IHC Loadstar loosing power

F

FredBear

New member
We are dealing with either a carb issue or ignition issue (hopefully) so not being sure I went with the basic forum. We have a 1975 International loadstar fire truck with the 446 engine. The truck starts good, idles smooth and has normal power under acceleration untill you enguage it into high range at approximently 45 mph. It acts as if its running out of fuel, if you pull out the choke you May pick up another 5 mph then it starts back firing. If you come to a complete stop and start all over again it takes right off with plenty of power untill you reach the same point and the issue repeats its self. Originally we thought it May be the fuel pump since this truck has a electric fuel pump that supplies gas to the engine along with a generator unit. We replaced the fuel pump and filter with no change in the issue.
The carb was rebuilt a couple years ago and in checking the floats everything seems to be adjusted correctly. Which brings us to the ignition, none of us are familiar with the type of distributor and vacuum setup it has. Does anyone have any ideas as what could be causing our power issues? And where should we go from here in trying to correct it ? Our biggest dilema is this is still an active fire truck and no one around here knows how to work on the IH gas engines when they are having technical issues! Thanks
 
The mv series of engines are not the same as the sv. As a consequence the care and feeding of the mv is a little different from the sv engines.

Some of the same stuff applies since we are talking about old school gas engines.

It sounds to me more like a fuel delivery issue than ignition.

Since you have ruled out the pump and filter (check to make sure there isn't another filter in the line somewhere) I would check to make sure the governor isn't kicking in when it shouldn't be.

We had one bus with the mv404 that got sent down the road due to fuel delivery issues. The ethanol blended gas played havoc with the tank. Even after cleaning and lining the tank we still had issues of crud and corruption blocking the lines. To solve the problem we finally traded the bus off.

If it has the stock carb on it still it should have vacuum operated throttle plates. What your truck is doing sounds exactly like the governor doing what it is supposed to do but at a lower speed. It might be time to rebuild or replace the carb.

The ethanol blended gas really plays havoc on old school gas engines, particularly ones that don't get a lot of miles or hours on them.
 
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