Quitting Trouble

[CF686F1292]

I co-own a 47 model 19 fire engine with a 707 thermodyne gas motor. Recently when you get to operating temp. or near,she bogs down when you apply pressure to the accelarator,and trying any kind of hill is a definite no-no.if you let it cool down she'll restart. Has new gas filters,and fresh tank of gas....now I have hardly ever worked on gas engines,and she has a dual ignition set up(diesel man through and through). was wondering if it was from running years of unleaded fuel or maybe sludge built up over years? Trying to get it to run properly as we want to take it on a 45 mile round trip to an antique fire apparatus show,and would like to run the pump while there. Thanks for any,and all help.

[Firemack]

CF Dieselman

Have you changed anything on the engine recently that might have caused the problems?

Changed the timing, adjusted the valves etc?

It is not likely that you have any problem with the dual iginition system. You can check that by running on one, then the other, then both while hot to see if you get any change in performance- however I doubt that the ignition is the problem unless you changed the timing on both distributors recently and then started to have these problems.

More likely is the fuel system- it could have vapor lock and fuel starvation when hot, the fuel pump could be the problem- or the fuel pickup in the tank could clogging and be causing the fuel starvation. Set up a fuel pump pressure gauge inline (with a temporary "T" fitting) so you can run the engine and monitor the fuel pressure (while revving the engine or driving) to see if it drops when hot or when pushing the engine. You should have between 5-6 pounds (check the 707 specifications) if it is running out of fuel you will see a drop in pressure and then it will start to run poorly.

You may have a tank mounted pump or engine mounted pump or both, and will be need to monitor at the carb to see what is happening.

Let us know what you find out.

Firemack

[CF686F1292]

Nothing has been done to the motor,except for filters,there is a "juryed"rigged intake hose to the carb. Think plugs have been in for a while. Guess next chance I get will check carb internally for gumming,and get a gauge to check pressure of gas. co-owner ran it today,and she was cutting out as he was running it. I believe you are correct as in fuel supply problem.

[vanscottbuilders]

Nothing has been done to the motor,except for filters,there is a "juryed"rigged intake hose to the carb. Think plugs have been in for a while. Guess next chance I get will check carb internally for gumming,and get a gauge to check pressure of gas. co-owner ran it today,and she was cutting out as he was running it. I believe you are correct as in fuel supply problem.

If I were a betting person, I would put money on the "jury rigged" fuel supply hose. If it is getting too hot, it could certainly cause vapor lock. And not being original, it is likely not routed in the original manner, either. So it could be too close to something hot, which could lead to unpleasant surprises while driving !

The fuel pressure gauge is a good idea, but I think clogging of the pick-up line would occur at any temperature.

Just my two cents.

See if you can a response from Freightrain - drag racers probably know more about vapor lock than anyone on the planet.

Good Luck,

Paul Van Scott

[CF686F1292]

Sorry intake hose I was talking about was air intake into carb. THANX so very much for the responses,am getting ahold of co-owner so we can go check out these ideas. Got 1 more question..could it be the carb to manifold gasket is split? getting hot it spreads,and gets to much air,and causes her to quit?

[Charlie Hatfield]

An easy quick check os to start the engine and spray starting fluid around it. If it is leaking the engine will speed up!