I had the entire 1989 GM TBI wiring harness in my Jeep and ready to fire when I realized I don't have my fuel pump wired up. Can anyone help? I went back and pulled the wiring harness so I can work with it. Off the fuel relay (on the firewall) all wires go to the ECM exept one wire that is pink with black stripe. But that one goes to the knock sensor module (?) - (which is not what the wiring diagram shows) near the throttle body on the intake. So, the burning question. Does the fuel pump need to communicate with the ECM? If so, does it go through the fuel pump relay or just through the fuel pump fuse (also located on the firewall). If not, can I just wire the fuel pump to a wire that is hot in "run" and "start"? Then where would the fuel sending unit wire go to? I'm so confused and a little upset that I missed this wiring detail when I was plugging everything in.

TIA.

http://www.photodump.com/direct/Yetti/the-other-page.jpg

hope that one helps

It goes thru the computor, when you turn the key on the pump should pressurize then stop, when you start to crank it gets a signal from the ignition thru the relay. Somewhere in there the oil pressure sender comes in, so when pressure is really low it kills the pump circuit, I think. [on the oil press. switch]

its not hooked to oil pressure switch. actually very few ever were.

Did a little more investigating last night using my harness and a spare harness I have. Here's the deal.

4 wires go from ECM to fuel pump relay.
1 pink and black wire (the 5th wire coming from the relay) goes from fuel pump relay and splices into
1 pink and black wire from fuel pump fuse (on firewall) and into the harness.
1 tan and white wire also goes from fuel pump fuse somewhere into the harness (not to the ECM).

So, would we assume that the pink and black one should go to the fuel pump? If so, where does the tan and white wire go?

Yetti, I'm no electronics genius, but it looks like the only fuel pump reference on the schematic you posted says to go to page 52? Before long I am going to tow my CJ to your place and have you take a look :D I only live in Manchester, so I could end up on your doorstep if I don't figure this out :D (j/k, it can't be as difficult as I am making it)

duh, I just saw it at the bottom.
Manchester isn't far. where abouts are you?

I'm right on the south edge of town. I was just at the corner of Sylvan Rd. and Grass lake road tonight. Had to drop off a guy from work since his truck is in the shop.

So, where is page 52? :D

this is the page you asked for....

http://www.photodump.com/direct/Yetti/pg-52-v6-harness.jpg

Well that's interesting. The colors on this diagram are similar to the schematic I have from Haynes, but the wire colors don't line up with either of the harness' I have. The pink/blk wire I have is in position 120 of the fuel pump relay. According to your page 52 that is gray wire 120-1.0. So, where does that wire go on page 53 of your manual? It looks like it comes back to the fuel pump oil pressure switch on page 52(Is this the fuel pump?). Does it connect to the 20amp fuel pump fuse anywhere on page 53? Also, I'm assuming that diagram is for an '89 5.7 L engine? Because according to Haynes my TCC switch should have been connected to a pink wire. According to your diagram it connects to a pink/black wire. I hope Haynes hasn't caused me to mis-wire the whole thing :shaking:

BTW, what manual is that. It has nice diagrams.

Thanks.

Pg 52 is for the V6/305

BTW, what manual is that. It has nice diagrams.

I am sorry to say it might be the cause of the problems. its the wiring diagram book for the `91 GMC C/K.
I have a `90 S/T also.
when I worked on the vehicles at the dealer I never ran into problems crossing over. the model years didn't differ enough unless there was major changes like port fuel.

I called up two dealerships today. Both said "good luck" finding a manual for a 1989. I described the situation to the one service guy and he says that the wire that goes to both the fuel relay and the fuel pump fuse is likely the wire I want to run to my fuel pump. So, I'm moving forward with connecting the pink/black wire to my fuel pump. I still don't know where the other (tan/white) wire off the fuel pump fuse goes. Any guesses? Looks like it might go to a connector on the brake master cylinder??

I went back and pulled the wiring harness so I can work with it. Off the fuel relay (on the firewall) all wires go to the ECM exept one wire that is pink with black stripe.


I went to the dealer today, they have FULL library of manuels. the `89 C/K book was there...no diff. the best info I got was from Andy my buddy there. he said something to effect of Ignore the wire , and wire the pump seperate

So just wire the fuel pump into a fuse on the panel that is hot in start and run, such as the IC spot? I may try the pink/black first, and if no gas go that route. Still need to know where that other wire off the fuel pump fuse goes though. Any ideas from Andy?

What GM dealer was that? The one in Ann Arbor and Clinton said they doubted any dealers would have book that old.

if its the one he thinks it is then it goes to some applications for the T case, he couldn't remember what it did. he said he had chased that exact wire to no end.
by the way what plug end is on it or is just something hanging without a place to go?

he(Andy) made referance to drinking Bud Light, if you need more help.

if its the one he thinks it is then it goes to some applications for the T case, he couldn't remember what it did. he said he had chased that exact wire to no end.
by the way what plug end is on it or is just something hanging without a place to go?

Both wires coming off the fuel pump fuse go to a large connector that was on the end of the wiring harness in the donor truck (with a whole mess of other wires going into the same connector). I don't know what was on the other end of the connector, possibly the fuse panel or another connector leading to the back of the truck. I looked closely at the relay tonight with my Haynes in hand. Since the relay has the current diagram on the case I was able to determine with some degree of confidence that the pink/black wire is what the book is calling grey. So I am fairly certain this goes to the pump. The big concern now is what the tan/white wire is. I mean, there are only two wires feeding into that independent bus fuse called the "fuel pump fuse". If one goes to the pump, the other must be a feed or return wire for the current, right? So if the tan/white wire is going to a dead end doesn't that mean I won't have any current through the fuse (therefore no current through the pump)? I should have spent more time in college paying attention to energy discussions in physics class :shaking: