Ignition problem when hot

[tunkx90]

Started up my '73 FJ over the weekend and drove 5 minutes away to a gas station. Seemed to crank more than usual to start after filling up. Drove another 5 minutes and shut it off. Then I started it again which required even more cranking. Then drove it about 30 minutes, it rain fine. Got to my destination and it wouldn't start. While stranded, I swapped out the coil for a brand new one and nothing. Had to get towed home. The next day I put the original coil back in and it fired right up. Anyone know what's going on here?

 

[Skreddy]

Did it have spark when you tried starting/swapped the coil? Is it still points? What condition are they in? Where’s the fuel in sight glass (is it stock carb)? Valves adjusted lately? Using choke? Pumping gas when trying to start? Good battery? Good gas? What engine? Lots of variables.

 

[tunkx90]

I think very weak to almost no spark when coil was swapped. It's an F engine with brand new distributor and internals. Carb is also freshly rebuilt by the expert, Jim. C, so fuel couldn't be the issue. Fuel in the sight glass is half full. It's also got a new head gasket, good compression, and freshly adjusted valves. Everything points to an electrical issue.

 

[JackA]

What kind of distributor? Still points?

 

[tunkx90]

Factory Toyota OEM distributor with points.

 

[Green Bean]

I had similar issue once and traced the problem to poor electrical connections at the ignition. (where the wires plug into the back of the key cylinder). It was intermittent and difficult to hone in on the problem but once identified it's an easy fix.

 

[tunkx90]

Yeah, I thought the same thing and checked that. Doesn't seem to be the problem...connections looked good. As another test, I ran a jumper wire from positive side of battery directly to the coil. That eliminates any switch issues...still will not start.

 

[4x4veteran]

Yeah, I thought the same thing and checked that. Doesn't seem to be the problem...connections looked good. As another test, I ran a jumper wire from positive side of battery directly to the coil. That eliminates any switch issues...still will not start.

Check timing even if you think it is right. Vac advance hooked up?

 

[brooklyn]

So, the old coil gives you good spark? I would suggest getting a remote start kit from harbor freight and then test for spark when you have the no start condition.

If you don’t have good spark, You can also directly wire the coil to check if you get spark then. Once you confirm spark, you can trouble shoot other ignition components if the trucks not starting.

 

[JohnnyC]

73 like my 74 had an ignition fuse … you may want to check the fuse block … I think it’s the second fuse from the top?

 

[Kevin Basner]

73 like my 74 had an ignition fuse … you may want to check the fuse block … I think it’s the second fuse from the top?

Hi Johnny, can you please respond to my PM when you get the chance?

 

[Grayscale]

If the valve lash is too tight, the valve won't close when the engine is hot, and you lost compression, until it cooled down.
?

 

[B y r o n]

Something else you might consider.

 

[Grayscale]

If I checked the resistance across low tension coil terminals, I'd want to do it when hot (greater resistance), right? (Checking for damage as a result of overheating the coil - leaving the ignition in the on position with the distributor static) Do I have to unwire it first?

Check dwell angle and inspect plug and its gap?