Hemi not starting when hot

[Rippin]

I've had this problem for years and have tried about everything. My latest effort failed today as well. Hoping you guys may have some ideas. When it is hot it will not start even if priming with gas or even ether. Which began me wondering could an electrical issue be in play when hot. Today, I replaced the coil (know they can be subject to overheating)... I thought that might be it...but no difference, still will not start until in cools all the way down.

Things I've already done:

1) Replaced points system with electronic ignition

2) tried a different fuel pump & added thicker gasket to mounting plate

3) thermal wrap on fuel lines

4) thicker gasket under carbs

5) made sure all fuel lines are not touching heat source, stock routing

6) replaced coil

7) Orange box mounted inside car away from heat

I'm frustrated!!!!

 

[rrowdy]

I had a wedge that would not atart when hot, I tried a lot of different things ignition related and no luck.
Turned out it was dumping fuel into the manifold when it was shut down while hot and I tried another carburetor . Big difference.
Not saying this is the cause but it might be an area to look.

Good luck!

 

[Cranky]

Last time I had this issue, it was the same thing that rowdy mentioned. I found when I shut it down after it was hot, I pulled the air cleaner off as fast as I could and saw fuel trickling down into the intake which made for a flooded condition. Sounds like what you might have since the ether won't do anything either. Ether won't help much when flooded bad enough. Have you tried flooring it and holding it there until it fires up? If it doesn't start up after grinding on the starter for 10 solid seconds, give the battery and starter a rest but DO NOT let up on the throttle. Keep it floored and after waiting about 30 seconds, try it again and see if it'll fire up. I had one where I ran it through 3 cycles of this and it fired up finally but like I said, do not let off the throttle or you will just pump in more gas when you try it again.

 

[Rippin]

Thanks rowdy & cranky.

Worth a shot. I replaced the rear carb several years ago for different reasons and that did not help either. It could be front carb draining as you mention since that one has been in place throughout the issues so will check that out...heck, got nothing to lose.

 

[snakeoil24]

a return line to the tank will help if your runing either a mechanical or electric pump, also a vapor lock cannister made by ma mopar was the best one i ever seen.

 

[Hemi Rebel]

When it wont start, hold the pedal to the floor when cranking. Dont pump it, just push it to the floor and hold it there till it fires up. If it starts, you know you have a flooding issue. It most likely wont fire right up, you will have to keep cranking about twice as long as usual.

 

[snakeoil24]

Hemi Rebel good idea I'm forgetting this good advice.

 

[Bigal75]

You've been tolerating this for years? If fuel is pouring into the intake then I assume the oil would smell like fuel. Whenever I flooded an engine I could smell it. Is the timming OK? Something is definately wrong.

 

[Northwest]

1) Are you using a new Chrysler-style distributor with a pick up coil?

2) Have you checked for spark at the coil when cranking hot?

I had the exact same problem. Car would start when cold, and would restart hot after maybe 5-10 minutes, but then would not start if it sat for 10 minutes to 90 minutes until it cooled all the way down.

Turns out that the new pickup coils in the distributor simply won't put out the proper voltage when hot to trigger the box to send a spark. I wouldn't get spark from the coil when hot because of it.

Solution is to close the gap between the pickup and the wheel to as tight a tolerance as you can without them hitting. Worked for me and now it fires up hot.

 

[Pops1967GTX]

Check your timing ..advanced too far cause hard starting...reluctor gap for the electronic distributor...

 

[oldbee]

rippin--sure sounds like rowdy says..Maybe your float level needs to be lowered a tad. 90's next week on northern Ohio, so it'll only get worse.

 

[Rippin]

Thanks guys. I disconnected linkage to front carb (in case it is leaking, though see no evidence) and got car hot. It did start using holding pedal to the floor method. Though description Northwest provided is identical to what mine does. Any post on the site on exactly how to adjust pickup and wheel as mentioned?

The motor has 11.25:1 compression so my battery does not last long when in this situation too.

 

[Hemi Rebel]

Im leaning toward a fuel issue. What happens is the fuel in the lines and carb are so hot it expands and pushes out of bowl into engine. Should try to find some way to shield carbs from heat. I feel it has to do with the oxygenated **** that passes for gasoline today. Course, vapor lock happened way back when too i suppose.

 

[Sixer]

Original cast iron or original type intake manifold has heat chamber under both carbs. All the heat shields in the world won't help if this is that type. Block off that heat riser at the manifold and it will be more cold blooded but no more heat issues. In manifold type choke thermostat will also stop opening however.

 

[Hemirunner]

Thanks guys. I disconnected linkage to front carb (in case it is leaking, though see no evidence) and got car hot. It did start using holding pedal to the floor method. .

If it started using this method, it's not ignition related. This thing is dumping raw fuel down the intake for some reason. Holding pedal to the floor allows it to get more air and lean out enough to fire it. Set the floats and put in off road(spring loaded) needle and seat assemblies. Check fuel pressure while you're at it as these carbs don't like alot of fuel pressure. Off road needle and seats will help with that situation.

 

[Northwest]

Rippin -

I agree with Hemirunner / Hemi Rebel.

My situation was ignition and I found out by putting the timing light on the coil wire when it wouldn't start. Problem was that it was somewhat intermittent because the pickup coil still provided some signal when hot, just a weak one, so I would get inconsistent spark. Sometimes it would fire up, but most times it wouldn't.

Narrow it down by getting a timing light on it when it is in the situation, if you get consistent spark - its not ignition.

If you don't get spark when it doesn't start and it sounds like the situation I described, you may want to try narrowing the reluctor gap. Just loosen the screw in the distributor holding down the pickup coil and narrow the space getting it as close as possible without touching and snug it down. Make sure it won't hit though.

 

[Rippin]

Thanks Again guys. I'll tinker with it some more to narrow possibilities. Will re-hook up linkage to front carb and see if it will start with pedal to floor method...perhaps I've been using wrong technique to start. If it does not start, front carb likely causing leaking. Can re-do it.

Also will check voltage at coil as mentioned and see what I have going there...may be a combo of items happening.

Thanks again.

 

[oldbee]

Rippin-- unhooking the linkage won't help with gas boiling over. It'll do it all by itself out the gas bowl. Just too much heat radiating up into the carb. Years ago, somebody had a carb gasket setup with an aluminum plate sandwiched in between the gasket.. Used to work good for me. Probably Mr. Gasket(?)--