Thank you. Your message about wiring a relay in the circuit for the lift pump saved my ecm. Yesterday I lost fuel pressure and the auto reset breaker got so hot it stuck in the on position. I couldn't hold it in my hand. I can't imagine what this would have done to the ECM. IMHO all should wire a relay in the circuit to the lift pump. Thanks again.

Edited February 19, 20178 yr by klcammie

Basically, hook the black/white to pin 85, yellow/white to pin 86. You can reverse the 85 and 86 with no harm.

 

and the black wire coming off the lift pump just goes to the ground correct

 

2001cummins

On mine I cut only the power lead, then routed the wire up to the fender. Mounted the relay. Then routed the wire back to the cut. Got power from the battery using a in line fuse. The ground is the screw that holds the relay to the fender. That way I only cut one wire.

Hey guys real quick guestion. Do I need to use the ground from the ECM when I install a relay or can I just run one to the chassis?  Thx in advance

 

L8tr

D

I just chassis ground.

Thank you sir, much appreciated

 

L8tr

D

My in tank pump had a relay on it. Maybe dodge was getting smarter 

4 minutes ago, Royal Squire said:

My in tank pump had a relay on it. Maybe dodge was getting smarter 

Thanks. I was looking at a harness in my shop and could not remember what it was for. Now I remember. Kept thinking it was for the booster pump I p pnut after the in tank pump was installed.

@klcammie  I am by no means trying to hijack your thread as I got a relay installed for the LP yesterday.  It was a pretty straight forward task.  The longest part is making the wire harness to connect the relay.  I lucked out on that because there was a short extention between the LP & the ECM feed with the proper connections (i forgot it was there and pic below).  It must have been from the second carter pump that was installed by the PO.  That made it it much easier as I could make the new harness on my bench.

 

 

L8tr

d

Hey take all the luck you come by.There will be days when you need some. Hopefully you will never need the relay harness.

Hopefully I won't need the luck .  It apprears that I have am little more fuel pressure now too.  Using 14g wire to power the pump and connecting to the PDC probably helped there.

On ‎2‎/‎11‎/‎2017 at 5:55 AM, klcammie said:

2001cummins

On mine I cut only the power lead, then routed the wire up to the fender. Mounted the relay. Then routed the wire back to the cut. Got power from the battery using a in line fuse. The ground is the screw that holds the relay to the fender. That way I only cut one wire.

thank you, just got back into town and will wire up this evening.

12 hours ago, SilverMoose said:

Hopefully I won't need the luck .  It apprears that I have am little more fuel pressure now too.  Using 14g wire to power the pump and connecting to the PDC probably helped there.

Yes I think I picked up 1-2 psi.

all I can find locally is a 30 amp relay. Will that work and then I can just use the 20 amp inline fuse going to it?

30 amp should be fine.  All I could find was a 40.

 

L8tr

D

  16 gauge wire will handle 20 amps up to 10'.  The relay should be at least twice the amp draw of the motor (20-40 amps).  If your fuel pump motor draw 10 amps at start up then the minimum relay will be 20 amps.  The relay should also have a resistor or diode in parallel with the coil to suppress back flowing voltage spikes that can damage the ECM.  These voltage spikes can reach well over 100 volts and are caused when the power to the relay is shut off and the magnetic field around the coil collapses.   Most relays denote the use of a suppressor as a symbol of a resistor or diode in the wiring diagram on the side of the relay.   

  Don't go high amperage on the fuse or every thing will burn before the fuse blows.  To find the fuse size calculate the load and multiply by 135% (1.35).  You can find the load by doing an amp draw test.  My back up fuel pump draw tested at 6.5 amps, times 1.35 = 8.77 amps, next size fuse is 10 amps so I installed a 10 amp fuse.  

 

@ibmobile  How do you know a relay has the resistor or diode?  Is that something we should add

 

Thnx

d

Edited February 17, 20178 yr by SilverMoose

A relay will have the protective resistor or diode built into it.  A wire diagram will be either printed on or etched into the cover.  The one below is printed on and shows that it has a resistor running parallel with the coil.

 

Here are some basic wire diagrams you will find on the side of an automotive relay.  Terminal 87a is not shown.

well looks like I need to get a different relay then, mine is just the basic relay you buy at autoparts store there is no resistor or diode diagram on the ones I saw locally.

 

Where are yall finding a 30 to 40 amp relay with a resistor or diode built in.

Edited February 17, 20178 yr by 2001cummins
add

Napa has a 30 amp relay that will work, part # ECH AR272

https://www.napaonline.com/en/p/ECHAR272