M45

[JDS]

That spider harness should be connected to wire #27 which is +24V. The gauges are grounded through the gauge panel to the body.

 

[Recovry4x4]

We should both stand corrected! JDS pointed out that the spider wire is hot with 24V and that's correct. My previous post stated that it was a ground and thats not correct. However, the gauges function through the variable resistance to ground through the assiciated sending units with the exception of the voltmeter which has a direct wire to ground. I'm glad we have people policing other people, I could have gotten somebody zapped. JDS, thanks for your most worthy post!

 

[SixBuy]

If I were betting, I'd bet on it being an ignition problem. Most likely a coil going bad. Most of the battery-and-coil ignition systems also carried a ballast resistor in series with the coil to keep it from burning up if the points were closed 100% of the time. I don't know if that's the case here but it's worth a look. They were either a piece of resistance wire from the ign. sw. to the coil or a wirewound ceramic resistor on the firewall. Often, the less educated would bypass them to get more 'fire' and wind up frying the coil. Measure the voltage on the 'hot' side of the coil when first started and then again when symptoms appear. That may be a clue. Good luck.

 

[jrosbo]

How do you check voltage on the hot side of the coil when started? You have to remove the dist. cap to get to the coil. Also the resistor is inside the dist. It also has two condensors inside the dist. I ordered a new coil which should be here on Friday just in case. I am going to go through each of these posts on Saturday till I can find the problem. Thanks for all your help on this and I will let everyone know what I find.

 

[red devils dude]

plug the coil straight into a spark-plug.

 

[Westech]

the coil is a very good guess, I have had the happen befor. Also check to see if its vapor lock ( boiling gas in carb or lines) make sure all lines are away from heat.

 

[jrosbo]

Ok, run about 15 gallons through the fuel lines into another fuel tank, cleaned it all up, blew air through the vent line for about 5 minutes, changed the fuel filter, and replaced the coil. Good news no vacuum in the tank. Truck ran great, drove it for over an hour, worked it hard, not a single problem until BOOM, backfired, now it wants to backfire through the exhaust. Any ideas? Timing? Air-fuel mixture? Anybody know how many turns out on the mixture settings. Turning them does not seem to make much difference until you shut them both all the way down. Thank you all for all your help you are a great bunch. Hopefully I can pass on what I have learned to someone else that needs help someday.

 

[ida34]

I had a similar problem with a garden tractor and it turned out the float in the carb was bad. When the engine was cold it would run great. When it was warm it would surge then die and would not be restarted. After an hour or so it would start up again like everything was fine. The engine ran worse and worse until it flooded itself out. This would seem to agree with the fact that the mixture screw have little effect. Maybe this helps and maybe not but it is another thing to try.

 

[SixBuy]

Back to the coil - I should have said "Check the voltage on the hot side of the PRIMARY" ( that's the screw terminal other than the one that goes to the points). It's marked with a "+" on most coils. Incidentally, reversing the primary connections to a coil will often cause misfires because the spark jumps the plug gap in the wrong direction and needs a higher voltage to fire!