Vapor lock?

[RimBenty]

That is a vented cap, if your Jeep runs fine in normal driving it should be working. A symptom of a gas cap not venting would be the engine cutting out when driving at speed or under a load.

In your second photo, of the underside of the cap, you can see the four external (to the tank) openings along the edge between the inner and outer halves of the cap. The internal vent is the hole in the center.

A previous owner of my Jeep drilled a hole in top of the cap, I assume because the original vents became clogged. Going around a turn with a full tank would cause gas to leak out. I replaced it with a locking gas cap off of eBay, Stant model G95.

 

[Beach66Bum]

That is a vented cap, if your Jeep runs fine in normal driving it should be working. A symptom of a gas cap not venting would be the engine cutting out when driving at speed or under a load.

In your second photo, of the underside of the cap, you can see the four external (to the tank) openings along the edge between the inner and outer halves of the cap. The internal vent is the hole in the center.

A previous owner of my Jeep drilled a hole in top of the cap, I assume because the original vents became clogged. Going around a turn with a full tank would cause gas to leak out. I replaced it with a locking gas cap off of eBay, Stant model G95.

I bought 2 of those in chrome. They were an optional gas cap in the accessories brochure.

 

[PeteL]

I'd suggest checking and verifying all other 'tune-up' specifications. Plugs, points, timing, etc.

 

[mickeykelley]

I’ll try that next time.

The video above was good. I’ll see if I can get a fuel filter with a return outlet as well

My ‘58 does not have the return inlet at tank. I have experienced the vapor lock during summers and after driving a while. I planed to add the electric fuel pump tied to oil pressure switch.

 

[RimBenty]

So this thread got me thinking about why I have to hold the gas slightly open to start my Jeep when it is hot. When it does start it runs rough for a little bit before settling out. Another problem I have is that I would occasionally smell gas after parking it and sometimes it would drip out the throttle shaft onto the intake manifold. So I did some looking around and found this video -

I pulled the carb off and tested the accelerator pump checkvalve ball as he instructed. Sure enough it did not have a tight seal to the seat, that was fixed with a couple taps of hammer. While I had it apart I checked the float level and it was about 4/32 too high according to the chart here. https://www.carburetor-parts.com/ro...h8z0UNu_A_qT1svl6pduyLwFNBSFAHTv2pZhktveL0NdF

I did go on a short test drive and didn’t see any fuel leaking from the venturi after shutting it off. I don’t know if that fixed my problem yet but it’s too darn hot to mess with it anymore today.

 

[Beach66Bum]

So this thread got me thinking about why I have to hold the gas slightly open to start my Jeep when it is hot. When it does start it runs rough for a little bit before settling out. Another problem I have is that I would occasionally smell gas after parking it and sometimes it would drip out the throttle shaft onto the intake manifold. So I did some looking around and found this video -

I pulled the carb off and tested the accelerator pump checkvalve ball as he instructed. Sure enough it did not have a tight seal to the seat, that was fixed with a couple taps of hammer. While I had it apart I checked the float level and it was about 4/32 too high according to the chart here. https://www.carburetor-parts.com/ro...h8z0UNu_A_qT1svl6pduyLwFNBSFAHTv2pZhktveL0NdF

I did go on a short test drive and didn’t see any fuel leaking from the venturi after shutting it off. I don’t know if that fixed my problem yet but it’s too darn hot to mess with it anymore today.

The accelerator check ball (if your carb has it) is aluminium! Don’t accidentally swap with the steel ball!

 

[Cj5dale]

I'd suggest checking and verifying all other 'tune-up' specifications. Plugs, points, timing, etc.

Thanks for the reminder. It makes sense to get everything adjusted to spec before going too far with troubleshooting.

I will also check to make sure the return line is open while I’m at it.