1996 4.3LX Fuel Pump Issue (I Think)

[boatingguy]

All,

I have a 1996 4.3LX that I just had rebuilt. I have it in the boat and it will crank and run if I pour gasoline in the carb; however it will die once it runs thru that gasoline. I also get the alarm, but have plenty of oil pressure (not sure where the alarm is coming from). I have checked the wiring at the starter, alternator, and pressure switches.

From what I can tell I am not getting any fuel from the electric (torpedo looking) fuel pump. With the ignition on, I have about 7 volts to the fuel pump at the plug, but it is not pumping fuel while cranking the engine (took off line to verify). The water/fuel separator is full of fuel.

From looking at my wiring diagram, I do not see any problems. Pump worked fine before the engine was rebuilt.

Any help on what I should be looking for would be appreciated.

I hope I am not new threading something that is already here.

Thanks in advance
Randy

 

[Bondo]

Re: 1996 4.3LX Fuel Pump Issue (I Think)

From what I can tell I am not getting any fuel from the electric (torpedo looking) fuel pump. With the ignition on, I have about 7 volts to the fuel pump at the plug, but it is not pumping fuel while cranking the engine (took off line to verify). The water/fuel separator is full of fuel.

Ayuh,.... Welcome Aboard,... It sounds like ya screwed up the wirin' harness, puttin' it back together...

You should be seein' 0 volts, motor off, key on...
You should see 12 volts, key Starting/ crankin' the motor over...
And,...
You should see 12 volts, key on, motor runnin'....

The starting power comes from the tiny terminal on the outer edge of the starter's solenoid....
Runnin' power comes from the ignition, through the oil pressure switch...

 

[Don S]

Re: 1996 4.3LX Fuel Pump Issue (I Think)

This might help.

 

[boatingguy]

Re: 1996 4.3LX Fuel Pump Issue (I Think)

Thanks for the replies. After some more trouble shooting of electrical I think I may have the answer, but would like to see if anyone agrees. I have twin engines(one actually runs!!!|), so I am comparing readings.

On the engine in question I get about 8.8 Volts at the fuel pump connector with just the key on. When I disconnect the purple yellow wire from the starter terminal, I have 0 volts at the starter terminal, but still 8.8 at the ring terminal on the wire (so not coming from the starter terminal). I have checked all contunity and all is ok. All of this being said where is the voltage coming from? I think it is bleeding thru the Oil pressure switch (the one that "t"s off the lower block and also has the oil pressure sender). With the key on, but engine not running, I get continuity with resistance. I also get the same 8.8 volts on the downstream side of the switch. On the good engine under the same conditions, I get no continuity and no voltage on the downsteam side. On both engines, I get 12V on the up upside of the switch.

Real question is this. Is the switch allowing current to bleed thru to the fuel pump with the switch on? Once I turn the starter via the key, the voltage at the pump drops off.

Again thanks for the help.

Randy

 

[boatingguy]

Re: 1996 4.3LX Fuel Pump Issue (I Think)

This might help.

Thanks Don. If you have time, please take a look at the thread again.

Randy

 

[Bondo]

Re: 1996 4.3LX Fuel Pump Issue (I Think)

Real question is this. Is the switch allowing current to bleed thru to the fuel pump with the switch on? Once I turn the starter via the key, the voltage at the pump drops off.

Ayuh,.... It sounds like the switch is faulty,...

Is there 12v at the tiny starter terminal, when crankin' the motor on the key,..??

 

[boatingguy]

Re: 1996 4.3LX Fuel Pump Issue (I Think)

Ayuh,.... It sounds like the switch is faulty,...

Is there 12v at the tiny starter terminal, when crankin' the motor on the key,..??

Yep.

 

[Don S]

Re: 1996 4.3LX Fuel Pump Issue (I Think)

You either have a poor connection somewhere. Is the voltage also low at the automatic choke? It could also be the sender itself if the contacts are burned and have high resistance.

 

[boatingguy]

Re: 1996 4.3LX Fuel Pump Issue (I Think)

Still having problems. What noise, if any, should the fuel pump make. I get a "click" when it recieves power, but not any continuous sound. Kind of sounds like it is stuck, but I'm not sure what it is suppose to sound like. Also, no fuel comes out with the line at the carb disconnected, even though there is fuel in the input line and the water separator (brand new, but filled with fuel per MM).

Is there any way to test this pump without the pressure guage per the manual? Can it be connected directly to the battery to check operation?

As always, any help is greatly appreciated.

Randy

 

[Bondo]

Re: 1996 4.3LX Fuel Pump Issue (I Think)

Can it be connected directly to the battery to check operation?

Ayuh,... Sure...

 

[Don S]

Re: 1996 4.3LX Fuel Pump Issue (I Think)

They make a whining noise when they run, not just a click. Depending on how and where you are taking your voltage measurements, you could have a bad pump. Wouldn't be the first electric fuel pump to bite the dust (or water, or air, or .....}

Hook up some jumper wires directly to the pump and see if it runs.

 

[ENSIGN]

Re: 1996 4.3LX Fuel Pump Issue (I Think)

If your pump runs connected to a battery put a jumper across the oil switch terminals and reinstall the pump.If it runs replace the oil switch. There have been alot of problems with them.