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Old May 24th, 2019, 11:00
BSOD77 BSOD77 is offline
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Fuel pump wiring for different harness

Howdy all, new to the board. I'm working on my project XJ. So here's the rub. It has an 89 body, a 94 harness, and a 97 engine.

So I have a new tank and fuel pump in, had to cap the fuel return line since the 97 doesn't have a return, but no bid deal. The problem came when trying to connect an 89 fuel pump to a 94 harness. The harness has a 6 flat pin connector, while the pump has a 3 round pin connector. Mechanically, I can get almost anything going. Electrically, I'm a complete waste of time trying to figure out how to hard wire the pump. Anyone ever had something similar that you could point me in the right direction?

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Old May 24th, 2019, 11:01
BSOD77 BSOD77 is offline
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Re: Fuel pump wiring for different harness

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Old May 24th, 2019, 11:09
BSOD77 BSOD77 is offline
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Re: Fuel pump wiring for different harness

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Old May 24th, 2019, 11:10
BSOD77 BSOD77 is offline
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Re: Fuel pump wiring for different harness

Ok, I give up trying to post a photo.
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Old May 24th, 2019, 13:04
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Rob Mayercik Rob Mayercik is offline
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Re: Fuel pump wiring for different harness

Cant offer a direct answer, since I don't have either an 89 or 94 myself.

First thought off the top of my head, though, is that you'd need to sit down and compare the wiring diagrams for the two to figure out if you can just splice things together. This would require ideally the FSMs for the two years. You could probably also try the Haynes or Chilton manuals for the XJ - these tend to cover all of 84-01 in a single book, though it's been a long time since I looked in my Haynes manual (I bought the FSM for my '92 ages ago, so haven't used it in a while), and are pretty inexpensive ($20 or less for the Haynes, IIRC).
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Old May 25th, 2019, 11:50
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Re: Fuel pump wiring for different harness

Quote:
Originally Posted by BSOD77 View Post
Howdy all, new to the board. I'm working on my project XJ. So here's the rub. It has an 89 body, a 94 harness, and a 97 engine.

So I have a new tank and fuel pump in, had to cap the fuel return line since the 97 doesn't have a return, but no bid deal. The problem came when trying to connect an 89 fuel pump to a 94 harness]
The 1997 XJ's fuel pressure runs at 49-psi, where the earlier models used around 39-psi. Your 1989 fuel pump will not deliver the right pressure unless a different pressure regulator is used or the injectors changed to match the lower pressure.
The lack of the return line would seem to complicate things. Why not use the 1989's fuel rail, retain the return line and use the 1989's injectors. I assume you are using a fuel tank from an older model.

Why can't the 1989's fuel pump plug be cut off and spiced into the 1994 harness, making sure to get the polarity right ?
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Old May 25th, 2019, 12:08
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Re: Fuel pump wiring for different harness

Or just buy the loaded assembly for a '94. It should drop into the older tank.
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