Please hang in there, this is going to be a bit lengthy...


I have an '03 Ram 1500 5.9L. About 2 months ago, the truck died on me, no fuel pump. So, I replaced the pump... Nothing. Checked all fuses and relays... All Good. Disconnected plugs to check voltage at the plugs... All Good. Put the plugs back together and the truck started and has ran great since. The old pump was not dead and still works (just sits on the shelf as a spare).

The other day the truck died on me again, fuel pump. Looked like it was turning into the same issue so I disconnected the plugs, tested voltage (12.3V at pump), cleaned them, and applied a little di-electric grease and plugged them back in, checked fuses & relays... Nothing. Checked the ground on the fuel pump plug... 10.3 Ohms. I then disconnected the ground, spliced in new ground wire and grounded to the frame... 0 Ohms. Still nothing.

I disconnected all plugs from the fuse box and removed the entire box to check for corrosion... All good, no corrosion.

Still have no clue as to what is causing problems so I replaced the plug at the pump with a new OEM plug, reads 12.3V and 0 Ohms. Plug it back in and nothing. I then plugged in the old pump knowing it is good... nothing.

So in a last ditch effort to test the pump, I connected a wire from the power side of the plug direct to the + on the battery... IT WORKS AND THE ENGINE FIRED RIGHT UP.

For what it's worth, both times the pump started acting up, it was raining.

It's probably totaly unrelated, but the wiper motor stopped working at the same time. I have 12.1V and .01 Ohms at the plug.

Any thoughts?

Thanks - Brandon

 

Did you look inside the fusebox for corrosion? You won't see it unless you pry it apart a bit to see the internals. When mine acts up it's usually in the rain. I've been regularly dousing my fusebox with electrical cleaner and haven't had problems in awhile.

 

No, I did not check inside the fuse box, but I did give it a good soaking with electrical cleaner.

 

I removed the fuse box and pulled it apart to check for corrosion... No Corrosion. I gave all the terminals a good cleaning with electrical cleaner. Put it all back together... 12.1V at fuel pump. Still nothing.

My steps for checking voltage at the pump.
1. Remove plug from pump
2. Attach multimeter to + and - of plug.
3. Turn the key to ON.
I read proper voltage, but is it suppose to drop back to 0 after a second or so?

The pump will engage if I connect direct to Battery. This will skip all fuses, relays and computer. Is there a chance it is the computer? Or is there some other sensor or switch that tells the pump to "pump"?

 

I'm just trying to think of all possible options.... Camshaft or Crankshaft sensor?

 

You need the FSM so you can trace out the circuit on paper. The fact that rain has somthing to do with it may be pointing towards a board. One of the other guys will most likely chime in.

 

Here is what I found... Could the PCM be going bad?
Is there any way to test the PCM?
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I think I had attached the wrong diagram. Attached new diagram for JTEC. (old one was NGK)

 

I really hate to sound like I am begging, but that's about where I am at this point. I have looked into every possibility I can think of, harassed all my personal contacts and cannot come up with anything. I need to get this truck running.

Anybody have an opinion?

 

Ok,
Looking at your attached, you have a elay in the "fuse box" Change it!!!!

You also have a fuel pump relay find that and check it, it may be the roll over module

If you look at the circuit path, there may be a input wire on the main harness that could be giving you problems too. My first guess, is the PCM relay in the fuse box
in the engine bay

 

Gone Fishin, Thanks for you help. It is greatly appreciated. This truck is giving me a serious headache and any input helps.

I have looked into every possible wire, fuse, relay option I can find.

I was working on it a little more this evening. I got it running and now fires up everytime.. Kind of (with a little rigging).

I checked the 19 pin on the C3 connection at the PCM to make sure the wire was ok...12V. I then put the plug back in the PCM, backprobed pin 19, and grounded that pin to the chassis. Fuel pump enganges as should and truck fires right up.

Sounds like PCM is not grounding the circuit as it should. Bad PCM?

EDIT: No CEL, No Codes