Water In Fuel Sensor Replacement

[crash-harris]

Going on the 18th to get a new old truck. My first dually and my first diesel. Current owner says the water in fuel light has been on since he got it and was told that the sensor is bad (had also run 10 tanks worth through the engine with no troubles). So my question is, what is the procedure for replacing this sensor?

On a side note, he says only the rear tank works. I know my 1990 300 six cylinder has FDM's in each tank that switch power, and since the 7.3L IDI is a mechanically injected diesel, I'm assuming that they use the older mechanical selector valves to switch between tanks. I'm curious if anyone had rebuilt these worth positive long term results or what is involved in replacing it with an aftermarket, electronic controlled switching valve.

 

[madpogue]

What year truck are you buying?

 

[icanfixall]

What year truck are you buying?

Good question....None of the idi trucks or vans have any kind of a pump in the tanks. Most have added an electrical lift pump because they purge air so much better than the oem mechanical. A s for replacing the water in fuel sender if you have the 7.3 filter head with the removeable bottom aluminum piece its simple. Remove the filter. then remove the bottom aluminum filter cover and see the black sender in the bottom. Just unscrew that and replace it. They can be found on ebay most of the time. Might also check if the wire to the sender has fallen off the sender too. Years ago when its gets humid around here my light would come on. I have never gotten any water out of the filter drain. So I just drove the truck till engine temps came up and dried out the sender connection.

 

[crash-harris]

Forgot to mention the year, oops! 1990. Happens to be a crew cab, long bed dually that's been to Western Hauler at some point in its life.

As for the pumps, I'm more interested in the tank selector valve. I know that Ford did away with the mechanical selector valve on the gassers in 1990 and that I've never heard of them really being rebuilt (lots of TSB's on them). But do the diesels have electronic selector valves, or where the mechanical ones still in use in '90? Any links to repair or replacement? Can't seem to find the search link....

 

[madpogue]

The selector valve is electromechanical, not electronic. OEM replacement is $$$$$-y. The OEMs were made by Pollak, and generic 6-port Pollak valves are available for a LOT less. Only differences are the fittings, and where the fittings are oriented. So a generic swap would require some fab of the lines. There are tests you can do on the switch, and on the valve, before condemning it, however.

Some hardcore folks have replaced the selector with a pair of true mechanical valves, that is, brass plumbing ball valves. They poke a couple holes in the floorboard, and mount the valves so the handle stems go through the holes, then install the handles inside the cab. Then they re-route the sender wiring (the Pollak valve also does the sender switching) up to the dash, and commission a double-throw switch for switching the senders. Very Mad Max, but it works.....

 

[crash-harris]

I've thought about doing that on my current truck when I get to the repower, but for this one I was thinking of the pollak valve. Seems a lot cheaper and smaller.

 

[crash-harris]

I have one more question regarding fuel switching.

We're going to see the truck tomorrow (1990 F350, CC, LB, dually, 7.3L IDI) and the seller thinks that the fuel selector switch is to blame. I looked, but I can't seem to find replacement selector switches for trucks with diesel engines. All the switches I've found specify gas engines.

So what's the difference between the fuel selector switches in gas and diesel powered trucks?

 

[jim_22]

The owner could be right, I had one go bad and it is a cheap and easy replacement. I just looked at my receipts. In 2012 I bought the switch for $15.69 at a local NAPA store. The part number was 730-5602. I did notice that the connector was ever-so-slightly different shape but with a little persuasion it plugged right in.

PS before you replace the switch check the fuse. It is on the same circuit as the air compressor.

 

[madpogue]

It's most likely the selector valve itself, not the switch. And the valves do have subtle differences, and the diesel ones are hard to come by used, and wicked expensive new.

 

[crash-harris]

I'm guessing it's the valve as well, but I will for sure check the fuse. Thank you for the part number too!

 

[crash-harris]

So I got a new water in fuel sensor, but I can't seem to find where is located under hood to replace it! Searched Google worry no avail. Where's it at?

 

[icanfixall]

On the 7.3 fuel filters the wif sender is located under the filter in that aluminum bottom case cover.

 

[crash-harris]

Well that explains why the light is on. Mine has a Wix filter with no bottom cap, all one piece. Looks like I'll have to get one before I do the return lines and new filter.