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1989 560 SEL, 1993 400 SEL, 1986 420 SEL, 1977 450 SL, 1984 300D, 1981 380 SL, 1983 500 SL
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606 Posts
Discussion Starter · #1 ·
Under the car today and this is what I did:

Attached a wire to positive terminal of battery about 8 feet long so that I could pull the other end below the car to check my fuel pumps.

With the key in the "OFF" position, I took the other end of this wire and held it against the "POSITIVE" terminal on both of my fuel pumps, first one, then the other, and both work as they should. Now...

I disconnected the "POWER" wire to one of them, had my wife turn the key to the "ON" position, and nothing, no noise at all.

Put the wire back on to the fuel pump, had the wife turn the key to the "ON' position, and I hear the pump go on as it should but can't tell if both are going on.

Shouldn't the other fuel pump come on if the other fuel pump is disconnected? If anyone has some answers for me, I would greatly appreciate it. I know that the "Grounds" are good, because both fuel pumps come on when I apply power to them with the direct jumper from the battery. I am not sure if there are two fuel pump relays or just one. Again, any thoughts about this matter would be greatly appreciated.

Thanks
 

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1993 W140 500SEL Black/Black, 12014 Ford Fiesta ST Blk/Blk
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1,128 Posts
Perhaps only one primes the system. You have confirmed they both work, ok. Take a test light under there with the vehicle running, parking brake set firmly for safety, with either a test light or meter check the conductivity of the leads...

Hope this helps. Are you having running issues?
 

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Registered
1989 560 SEL, 1993 400 SEL, 1986 420 SEL, 1977 450 SL, 1984 300D, 1981 380 SL, 1983 500 SL
Joined
·
606 Posts
Discussion Starter · #3 ·
Update: Figured out that one of my pumps were bad. Pulled the bad one out and hooked up the good one only and this car runs fantastic with just one fuel pump. It doesn't need two pumps afterall!
 
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