I recently bought a low-mileage f600 from the city street department where I live. It originally had a water tank with an auxilliary engine for street cleaning. The tank rusted out years ago and the truck had a flat bed installed and had only been used once or twice a year since the tank was removed in the late 80's. Anyway, with all that being said, when I bought it, the accelerator pump was leaking and it smoked like a freight train. I rebuilt the carburetor and replaced plugs, points,and distributor cap. Found diaphragm busted in fuel pump, replaced pump. Ran fine. Replacement of pushrods (2 bent) stopped the smoking. Now it stumbles/backfires at high rpms. Dwell is (29.6), timing is set a 6 degrees and 550 rpm idle. I have adjusted the carburetor float every which way with no major change. Any ideas?

 

Sounds like The coil might be breaking down at high rpm's? Fuel filter half plugged?
Trash in the tank? did you flush the tank when you did the other work? if it set for a long time with old gas it may have got trash in the carb?..

 

Thank you so much for taking the time to respond. You had some great suggestions, I'll try them when I get home. Thanks again.

 

Also, check for ''Water'' in the fuel? pump some into a glass jar right from the fuel line before the carb, the new ethenal fuels they are selling us now Draw water into the fuel like crazy! I try and run non ethenal fuel in my truck when i'm not going to drive it for a few weeks!.....hope you get her running smooth so you can enjoy!

 

What engine is installed?

I would pull the carb and have it rebuilt. Sitting a year or two can play heck on the seals and needle valve.

Garbz

 

Is the dwell steady at high RPM? When these distributor bushings wear out it causes the shaft to shift back and forth which causes the dwell to vary. Only one degree of dwell variation changes the timing by two degrees which could cause the problem. You may also consider a new set of plug wires. A bad plug wire will often cause a rough ilde but not always. Hope this helps.

 

Thanks to all who took the time to respond and offer help. Installation of electronic ignition and a hotter coil seems to have done the trick. I have used the truck all weekend. Runs fine so far. Thanks again.

 

Just out of curiosity, what was the appeal of a f600 water truck?

 

Glad you got the beast tamed down!....enjoy!!

 

The truck is nothing special by any means. I had a 1965 f35 with a dump bed that was a wore out truck with a good hydraulic operated bed. I have been the engineer for the city where I live for about 15 years. I knew the street department had this old truck sitting around out back that they would get out and play with every now and then. We would all stand around and marvel watching them try to overload the thing around the yard, and at idle you could put your hand on the cab and couldn't tell it was running. One time that they had it out and I asked about the truck; it has 10,650 original miles. They have complete records from day one on both the truck and the Continental engine from the water tank. Long story short, put dump bed on this truck, scrapped the one-ton. Still got an old truck, but have a much better one now.