HELP a Bonehead with gas gauge issues !

[DirtDonk]

That’s going to be hard with a digital meter. Remember the pulsing effect?
If it’s aftermarket then a steady 5 V would be what I was looking for. If it’s original it’s going to pulse between three and seven if I remember.
But it’s been a long time.

If you also test that voltage at the output of the IVR behind the dash and compare the two, you can see if there’s much of a voltage drop at the sending unit. If there is then you probably have a wire problem with the old wires.
In addition to anything else!

Knowing what your battery voltage is at any given time is a good practice. That way when you’re testing around with a meter and you notice a discrepancy you can then go into figuring out why.
So before each test session measure the battery voltage. If it’s 12.6 at the battery and only 13.2 at the device you’re testing, you know there’s a problem in between.

 

[DirtDonk]

Obviously those numbers don’t apply directly to the IVR and the fuel gauge issue. But they’re still related.

 

[Dr. Johnson]

That’s going to be hard with a digital meter. Remember the pulsing effect?
If it’s aftermarket then a steady 5 V would be what I was looking for. If it’s original it’s going to pulse between three and seven if I remember.
But it’s been a long time.

If you also test that voltage at the output of the IVR behind the dash and compare the two, you can see if there’s much of a voltage drop at the sending unit. If there is then you probably have a wire problem with the old wires.
In addition to anything else!

Knowing what your battery voltage is at any given time is a good practice. That way when you’re testing around with a meter and you notice a discrepancy you can then go into figuring out why.
So before each test session measure the battery voltage. If it’s 12.6 at the battery and only 13.2 at the device you’re testing, you know there’s a problem in between.

You're 100% on battery voltage. Thankfully that is not a variable, I always charge them to 12.6-12.7 before I start any of these shenanigans. I've done so much electrical diagnostic I don't leave the battery to guess anymore. I'll see if I have an old style sweeping meter around.. I know I HAD one many years ago but I'm pretty sure I threw it out when I got a couple new fancy meters... new, fancy and won't help me here lol

 

[Dr. Johnson]

That’s going to be hard with a digital meter. Remember the pulsing effect?
If it’s aftermarket then a steady 5 V would be what I was looking for. If it’s original it’s going to pulse between three and seven if I remember.
But it’s been a long time.

If you also test that voltage at the output of the IVR behind the dash and compare the two, you can see if there’s much of a voltage drop at the sending unit. If there is then you probably have a wire problem with the old wires.
In addition to anything else!

Knowing what your battery voltage is at any given time is a good practice. That way when you’re testing around with a meter and you notice a discrepancy you can then go into figuring out why.
So before each test session measure the battery voltage. If it’s 12.6 at the battery and only 13.2 at the device you’re testing, you know there’s a problem in between.

You know, now that I think about it.. I'm pretty sure when I tested power behind the cluster months ago I could see a pulse with the test light. perhaps its an OE style IVR.

 

[DirtDonk]

Good probability. Still a lot of them in use out there.

 

[Dr. Johnson]

Good probability. Still a lot of them in use out there.

I likely won't get a look at it until Tuesday night. Will report findings.

 

[Dr. Johnson]

Well... I did a LOT more poking around. Here are the 7 steps of suffering:

1. Tested the IVR, it wasn't holding at the 6V pulse long enough IMO to keep the fuel gauge wiring charged... call this a crackpot theory if you want because it's about that.

2. Installed a new gauge with the old IVR in place and really didn't see much change, but I did see more response in the lower gauge readings, which is the bermuda triangle of the gauge issues.

3. After confirming the IVR was in fact the old pulsing style unit, I installed a solid-state IVR and immediately got more steady response from the sending units.

4. check the sweep on the sending units while plugged into the truck and grounded them with a jumper wire just to be double grounded (senders dangling outside tank). So using the gauge for reference moving in increments from E, 1/4, 1/2 and F. Making witness marks on the sending unit housing for the location of each level. I then see that both senders show E on the gauge when the sweep is a quarter of the way through it's 1" sweep range, effectively making 1/4 tank E. So, I took BOTH sending units apart and adjusted the brass finger inside by about 1/8" to get E moved back to actual E.

