I have a 1991 RS that I converted to multiport with Street and Performance's integrator. It is a ZZ383 with TPIS Mini Ram and 32# injectors with adjustable fuel pressure regulator at 45#. It makes about 380 rwhp and I had to put a 255 Walbro fuel pump in it as it was running out of fuel on the dyno pulls at high rpms. If it gets warm and is low on fuel, sometimes I can hear the fuel pump start to whine then it starts to stall. If I run it at heavy throttle and high rpms, it will keep running but as soon as it gets to lower revs and lighter throttle, it will completely stall and won't start unless I add fuel or let it completely cool down. I have had three fuel pumps in it and have insulated all the fuel lines anywhere close to sources of heat and the problem has never changed. The whining fuel pump must be the key but I don't know why, any ideas? Thanks.

 

Well the intank fuel pump is kept cool by the gas, running low on gas all the time isn't good.

If your gonna run it low on gas all the time for weight, get a smaller racing type tank.

 

I could do that but it seems to not be addressing the problem. I think there is a problem and I am trying to identify it. Do you have any other ideas?

 

 

Do you mean air from the gasoline boiling? I know it's not running out of gas as it has happened with a lot of fuel in the tank. What would cause the fuel pump to make noise before it happens? It sounds like it's deadheading.

 

 

Does anybody think running the fuel pressure higher than stock can put more stress on the fuel pump and cause it to cavite when it gets very warm?

 

fuel pump sounds like to be the problem (usually doesn't do that with aftermarket pumps)....I had problem with vapor lock when warm as well. Higher than stock fuel pressure does more stress on pump for sure.

I would replace pump (with another good performance one)....then change your fuel filter (and do so every other oil change, they are cheap and usually are cause of burning out pump), change the gas tank vent (located in front of fuel tank, drivers side, gray vent attached to hose to top of tank), then a good trick to do is buy a muffler heat sheild and place it between tank and muffler to help keep some of heat off tank. Also the wiring inside tank sometimes goes bad, inspect that as well, and ALWAYS keep at least 1/4 tank or more of fuel in.

 

A typical TPI/EFI system operates its fuel lines at about 37-44 PSIG. Using 44 PSIG as a sample operating point for calculations (3 BAR), the temperature for gasoline to vaporize and create a "lock" in such a pressurized fuel line would have to be close to 160ºC (320ºF). If that were the case, I'd be more concerned about the plastic and other things dripping off the bottom of the vehicle. Even the lowest octane winter blend gasoline with a Reid Vapor Pressure of about 13.5 would require about 140ºC to overcome the 44 PSIG of the pump.

True vapor lock, as was suffered in older vehicles with engie mounted mechanical pumps is all but nonexistant in EFI systems with the pump in the tank. Fuel under atmospheric pressure could easily vaporize in a fuel suction line at relatively normal temperatures and prevent the mechanical pumps from sucking liquid fuel. That just doesn't happen in pressurized EFI systems.

 

Thanks. I already have a new fuel filter, a new fuel pump, a new vent, and have insulated the muffler, heat shield and exhast pipe. I think I will go back to a stock fuel pressure regulator since I'm going to do some dyno tuning for the new engine. This hopefully will take some stress off the fuel pump and if I remember correctly, I never had this problem before I went to an adjustable fuel pressure regulator. Thanks for the input.

 

Thanks for the numbers on vapor lock, it must be related to the fuel pump. Please see my previous post.