Fuel sending unit advice needed

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Feb 26, 2020
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Beaverton, Oregon
Got my Downey fuel cell from @65swb45. What would be the best options for a sending unit. The one in my current tank has seen better days, but does work. Is that something I can modify and use? For now I will only be using the fuel cell by itself. I have the stock ‘66 cluster in the dash. Also, will all sending units work with diesel?

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You could use the old sender (if it is still alive), but (a) you want to drill the mounting holes in the top aluminum plate so that the float arm points towards the rear of the tank, keeping the float on the centerline where the fuel level is the most constant, and (b) you'll have to lengthen the float arm for the 10" deep rear tank. If that sender is dead, I'd get the Centroid Products electronic sending unit mated up to an aftermarket 2 1/8" diameter dash mounted gauge.
 
Despite its rough appearance, it did still work. I may try to fix up the old tank in the future, so maybe I’ll get a new sender. Thanks for the info!
 
Also, will all sending units work with diesel?

Looked up sending units for multiple years and all list BJ4X, FJ4X and HJ4X the same for the each year range. Didn't mention 12 or 24 volt which would think be the only reason might be different.
 
I think @Downey probably knows as much as Mark (@65swb45) about the Downey fuel cell;)

This link has a lot of great information about fuel senders and fuel gauges - especially the Rudi and Downey threads.

I don’t know what year FJ40 you’re building , but pay attention to the empty-full ohms values - pre-72 and post-71 use different ohms values - as do aftermarket senders/gauges - and your sender ohms values must match your gauge ohms values.

Centroid is an outstanding company, with great customer service and a great reputation. They even sent me multiple senders, at their own expense.

I wasn’t able to use them, I could never get my oem gauge to work, with their custom senders, using a Pollak 6-port electric switch and tank-specific electric fuel pumps and senders.

I finally gave up... I needed to get everything working for a long trip. I went to a matched-ohms Autometer gauge/sender and run separate, tank-specific fuel gauges.

But, I’m not saying it was Centroid’s fault.. it could have something to do with my configuration... I just ran out of time and have been happy with two gauges.

Edit: I don’t know about diesel, but I’d expect the senders to work with any liquid... just not positive ... Centroidtell you.
 
Edit: I don’t know about diesel, but I’d expect the senders to work with any liquid... just not positive ... Centroidtell you.
Thank you for the info. I’ll be reading up on all of that. Completely new subject for me, lots to learn. I did see in Centroid’s website I just have to specify what fuel I’m using when ordering, so that shouldn’t be an issue at all.

if the @Downey tank is 10.5” deep I’m guessing I’d want a 10” sending unit to not have contact at the bottom of the tank?
 
I wouldn't attempt to use your stock dash fuel gauge with any other sender since your sender/gauge work on a 7 volt drop- - -way too hard to get correct as Solace in Vegas found out. Get an aftermarket 2 1/8" diameter dash gauge, let me know the empty and full ohms values, then I'll give you the correct Centroid part number to order- - -easy deal.
 
240 ohms empty, 33 ohms full
Ok, then order Centroid #CGFP-10-12V-240/33-5H.
The 10 is for our 10" deep tank, order for the depth of your tank.
The 12V is for 12 volts.
The 240/33 is for the ohms values of your dash gauge.
The 5H is for 5 hole mounting.
Also let them know if you are using gas or diesel, there is about a 5% difference in gauge reading, so Centroid compensates for this difference.
 
Another fuel sender question.

Does anyone know an aftermarket gauge that will work with the stock senders ohm range?
 
Another fuel sender question.

Does anyone know an aftermarket gauge that will work with the stock senders ohm range?

No.

I don’t believe you will find one.

Gauges and senders are paired by ohms-range.

As @Downey said, in post# 8, above, and Rudi (@bj40green) has discussed so many times, the oem gauge has it’s own built-in voltage regulator that drops the voltage by (5v as I recall Jim says), 7v... I take his memory as more accurate than mine.

Aftermarket work at 12v.

Centroid worked with me, to try to make their custom sender work with the oem gauge, but we were never successful.

The fact that you are apparently installing an aftermarket gauge makes this easy... just buy a paired-kit that includes a gauge and matched sender.

The sender is very easy to install... unless your 40 is 1979-newer... then, I do t know... I’m guessing you have to drop the tank.
 
I do have an aftermarket gauge set. And it did have a matched sender. But whoever installed it butchered up the gas tank threads that secured the sender, anyway it was a mess. So I installed a stock sender not realizing that it would be a PITA to match it up.
 
I do have an aftermarket gauge set. And it did have a matched sender. But whoever installed it butchered up the gas tank threads that secured the sender, anyway it was a mess. So I installed a stock sender not realizing that it would be a PITA to match it up.

Unless the sender screw holes are just too huge, you can use larger self-tapping sheet metal screws... you may have to enlarge the holes in the sender.
 
Did you used to own my truck?;) That’s how it was mounted. Along with a bunch of sealant. It leaked like crazy.

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NO!!! But, that DOES look like my handiwork.

Did it have a gasket, or did the PO just like the looks of his sealant work?

Hey! That’s not an oem sender, maybe the screw holes didn’t align with the tank Screw holes.
 
@Slapshot
Did you used to own my truck?;) That’s how it was mounted. Along with a bunch of sealant. It leaked like crazy.

View attachment 2413577

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If those self drilling, self tapping screws are what were attaching your sending unit, you may have a worse issue.

The OEM tank had a flange for the sender screws, which stood above the actual tank. The screws were less than a 1/2" long. Longer screws would hit the tank, preventing the screws from squeezing the gasket.

Those self drilling screws may be long enough to go right through the tank wall.
 
To answer some questions,
It was sealed (poorly) with a cork gasket. Yeah, drilled right through into the tank , which creates 5 holes for gas to come through.
I was concerned about particles in the tank so I replace the inline fuel filter with one that should filter out any metal shavings. It still leaks. :(
 

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