My 40 shut off on the fwy, any thoughts?

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If it sputters and dies like it's not getting gas, you may have a vapor lock. Burn thru your tank of alcoholed gas and try non-ethanol. Alcohol vaporizes earlier than petroleum gas. Worked for me.
 
When it dies you should check for spark with an inline spark tester. Cheap tool that visually lets you know if you are getting spark at the plug. Plugs between plug and plug wire. Spark, fuel, air. One of them ain't right.
 
An over heating coil can feel like running out of gas.

Yes, I actually called and spoke with Mel at JT Outfitters about this specifically and he personally sent me a coil (his modified Pertronix coil) and guaranteed it was not the coil overheating. I spoke with him for about 45 minutes as he was an absolute wealth of knowledge.
 
If it sputters and dies like it's not getting gas, you may have a vapor lock. Burn thru your tank of alcoholed gas and try non-ethanol. Alcohol vaporizes earlier than petroleum gas. Worked for me.

I've never run anything but non-ethanol gas. The first time it happened I thought for sure it was vapor lock. I wrapped my gas line in heat reflective cover too just to make sure. Problem still rears its ugly head. No idea what the cause is.
 
Just a wild guess...but, take off your gas cap and drive around and see if the problem goes away. Perhaps it is not venting properly and when the vacuum builds up, the fuel supply gets choked off?

Yup. Tried that as well one of the first times it occurred I immediately pulled the gas cap off hoping to hear an audible pop of suction. Just to make sure I even replaced the gas cap with a new venting gas cap. Still the problem persists. Mind boggling all of the things I have done to chase down this gremlin.
 
Yes, I actually called and spoke with Mel at JT Outfitters about this specifically and he personally sent me a coil (his modified Pertronix coil) and guaranteed it was not the coil overheating. I spoke with him for about 45 minutes as he was an absolute wealth of knowledge.

Can you explain why he needs to "modify" an existing coil ? I am still using the coil from 1969, with a pertronix, and I live in Arizona with huge heat.
 
My coil story from another project. PCM ford 351 boat motor. Two new coils, both would not fire when they got real hot. Found out that PCM started getting cheapo chinese coils that were oil filled and really not designed to be mounted sideways. Bought an Accel epoxy filled coiled designed to be mounted sideways and never had another problem. Diagnosed by checking for spark when it wouldnt start.

Sometimes you cant trust new parts.
 
You could possibly have trash in your tank that plugs the pick-up and then when the suction breaks it releases and will repeat again later. I had this happen the rubber hose that connects the filler neck to the tank disintegrated and was flaking off rubber plugging the pick-up
JP
 
Can you explain why he needs to "modify" an existing coil ? I am still using the coil from 1969, with a pertronix, and I live in Arizona with huge heat.

Nope, I can't but he used to build stock cars and dragsters back in the day and apparently in the area he lives he is somewhat of a local legend amongst the race crowd. He does some type of a mod to both the electronic ignition system and the coil to make it even better. I'm not an authority on either so I can't add any value to the reasons why.
 
My coil story from another project. PCM ford 351 boat motor. Two new coils, both would not fire when they got real hot. Found out that PCM started getting cheapo chinese coils that were oil filled and really not designed to be mounted sideways. Bought an Accel epoxy filled coiled designed to be mounted sideways and never had another problem. Diagnosed by checking for spark when it wouldnt start.

Sometimes you cant trust new parts.

Agreed, which is why I had 2 new coils I installed and the problem still persists. I thought the same as you did so I bought another new coil and the issue occurred again. Fortunately, the shop I bought the first new coil from was kind enough to take it back as they thought perhaps the new coil could have been bad. Turns out it is not a coil issue.
 
You could possibly have trash in your tank that plugs the pick-up and then when the suction breaks it releases and will repeat again later. I had this happen the rubber hose that connects the filler neck to the tank disintegrated and was flaking off rubber plugging the pick-up
JP

I scoped my tank with an fiber optic scope from a local mechanic had and got a very good look at the entire interior of my tank. For a 40 year old tank it looks amazingly clean. Very minor rust spots only in a few places but no flakes nor debris floating around. if you look at my picture of my engine bay you can see the second fuel filter I am running so I can catch any debris that might make it past the first fuel filter which I have mounted in between the tank and the fuel pump. So far I've changed out the second fuel filter twice and each time I inspect the filter there is no debris at all.
 
Good advice. The first thing I would check are the basics and go from there. BTW, I have found that owning a 40 is a life long chase of gremlins--especially electrical which Mark had noted in in a post in another thread.
 
My 2 cents. Always buy the ACDelco unit if you have a choice. Yes they are more expensive, but cheaper than replacing several failed Chinese knockoffs as a friend of mine has. My original module was out of a donor car and lasted nearly 30 years.
 
Good advice. The first thing I would check are the basics and go from there. BTW, I have found that owning a 40 is a life long chase of gremlins--especially electrical which Mark had noted in in a post in another thread.

Yes, this is where I think the problem persists but candidly I don't really know where to start.
 
When I bought my 40, I had the orig. carb rebuilt. I would consider that If I were you. At a minimum that process will get your carb cleaned and you can eliminate one source of potential problems. Sounds like fuel starvation to me btw.
 
When I bought my 40, I had the orig. carb rebuilt. I would consider that If I were you. At a minimum that process will get your carb cleaned and you can eliminate one source of potential problems. Sounds like fuel starvation to me btw.

I ran two different carbs on it to see if it was a carb issue and the same shut off occurred on both carbs.
 

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