Looking for some advice or answers, a friend of mine has an 89 Humvee that he converted from the 6.2 to a 454. We were wheeling last weekend in the most amazing terrain and it was 107 degrees. His tank would not vent and he continuosly faced a vapor lock situation. Here is the question. With the cahnge from diesel to gas, is it necessary to also change the fuel tank? What would be the recommendation to move to and yes, he has a venting cap, that did not work. I do not know if it was the extreme heat or the near vertical walls that we were scaling that contributed to the engine cutting out, but we are curious and will change the tank if necessary. thanks

Looking for some advice or answers, a friend of mine has an 89 Humvee that he converted from the 6.2 to a 454. We were wheeling last weekend in the most amazing terrain and it was 107 degrees. His tank would not vent and he continuosly faced a vapor lock situation. Here is the question. With the cahnge from diesel to gas, is it necessary to also change the fuel tank? What would be the recommendation to move to and yes, he has a venting cap, that did not work. I do not know if it was the extreme heat or the near vertical walls that we were scaling that contributed to the engine cutting out, but we are curious and will change the tank if necessary. thanks

Looking for some advice or answers, a friend of mine has an 89 Humvee that he converted from the 6.2 to a 454. We were wheeling last weekend in the most amazing terrain and it was 107 degrees. His tank would not vent and he continuosly faced a vapor lock situation. Here is the question. With the cahnge from diesel to gas, is it necessary to also change the fuel tank? What would be the recommendation to move to and yes, he has a venting cap, that did not work. I do not know if it was the extreme heat or the near vertical walls that we were scaling that contributed to the engine cutting out, but we are curious and will change the tank if necessary. thanks

A couple of things come to mind.

I gather that the truck is fuel injected. If not, that's your number one problem. Carb'ed trucks have to be modded with a specialized carb to prevent starving the engine.

Inside most fuel tanks of the H1's, there should be a gridded, angled piece of metal that helps prevent or reduces abnormal shifts of fuel during off camber situations. Sometimes that piece gets loose. Also make sure that the fuel pickup line isn't angled wierd.

I don't know if the HMMWV's tanks are the same as the civvy versions.

my dad alway used an in-line elect fuel pump to solve vapor lock. if thats the problem its easy to install. put an inline fuse and a temperary switch in the drivers area. if thats the problem just make it permament.

How would the heat have affected the fuel within the tank and would this have had an affect on the performance? We had to stop a few times a manually vent the spare fuel cans becasue they had expanded so much. When we vented the fuel cap it was a long and messy process. Are the tanks made to expand differently becasue of the differing properties of the fuel. I will also relay the injector information as the engine is carboreted(sp).