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89 350 wth street& performance gm tpi unit with harness: problem has exsisted for 10 years.....car will run and at any give time will start to miss and finally die. wait for a few minutes car may or may not start...when it does start it may run 2months touble free or two minutes and die. have replace fuel filters {multiple times} fuel pressure reg and now on my 5th in tank fuel pump. las two pumps are a delco. both have less than 500 miles (and they start howling. Car has s/s fuel tank and lines have been wrapped. S&P thought vapor lock...engine runs at 215 degrees can an external pump be put in this configuration. Any suggestions would be appreciated
 

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89 350 wth street& performance gm tpi unit with harness: problem has exsisted for 10 years.....car will run and at any give time will start to miss and finally die. wait for a few minutes car may or may not start...when it does start it may run 2months touble free or two minutes and die. have replace fuel filters {multiple times} fuel pressure reg and now on my 5th in tank fuel pump. las two pumps are a delco. both have less than 500 miles (and they start howling. Car has s/s fuel tank and lines have been wrapped. S&P thought vapor lock...engine runs at 215 degrees can an external pump be put in this configuration. Any suggestions would be appreciated
I think 215 is rather warm for old iron 350's. This is at an edge that doesn't allow much room for a problem. I'd work on getting that down to more like 180-190.

Constant pump failures indicate something is wrong. These early pumps do not cycle on to off to on again like modern EFI pumps. They run all the time and must be cooled by being submerged in fuel. That means not running the tank low let alone dry and there must be a return line from the regulator to the tank. Vapor lock should not be a problem with an intake pump as its intake side is flooded under cool fuel and its output is pressurized all the way to the regulator. This keeps the fuel from flashing to vapor as it can do when the pump is located in the engine compartment and pulls fuel from the tank which essentially creates a vacuum on the fuel between the tank and pump. When the fuel is hot enough the reduced pressure can permit the fuel to flash to vapor which the pump can't pump.

The pump can be moved outside the tank but it must be a mini tank that keeps it submerged in fuel and a return still needs to go to the main tank to dilute the hot pressurized returning fuel into the cooler fuel reservoir of the tank. Simply looping the return back to the pump inlet causes pump overheating problems. It's also necessary to direct the returning fuel in such a way that it doesn't stir up any sediments collected on the tank bottom such that it keeps this crud from being ingested by the pump. Filters especially that spun plastic thing on the pump inlet are only so good which is usually not good enough. They keep the rocks out but not a lot smaller so you've got to prevent stirring sediments as much as possible.

Bogie
 
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