Fuel Tank Selector Switch?

[Bullnose Gator]

My gas gauge only reads the front tank sending unit even when I flip the switch to the rear tank.  I have the tanks out, so I'm manually manipulating the float as I experiment with switching the sending units from front to back and back to front.  Both the front and back sending units register on the gas gauge when they are hooked up to the front tank socket, but nothing registers when they are hooked up to the rear tank.  

I don't know anything about electrical systems or how to troubleshoot them, but rock auto sells the selector switch for $50.  What are the odds it's just the switch?  Should I gamble and replace the switch or ask y'all to post a link to the "testing electrical systems for dummies" thread? lol

[Gary Lewis]

Assuming your system is wired the way the '86 EVTM shows, below, then the switch is the only thing in common with the front and rear sending units.  So it could be the switch.

But it could also be the wiring.  If it was me I'd pull the Y/LB wire off of the switch and test it end-to-end.  One way would be to ground one end and see if the other shows a direct ground.  If it is broken somewhere then a new switch won't fix it.

[jdavidsmi]

You need to double check that switch on Rockauto, it’s only a 5 blade switch and our 86s uses a 6 blade. Don’t ask me how I know. At least on my 86.

[RenoHuskerDu]

I'm going to be a Thomas here and say that in our experience the best thing to do with dual fuel tanks is to junk them and convert to big single tank. Or bed tank with gravity flow into your rear tank. Junking the front tank gives you more dual exhaust options.  All the stock fuel tanks we have pulled turned out to be at least sweating fuel from seams, on close inspection.

Supposedly Furd improved the system as of mid Bricknoses, but we still have trouble with them right up thru Aeronose trucks.

[grumpin]

That’s a good point Reno, if I run into any more fuel tank problems I may go the route. Didn’t think of the extra room.

I would like to keep the spare down there, but one tank would be nice.

Going to have to wrap my head around the wiring for that.

[swampedout]

Just when I was starting to tackle fuel problems, I see this...
My front tank works fine most of the time.
The rear reads properly but doesnt pump

[RenoHuskerDu]

We fought fuel tank problems for years in Puddles, our first Bullnose. Senders go inop, have to watch the trip odometer. Pickups break off half way. Solder repair fails. Tried 36 gal rear tank from Bezos, it was thin metal junk, failed. Dual tank valve was new and the only thing that worked, kinda sorta.  Still have it somewhere, discontinued part now I hear.

Final solution is 100 gal bed tank and electric fuel pump.  Still to come is a custom bed tool box with a ramped floor, to hide the tank and give some storage.

[swampedout]

I like that solution and might do something similar at some point. I dont like the idea of giving up bed space though..

[RenoHuskerDu]

swampedout wrote

I like that solution and might do something similar at some point. I dont like the idea of giving up bed space though..

At least we can still roll in a round bale of hay