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Posted by David Sherman on Thursday, April 30, 2009 at 00:20:22 :
This should be simple, but it's got me stumped. The weather's getting decent so I got back to work on the ambulance. When I quit for the winter, I'd just overhauled the sealed military distributor, and had put on a 24 volt starter, a military generator and regulator. The truck came with the military distributor (24 volt coil on a 12 volt system) and military carburetor and air cleaner. I think the engine itself is civilian since it had a small hole for a mechanical temperature sender, and it has a civilian crankshaft pulley. I'm trying to put the truck all the way back to military configuration eventually. So, that's the setup.
Last year I pulled the head so I could drill and tap a 1/2 IP hole for a military electric temperature sender. The engine looked great inside. I also pulled the manifold so as to braze up a big hole and a small crack in it. Since it's a big deal to get the military carburetor off, which I had to do anyway to fix the manifold, I overhauled the carburetor and cleaned the PCV valve. I also put a military (double-acting) fuel pump on it, hoping it would make the wipers work better. While I had the manifold off, I adjusted the valves (cold). After I got the head, manifold, and fuel pump back on, I fired it up and it ran okay, though I think I misadjusted one of the valves because it didn't run as smoothly as before. Still, it started quickly and ran pretty well.
So, today I went to fire it up, and it would not fire at all. The generator and regulator can't have anything to do with it. The only thing I did since it was running well was to take the distributor out, take it apart, clean it and paint it, put new points in it, and put it back on. I used half a can of ether trying to get it going, without it starting even briefly. It backfired enough one time to light the ether in the intake elbow on fire, but that was it. I initially tried with no choke, just ether, so I doubt I flooded it.
I can draw a spark about 3/8" long from the #1 spark plug wire, so I'm pretty sure it has adequate spark. If I crack the fuel inlet nut at the carburetor, fuel spews out vigorously when I crank it -- but even if it didn't it should have at least started on ether. A timing light shows the timing is spot-on. After many attempts to start it, I took out the #1 plug and it was dry and clean, which again tells me I probably didn't flood it.
It seems to me that if an engine won't even fire briefly on ether it must either have no spark, or terrible timing. I know I have the spark plug wires hooked up in the right order, which I double-checked. 3/8" spark seems pretty snappy to me. The timing light shows that the timing is right. I haven't had the timing cover off and I highly doubt that it's jumped time.
Any ideas? Is it possible to put the distributor in wrong (either the tang or the drive gear) such that a timing light would show correct timing but it would be 180 degrees off? Before I put the distributor cover on, I made sure that the rotor was pointing at the #1 plug position when the timing mark lined up with the pointer. If the timing was even somewhat close, like within 45 degrees, I would expect it to try to run a little bit, or backfire a lot. The only other difference I can think of is the 24 volt starter doesn't spin the motor as fast as the old starter did, which was probably a 6 volt starter on a 12 volt system.
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