I have a 1991 f350 with a 460 engine, fuel pumps will not run. I have changed relay, pumps then noticed there is only 7.5 volts at the pumps. Ran KOEO test and code 95 displayed "Fuel pum circuit failed"- PCM-GRD.
Curious if it is the ECM? Looking for any suggestions

 

Welcome to the site..

Ground the Dignostic Connector fuel pump circuit with a test lead, do the pumps run?

 

I grounded the fuel pump connector before I changed the relay and the pump and it did not run. I have not done since changing, I will try it to see if it will run. Thanks for your suggestion. I am still concerned with the voltage reading at the pump

 

Sometimes working backwards can help with a cause.

Since the PCM controls the ground/pump run time, the Diagnostic Connector test would or should take the PCM out of the search. Can help prove out the pumps too and help extend pin point test times on the connectors/wires as well since the run time will be constant as long as the circuit is grounded. Did you first check for 12v to the relay block connect, then add 12v to the inertia connector,,, did pump/s run? If so, and voltage is low at the relay terminal, work,backwards from there..

 

I grounded the fuel pump at the test connection and the pump started running and the truck started. I unhooked the groung from the test connection and the pump seems to work like it should. Do you think it is a faulty ground that fails occasionaly? faulty relay? thanks

 

Since you jumped the DLC closing the relay and the truck runs continuous, it would 'seem' a relay or connection problem, but you replaced it with a new unit. Wasn't the PCM/EEC module power relay replaced? Had to ask..

The PCM/EEC controls the fuel relays coil ground to close the relay for power distribution. If by grounding the DLC/Fuel terminal starts the truck, the ground circuit needs to be pin point checked. Also all the terminals at the relay to make certain for applied voltages there. If the truck doesn't start, you might first try a light tap on the top of the relay. If its a bad relay, or possibly a connection problem it may be related or close within the relay box. If you need to pin point test the ground from the PCM, this is where a Break Out Box comes in handy if there is a circuit fault somewhere between the relay block and the PCM connector, or to varify a failing PCM..

If it doesn't start, try pulling the relay and see if your getting a ground on the relay leg/terminal. Or, if you suspect the PCM, you can check the LB/O wire (pin 22) coming out of the PCM connector for a ground command. (Timed) If the truck doesn't start, you can add a pin out ground on the LB/O-22 at the connector and if the truck starts, it would take the relay, box, and anything outward fom the PCM out of the diagnostic. You could also OHM ckeck the circuit, checking the condition of the 22 pin/connector, then on out/through and to the relay from the PCM connector.

 

Thanks, The truck runs with out the jumper . I am checking the ground from the EEC, I have not changed the relay for the power relay. I am going to replace and continue to check for faulty ground curcuits. I am glad the truck finally ran. I bought the truck a while back and just have had time to try and get it running. I appreciate your help. Thanks again