No power to fuel pump

[SONIC]

Do you have spark?

[secondsupra2004]

I am holding my multimeter leads to the connections on the pump while someone else cranks the key. No voltage at any point.

I have a service/ diagnostic manual for the MEFI 4 system. In it, it states that when the key is first turned on you should have fuel pump run 2 seconds. The ECM sends a signal directly to the fuel pump relay and then after 2 seconds it does not receive an ignition signal it shuts power to the fuel pump relay. I wouldn’t think that coolant temp sensor or oil pressure sensor would be in that initial 2 second circuit.
I would recheck the fuel pump relay fuse and the relay.

[HFarr]

Is there by chance another fuse holder that was added anywhere in the circuit? Really does sound like it would end up being something simple like that by how you described it suddenly not working. Of course I guess a failure in the control module could also just suddenly happen too. Double check to make sure it's not a loose connection or corrosion in a fuse holder prior to it reaching the pump. See if there is voltage on either side.

Sent from my moto z4 using Tapatalk

[secondsupra2004]

I have a service/ diagnostic manual for the MEFI 4 system. In it, it states that when the key is first turned on you should have fuel pump run 2 seconds. The ECM sends a signal directly to the fuel pump relay and then after 2 seconds it does not receive an ignition signal it shuts power to the fuel pump relay. I wouldn’t think that coolant temp sensor or oil pressure sensor would be in that initial 2 second circuit.
I would recheck the fuel pump relay fuse and the relay.

fuel pump circuit photo.jpg
Here is a copy of the circuit diagram. It should be the same as your boat. There is a procedure for diagnosing, but it requires a scan tool. Maybe the schematic can help you at least trace down the circuit. Hopefully there's nothing wrong with your ECM. Thats where the initial signal to the fuel pump relay originates.

[Holdmybeer]

fuel pump circuit photo.jpg
Here is a copy of the circuit diagram. It should be the same as your boat. There is a procedure for diagnosing, but it requires a scan tool. Maybe the schematic can help you at least trace down the circuit. Hopefully there's nothing wrong with your ECM. Thats where the initial signal to the fuel pump relay originates.

Huge help.

What I see here is the ECM is the ground for the fuel pump relay (Dark Green/White) - Check continuity to ground while turning key to "RUN" position. This would assure that ECM is triggering.

Check Pink wire from fuel pump relay fuse with ignition in "RUN" - should have +12V - if not check fuse or connection at fuse block
If the relay is clicking - should be able to feel this also - when switched to "RUN" then control circuit is good.

Another way to check is to test 87A (unused) on the fuel pump relay - it should have +12V at all times unless the ECM is telling the fuel pump to run. After 2sec, this should go back to having power, if the circuit is working correctly.

Not sure where "FROM SYSTEM RELAY" is providing power, but this could be the problem if no power anywhere in this circuit, and fuses are all good.

I know for certain, that the ECM will be in lockout mode and not start the engine for the other sensors I mentioned earlier, but the initial 2 sec run should function every time the key is switched and the gauges go through the reset process.

[secondsupra2004]

Huge help.

What I see here is the ECM is the ground for the fuel pump relay (Dark Green/White) - Check continuity to ground while turning key to "RUN" position. This would assure that ECM is triggering.

Check Pink wire from fuel pump relay fuse with ignition in "RUN" - should have +12V - if not check fuse or connection at fuse block
If the relay is clicking - should be able to feel this also - when switched to "RUN" then control circuit is good.

Another way to check is to test 87A (unused) on the fuel pump relay - it should have +12V at all times unless the ECM is telling the fuel pump to run. After 2sec, this should go back to having power, if the circuit is working correctly.

Not sure where "FROM SYSTEM RELAY" is providing power, but this could be the problem if no power anywhere in this circuit, and fuses are all good.

I know for certain, that the ECM will be in lockout mode and not start the engine for the other sensors I mentioned earlier, but the initial 2 sec run should function every time the key is switched and the gauges go through the reset process.

Check out this schematic- MEFI relay circuit. I beleive this is the "FROM SYSTEM RELAY" you mentioned.MEFI relay circuit.jpg

[Probably the Killswitch]

Thank you for the wire schematics- huge help! Unfortunately I did not see these until just now (been down at the boat all day).

I have some developments- not sure exactly what they mean though. Let me know if this makes any sense to you guys:

I removed the fuel pump relay. When I jump the wire from pin 30 to 87 the pump kicks on- so I have good power and ground for the pump itself.

Now this is where things start to get interesting- The multimeter reads 12v on the control side of the circuit (female connectors for pins 85 + 86) when the key is in "run". I removed the two control wires form the connection housing and plugged them directly into the relay, no click and the meter reads 0v.

Can anybody think of a reason why a circuit would drop to 0 volts when connected to a relay (again, the relay itself is fine)? Maybe a bad ground for the ECM? I'm looking for the ECM ground on these diagrams but I'm no electrical engineer. Does anybody know where it is in the physical world?

[secondsupra2004]

Check out a video on YouTube called
“GM FUEL PUMP RELAY TESTING “. It about. 30 minute video and describes in detail the biased voltage produced by the ECM. 12 volts with a test light plugged in to the socket without the relay and 0 volts with the relay plugged in. Check it out.

[Holdmybeer]

Thank you for the wire schematics- huge help! Unfortunately I did not see these until just now (been down at the boat all day).

I have some developments- not sure exactly what they mean though. Let me know if this makes any sense to you guys:

I removed the fuel pump relay. When I jump the wire from pin 30 to 87 the pump kicks on- so I have good power and ground for the pump itself.

Now this is where things start to get interesting- The multimeter reads 12v on the control side of the circuit (female connectors for pins 85 + 86) when the key is in "run". I removed the two control wires form the connection housing and plugged them directly into the relay, no click and the meter reads 0v.



Can anybody think of a reason why a circuit would drop to 0 volts when connected to a relay (again, the relay itself is fine)? Maybe a bad ground for the ECM? I'm looking for the ECM ground on these diagrams but I'm no electrical engineer. Does anybody know where it is in the physical world?

Pin 85 & 86 - are these wires Pink and Dark Green/White?

The Dk Grn/WHT wire is ground. The ECM completes the ground for the circuit. A meter measures voltage differences between the wires. It looks like the relay is shorted and the wires have 12V on both, which is why you are measuring 0v potential difference.

A new ice cube 30A 12V relay is $10. I would try it out and see what happens. You have one in your truck fuse box you could try out and see if it works.

[austin.james07]

Pin 85 & 86 - are these wires Pink and Dark Green/White?

The Dk Grn/WHT wire is ground. The ECM completes the ground for the circuit. A meter measures voltage differences between the wires. It looks like the relay is shorted and the wires have 12V on both, which is why you are measuring 0v potential difference.

A new ice cube 30A 12V relay is $10. I would try it out and see what happens. You have one in your truck fuse box you could try out and see if it works.

Was out today and the boat fired right up and ran fine.... went back to the dock and let it idle for a while and then eventually the boat shut off..... i could not get it started again after that.... I thought I ran the boat out of fuel but that was not the case. The engine is for sure not getting fuel for whatever reason.... I have almost identical systems and this is what I have checked so far....

1. fuel pump power on when bench tested and when I jump the pink to grey wire on the fuse block
2. all (3) blue fuses are good
3. the fuel pump does NOT prime and does NOT get the 2 seconds of power at key on. There is no power running to the fuel pump
4. the relays do not click
5. Waiting to try and swap relays but I did rotate them around as they are all the same and no result was different.

any thoughts here? PLEASE HELP!