Help? Aux Tank Sender to Stock Gauge Issues (1 Viewer)

[Solace in Solitude]

Hi All,

I've been working predominantly offline (PM) with Jim ( @Downey ) on gathering information and parts and am now int the process of starting to set this up on my '78 40.

I wanted to share the stock gauge between the two tanks and have a Pollak 6-port and a Centroid Sender that is rated at E120/F17 ohms.

I bought the Centroid Sender from Centroid and asked for it to be 11.5" long. Once I received it and saw that it will require 1.25" of clearance from the bottom of my tub, I cut it down to 8", so that it will mount in the trough on top of my tank:

I realize that that will mean my aux tank will register on the gauge as 'full' for 3.5 additional inches of gas - about 5-7gals of a 22gal tank. Not a problem. The white X is where I was going to mount it - I'm now mounting it to the right of the white X, in the trough.

However, when I tried to perform the "manual empty" calibration, from Centroid, I ran into problems. The stock gauge doesn't respond as Centroid expected.

I have performed various tests, requested by Joel at Centroid, and he's becoming convinced that I don't have an E120/F17 fuel gauge.

I've compared my fuel gauge to the 1978 version in Rudi's ( @bj40green ) excellent gauges and speedo thread and it looks like a 1978 FJ40 gauge to me.

The sender on the main tank sure appears to be an FJ40 sender (it even says FJ40 on top)

Before I give up and install a second gauge...

My main tank is 5/8-3/4 full right now and the ohms from the main tank sender measure right at 65ohms - I know 1/2 full is supposed to be around 49ohms, so 65 sounds realistic to me. Edit: I think I'm looking at this backwards... maybe 65ohms is too high for 5/8-3/4 full...

I have cut the YR sender wire, behind the fuel gauge, so I can wire the Pollak and DPDT switch. When I read voltage on the piece of YR wire that feeds into the gauge, I read 11.89V initially, then it jumps all over the place.

Does anyone know if this erratic voltage means that the stock gauge pulses a signal to the sender, or that the supply to the gauge has a mechanical regulator which pulses 12 volts to the gauge as a means of making an old-fashioned average voltage of say 5 volts?

These questions are Centroid's, not mine... but, I'd like to know nonetheless.

Also, I see that MUDders like @bsevans has gone before me with this Aux-Tank-Sharing-Stock-Gauge journey... has anyone encountered an issue with using an E120/F17ohm sender for their aux tank?

Thanks!

 

[bj40green]

Here we go...... It should work with a SPDT switch and a second OEM fuel sender.
The problem is probably the length of the float arm. More about that later.
First how the electric part works. I'll copy this from my thread on page# 2 post#27:
https://forum.ih8mud.com/threads/clusters-gauges-speedo-odo-meters.544543/

---------------------------------------------------------------------------------------
The Voltage Regulator

So the FUEL and TEMP gauge work on 7 Volt but where is that coming from?
In the picture below you'll see the VR on the left.
A wire wound resistor is wrapped around a bi-metal switch (It's the same principle as for the gauge needles).
The resistor heats up, the bi-metal strip bends and the switch opens. The current flow stops, the bi-metal strip cools down and the switch is closed and this process repeats itself. Now here is the kicker..... heating up/opening and cooling down/closing takes each ± 1 second or so. So one second 12 Volt, one second 0 Volt means an average of 6 Volts or when the engine is running 50% of 14 Volts is 7 Volts.
This 7Volts is the value the FSM (posting #7 pages 12-27 and 12-28) is speaking of and also says:
[QUOTE:] -Caution- Do not check the 7V terminal at 12V or 24V. [END QUOTE] because you'll measure only an intermittent 0 and 12Volt.
This "switching" behaviour is also responsible for the "flashing" of the light bulb when you test the FUEL or TEMP gauge with a test light as per the FSM (see posting #7 page 12-26 of the FSM).

If you look at the pic in the previous post you can see an adjustment screw on the rights side of the "breaker" points. Here you can adjust the interval time for the VR. The problem is that you can do this only when you have it all apart and in a test situation on your work bench. I don't see the need to change this setting unless your gauges are really off spec. BTW the screw is sealed/fixed with a greenisch ....... I call it "nail polish" but if somebody knows the right word, please tell me.
---------------------------------------------------------------------------------------

So, yes the working voltage is around 6V at idle and 7V while driving.

