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Discussion Starter · #1 ·
A few days ago my '90 Dodge Ram would not crank right after I parked it. I switched fuel pumps because of it not turning on... Well, that wasn't the problem. The best solution I received was to run a wire from the fuse box to the tank. I don't know which wire is considered the hot wire in the picture below. Had someone tell me that the Blue/Yellow wire was it, but the word guess was involved in the sentence. Can someone guide me to the light on which wire is the hot wire? Thanks in advance.

 

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Would it be too difficult to follow each of those wires back to where they are landed and find out how they are being fed. That should quickly tell you which is your hot leg.
 

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When you first turn the key, can you hear the pump run for a couple seconds?  It'll be quick just to build up some initial pressure.  Might have to have a helper either listen or turn the key for you.  And it'll have to be a couple minutes after turning off the key.
Your fuel pump power is controlled by the ASD (Auto Shut Down) relay.  The computer controls the relay based upon whether or not it's receiving a signal from the Hall Effect sensor in the distributor (basically, the pickup in the distributor).  If the computer isn't seeing this signal while cranking, it won't turn on the ASD and your pump won't run.  Also won't fire the injectors or coil.
Easier thing to do is jumper the wiring at the ASD.
I don't have a diagram handy at the moment, but Dodgeboys is usually good for those.  The ASD will be located on the driver's side inner fender - along with the starter relay.  I know there's a picture on here somewhere, but not real sure where at the moment.
 

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Discussion Starter · #4 ·
Hybrid - I tired that, but the wire that suppose to been the hot was false advertising.

cjohnny - I cannot hear anything when the key is being switched on.
 

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Kind of going in line with cjohnny's suggestion, try finding the fuel pump relay, put it, and jump the hot contacts (bigger pair) and see if you hear the fuel pump kick on.
 

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its the DG/BLK [darkgreen/black] wire is power and the GRY [grey] wire is ground / you can access this wire at the ASD relay
 

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Discussion Starter · #7 ·
Got up this morning and decided to play with it before I go to class. Come to find out that the plug on the tank is in bad shape. You can wiggle it and the truck will fire right up until the vibration kills it. I'm cutting the wires and adding another plug this afternoon.

Thanks for the help that was offered.
 

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I have almost the same pump on my 89. My pump is modded all to hell. That Green wire there, with the electrical tape, gave me all kinds of problems when i dropped my tank. You would think that the green wire has a connector terminal on the bottom of the plug just like the 3 other wires. It doesn't! When i dropped my tank there was tension on the harness, the plug came off and the green wire slipped though the cap still attached to the tank under the plug.

So now as you can imagine there was about 3 inches of that green wire underneath the plug and totally in the way from plugging it in. I couldn't get the plug to slide back down the green wire so i had to notch out the female on the tank so the wire could loop out and back in giving me just enough room to snugg the contacts in and silicone it into place. I dont know if your following this but just...... 

BE CAREFUL BEFORE YOU CUT!!! Unplug that thing slowly and see if that green wire isnt solid to the tank on the under side of the plug. If it is, maybe just get a whole new sending unit. Thats way everything is together and ready to go. Or if it vibrating loose is simply your problem you may be able to hold it in there like I did with some light silicone. 
 
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