5. Plugged in both sending units, tested again @ E, 1/4, 1/2 and F. This time its right on the MONEY! I have E on E, F on F and the other ranges are TBD since that is up to the fuel to decide.

6. I measured from the center point of the opening where the sending unit goes into the tank to the bottom of the tank (about 4.5"). I then hold the sending unit up and measure from the pivot pin on the sender arm which is also aligns dead center in the hole for the sending unit, I bend the float arm until it too is 4.5" from the center pin to the bottom of the float... Now call me crazy here, but I would think that puts the float smack dab on the bottom of the tank unless there is a secret black-hole space time warp where inches become metric and reality becomes fantasy.

7. Re-installed the sending unit into the auxillary (side) tank, put 5 gallons in AAANNNND DRUMROLLL... The gauge still reads E with 5 GALLONS IN THE TANK!

I should have mentioned I was doing this after a 10 hour work day and installed the sender at about 10:30 PM. I had to walk away, now I don't know what the hell happened, it did seem as if there was an obstruction in the tank that I was fighting with while re-installing the sender so perhaps the float is trapped by some fuel tank sea god that I don't know about? I don't recall having that issue the last 20 times I installed it. I can't get a good look into the tank to see what is in there either.

Aside from just setting the truck ablaze, I'll just give it a day to sit in the shop and revisit.

Anyone know what king of strapping or bracing may be inside that side tank? a sight glass on the side of these tanks would've made all of this a helluva lot easier.

 

[DirtDonk]

Congrats on the adjustment successes!
Not sure you want things to read E when the tank is actually empty though, unless you are one of the dligent-few that knows to fill up before E is reached!
I think the manufacturers leave a gallon or four in the tanks of every vehicle so that we have time to fudge the numbers a bit and not run out of gas.
With it actually on the bottom, you might find yourself sucking air when going around a corner or down a long hill even though the gauge read 1/4 remaining. Time will tell, but it's great to see that work pay off in consistent readings.
Well... at least they were consistent outside of the tank!

Did you get a reading on the main tank with the sender installed?
I'm not aware of anything inside a plastic aux tank that would interfere with the float or arm, but I seem to remember others having this issue as well.
I wonder, did you get the correct sender for the aux tank? I think you mentioned them being a different shape earlier in this discussion? If so, then you probably have the correct one. Could something have become jammed up during the install that simply keeps the arm from floating up?
Did you check the flotation of the floats while they were out? Seems like you did, but I don't remember if it was for the new senders, or the old.

Relax. Enjoy the weekend and maybe it'll fix itself (as often happens!) while you're away.
And when you get back, give the tank a really good whack with a big implement-of-destruction! See if that helps...

Paul

 

[Dr. Johnson]

Congrats on the adjustment successes!
Not sure you want things to read E when the tank is actually empty though, unless you are one of the dligent-few that knows to fill up before E is reached!
I think the manufacturers leave a gallon or four in the tanks of every vehicle so that we have time to fudge the numbers a bit and not run out of gas.
With it actually on the bottom, you might find yourself sucking air when going around a corner or down a long hill even though the gauge read 1/4 remaining. Time will tell, but it's great to see that work pay off in consistent readings.
Well... at least they were consistent outside of the tank!

Did you get a reading on the main tank with the sender installed?
I'm not aware of anything inside a plastic aux tank that would interfere with the float or arm, but I seem to remember others having this issue as well.
I wonder, did you get the correct sender for the aux tank? I think you mentioned them being a different shape earlier in this discussion? If so, then you probably have the correct one. Could something have become jammed up during the install that simply keeps the arm from floating up?
Did you check the flotation of the floats while they were out? Seems like you did, but I don't remember if it was for the new senders, or the old.

Relax. Enjoy the weekend and maybe it'll fix itself (as often happens!) while you're away.
And when you get back, give the tank a really good whack with a big implement-of-destruction! See if that helps...

Paul

Afternoon!

I did check my readings at the main tank(installed) and pumped about 6 gallons in. Reads 1/2 tank. I’m satisfied with that.