About the sender..... The sender for a 09/73 till 01/79 is #38320-60050
The sender for a 01/79 till 04/86 is #38320-60051
Both senders are identical but the later one has a ground terminal and the floater arm is longer.
Maybe the later one with the longer floater arm fits better for your tank.
Here you can see the difference between the senders.

HTH,

Rudi

 

[Solace in Solitude]

Hartelijk dank Rudi!!

 

[bj40green]

Hartelijk dank Rudi!!

Geen dank.

1 Gauge - 2 senders

Rudi

 

[Solace in Solitude]

The sender I bought is a Centroid (recommended by Jim ( @Downey )) - he was sure it would work for me. It's not a float sender - it's a tube - it looks like this:

It was built specifically for 120Empty and 17Full. But the Centroid tech rep is telling me that their senders don't work well with fluctuating voltages on the 'send wire'.

I passed your info back to the Centroid tech and this is how he responded:

"Yes, that's the old fashioned mechanical regulator (pulsing) that gives us trouble in with the old Mustangs. For our sender to work sensibly you'd need to supply the gauge with a modern, DC regulated voltage rather than a pulsed voltage. I've attached the drawing we send to Mustang owners. To me it would be less work to get an E240/F33 ohm float sender like a Wema or Isspro. An actual resistor like those units doesnt care about pulsing-- our electronic output does, though."

His Drawing:

​

I'm leaning toward eating the $68 I spent on this sender and ordering the OEM sender - I really don't have room for another fuel gauge.

Given our U.S. Thanksgiving holiday , I'll wait 'til Monday and see how he responds after the he returns from his Thanksgiving vacation.

Bedankt Rudi, je bent een IH8MUD schat!!

 

[bj40green]

Yes, that could be a solution but....... there's always a but, The existing VR is inside the FUEL gauge and that means that you have to modify the FUEL gauge and also change the wiring for the TEMP gauge because that gauge works from the same VR.

My option would be adding a second OEM sender.

Greetings from "schat" as in treasure or do you mean darling?

Rudi

 

[Solace in Solitude]

I meant treasure, but you could be a MUD darling as well - given all the good documentation and assistance you provide!

Yeah, even the Centroid tech said it was probably more work than it was worth. I know the stock sender and gauge work, so a second oem sender should work as well.

I already have the other parts (Pollak Switching Valve, DPDT switch, etc.) - I'll see what Monday brings and will most likely order an oem sender then.

I started another thread to try to find out if any one knows the depth of the stock tank, so I can try to gauge (pun intended) what kind of modifications the oem sender will need in order to reach the bottom of my aux tank. I'll pull the sender out this weekend and measure the depth, if I on't have an answer by then.

Thanks for your help!

 

[FJ404345]

Danny gaat dit nog steeds over diezelfde tank ?! Je neemt er wel de tijd voor zeg

 

[bj40green]

Tijd hebben we zat, nietwaar?
Anyways, hope this helps a bit. Pictures from MUD member fj718. Scale is in inches.

Nou doei.

Rudi

PS. Have a look here: https://forum.ih8mud.com/threads/76-fj40-build-saga.602423/ post #11

PPS. IIRC those pics are from a '76 fj40 (tank under the passenger seat).

 

[Solace in Solitude]

Danny gaat dit nog steeds over diezelfde tank ?! Je neemt er wel de tijd voor zeg

het is nog steeds dezelfde tank en je mond is nog open!

 

[Solace in Solitude]

Tijd hebben we zat, nietwaar?
Anyways, hope this helps a bit. Pictures from MUD member fj718. Scale is in inches.

Nou doei.

Rudi

PS. Have a look here: https://forum.ih8mud.com/threads/76-fj40-build-saga.602423/ post #11

PPS. IIRC those pics are from a '76 fj40 (tank under the passenger seat).

Ja, veel tijd. Ik werk voor mezelf!!

I had seen those pictures a while back, but never thought about them in the context of tank depth - perfect!!

Veel dank Rudi!!

 

[roadstr6]

When the sender in my old con-ferr tank failed I bought an OEM '78 sender and just lengthened the arm to make a full sweep top to bottom. It is surprisingly accurate. To lengthen the arm I cut it near the middle and used another arm from a non-working sender in my parts stash to add length. I attached the arms using a roll pin and clamped it tight with my bench vise. It's in my build thread. Check it out if you have time.

 

[Solace in Solitude]

Will do - thanks! I actually pulled the stock sender from my main tank today and it fits my aux tank perfectly - so, I'm going to just write off the $68 I spent on the Centroid sender and order an oem sender from toyotapartszone.com - its $66 + $10 shipping.

