Fuel pump wires

[seattle_Jerry]

I have a 67 230SL and forgot which wire went where on the fuel pump... As it sits mounted in the car does the tan wire go on the right or left. "Logic" dictates that no matter which I choose it will be the opposite.

[waqas]

Assuming your wiring is still original, I beleive the brown wire goes to the negative post.

The best way to confirm this is to test the voltage that shows up across the leads when you switch on the ignition. Careful not to cause any sparks back there, especially if any fuel vapours are nearby.

[seattle_Jerry]

Yes its original wiring. The question was more which one is the negative post. If it was marked on the body I can't tell due to surface corrosion.

[Naj ✝︎]

This may help:

Not very good pic 

naj

[seattle_Jerry]

Yeah I saw that pic...but can the wiring really be trusted since all he was doing was testing flow...it didn't matter which direction the pump spun. I guess I can try that way and see if it works...

[Naj ✝︎]

Yeah I saw that pic...but can the wiring really be trusted since all he was doing was testing flow...it didn't matter which direction the pump spun. I guess I can try that way and see if it works...

With the wires turned around, the motor will run in the wrong direction and not pump unless you turn the pipes around as well.

naj

[al_lieffring]

If the car has the original large body pump, it doesn't matter, because it is not a permanent magnet motor. it will turn the correct direction no matter how it is hooked up.

The later small body pump does have a permanent magnetic field so it is marked with red and brown plastic on the terminals.

Al

[waqas]

Yes its original wiring. The question was more which one is the negative post. If it was marked on the body I can't tell due to surface corrosion.

Sorry, I misunderstood your question. On the old-style pumps (large body), if you look closely directly below the wire-connecting posts, there are some numbers etched into the pump body. These numbers correspond with the numbers in the wiring diagram. The left post should be marked 30 and this is the positive post. The right post should be marked 31 and this is negative.

On the newer-style pumps (small body), the wire connector posts are set inside coloured plastic pieces with moulded polarities for each post. In this case, the negative post is on the left and the positive on the right. (reversed from the large body pumps).

The wire colours are as follows: brown for the negative (ground) and black/white/red patterned for the positive.

[seattle_Jerry]

Well my pumps posts plastic surrounds are both off white. I can't read anything etched into the pump body because the body is corroded. I'll take a pic. I'll look up the difference betweeen big and little pumps.

[seattle_Jerry]

Positive goes towards the posterior of the car. Brown(-) is right terminal