Fuel pump didnt turn off.

[Highlands]

Just finished installing 4bbl GM intake manifold and 4bbl edelbrock 1409 carb on my 2008 4.3 alpha one. Putting it through some trial runs last night at home with the dog ears attached. Ran good, timing may be out a bit, but my problems started when I attempted to turn off the engine. Put the key to the off position and remove it but engine runs perfect. Sat around for a few minutes thinking it was going to die when the fuel from the carb was used up....but it never did. Kill switch didnt even work. I had to manually idle it way down with the idle screw on the carb till she stalled. Then i still hear a buzzing sound from the fuel pump. I had to disconnect the fuel pump at the harness, to kill it. The pump was very warm to touch, curious if this is normal? I take the the flame arrestor off and see my choke on the carb is wide open, and some condensation or exhaust coming from the carb....thinking this is a timing issue possibly?? Let it sit for the night do a visual this morning choke is closed now and hooked the fuel pump back up to the wire harness and it was fine. Anyone have any idea why my fuel pump or engine would not kill with the key in the off position?

 

[Don S]

Re: Fuel pump didnt turn off.

You may have a defective ignition switch that doesn't shut off.
When it does it again, use the lanyard kill switch to shut it off.

 

[Bondo]

Re: Fuel pump didnt turn off.

You may have a defective ignition switch that doesn't shut off.
When it does it again, use the lanyard kill switch to shut it off.

Ayuh,... 'n the electric fuel pump ain't wired properly, through an O/P switch....

And/ or ya screwed up the wirin' puttin' it back together...

 

[Highlands]

Re: Fuel pump didnt turn off.

Hard to screw up the wiring when I didnt take anything apart other then the quick connects from the harness, which only go one way.

I did use the lanyard kill switch, that didnt work either.

 

[Highlands]

Re: Fuel pump didnt turn off.

You may have a defective ignition switch that doesn't shut off.


Was thinking this as well. I will have to put the volt meter on the ignition if it happens tonight. Would it be normal for the fuel pump to run very warm, or is this just a symptom of not being cut off?

 

[Don S]

Re: Fuel pump didnt turn off.

Fuel flowing through the pump helps cool it. But it's still an electric motor, and motors get warm when in use.
But, even if it's a bad ignition switch, it doesn't explain why the pump was still running after the engine was shut off.
Besides the manifold and carb, what other work have you done to the engine? Anything around the starter or oil pressure switch? Wiring changes on the engine perhaps?

How about the main battery cable on the starter solenoid. Is it by some chance touching the small terminal on starter solenoid? That would make the pump run, and would keep the ignition energized.

 

[Highlands]

Re: Fuel pump didnt turn off.

Fuel flowing through the pump helps cool it. But it's still an electric motor, and motors get warm when in use.
But, even if it's a bad ignition switch, it doesn't explain why the pump was still running after the engine was shut off.
Besides the manifold and carb, what other work have you done to the engine? Anything around the starter or oil pressure switch? Wiring changes on the engine perhaps?

How about the main battery cable on the starter solenoid. Is it by some chance touching the small terminal on starter solenoid? That would make the pump run, and would keep the ignition energized.

No wiring changes. Did replace the starter and 90amp fuse while back. I will check the connection on the starter, maybe turning the engine over knocked something loose down there. If the ignition was energized wouldn't I constantly hear the "beep" that signifies the ignition is "key on"?

 

[Highlands]

Re: Fuel pump didnt turn off.

I was running my engine for the second night in a row, after the motor got up to normal operating temp, every time I attempted to turn the boat off it would remain running. Even killing the lanyard safety switch would not kill the engine. The only way I could kill it was to flip the 50amp circuit breaker in the engine compartment. After I flipped the breaker and stopped the engine, if I reset the breaker my fuel pump would continue to run. This occurs only when the engine is warm. This morning after letting it sit all night and cool down I flipped the breaker to the ON position and the fuel pump was doing what it was suppose to do, nothing. I also noticed last night when the engine was running that the alternator housing was so hot I couldn't touch it. What is going on? Looks like I may have a short somewhere? Maybe some type of solenoid that is not switching the fuel pump or alternator off? Looked around the starter nothing is shorted out down there.......

 

[Failproof]

Re: Fuel pump didnt turn off.

Turning off the switch, or flipping the kill switch should have killed power to the ignition and the fuel pump. Its not so much that the pump stayed running as the ignition stayed energized. The pump is fed from the run position. If any relays, they may be sticking. Could also be that the alt is feeding power due to the field not colapsing. Next time it stays running try disconecting one of the field wires on the alt and see if it kills the engine.

 

[Highlands]

Re: Fuel pump didnt turn off.

You are right about one thing Failproof, turns out to be my alternator. Faulty diode inside the alternator was feeding power back into the fuel pump and electric choke. Replaced alternator all fixed.

Thanks for the help.