I would have gone that way to begin with, but read so many instances of MUDders using the Centroid, with no issues. But, it won't work for my 40.

I suspect the Centroid-FJ40 successes are based on analog Centroid senders and it appears that Centroid has changed to capacitance-based digital senders and their's simply doesn't work with 'pulsing' fuel gauges, like our stock FJ40 fuel gauge.

I'm trying to find out if Centroid still makes the sender I ordered (CGS model) - the CGFP model, I received, definitely does not work with the stock gauge.

I haven't given up yet on getting a refund, but I certainly won't hold my breath.

 

[Coolerman]

Hmmm... This may be bad news for a customer I recently built a radically custom rear chassis harness for. It incorporated a quick disconnect Pollack 6-Way valve, a quick disconnect for the Centroid sender for the aux tank, trailer converter, and speaker wires! He was assured the sender would work with his 1976 stock gauge. He is not going to be happy if it doesn't...

Rudi, is this OEM regulator built into the gauge cluster? Got a pic of it's location? The sheet Centroid sent pngunme, shows a simple 3 terminal +5V regulator that could potentially be placed inside the cluster itself.

 

[Solace in Solitude]

I still haven't gotten an answer from Centroid as to whether they still make the model that worked with our E120/F17 gauge - but, in their defense, they were closed for Thanksgiving - I should hear from them today - If I learn anything, I will report it back here.

In the meantime, I've ordered the oem sender - I know it will work.

 

[bj40green]

Rudi, is this OEM regulator built into the gauge cluster? Got a pic of it's location? The sheet Centroid sent pngunme, shows a simple 3 terminal +5V regulator that could potentially be placed inside the cluster itself.

The existing VR is inside the FUEL gauge and that means that you have to modify the FUEL gauge and also change the wiring for the TEMP gauge because that gauge works from the same VR.

Here is a pic from a defective FUEL gauge which I used for explanation to replace the OEM "pulsing" VR for an electronic VR.

In Diagram:

Rudi

 

[Solace in Solitude]

@Coolerman , @bj40green , @Downey

I finally got an answer from Joel at Centroid - Remember, I ordered an 11.5" version of the sender recommended by Jim (Downey) - e.g. The #CGS-11.5-12V-120/17-5H (apparently it used to be CGF, not CGS) - here's Joel's reply:

"There actually is no such thing as a CGS. You may mean CGF, which is the older sender version with potentiometers, versus the modern programmable version CGFP(P for programmable). We dont sell the older version any more, but the output circuits of the two senders are the same and I'd bet against the difference between CGF and CGFP being the source of your problem.

We can refund your money if you'd like. I'd rather not waste any more time on it either.".
​

I have ordered an OEM sender from ToyotaPartsZone - it should be here late this week.

Note: Joel followed up with another email, confirming my main tank sender and gauge are operating at E120/F17 - here's what he said,

Background: Joel had me disconnect my main tank sender and instead connect five 47ohm resistors, one at a time (in series), and report what the fuel gauge reported.

"Three resistors (x47=141 ohms) reading below E does make sense for E120/F17.

I'm amazed that such brutal pulsing could work with our output (according to the other folks). I know it doesnt work with the 1965 Mustang gauge from having tested it directly myself, and there's a version of Autometer gauge that pulses a signal to the sender and that also does not work by my personal testing (after the customers didnt get either to work). I say "brutal pusling" because it's so slow that it would not get filtered in our electronics.

On the other hand I see a number of folks have bought CGFP E120/F17 before you for Toyotas and I dont recall troublshooting with any of them."
​

He provided me a list of several customers - I prefer not to broadcast them here.

I recognize a few of them as MUD members. If someone with more electronic knowledge wishes to follow-up on this, with other Centroid customers, please PM me.

Otherwise, I'll install the OEM sender, when it arrives, and forget this whole frustrating episode.

Thanks,

 

[bj40green]

Here is a video I made when testing a refurbished gauge cluster.
All senders are replaced by a test light bulb as described in the FSM.
Note that the OIL bulb doesn't blink (because the VR is inside the OIL sender) but that the FUEL and TEMP bulbs do because of the VR inside the FUEL gauge.


Rudi

 

[Coolerman]

Awesome Rudi! Especially love the videos... I added those pics to my "Sender" photo section. This is one area of FJ40 electrical I am not versed in yet and this has been very helpful to me.