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Discussion Starter #1
I have a 1988 Dodge dakota v6. It has had some modifying done to it such as a 318 being placed in it and a bit of wire splucing but my main issue now are the gauges. My heat, seat belt, battery power, and oil gauge work but the gas hand and speedometer do not. The speedometer is an easy fix but the gas hand is a bit more complicated. This is what I have done so far:

I have switched out the whole sending unit, no change.

Switched out the old and new sending units with old and new gas tank arms, no change.

By passed the 5 prong connector going to the unit and it had no effect.

I seen there was a alot of grease inside the connecter cleaned that out with a wire brush and got better results. the gauge stayed accurate for about ten tests. It kinda shifted to where it was 90 percent accurate, empty was a tad before E and full was a tad after F and with me being a perfection i went and messed with that and it went back to its original issue of staying in the middle then i got it to register on full but it stops responding right above the half way mark..

another huge issue is tracking the wires. The color scheme changes between 3 and 6 times.. it starts as green, light green, and yellow in the fuel sender, comes out of the 5 prong plug as black/white, purple/ blue, and something else, goes to the fire wall, goes to the multi connecter that had grease in it. from there two of the wires stay the same but the blue / pink one turns baby blue, goes into a huge wiring harness, then goes into some type of multiconnecter on the fire wall which looks good internally then from there i can no longer trace the wires. i seen 3 wires matching the original wires from the sending unit going into the back of the gauge cluster but now im not sure if that means im back on the right track since it changes colors so much..

My question is which all the metal components inside the arm looking good and with me getting it to work about ten times how much more do i need to bypass to get a direct connection from gas arm to gas gauge? Does anybody know the wiring schematics for this 1988 dodge dakota? I cant find the guide anywhere online or at the stores or library and thats a fact.

I'm thinking i can just bypass everything and get a straight line from the gauge to the arm unit but i dont know if anything specials happens to the wire before it reaches the gauge other then going thru these connecters which look pretty basic.

Has anyone has the issue, am I on the right track, what can i do since i know the arm still functions properly?
 

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The closest wiring diagram I have that would be similar to a 1988 Dakota is one for a 1988 Dodge Caravan. Since for engineering design purposes the first generation mini-van was considered a truck, I would expect wiring diagrams to be similar if not the same.

The 1988 Caravan has 2 connectors at the fuel tank. One for the fuel pump which is 2 wire, Dark green / black tracer which is 12 volt power and gray which is ground. There is another 3 wire connector at the fuel sending unit. Gray which is ground, light blue which is signal for low fuel lamp, and dark blue which is signal for the fuel gauge level indicator.

Is the fuel tank metal on your vehicle? In 1988 I believe Chrysler was still using metal fuel tanks on cars and trucks and mini-vans. I believe the switch to plastic tanks occurred around the 1991 model year.

You mention a 5 prong connector at the fuel tank. Through 1990 the fuel tanks were metal and there were 2 openings in the top side of the tank. One was for the electric fuel pump and one was for the fuel sending unit. Since these were separate devices the wiring connectors were separate as mentioned. The electric pump has a 2 wire connector and the fuel sending unit has a 3 wire connector.

I suspect that a previous owner swapped in a later model plastic tank(???) with integrated fuel pump module (pump and sender combined) with the combined 5 prong wiring connector. And somehow that 5 prong connector was spliced (or attempted to spice) into the 1988 wiring. The green wires you mention at the tank do not match the wiring scheme for a 1988 Caravan.

I think you have a real wiring mess on your hands. You will have to find fuel level sensor wire at the sensor and trace it back to instrument panel. You might have to unwrap wiring harnesses along the way to make sure you follow the correct wire. This will be tedious.
 

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Welcome to the forum. First of all, you do have a bit of a mess. All that grease in the connectors is dielectric grease, to prevent rust/corrosion for occuring, so it isn't a bad thing, it is messy, but it is a good thing, really. Try looking at a wiring diagram for a 1989-1990 Dakota, it actually should be the same all the way through 1996 or so, but if not mistaken, Haynes manual has the 1988 wiring diagrams in it, I would double-check, but my book is about five miles away, but it has all the wiring diagrams for first and second generation.

From there, is this one of the large gas gauge that is in the left side of the cluster or the little on on the top left? Since the wiring appears to change color from rear to front several times, it may be one of the connections itself that is causing the problem. I think a jumper wire after tracing from the tank to the cluster connection installed location to location may help identify the bad wire or connection. Time consuming, sure, but no other way to get it done otherwise. At least you can get to the connection on the tank without having to remove the tank (through the wheelwell).
 

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Discussion Starter #4
The closest wiring diagram I have that would be similar to a 1988 Dakota is one for a 1988 Dodge Caravan. Since for engineering design purposes the first generation mini-van was considered a truck, I would expect wiring diagrams to be similar if not the same.

The 1988 Caravan has 2 connectors at the fuel tank. One for the fuel pump which is 2 wire, Dark green / black tracer which is 12 volt power and gray which is ground. There is another 3 wire connector at the fuel sending unit. Gray which is ground, light blue which is signal for low fuel lamp, and dark blue which is signal for the fuel gauge level indicator.

Is the fuel tank metal on your vehicle? In 1988 I believe Chrysler was still using metal fuel tanks on cars and trucks and mini-vans. I believe the switch to plastic tanks occurred around the 1991 model year.