And I’m with you on the E not actually being E but rest assured I am budgeting some hope and prayer fuel. I’m trying to make sure the pickup sock is still in fuel when it’s on E but not by a lot. These tanks are so small that if I leave much reserve it’s going to be hell getting a normal gauge function range. Or at leas that’s my thought.

Working on it today for a bit, just double checked the main and it reads good.

Gonna drop the aux sender now and see what the heck is going on.. my guess is there is something binding it up. I tested so thoroughly that I couldn’t believe it when I got zero response after putting it all back together.

 

[DirtDonk]

I know, right? What a frustrating turn of events. Not everybody gets to the point where the center will even talk to the gauge so accurately as yours did. Very interested to hear what you find in your digging.
Maybe in the meantime compare yours to pictures of known auxiliary tank centers as well. Just to be sure that you didn’t get an incorrect one in the box.

And retest the float to make sure it’s floating.

 

[DirtDonk]

Back in the day I used to just run both tanks dry regularly. I figured it kept any moisture from ever building up and it wasn’t that bad because I got my full use out of every gallon in that stupid little auxiliary tank!
In my case because the (original) fuel pump was so well worn in but of good USA quality back then, it took many years before I wore it out possibly from running dry constantly.
But I did get good and fast at switching tanks!

I would only do that now for occasional testing on a modern pump with modern gas. Especially if it sits for a while.
And I would never do it on a new pump until it had many thousand miles on it.

 

[gnpenning]

(6. I measured from the center point of the opening where the sending unit goes into the tank to the bottom of the tank (about 4.5"). I then hold the sending unit up and measure from the pivot pin on the sender arm which is also aligns dead center in the hole for the sending unit, I bend the float arm until it too is 4.5" from the center pin to the bottom of the float... Now call me crazy here, but I would think that puts the float smack dab on the bottom of the tank.)

Which way did you bend the arm when you did this?

What was your gauge reading after you bent the arm before you put fuel in?

 

[YNOTBOB2007]

I just removed my auxillary tank because the fuel was incredibly dirty....almost creamy colored. It could have reaked havok on my newly installed rebuilt carb....and now my fuel pump (original, plus an aftermarket electric one) are not sending fuel to the carb. Anyway I digress.... I found 2 socks in the tank....for some reason they just don't stay on well...just pressure fit onto the arm. The point is maybe the float is hitting a rogue sock. But I would think that would cause a higher reading. Also, I added 2.5 gallons to that tank earlier (there was probably a half gallon in there) and my guage registered 1/8 tank. I thought about bending the float arm to get it lower but when it's that low the float may end up bouncing on the tank bottom and causing the float to crack.

 

[CopperBronco]

I went through this ordeal last fall, it’s mind numbing work! Agreed that sending units often don’t work right. What got mine to work was moving back to original IVR, got one from Kevin at Classy Gauges in Utah, and then I replaced all wiring, and the fuel gauge itself from the manufacturer was bad. I don’t know how he did it, but the gauges themselves can be adjusted to ohm ratings, and Kevin at Classy Gauges said mine was way off from the factory… once that was fixed it works fairly well. It still drops a little fast to empty, but overall works well.

I also spoke to a Bronco only restoration shop and they said with old school sending units they rarely worked accurately and you’re lucky if it reads empty when it should. Just finnicky by nature, they only installed those when customers requested them. Your effort is admirable, i pulled my hair out too doing this!

Even if gauge pegs, that doesn’t mean it’s working right, which none of the forums told me when I hunted the depths of the internet to solve this. Bear in mind I’d never wired anything before either!

 

[DirtDonk]

Yeah, I've often wondered if the needle pegging when the wire is grounded is an accurate test of the gauge itself. But it does help to show that things "work" at least and that the wire and any connectors are likely still good. Just no proof that the gauge is reading accurately. Just that it also "works" to a certain extent.
I've recommended grounding the wires several times just this week to try to narrow down a problem (not just fuel gauges) so hope it helps lead to the main culprit.

