1999 E320, 100k miles. The fuel pump fuse kept blowing. Then i momentarily hot wired the pump straight off of a battery and it ran. then i put a new fuse in, reconnected cars pump wiring and all is OK now. Wiring all looks good but not sure what caused fuses to blow. Pump spec is 8A max draw. I measure 5.5A draw and the pump is quiet. any ideas?

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1972 450SL
1982 300D Turbo

Change your fuel filter and check the draw again.

Fuel filter was changed 15k miles ago, but what does the fuel filter have to do with it. Whan the filter starts clogging it doesn't let more garbage through. the sign of a failing filter is fuel starvation. please explain your logic, maybe mine is wrong?

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1972 450SL
1982 300D Turbo

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A clogged filter creates high head presure on the pump.
Also, when you took an amp reading, it would be better to take it across the fuse [ w/fuse out] so that you get the amp draw of the actual circuit rather than just the pump...this would give you are reading including the wiring and relay parts of the circuit. You were just getting a pump draw reading by bringing power over to pump. The pump is just one part in the circuit that was blowing the fuse.

I will measure the current draw at the fuse as you sugested. Thanks

High head pressure causing the fuse to blow would mean that the pump and circuit is drawing more than the fuse can handle. Since the pump is drawing well below the rated max high head pressure because of a partially clogged filter is not the problem.

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1972 450SL
1982 300D Turbo

I see..