You mention a 5 prong connector at the fuel tank. Through 1990 the fuel tanks were metal and there were 2 openings in the top side of the tank. One was for the electric fuel pump and one was for the fuel sending unit. Since these were separate devices the wiring connectors were separate as mentioned. The electric pump has a 2 wire connector and the fuel sending unit has a 3 wire connector.

I suspect that a previous owner swapped in a later model plastic tank(???) with integrated fuel pump module (pump and sender combined) with the combined 5 prong wiring connector. And somehow that 5 prong connector was spliced (or attempted to spice) into the 1988 wiring. The green wires you mention at the tank do not match the wiring scheme for a 1988 Caravan.

I think you have a real wiring mess on your hands. You will have to find fuel level sensor wire at the sensor and trace it back to instrument panel. You might have to unwrap wiring harnesses along the way to make sure you follow the correct wire. This will be tedious.
FIRST LET ME SAY THANK YOU FOR RESPONDING! I have posted this issue on 5 or 6 different dodge forums with plenty of views and no feedback so thank you guys.

Now the 5 prong is for the sender and the fuel pump which i don't use. I have a 318 in here and i use the mechanical pump so im good there and then we have the 3 wires going to the fuel sender / arm. those start out as 3 thich wires, a yellow, a green, and a light green.. i really dont think its the previous owner's modifying that lead to this wire maze. like i said it starts out as those 3 colors underneath the sender, above the sender going into / thru the 5 prong plug we see those 3 wires change into 3 striped cables, i trace that to the engine area where those same 3 wires well all 5 go into a connector. on this connector i can see plain as day where the 3 wires from the sender end up at. i then trace those thru the connector and 2 of the wires keep the same striped color scheme while one changes to a baby blue wire and they continue from there to the firewall to that connector with the rubber boot over it that ends up going underneath the steering wheel and underneath the fuse panel inside the cab. from there things get quite confusing because once the wires enter that boot u got like 35 wires beside each other in formation going through to the other side and coming out as a bundle. my question to you all is which wires going to the back of the main gauge above my steering wheel have to do with the 3 coming from the sending unit. what color are those wires RIGHT BEFORE they hook into the back of the gauge cluster unit and can i hook the sending arm unit directly to the gauge and the gauge still respond to movements properly with the needle being accurate. Thats what i need because i know this is a wiring issue because it works enough of the time and i can see the metal connectors in the sending arm are not damaged. no one can give me this info though it seems.

DANA44 i have the one with the large gas hand on the left, the speedometer in the middle and the 4 other gauges on the right. My 89 gauge cluster which will not work at all properly in this truck hasthe little gauge for the gas your talking about. it seemed like the first time i cleaned some of the grease out in that connector near the fire wall things got back on track and thats why i thought it was bad. ill try to get pictures of everything guys. it does have a plastic tank, i do not knoe if it came with a metal one stock but i doubt the old owner would had put a plastic one on it just because he put a 318 in it. theres no reason for a gas tank swap, the sending unit is for that truck, all the other trucks at my junk yard have the plastic tanks on the 88, 89, etc. i dont think the caravan info applies here even though i know chrystler re uses alot of parts and internal designs on its cars. The tank has been off for a few weeks and i just want to know what the wiring colors end up as right behind the gauge cluster and then take it from there. im not sure i understand what you mean by jumping it off. There is no wire splicing with this sending unit, everything belongs, everything is stock accept the engine and tranny perhaps and the wires from the sending unit snap in to the right connector on the firewall/in the engine compartment. like i said it works at times just not always.
 

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Wiring diagram. that's what you need. If the wires are changing that often and all, reqire it using a diagram. You have the non--tach dash, was kind of thinking the two dashes would swap for the first generation since it is the same two dash clusters from 87 to 96, which is not to say the wiring diagrams are all the same, but you should still have a couple years that are the same. Skip the wiring guesswork, a wiring diagram that has your three sending unit wires and the plug-in the same style as yours, should be able to get everything you need and bypass the mess that exists, and, if there are other wires running power with the sending unit wires, if the wiring coming from the tank is clipped, it will allow everything else that is still attached to operate properly.
 

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Just wanted to sum up DJ's main need;

What he needs to know is where does the wiring change from the fuel pump to the fuel gauge. He wants to wire the gauge directly to the fuel sending unit, but since the color code on the wires change at several points from pump to gauge it makes it impossible to know which wires entering the gauge cluster are for what.

We need to know which of the wires connecting to the gauge cluster are those that come from the fuel sending unit.

There are no wiring diagrams out there, at least that we've found that speculate on the gauge cluster pin out diagram or have the wiring diagram for the wiring harness that comes into the gauge cluster and connects.
 

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Discussion Starter #7
yea dana but i can never track down a diagraphm and we looked in 865's uncle's guide and it doesnt give us that info either. its been really hard to find a book for this truck and i dont know why. if u know where dana i would be greatful. now as for the tach version thats on the 89 and the connectors all line up and fit but they dont activate the same things, the interface does not mesh very well. i got one out there i gotta take back but i know the tach version / later models arent going to interchange with the 88 and i guess 87 cluster.
 

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I picked up a Haynes manual from a Kragen/O'Reily, it's first generation, 1987 to 1996. I would track it down for you, but it would be a couple days, the book is across town. Sorry.
 

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I picked up a Haynes manual from a Kragen/O'Reily, it's first generation, 1987 to 1996. I would track it down for you, but it would be a couple days, the book is across town. Sorry.
give me a word up on it when u do. i just hope it has the right info in it
 
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