Paul

 

[Oleguy 74]

a little info here.according ford with all wires disc from gauge connect ohmmeter to gauge term's.gauge resistance should be beetwen 10 and 14 ohms.with sender out connect ohmmeter accross sender terms.check and se if you get 10-73 ohms when you sweep sender through it's full range.here is some readdings from10 years a go when i first went through this.

fuel as follows: oil as follows: temp as follows:
full --- 10 ohms 90 psi----10 ohms 120 deg ---- 73 ohms
3/4--- 21 ohms 70 psi---- 20 ohms 195 deg ----21 ohms
1/2--- 25 ohms 40 psi----30 ohms 230 deg ----10 ohms
1/4--- 33 ohms
E------ 73 ohms

you can see by the readings it is not linnear kevin at classy chassiss i think syill uses a test box i built to test with.also i think you should useing acc pos when testing with every still in the bronco as this doesn't power up every thing else.

 

[Dr. Johnson]

Well everyone, I think I have FINALLY solved the fuel gauge blues...

I dropped the aux sender and had a gander at why it was reading E after all of my lengthy testing... My investigation with a flashlight and iphone video inside the tank displayed 3 HUGE impediments to the float. For some reason, the fill neck pipe, the metal return line and the metal overflow line going into the tank protruded between 10-12" into the tank. So every time I was fishing the sender into the tank I was navigating these three tubes and not even realizing it. I freed up the float arm and double checked that the gauge was reading before re-installing. this time, I was very studious and feeling for contact between the float and the tubing in the tank. To top off the pain and agony, the BRAND NEW float I bought from Wild Horses 4x4 was about 1/8 full of gas! Not happy about that. So I had to scrounge up the old float I had replaced that didn't leak and re-install that... (I only replaced it as a precaution since I had it all apart).. shame on me for doubting the old float apparently. that was a waste of a few bucks and would've been another problem down the road some miles.

Long story short, here are my gallons to reading on the gauge respectively:

1.2-1.5 gallons, gauge needle on E line
4 gallons, needle between 1/2-3/4
5 gallons needle on F
6 gallons, needle just past F.

At this point, I'm calling it good enough and running with it.
Seems like, the tank will be pretty dang accurate from Empty to 1/2 tank, after that is gets a little witchcrafty but I think the lower portion of the tank is priority for accuracy.

 

[Dr. Johnson]

I went through this ordeal last fall, it’s mind numbing work! Agreed that sending units often don’t work right. What got mine to work was moving back to original IVR, got one from Kevin at Classy Gauges in Utah, and then I replaced all wiring, and the fuel gauge itself from the manufacturer was bad. I don’t know how he did it, but the gauges themselves can be adjusted to ohm ratings, and Kevin at Classy Gauges said mine was way off from the factory… once that was fixed it works fairly well. It still drops a little fast to empty, but overall works well.

I also spoke to a Bronco only restoration shop and they said with old school sending units they rarely worked accurately and you’re lucky if it reads empty when it should. Just finnicky by nature, they only installed those when customers requested them. Your effort is admirable, i pulled my hair out too doing this!

Even if gauge pegs, that doesn’t mean it’s working right, which none of the forums told me when I hunted the depths of the internet to solve this. Bear in mind I’d never wired anything before either!

Mind numbing is correct! I set the shop record for how many times I had the same truck up and down on the lift. I swear I had it up and down 10 times every day.

 

[rydog1130]

are your floats plastic or brass? swap em out to plastic so they don't fill up w/ gas. Mine will read empty sometimes then i hit the brakes and it fixes itself... ha

 

[DirtDonk]

What a relief! And what a pain… I think someone else a few months ago mentioned how far their tubes extend it into the tank, but I don’t remember if it was just a general discussion or if they were having trouble getting the sending unit in as well.
Glad you got it fixed. Hope it stays that way!

Is it a plastic float or brass? Either way it could’ve been defective from the get-go, or damaged enough while navigating the tubes to leak when you put gas in it. Seems more likely to me that it was bad right out of the box.
But not to worry!
I’ll PM you when I get back to the computer and we’ll get that sender back from you for full refund or credit.