Where to put fuel sender in MAF aux tank? (1 Viewer)

[bikersmurf]

I've got an older MAF 22 gal auxiliary tank. I'm going to install a fuel sender and am trying to decide if I should install it at the very top of the tank or on the step down. I'm planning on using the stock 74 fj40 sender.

If it's at the very top the tank will need to be somewhat lower to allow for clearance of wires etc.

It it is on the step down the fuel level will be higher than the top of the sender increasing the chance of a leak.

No baffles to worry about.

The tank bolts to the floor... No problem now since the floor is thicker steel than the frame. (Makes for excellent traction.)


Thanks

 

[alkarich]

What sender are you going to use? OEM or aftermarket? If it is OEM will the float reach the bottom?

That would be my biggest concern on placement.

 

[bikersmurf]

OEM Sender

This tank is 10" deep and the OEM gage should be close enough to the bottom. I'll adjust the float level it necessary.

 

[alkarich]

If the float of the OEM sender will reach the bottom of the tank mounted on the top I'd place it there.

 

[fieldsken1]

put it on the step down it wont be lower then the fuel it wont fill up all the way anyway. it will trap air first

 

[bikersmurf]

Depth of stock 74 tank

Does anyone know the depth of a stock tank?

 

[Downey]

Here's the deal---You can use 9/72 thru 1983 sender (120 ohms empty, 17 ohms full). Mount it into the right front corner of tank (lower level), in a location that positions the actual float on the center line of the tank. This is where the fuel level will be the steadiest and give the most accurate dash gauge reading. As I recall the sender hole would be about 5" in from right (passengers side) of tank. Be careful when drilling mounting holes (screw holes) so that sending unit position in fact has float in center of tank. Mis-drill the holes and the float swings around into front wall of the tank, or rearward into no-mans land??? If you are also using a stock front tank and sender, use a double pull-double throw switch (DPDT) because it can switch from tank to tank AND switch from sender to sender simultaneously.

 

[bikersmurf]

Thanks, I couldn't ask for a more detailed reply.

 

[bsevans]

I have the same style tank and it came already drilled to mount the sender in the step down. I had to TIG weld an additional length of rod to get the float to the right length so it would give the proper reading from empty to full. If you want to switch the tanks and fuel sender then I would reccomened the Pollak setup. It is a fuel switching valve that only uses power to make the switch and then shuts off. See Fuel switching valve The DPDT switch is a non standard switch that reverses the + and -. A regular DPDT switch will not work.

 

[alkarich]

Here are the parts I used for my aux tank. With this set-up I am using my stock gauge for both tanks. The dash switch operates the fuel valve and also reads the appropriate fuel sending unit. The positional switch plate "aux/main" was that has the Hope this helps.

 

[alkarich]

So I think the valve ended up being the FV1 or FV-1. Purchased on line at Rockauto.com. ($40.79)

The part FV2 or FV-2 is the switch plate. ($1.84) Type these part numbers into the search link below. Try without the dash.

RockAuto Parts Catalog

The switch itself is listed on the receipt in the prior post. ($13.83)

Below is the schematic for wiring and fuel lines.

 

[bikersmurf]

Thanks for all of the replies. I'm planning on ditching the original tank and just use the "auxiliary" tank. I don't need to cary the extra fuel and plan to make use of the space inside where the factory tank was.

 

[bikersmurf]

I finally have the tank installed (only taken 3 years), and filled... The sender has infinite resistance across it.

Guess I'll have to get out the Oxy-Acettelene torch and cut a hole in the floor to access the sender... More seriously, anyone know a reason the sender isn't giving me a reading?

I used the sender that had been working reliably for years in the stock tank... tested the ground. Tested the wiring to the sender.

Guess I'm not going to have a fuel gage in the new tank... at least not any time soon.

 

[Sando Serious]

Subscribed. I'm about to pull the trigger on a universal sending unit that will work with the 240/33 ohm fuel gauge about I'm also about to pull the trigger on. Anxious to hear what some solutions are for you. Good luck.

 

[bikersmurf]

Progress. I think it's the spade connector. In the testing process, I had pulled the connector off... my hands were to big to plug it back, so I had to think about it. While looking for my pick up tool, I came across a welding rod. I then was able to use the Gas welding rod to slip the connector back together.

Next, I decided to measure how much voltage got through... 13.54v... (from the battery charger)

Switched back to ohms, 83 ohms. not the 17 for a full tank, but a whole lot closer.

Things to determine:
1) how to reach the sensor to clean and reconnect (should have polished while it was siting on the bench for most of 3 years)

2) should I just hook it up and see what it does... What sort of reading... Will it get better...

3) should I run 120 through it and see if that'll help.


Other than this little bump in the road, using a stock sensor seems like the best option... especially for dual tanks. It reached very close to the bottom, and it's a match for the sender in the second tank... oh ya, so far I've kept the stock tank.

 

[jimkyser]

Isn't there a possible problem with the two-to-one (three way) fuel valve if you have the return line(s) hooked up. Basically, with that valve you're only switching the input to the pump and the excess will always be sent to the same tank. Since this is usually the tank under the seat, when pulling from the rear tank the under seat tank will overfill. That is why you need a 'six way switch' that switches both the input and return lines.

 

[Sando Serious]

I wasn't aware that a 3 way fuel valve could be used with the return lines hooked up. I was under the impression that would have to be a 6 way valve.

 

[jimkyser]

I wasn't aware that a 3 way fuel valve could be used with the return lines hooked up. I was under the impression that would have to be a 6 way valve.

It can't be used for the reason stated. You could actually hook it up, but the one tank getting all of the return flow will eventually overfill.

 

[bikersmurf]

From what I understand, most of the MAF & Confer tanks were set up without a return line. Often they were set up with a transfer pump to refill the factory tank. This simplified the return, and fuel sender issue. You'd know you could "refill" the factory tank 1.5 times (more or less).

The Qjet I'm running doesn't have a return line. Rather than an electric valve, I've got a brass three way fuel valve that I picked up at one ofthe local marine shops. The manual valve should be simple and reliable (and not cheap plastic). I'll also need a switch to select which tank the guage is reading. Perhaps not as user friendly, but it should be very reliable.

 

[SteveH]

My 1978-mfg ConFerr tank has a return port fitting, and I used the 6-way Pollack valve and a DPDT switch to plumb it. This tank was dealer-installed on a '78 FJ40.

I installed a Sun-Tune (cheapie) fuel sender and gauge (GM-style) near the edge of the tank so that the float was near the middle of the tank - but watch for baffles, etc. I have a '73 Ford Bronco fuel selector switch mounted on the dash (nice retro look) that flips the valve one way or the other. This setup has worked perfectly since 1990, so I cannot complain. I agree that you need a 6-way valve to properly route the return fuel to the correct tank, if you have a return type fuel system.

I set up my system so that if the power failed to the Pollack valve, the system would default to the stock fuel tank. I always use my aux tank first, and then switch to the main.

Just my .02 on this. A 6 way valve requires more plumbing and is more expensive, but results an idiot proof system, which benefits me as a I get older