Ram Promaster Forum banner

fuel pump relay issues

942 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.
1 - 4 of 4 Posts

· Registered
'16 2500 159 HT Granite Window - OH(io)
Joined
·
625 Posts
As 83Grumman stated, there is more involved with the fuel pump than just the relay. See attached diagram.
I believe that the "Fuel Heater Shutoff Switch" is mislabeled. "Fuel Pump Shutoff Switch" is probably a better description.
It combines signals from the BCM and the Powertrain Control Module. What generates those signals is anybody's guess.

Rectangle Font Parallel Slope Pattern
 

· Registered
'16 2500 159 HT Granite Window - OH(io)
Joined
·
625 Posts
Thank you so much for taking the time to find and forward that.
Think it's worth replacing the fuel heater shutoff swich? It seems to be right smack in the thick of things.
You are welcome, glad to help out.
The shutoff switch is also an impact detector, so it has mechanical parts. Very possible that it could be intermittent.
 

· Registered
'16 2500 159 HT Granite Window - OH(io)
Joined
·
625 Posts
@LarryK
That's a great diagram for anyone looking for a engine running signal. Nice to see the fuel pump is on a 30A fuse.
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!
According to wiring diagram, find it at C5 pin 11 of the underhood Power Distribution Center (PDC)
 

· Registered
'16 2500 159 HT Granite Window - OH(io)
Joined
·
625 Posts
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?
You are correct Sir. Being that the blue wire is a ground path from the BCM, the current may be monitored by said BCM, and cause a fault code if additional load (the new relay coil) is added.
Think I OD'd on turkey yesterday. :)
 
1 - 4 of 4 Posts
Top