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fuel pump relay issues

941 Views 17 Replies 3 Participants Last post by  83Grumman
I have a 2016 RAM 3500 Promaster where the fuel pump relay occasionally gives out.
Sometimes while driving. Which is always unexpected and can be dangerous.
Usually, I pull over and wiggle it, or re-set it, or transfer one of the similar relays from the power distribution box to it's slot. This usually works, but is super annoying. My mechanic actually put in a whole new power distribution box, so I have the old one in the truck with all the fuses and other relays as spares. But it's interesting that this has happend with both PDB boxes. The old and the new. In fact, he told me that the one he replaced was stamped as a 2018 part, which indicated it had been replaced before, as the truck is a 2016. I've been to forums, but not seen this reported as a big time problem for the Promaster series. Anyway, I was wondering if you anyone has created a fuel pump relay by-pass for this Ram model. Thank you. Any light anyone can shed on this would be apppreciated.
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...fuel pump relay by-pass for this Ram model. Thank you. Any light anyone can shed on this would be apppreciated.
I've rigged up a few switches to by pass pump relays on other vehicles, basically a switch, two wires with spades plugged into the PDB.

If I was you I'd be looking at other components than the relay and box. You might have a ground or power connection issue between the relay/chassis and the pump. Maybe the pump is defective?
 

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So, if I rigged up a switch, and it worked...
I don't actually recommend using a switch but it can work.
You would need to turn it on every time you start the engine and every time you turn it off. It's easy to forget.
I'm kind of a gearhead so it was easy for me but if you're not in tune with all the little nuances and sounds of your van you might not want to do it.
The vehicles I used a switch on were 80's so less sophisticated engine management. I can't ever say for sure it will work although I suspect it would. BTW I use an old 120v light switch.
 

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I don't think the OBD code will be that specific. Find out where the fuel shut off switch is. If it happens again don't do anything except rap on the fuel shut off switch box and see it that gets the pump going again.

It might be a good idea to go the the fuel shut off switch and pull/pull the connector off and on a few times to make sure it has a good connection.
 

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One could use the "Fuel Pump Rly Ctrl" coming from the Shut-Off Switch (blue wire in my diagram) to control a separate relay for engine running needs. Good idea!
I would prefer to tap into the gray wire because it is in a circuit that is fused at 30A. If a relay took .5A from that circuit you only add 1/60th load compared to what the circuit is fused for. I don't like to chance tapping into or adding loads to any BCM circuits.

Based on the diagram, doesn't it look like the blue wire (terminal 86) grounds the coil of the FPR relay with the positive (terminal 85) coming from fuse 16?
 

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I took off the Power Distribution Box. When I turned it over, which is not that easy to do because of the lack of harness slack, I found that one of the harness connectors was loose.
Good find. Thanks for reporting. I suspect it was not attached properly, it isn't a problem that I've heard before.
 
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