So walk us thru your system again? You still running two pumps?

I've never tried to touch my fuel rails after the engine has been running, so I can't tell you how hot is too hot. I have issues with brake lines being too close to my header and destroying a custom tube. I found some spark plug heat reflector sleeves and installed those. Seems to help quite a lot. Maybe you could find something similar for the fuel rail??

The fuel rail gets hot. It's metal and bolted to the hot intake manifold.

Fast forward, still not out of the woods. Turned a 5hr trip returning from Moab and made it 11. Was having problems the last 2 days when it heated up and the sun came out in full force. Planned to return yesterday when the sun was setting to try and keep it in the shade when its cooled down.

Tried 91 octane, removing the insulation and clamps from the HP pump, octane booster in a bottle (I was throwing darts at it was 1am I was willing to try anything to get through the passes), poured water on the fuel rail and let it sit for 10-15 mins at a time so we could get 15 more miles. Packed the rail with ice, then snow, I'm not sure anything but letting it sit helped much.

I have a thought.

My old setup never vapor-locked, running with an in-tank pump in the Sherman tank. However, in warmer weather, the tank would develop a tremendous amount of pressure. After removing the tank for the diesel conversion, I noticed the return line just dumps into the top of the tank. This is big No-No for fuel system design, as it aerates the fuel. Even the install manual for the Cummins warns again this.
Return fuel needs to be re-introduced below the fuel line and away from the pickup.

Since my HP pump was submerged and always pushing, I got away with it, but if your setup is on the edge of acceptable with two pump pulling fuel, it could be exasperating the problem by lowering the pressure on the suction side and forming vapor with already hot and aerated fuel.

Thanks Digger. I can see how that could be a possibility. I have a tank very similar to this one offered by Tom's https://www.tomsbroncoparts.com/product ... bronco-new

I did once change the sending unit because of inaccuracy, which it still isn't right unfortunately, but if I recall correctly, the pick up/return tubes welded inside the tank drop down and to the bottom. That very small sending unit hole is just enough to look down into it a little. The tank is baffled so I can't see the bottom through that hole. I will be dropping the tank again soon once its low on fuel and take another look..

Well, here’s something. I have a thought this may be the cause.


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I agree, the tube is so thick walled though I’m not sure I can move it without pinching it off. I’ll have to cut a hole in the top of the tank to get in there regardless, the sender is only about 2” around.


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So the return was dumping into the small diamond shaped pickup area? Can you hook it a bit of rope and pull it enough to clear it out of there? I mean, if you have to cut the tank to fix that, then you're asking for trouble in the explosion dept.

Sure, but you have to weld it back up...

The neighbor to my folks lost his life doing this.

I was thinking a cable type cutter, but you hate to introduce metal shavings into the system.

Do you know who made the tank?

May change to dual hydramats instead. Less plumbing and those things apparently work wonderfully. One on each side of the baffle will cost me just a little more than the walbros would have.


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I'm running a hydramat. Seems to work great. My tank was like yours and I ordered a hat/pickup from nwmp and went intank. drained my tank and filled with water a few times to flush it out. filled with water and drilled the hole with a hole saw. Drained the tank and wiped it all out. Put in a new walbro pump and hydramat. No issues left now.