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Wiring a NEG-earth SU solid state fuel pump

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rbardsley Avatar
rbardsley Ryan Bardsley
Manchester, MA, USA   USA
I may have been inhaling too many gas fumes, but I can't figure out how the heck to wire my new SU solid state fuel pump. I am trying to convert the car to negative earth, so I purchased the negative earth version of the pump. However, it does not come with any installation instructions. So, I have a white wire from the loom and a black wire mounted to the frame. On the pump, there is a connection at the "top" (away from the fuel connections and on the cap) and one that appears to be on the side of the pump almost under one of the fuel connections. I would think that this is the ground attached to the body of the pump, but there seems to be a cork gasket between it and the base. My multimeter is broken, so I didn't want to risk connecting it the wrong direction.

Any recommendations?

Thanks,

Ryan

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PeterC Avatar
PeterC Platinum Member Peter Caldwell
Madison Wisconsin, USA   USA
In reply to # 3905986 by rbardsley My multimeter is broken, so I didn't want to risk connecting it the wrong direction.

Any recommendations?

Thanks,

Ryan

Spend 6 bucks on a new multimeter.

Just sayin

Peter c


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ozieagle Avatar
ozieagle Gold Member Herb Adler
Geelong Victoria, Australia   AUS
1958 Wolseley 1500 "Wooly"
1966 MG MGB "Bl**dy B"
White wire goes to the terminal on the top cap, black goes to the terminal on the body.

Herb



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RJBrown Avatar
RJBrown Randy Brown
Queen Creek, AZ, USA   USA
Once the car is converted to negative ground the frame becomes negative and the white fuel pump wire becomes positive. A negative ground fuel pump will hook up with the white wire to the fuel pump and will ground through it’s body.
Hook it up in the normal fashion and you will be fine.
Verify polarity with a volt meter first. If you hook up a solid state pump backwards it will damage the pump.

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oleanderjoe Avatar
oleanderjoe Gold Member Joseph Baba
Fresno, CA, USA   USA
I have a prettier one made with a nice bulb holder and probes, but you can make this for about $2.00 POLARITY TESTER. When a car comes in, ESPECIALLY an earlier model, I check it’s POLAROTY FIRST THING. I don’t know if it has been converted or not. Saves opening up the battery compartment. This is ONE of about 15 or more LOW DOLLAR tools to make life easier. Cheers.

HOLY CRAP. What is this KINDERGARTEN. .?? Use RED wire on the POSITIVE leg, and BLACK wire on the NEGATIVE
Leg .




In reply to # 3905986 by rbardsley I may have been inhaling too many gas fumes, but I can't figure out how the heck to wire my new SU solid state fuel pump. I am trying to convert the car to negative earth, so I purchased the negative earth version of the pump. However, it does not come with any installation instructions. So, I have a white wire from the loom and a black wire mounted to the frame. On the pump, there is a connection at the "top" (away from the fuel connections and on the cap) and one that appears to be on the side of the pump almost under one of the fuel connections. I would think that this is the ground attached to the body of the pump, but there seems to be a cork gasket between it and the base. My multimeter is broken, so I didn't want to risk connecting it the wrong direction.

Any recommendations?

Thanks,

Ryan



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Edited 2 time(s). Last edit at 2019-03-09 10:28 PM by oleanderjoe.


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Basil Adams Avatar
About 12 miles from Sears Point, CA, USA   USA
On an electronic fuel pump, you just hook positive to positive and negative to negative - you can hook up an electronic pump the same way on a positive ground or negative ground car. Best of luck. Basil 707.762.0974 basiladams@yahoo.com



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rbardsley Avatar
rbardsley Ryan Bardsley
Manchester, MA, USA   USA
Thanks for the pictures, wiring diagrams, and suggestions. My multimeter is fixed (bad lead) and I sorted the wiring accordingly. Turns out I also had a bad and breaks new starter switch. This was the other strange thing that was mixing me up. Everything seemed connected and I couldn’t find anything consistent with the wiring diagram. With the multimeter back up and running I double checked everything and looks like I am closer to getting things back together. The dash is out too, so there is a mess of wires everywhere. Alas, fuel pump is in and a new starter switch is en route!

Thanks again.

Ryan

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  PeterC thanked rbardsley for this post
ozieagle Avatar
ozieagle Gold Member Herb Adler
Geelong Victoria, Australia   AUS
1958 Wolseley 1500 "Wooly"
1966 MG MGB "Bl**dy B"
In reply to # 3906095 by Basil Adams On an electronic fuel pump, you just hook positive to positive and negative to negative - you can hook up an electronic pump the same way on a positive ground or negative ground car. Best of luck. Basil 707.762.0974 basiladams@yahoo.com

Be careful here!!!

After market pumps may be isolated from chassis and have a black and red wire coming out, and can be used in either configuration. SU electronic pumps have the earth connection (chassis) on the metallic body and are not reversible, without danger of a short and consequent damage. They are differentiated by the part number with an EN, for neg earthe or EP for pos earth, as a suffix.


Herb



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binky Bill Blick (Disabled)
Disabled Account, Antarctica   ATA
I would expect a "solid state" su pump to work both pos or neg gnd.

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RJBrown Avatar
RJBrown Randy Brown
Queen Creek, AZ, USA   USA
In reply to # 3906606 by binky I would expect a "solid state" su pump to work both pos or neg gnd.

That expectation would be in error. The original pumps are not polarity sensitive.
The “solid state” ones are. When purchased they specify either positive or negative ground. (See picture)
Dave Dubois is the fuel pump expert and could tell you why.
Below is a screen shot from Moss.


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rbardsley Avatar
rbardsley Ryan Bardsley
Manchester, MA, USA   USA
This was my hesitation. I purchased the negative earth version, but it didn't come with any documentation about what was going on inside electrically. I didn't want to fry things, so I was trying to be safe and not make any assumptions.

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