The Trash Man

Sorry for the late response but anyways the guys who rebuilt the pump swore up and down it had to be right. Well after having no luck with them I decided to just put a remack pump on the truck and guess what? It fired right up and ran like a charm, shows right there that those guys didn't put my old pump back together right. I hated to have to resort to buying another pump but I just wasn't getting anywhere with those guys. I should have knew better though because I knew a guy who had the same kind of truck I did and he had his pump rebuilt there and had no luck either and had to put a reman on his. It was a very expensive lesson learned but I know I will never have that shop do any other work for me. I've been telling alot of my friends with diesel equipment to stay away from that place also. Oh well I guess you live and you learn. lol

I recently had the injection pump rebuilt on a '87 MR with the EM6 237 engine. The truck actually ran well before I had the pump rebuilt except it had a very rough idle and the pump was leaking some oil which the DOT frowned upon last time I got pulled over. Other than that the truck always fired up at the touch of the key and had plenty of power. Anyways I had the pump rebuilt by a place that is suppose to specialize in rebuilding Bosch pumps although I have heard some people not having good results with them. The ol' boy who rebuilt it told me he found that the throttle shaft was badly worn along with the throttle shaft bushings and said that's what probably caused the rough idle. He also told me that someone had turned the fuel screw on the pump all the way down to where it wasn't putting out much fuel so he claims he turned it back up and calibrated it to the right specs. Well apparently he didn't do something right because now the truck won't hardly run at all since I put the pump back on. When I cranked it over it didn't even sound like it wanted to hit. I figured it just had air in the lines so I cracked the fittings at the injectors and cranked it until it showed fuel squirting out of them. Still didn't even try to start. Finally after giving it a few shots of starting fluid and pressing down on the accelorator pedal it started. However it runs terrible, it won't rev up past 1600 rpms and you can't let it idle down below 700 rpms or it will just splutter and die. Also the throttle is not very responsive, you press down on it and it hesitates a second or two before it wants to rev up. One other thing I noticed is that my chrome exhaust stack got very hot and turned blue, something it had never done before. I called the place that rebuilt the pump today and they are like "well we set it to specs and they only thing we messed with was the fuel screw." Before I had the pump rebuilt the truck never seemed to be starving for fuel to me and it put out a decent amount of smoke, now when I do get it running it barely puts out any smoke at all. I just wonder could it be that the fuel was already turned up and they turned it down? I would think they would know what they were doing but I do know another guy who had a pump rebuilt there and they put it together out of time so I guess anythings possible. I was wondering if maybe I could try adjusting the fuel screw myself a couple turns and see what happens. I know you pull the cap off the top of the pump but I'm not sure which screw it is. I see one that has a jam nut on it, is that the one? If it is which way would I need to turn it to turn the fuel up? Maybe I shouldn't mess with it at all but I'm willing to give anything a try now to get this truck running again. Thanks.

No not yet, thinking about taking it to a mechanic here before long and seeing what they think. I'm thinking the injection pump probably needs some adjusting done on it or maybe even rebuilt. Sure would like to get the problem fixed, it would make the truck alot more enjoyable to drive. I don't mind my old hot rod '64 chevy having a rough idle but I don't like it on a truck I have to sit in 8 hrs a day. Lol

Yeah I know I've had international and volvo trucks and they always idled at 700, this is the first mack I've had though so I'm kind of new to them. I did notice the head on the idle screw that the throttle rests against is slightly wore down, maybe I need to replace it with a new one and see what happens. I had a friend of mine whose fairly smart on diesel trucks drive it awhile back and he described the problem as a "roll" in the engine. He said something about there may be a buffer screw on the injection pump that needs adjusted but he didn't really know either. It's a trash truck and alot of times I'll be out on my route and people will stare at it like their thinking "that truck surely shouldn't sound like that." Lol

It's an automatic, an Allison 654.

Ok I've got a '87 Mack MR that has a EM6-237 engine in it and it's a good sound truck with only a little over 90,000 original miles on it but it has a idle that is very annoying. Now the funny thing is the truck will idle real smooth when it's in neutral but as soon as you put it in drive or reverse it starts idling so rough that it shakes the whole cab. The truck will drive fine when your going down the road and everything it's just when it idles in gear. I recently changed the fuel injectors thinking that might take care of the problem and it did help just a little but the truck still idles too rough for me. I have also turned up the idle screw on the injection pump but that didn't really help either. Right now the truck idles somewhere around 600 rpm but I've noticed the tack needle jumps back and forth about a hundred rpm or so when it's idling. My guess is the problem is in the injection pump? Not sure what else it could be.