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914World.com _ 914World Garage _ fuel pump issues
Posted by: orangecrate Dec 15 2018, 12:58 PM
I'm not developing fuel pressure. Got power and fuel to the pump and it was turning free when I bench tested it. Black/red pos --- brown neg. However, all my manuals (factory and Haynes) show it wired one way yet the markings on the pump itself show the polarities reversed. Anyone else ran into this? Will i fry the pump running it backwards too long? It seems to have fuel in it that is being gravity fed from the return line. Factory style pump as near as I can tell. Not an aftermarket one. How do these go bad? By blowing an internal seal? The actual pump itself seems pretty foolproof and straight forward and looked in good shape.
Posted by: porschetub Dec 15 2018, 02:31 PM
I'm not developing fuel pressure. Got power and fuel to the pump and it was turning free when I bench tested it. Black/red pos --- brown neg. However, all my manuals (factory and Haynes) show it wired one way yet the markings on the pump itself show the polarities reversed. Anyone else ran into this? Will i fry the pump running it backwards too long? It seems to have fuel in it that is being gravity fed from the return line. Factory style pump as near as I can tell. Not an aftermarket one. How do these go bad? By blowing an internal seal? The actual pump itself seems pretty foolproof and straight forward and looked in good shape.
I haven't seen the factory 914 pump but other Bosch pumps I have used are marked positive and negative on the threaded posts,wire to that and you should be good.
Because the pump runs on the bench isn't always an indicator its any good,all you are doing is proving it spins when powered up,its ability to suck and deliver the fuel to correct pressure can be another thing.
Don't run it too long incorrectly wiring or dry of fuel,they don't like it.
Good luck.
Posted by: orangecrate Dec 16 2018, 02:08 PM
Turns out the pump was marked incorrectly!!! Cast into the plastic at the connections no less. I also discovered that when your fuel system is bone dry, it helps to bleed the air out at the pressure testing point.. Now she is awakened from a 4 year slumber. More like 10 actually since it only ran about 15 minutes 4 yrs ago. All those little things to sort out. But she runs!!! 
Just need to put the windshield in. And take her for a spin. 
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