no power at electronic fuel lift pump

[NELSON JA MLSS]

Hey guys, new here from kingston jamaica i hvae been following this forum and noticed that some very knowledgeable persons are here so I have an issue i need help with, a 2012 International maxxforce 9 ic school bus where after the bus has run for a while it shuts down and then no power at the electronic fuel lift pump connector but the fuel pump relay has power, has anyone experienced this situation? any help would be greatly appreciated.

[Jolly Roger bus 223]

you have power going to the relay but do you have a command signal to the relay and power out of the relay to the pump

[willyuphere]

It sounds like you might have a failing Electronic Control Module (ECM) or a wiring issue between the ECM and the fuel pump. Since you're getting power at the relay but not at the pump connector, I'd suggest checking the wiring harness between those points for any damage or loose connections.

[NELSON JA MLSS]

Originally Posted by willyuphere

It sounds like you might have a failing Electronic Control Module (ECM) or a wiring issue between the ECM and the fuel pump. Since you're getting power at the relay but not at the pump connector, I'd suggest checking the wiring harness between those points for any damage or loose connections.

sorry for the late response, I was trying to locate a proper wiring diagram for the bus. thank you so much for your input, i have been checking the wiring but what I really want to know is what are the two components between the relay and the fuel pump as the diagrams I have gotten are not clear.

[NELSON JA MLSS]

Originally Posted by Jolly Roger bus 223

you have power going to the relay but do you have a command signal to the relay and power out of the relay to the pump

Yes, all the powers are present just none to the pump.

[ewo1]

Originally Posted by NELSON JA MLSS

Hey guys, new here from kingston jamaica i hvae been following this forum and noticed that some very knowledgeable persons are here so I have an issue i need help with, a 2012 International maxxforce 9 ic school bus where after the bus has run for a while it shuts down and then no power at the electronic fuel lift pump connector but the fuel pump relay has power, has anyone experienced this situation? any help would be greatly appreciated.

I don't know if this document will help you with your problem but it does explain how to do a bench test of the fuel pump...

Title: MaxxForce DT, 9 & 10 electric fuel pump and fuel system diagnostic information
Applies To: EPA 2010 and later MaxxForce DT, 9 & 10

[NELSON JA MLSS]

OK.thank you..I have this information...the question though...what is the component with the two pin after the relay and what component is the 24 pin which should send the power to the pump...my pump is OK...just no power going to it.....

[PorchDog]

I would say the two pin connector (A B) is just a connector to allow you to disconnect the wires somewhere.

The 24 pin connector must be some kind of connector from the harness to the fuel pump or something. I don't think it is an active component, just a 24 pin connector for a bunch of stuff (fuel level sender, etc. maybe...) . When the ECM wants to turn the fuel pump on it supplies a ground from pin C-76 to the relay through pin A. While the fuel pump is supposed to be "on"-- pin A should be able to pull a test light connected to battery positive to ground, and illuminate the test light. It only runs for 10 seconds at key on, and then you have to cycle it again (after waiting 10 seconds) to get the pump to run again with the engine off. When the ECM knows the engine is running, it keeps the fuel pump turned on.

The ECM verifies that the fuel pump relay is on by looking for 12 volts on pin E-69.

[ewo1]

Originally Posted by PorchDog

I would say the two pin connector (A B) is just a connector to allow you to disconnect the wires somewhere.

The 24 pin connector must be some kind of connector from the harness to the fuel pump or something. I don't think it is an active component, just a 24 pin connector for a bunch of stuff (fuel level sender, etc. maybe...) . When the ECM wants to turn the fuel pump on it supplies a ground from pin C-76 to the relay through pin A. While the fuel pump is supposed to be "on"-- pin A should be able to pull a test light connected to battery positive to ground, and illuminate the test light. It only runs for 10 seconds at key on, and then you have to cycle it again (after waiting 10 seconds) to get the pump to run again with the engine off. When the ECM knows the engine is running, it keeps the fuel pump turned on.

The ECM verifies that the fuel pump relay is on by looking for 12 volts on pin E-69.

Looking at the diagram, i have top agree with your explanation. It is quite obvious....

School busses are notorious for having dirty, loose grounds...it just the way it is!

I would first for sure check to see if the ground signal is coming from the ECM.

I would visually and physically find the ground wire for the relay to...remove the ground connection. clean and re-attach. Also do the same for the pump connector ground wire.

No matter how much trouble shooting you do, these steps cannot not be forgotten!

Relays also go bad, check the pins/connections and verify if it overheats or not.

You mentioned the pump not getting 12v, well it only comes from on place, pin 30 on the relay.

verify that wire and any fuses that protect that wire.

keep us posted...

[NELSON JA MLSS]

OK thanks for the update..the ground is OK as I have connected a 12v to the two lower wires on the fuel pump connector and the bus now runs...the thing is I would like to connect the system back to normal...the wiring diagrams don't specify components and location...so I plan to do a continuity check on all the wires at the fuel pump connector....I'll give an update shortly....

[ewo1]

Some wiring diagrams for download, free....

https://pdfcoffee.com/2013-maxxforce...-pdf-free.html

[NELSON JA MLSS]

Originally Posted by ewo1

Some wiring diagrams for download, free....

https://pdfcoffee.com/2013-maxxforce...-pdf-free.html

Thanks to everyone who gave me the support and drive to have my issue resolved.
The issue has been rectified...
The reason the pump was not getting the 12v was due to a burnt ignition relay which in turn burned the fusible link that would supply the run 12v to the pump...so I bypassed the burnt fusible links and reran a new wire from the 24 pin connector to the pump and replaced the ignition relay with a new one...everything works fine now....as it should..thanks so much also for the electrical diagram....I cannot express how greatful I am to have this issue behind me....

[ewo1]

Originally Posted by NELSON JA MLSS

Thanks to everyone who gave me the support and drive to have my issue resolved.
The issue has been rectified...
The reason the pump was not getting the 12v was due to a burnt ignition relay which in turn burned the fusible link that would supply the run 12v to the pump...so I bypassed the burnt fusible links and reran a new wire from the 24 pin connector to the pump and replaced the ignition relay with a new one...everything works fine now....as it should..thanks so much also for the electrical diagram....I cannot express how greatful I am to have this issue behind me....

Great news!
Glad you got it done and thanks for not keeping us guessing on your efforts !