My 87 300 sdl has started to hesitate with acceleration. This usually occurs from a standing start and after a second or two the car takes off with a small puff of dark gray smoke from the exhaust. Today it stalled when I turned on the AC while at a light. It seems to accelerate ok on the highway, does not burn oil and has been running great, except a bit warm (100) since the outside temp is over 85. Any suggestions.

Brad,
I'm sure you will find a fuel system problem. check the obvious things first. Does your hand pump leak when used, if so air can be drawn in and cause problems. fuel filters? In tank strainer clogged with gunk? As a long shot has anyone else fueled your car lately. It will give the symptoms you indicate with a big shot of unleaded in the tank. Give it a sniff. If you have no joy with these let us know.

Bob D.

I cleaned out the vacuum line between the intake manifold, overload protection valve and ALDA.It was plugged solid. The acceleration is better but the car still hesitates at stops and mildly surges(like it is missing) when on highway. I am the only one who fuels the car, but I cannot say if the fuel was not contminated. I have recently switched to CITGO diesel and the problems started after the second tankful. If there is gas in the tank how would I know other than the smell. Could these problems be due to a bad injector or injector pump? Thanks

Brad,
Smell is the only easy way to tell. If there is enough to cause a problem you'll be able to tell. In my area CITGO uses a green cover on the diesel nozzle while Hess uses green on unleaded. This could lead to confusion if you're in a hurry or distracted. If so no harm done Drain the tank if it is bad or run it down if it's tolerable then fill up with a known good quality fuel. I should have read your post more closely the first time you don't have a hand pump on a 603.961 engine. They are used on the 617.951 engines used in earlier SDs and other earlier diesels. A small amount of air is normal in the pre filter but if the filter change coincides with your problem have your mechanic check for air leaks. The puff of black smoke with the hesitation could indicate a bad spray pattern on one or two injectors. If you run a can of lubromolly diesel purge ( I think the parts shop carries it ) through the system according to the directions on the can one can often have good results without having to resort to swaping out injectors. One last thing that I thought was common knowledge but might not be, is that diesels need to be run hard regularly to stay in top shape. Diesels will deteriorate if driven exclusively at low rpms and on short trips.