 2015 Did you check the wire on the back of the pump. The one on my R would come off sometimes. Quote Link to comment https://www.bigmacktrucks.com/topic/40411-86-r-engine-brake/#findComment-292884 Share on other sites More sharing options...
gearhead204 Posted June 10, 2015 Share Posted June 10, 2015 the clutch pedal can be a optional sw. the fuel pump sw. can be external or internal, the internal one can fail ( the little toggel strip can break off) If its being a pain to fix just get a jacobs floor mount switch that is foot activated and mount it to the right of the throttle pedal, that way its only usable when your foot is off the fuel, you can bypass the pump sw, and go right to the heads, i would still use the dash sw. to control power to the foot pedal. Quote Link to comment https://www.bigmacktrucks.com/topic/40411-86-r-engine-brake/#findComment-292891 Share on other sites More sharing options...
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