Fuel pump testing with an Ohmmeter.

[sr acalito]

Open? This enertia switch is shorted. I tried already using a jumper but still no good result. Written in the enertia switch is 'FIRST ENERTIA SWITCH' does this means there is still second enertia switch? I checked also the resistance on the two wires (pink & blue), there is no continuity. My car is '92 explorer xlt offroad.

 

[BrooklynBay]

There is only one inertia switch, and it should be electrically closed. It sounds like there is a problem with the fuel pump or possibly the connection on the pump since everything else in the circuit shows that there is voltage going to the pump. Lower the fuel tank, and check the electrical connector on the top of the tank. Be careful not to damage the fuel lines.

 

[sr acalito]

Ok I'm gonna do it. Thanks BrooklynBay!

 

[BrooklynBay]

The tank has a couple of straps holding it. Disconnect the fill hose before you lower the tank. Use a floor jack with a board on top of it. Don't put a lot of force on the jack when you raise the tank to reinstall it. The tank is fragile, and could get damaged. A motorcyle jack or a transmission jack has a wider top, and might be easier to use than a standard floor jack.

 

[sr acalito]

Thank you BrooklynBay! I'll follow your advice..

 

[rhauf]

Just thought i'd throw this out there, but an ohm meter won't tell you if the fuel pump is bad or not. you can see if it gets voltage when the key is turned to run (it should get voltage for a few seconds) that will tell you if voltage is getting to the pump (and if it doesn't run it must be bad)

Testing with an ohm meter probably wont tell you anything (a working pump would read the same as a jammed one, for instance)

 

[sr acalito]

thanks rhauf! i've just finished removing the skid plate. still long way to finish checking the pump. lets crawl again under the truck's belly!

 

[sr acalito]

I found the socket for the fuel pump, but I'm not sure which is the wire for the pump motor. The wires are black, yellow, pink and gray. Anybody there sure which wire I'm gonna connect direct to the battery to check if the pump motor is ok or not? Thanks in advance!

 

[sr acalito]

The voltage at the socket near the fuel pump tank, which is the supply for the fuel pump motor is only 8v. I tried connecting the pump motor to a battery, no action except a 'click' sound. Perhaps the pump motor is dead already.. Any help pls..

 

[BrooklynBay]

Are you sure that you have the correct wire? One way to test it is to connect a test light to that wire, turn on the electrical system, and see if the light turns on for a few seconds, and then shuts off. Did you have to lower the tank to get to the connector?

 

[rhauf]

be careful not to connect the fuel tank sender to voltage. this would most likely destroy the fuel tank sender.. and if the fuel level is low enough i suppose could possibly ignite the fuel tank.. i dont know.. just be sure you're on the right one.

i'd say it's the pump motor. remove it, and replace it.

 

[sr acalito]

The connector is outside the tank, but I'm not sure til I lower the tank. There are 4 wires in the connector, 2 bigger black & pink, and the other 2 which is smaller, orange and yellow. Just few minutes ago I connected a voltmeter to black and pink, as I switch ON the key, the pointer reaches 12v for a second then rest at 8v. Thanks GOD! I was correct yesterday when I connect a battery to the pump motor, which I heard only 'click'. The resistance on the motor is 1.2Ω only (don't know if this is normal). Now go back under my truck's belly to remove the tank, but before that, I have to check again the connector using a test light. Thanks a lot guys!

 

[rhauf]

1.2 ohms sounds about right, but the reason these usually fail is because the pump wears out and jams solid. the 12v for a few seconds on key on was to pressurize the fuel system. sounds like the electronics up to that point are working correctly. you're pump is the problem.

 

[sr acalito]

I did check also using a test light, and as I switch ON the key, light is ON for about 2 seconds then OFF, just as what BrooklynBay said. So I rermoved the fuel tank, man! it looks like a whale! The thing I'm thinking now is how to remove the fuel pump or sending unit. I think by rotating the cover counterclockwise this can be remove.

 

[sr acalito]

I removed already the fuel pump/sending unit and wondering, is this fuel pump or sending unit sold one set? I am planning to buy just the pump only.. Pls help..

 

[BrooklynBay]

They make a special tool to remove this sending unit/pump combo. It's possible to buy the pump separately. Check WWW.RockAuto.Com. There is a coupon code in the vendor's section for them.

 

[sr acalito]

I bought a new fuel pump/sending unit already, whole assembly, with the float for fuel gauge, here you cannot buy just the pump/motor. I found out that the resistance of the new pump motor is around 12Ω, compare to my old pump motor which is 1.2Ω only. amost shorted! I bought a new fuel filter also, but this is smaller than the one used now on the truck, the store person said maybe this is ramanufactured. Tom I will install this but I'm thinking of cleaning the tank first maybe a lot of dirt inside also. Any advise on cleaning the fuel tank? Thanks!

 

[BrooklynBay]

You could use a garden hose or a pressure washer to clean it. Make sure that there is no water left in the tank when it's ready to be reinstalled.

 

[sr acalito]

Thank you very much BrooklynBay & rhauf for your help! I've installed the fuel pump yesterday and it works well. Now my truck is back on the road.

 

[BrooklynBay]

Thanks for the update!