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Old 08-04-2010, 11:02 AM
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Air Randy Air Randy is offline
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Join Date: Aug 2008
Location: Franktown, CO
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Quote:
Originally Posted by kfuss View Post
I know what my vapor lock issues are with the FI, too much heat. I need to reroute my fuel lines to the back of the intake but that costs $$$'s.
Kirk,

I'm not 100% convinced your vlock issue is due to heat on the fuel lines in the engine compartment. The FI rigs I've worked on in the past with this same issue solved the problem by changing the fuel tank plumbing and their fuel pump location. The stock GM rigs with FI rarely ever had vlock issues. If possible, look at a stock GM truck that has the same engine that you have. Look at how many return lines to the fuel tank and vent lines there are and try to copy that as best you can. Most of these rigs also had the fuel pump mounted inside the tank which also helps keeps the fuel cooler. Remember when we started trouble shooting your rig that there was a LOT of pressure built up in the fuel tank. Once we released that pressure and then bled the air bubble out of the pump to engine section of line it started right up and ran pretty good the rest of the day. If it was vlocking due to engine heat I think you would have had recurring issues later in the day when it was warmer and the engine was working harder climbing those long hills. However, if it does turn out to be an engine compartment heat issue you can buy an aftermarket device called a "cool can". You install it in the engine compartment and route the fuel lines through it. The cheap ones you just fill with water periodically. The better ones you route a heater hose line to it and it uses the engine coolant water to keep the fuel cooler.

As far as my rig: I didn't have any vlock or loading issues. I ran premium fuel; I have a stock Aisin carb; I have a stock (but new) mechanical fuel pump; I do not have a carb fan; I do have a liquid heat riser installed on my intake manifold and I have a header versus a stock cast iron exhaust manifold. Maybe the premium fuel made the difference but I do know the liquid heat riser keeps the intake manifold and carb base from never getting hotter than the engines water temp, so as long as the motor isn't over heating the carb stays relatively cool. The after market header probably dissipates heats better than the stock cast iron unit too.

We may have had 4 totally different issues too that were calling "vapor lock". The v8/FI rig may have had fuel tank pressure issues, one FJ40 appears to have had a leaking carb/over rich issue, Ricardo's rig had an air lock between the fuel tank and fuel pump issue, and Marten may have had legitimate heat related vapor locking.
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