Good Afternoon, i have a 1996 Dodge Ram B3500 with the 5.9L V8 and a 35gallon fuel tank. all of a sudden one morning the van would not start, it would crank and crank and crank, but no start. running through diagnostics, my first check was spark, holding the plug against the block (i didn't have my test light) i saw spark on the plug, so it seemed that was ok. next i checked fuel, i usually hear the fuel pump engage to pressurize the lines, but i wasn't hearing it kick in. however this is a camper van, i had just recently installed new insulation below the floor above the fuel pump, so figuring that maybe muffling the sound i pulled the connection to the fuel rail off the engine then turned the key to on to turn the fuel pump on and see if fuel came out, it did not. next i had a friend turn the key to on while i crawled under the tank, still no fuel pump noise.

After determining the fuel pump wasn't turning on i started checking electrical stuff, the relay for the fuel pump was clicking, and after checking with a multimeter the #30 pin had constant power, and when using a jumper wire to connect it to the 86 pin the fuel pump still did not turn on. this was strange to me because i had replaced the fuel pump less than a year ago, so i was surprised that the fuel pump could be bad already. that being said i did order a cheap fuel pump from amazon, so it wasn't out of the question. i bought a new fuel pump, this time off rock auto (Delphi Brand). i dropped the tank and swapped the pump out, and once turning the key, the pump still did not turn on.

At this point i was annoyed that i had bought a new pump and that didn't seem to be the problem, but i continued searching for the problem. testing the harness that connects to the pump, i used my multimeter and the wiring diagram i found online from a 96 ram truck service manual to test the connections. I have a service manual for my van, but i left it at home and im away from home at the moment, so i was hoping this diagram was at least similar. this is where i got a little lost, the connector is a 6 pin connector, the wiring diagram shows the wires in order from top left to top right as BK, OR, and LB then in order from bottom left to bottom right BK, WT, WT. i assumed that these were supposed to be the colors of the wire, however this did not match my harness as i have no orange or white wires. Still, i continued testing as if the colors could have been different between the truck and van models or something, and using the locations of the pins the same as the diagram laid them out regardless of color. Doing this i had no power when my jumper wire was disconnected from the relay pins. when the jumper was connected if i had my multimeter positive in the top left (Wire from the relay according to the diagram) and my negative lead on the top right (sensor ground according to the diagram) that was the only way i got a reading on the multimeter, however it was negative, indicating to me that the sensor ground wire was actually the positive?

This is where I'm looking for help, if anyone has advice on other things to check, or where these wires actually run from the fuel tank forward, that would be incredibly helpful. as far as i can see it runs into the frame rail and should come out near the front somewhere but i cant find where. also maybe I'm testing the wrong pins in the connector? I'm afraid a mouse or something chewed up a ground wire somewhere because it seems strange to me that the sensor ground would be the ground for the whole pump, the diagram appears like the wire that is in the lower left on the diagram should be the ground, but maybe im misunderstanding how this diagram is actually laid out, ive attached a screenshot of the diagram im using. A​​​​​​any help would be greatly appreciated, thanks.

 

Pin 87 will be output to the pump. If the relay clicks, verify you are getting power back to the pump..... (gonna require a second warm body, as the PCM will only run the pump for about 3 seconds at initial key on, and after that, only if it sees the engine turning.)

You could try and jumper 30 to 87, and the pump should run, regardless of key position.....If you have power, and the jumper doesn't make the pump run, check the ground for the pump. Black wire, should ground somewhere in the "right rear" of vehicle...... Yeah, real specific there.

 

Sorry i meant that 30 and 87 are what i was using for the jumper. the relay clicks when the key is turned and i don't hear the pump for those 3 seconds, that was the test i ran with my friend as i crawled under the tank while he turned the key. i was able to have a buddy send me the wiring diagram from the fuel pump section of my manual and its actually verry different from the truck one (i should have expected that lol). using a multimeter on the correct pins this time, the pump should have power when the jumper is connected. i placed my multimeter leads on the pins that are either side of the "M" object in the fuel pump module shown below. i will look around for the pump ground right now. attached is the correct wiring diagram for my van, you'll have to ignore the highlighter and notes, clearly the previous owner of this manual also had fuel pump issues lol.

 

I notice he has a note in there about bad ground..... That's mighty suspicious.

 

Ok so i solved the problem, its a case of me unplugging things i shouldn't be lol. like i said this is a camper conversion, while i was working on the rear floor a few weeks ago i noticed plug connectors running through the floor of the van under the tail lights, further inspection showed these ran under the van for the trailer lights plug. well this also is the ground for the fuel pump as i found out when i plugged them back in and everything worked. so all in all i did all this work to figure out what those connectors do and get myself a higher quality fuel pump and cheap backup pump lol!

 

Ooops.

Yeah, I don't trust the cheap pumps..... Especially the air-tex fellers. They are notorious for lasting a day or two past the warranty, and then failing.