siroism Posted September 20, 2016 Share Posted September 20, 2016 Hello hope some one can help me. I have an E9-450 in a 1994 CL600. I'm having a problem with low speed drivability. I have replaced the air cylinder on the foot pedal and checked the lines to the cylinder on the engine. All seem to be working great. Engine accelerates fine and runs fine, except at lower rpm's. I lose all smoothness and it looks like the air cylinder on the engine moves like I'm giving it fuel with a pumping motion and i noticed that when the air compressor if filling the system the same problem happens then the air dryer kicks off and it runs smooth again,any ideaswhats going on its driving me crazy and i don't want to keep throwing money at it, any info is appreciated, Thank you, Mark Quote Link to comment Share on other sites More sharing options...
BAD DOG Posted September 20, 2016 Share Posted September 20, 2016 that air throttle was a nice set up when it works, we had a CL and and MH with it . Can't say I ever experienced what yours is doing mine either worked or it didn't we had to drive both of them home with the hand throttle because the piston on the pedal went . Since it does it when the compressor is pumping it sounds like an air problem is there little pilot Balve or a regulator between the tank and the pedal in the supply line ? I dont remember it's been a long time since we had ours. Quote Link to comment Share on other sites More sharing options...
BC Mack Posted September 20, 2016 Share Posted September 20, 2016 the system on my MH is similar to yours, however the process is pretty generic, you will need to plumb in a few temporary test gauges.... check air supply pressure to foot pedal, it should be tee'd off the protected accessory circuit, eg, air seat, air suspension, heater etc.... watch what it does as you pump down the brakes to kick in the compressor, if pressure is getting low you may have other air system issues... check it too at inlet at fuel pump actuator, possible pinched line or leak if a lot lower than pedal pressure. pulsing can be either an air leak in actuator unit (you have a new throttle pedal unit, right?), or a sticky piston seal... I assume there is no binding on the sliding rod to the fuel pump throttle lever. oil in the air tanks can swell or gum up the seals and make sure the exhaust is clear too pretty simple systems but you need to know the pressures before you start buying parts on a guess.. from your information, is would appear that on light throttle you are getting a surge, my guess is the air pressure at the fuel pump end is too low or there is a leak which gets compensated for with more throttle pedal movement... just my wild guess... not easy diagnosing on the internet.. :-) I used to work on air throttles on the old GM buses, worked better than 40ft cables but now it's all fly-by-wire..!!! as others will mention, not the best system for a truck, solid rods work much better but it could be something Mack put in the dampen the torque as you mash down the pedal. added pics for those not familiar with the air throttles... BC Mack 1 Quote Link to comment Share on other sites More sharing options...
gearhead204 Posted September 21, 2016 Share Posted September 21, 2016 Dumb question ..... it the spring strong enough to stop throttle bounce at low rpm caused by a worn or loosely set buffer screw adjustment? in the injection pump. I'm thinking the compressor may be causing the governor in the fuel pump to flutter and thus make it appear as the air cylinder is working the throttle, when in fact its just the opposite. Quote Link to comment Share on other sites More sharing options...
siroism Posted September 21, 2016 Author Share Posted September 21, 2016 thanks for the replys,the foot valve is new and it did help some what i have not replaced the slave on the engine yet ,looks difficult to do,the rod and springs are all ok no binding or line problems that i have found yet there is an air leak somewhere in the truck because the air ride goes down over night as does the cab any more hints are welcome ,i'll start checking more lines and maybe attempt the slave change on the engine. Quote Link to comment Share on other sites More sharing options...
gearhead204 Posted September 21, 2016 Share Posted September 21, 2016 I would suggest to unpin the linkage and "play" with the throttle and see if you feel a pulsing in the throttle rod at low rpm if so you may need to do some pump work to fix this issue. 1 Quote Link to comment Share on other sites More sharing options...
siroism Posted October 3, 2016 Author Share Posted October 3, 2016 to gearhead204 thank you for your response i did un pin the slave cylinder in the valley ran the engine and it still did the rough running when the compressor was filling the tanks hooked it back up took it for a ride and still the same when the compressor kicked out it ran smooth but if i held the rpm steady i could feel a little skip or rough skip but very weaker as compared to when the compressor is running but still there every few seconds or so, you think i should lean towards the pump having an issue or maybe the governor. Quote Link to comment Share on other sites More sharing options...
fjh Posted October 3, 2016 Share Posted October 3, 2016 Heres somthing you might try ! Re set the cam thrust screw on the front cover run the screw right in and back it out a 1/4 to 1/2 turn and lock it see if that helps the situation ! Quote Link to comment Share on other sites More sharing options...
siroism Posted October 12, 2016 Author Share Posted October 12, 2016 To fjh, thank you for your response,do you think the air compressor is causing drag on the gear train in some way, and adjusting the thrust screw will help. Quote Link to comment Share on other sites More sharing options...
fjh Posted October 12, 2016 Share Posted October 12, 2016 (edited) The gear is helical cut it could float back and forth sum I have never had it happen And it is a long shot in the dark! your comment about the compressor changing it makes me curious! that is why I sugested it! Edited October 12, 2016 by fjh Quote Link to comment Share on other sites More sharing options...
siroism Posted October 12, 2016 Author Share Posted October 12, 2016 (edited) ok i get what your saying i was thinking the same thing maybe small amount of cam walk i don't know what the the miles are on this engine or if it was ever rebuilt so I'm would think it won't hurt to just it ill try and see if it changes what the compressor is doing thanks for your response Edited October 12, 2016 by siroism spelling error Quote Link to comment Share on other sites More sharing options...
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