Fuel Pump troubles

[Mtn_Man]

Chek me on this: 94 Limited
1. The inertia switch is set (red button down)
2. I yanked the relay to the Fuel Pump and shorted the two connections to activate the fuel pump (not the field leads, the normally open connection)

Got a big nada. No sound, nothing. Truck has sat (with fuel in the tank) for about 4 years. I just rebuilt the motor and siphoned out the gas and was going to use the pump to finish the job as the filter is out right now. Shouldn't the pump just run once I short the relay leads? Is there a low fuel cut out switch or something like that? Is it just shellaced up? New battery so there is voltage. Is there something in the anti-theft that's blocking me here? The hood is off so I could get the motor in. I read that the hood switch needed to be cycled before the anti-theft could be activated if the system was brought up with the hood open. I realy don't want to drop the tank, but it won't be anything new. This rebuild has done nothing but nickle and dime me to death anyway. Ideas?

 

[MrShorty]

A new battery in the battery box doesn't guarantee there is voltage at the fuel pump. I'd get a voltmeter and a test light and find where the break in the circuit is. Don't forget to check the ground side of the circuit.

Have you checked the fuse.

 

[Mtn_Man]

Fuse and relay are OK. It worked before it was parked. In order to check at the connector I would have to drop the tank unless there is some other intermediate connector. There is voltage at the relay both on the coil and at the common terminal.
Oh well, guess it's drop the tank time.

 

[93ebx]

Mtn_Man

Keep us posted I have the very same problem. and have had no luck fixing it

Ace

 

[MrShorty]

Your '94 might be different, but on my '92, there's a connector in the driver's frame rail, just aft of the gas tank, kind of above the rear axle that's accessible without dropping the tank (if it's not already too late). You could also check at the inertia switch.

 

[DeRocha]

Fuse and relay are OK. It worked before it was parked. In order to check at the connector I would have to drop the tank unless there is some other intermediate connector. There is voltage at the relay both on the coil and at the common terminal.
Oh well, guess it's drop the tank time.

The fuel circuit will only register 12v while the engine is cranking.. Once the tach wire goes to Zero RPMs the fuel circuit will drop to 6-7v (which will not run the fuel pump). If you are trying use the fuel pump to push out the gas you will need to run a hot wire from the battery to either terminal on the inertia switch..

 

[btexpress]

If this sat for four years with fuel in the tank, you can bet the pump is gummed up. My snow blower wouldn't start this year, after sitting one year with fuel in the tank, gas went bad!

Fuel pump failures are extremely common on Explorers, leaving fuel in it up to four years most likely just added to the failure ratio here.

As MrShorty said, the fuel pump connector is on the left frame rail, check for voltage there while someone else cranks the engine, or turn the key on and you should have voltage for 2-3 seconds.

Change the fuel filter too while your at it.

 

[Mtn_Man]

Right On. Some good ideas. I fortunately (well, maybe not) had a doc appt so I did not have time to drop the tank this morning. If I have a connector just aft of the tank then I'll just wire it direct for the final purge. The gas that came out had the old gas funk, but not the usual dark caramel color of gas that is converting to crud. I bought a new fuel pump as insurance so I wouldn't have to go out once doused in gas because you know that's going to happen. Since the truck has 150K on it, I think I might just replace it anyway. I believe it is the original pump. Geez. $100 for a motor that looks like it belongs on an RC plane - and not even a good one. I guess it is payback for saying "Wow, that's pretty darned cheap" while standing at the Ford Parts counter. I had to get new spring fingers for the fuel filter line ends because the last clown that changed it out used the wrong filter with the short nipples. No way to get any tool in there so I had to cut it out. Lovely. I'll be on it first thing in the morning. Thanks guys.

 

[Mtn_Man]

Well the pump was OK when tested directly on it's leads - at the motor, bypassing the haness all together. Seems the negative lead has a break in it between the pin in the connector and the crimp on the sending unit. Good thing I checked before reinstalling. The float was toast as well so I picked up a new one of those and a retaining ring as the original died upon removal. The tools for getting the fuel lines off the sender are fairly useless (no news there) but I discovered that by cutting and splitting the dispense tubes that come with RTV and gasket makers you end up with a tool that does work. The problem with the tools is that they have two large gaps between the halves. I almost spent some time on the lathe making the two different sized tools needed, but the dispense tube trick was quick and easy. So today I will see about rebuilding the sending unit, but since RockAuto has the entire unit without the fuel pump (of which I already bought one) for $65 for the one with the nitrophyl float and $75 for the one from the OEM I won't spend too much time on it. On the upshot, there was only about a half a gallon of gas left in the tank, so I guess I siphoned it out well. Not too much crud in there either. Definitely cleaner than any of the 60's Mustang tanks I have messed with.