My 71 Duster work in progress

[Dr.Jass]

If your temperature gauge works and seems approximately accurate (mine actually reads exactly mid-gauge at 180° engine temp--and it was NOS) you can perform the pulse-voltage test for the ICL (limiter) at the tank wire. Same deal: ground the negative lead of your DMM and connect positive to the disconnected sender wire, looking for pulsed 12V. That would verify your wiring; if the temp gauge works chances are the limiter's OK. I'd still install the RTE limiter, personally... if the one in there fails, it's taking at least one gauge and probably the PCB with it when it goes.

Yes, everything else in the dash seems to work. It seems like there's a shit ton of unplugged connectors under there, for god knows what. Radio, etc. The wiring diagram I've got is minimal at best, for example I've got two female connectors on blue wires taped together, but don't see anything about that.

The fuel sender wires are dark blue from the tank right to the gauge. The factory connector is an 8-pin rectangular job right near the driver's kick panel. It's got an extremely-short wire for the door-jamb pin switch, if memory serves. I had it disconnected during the Valiant floor/frame replacement. I'm pretty sure this is it:

I looked for optional wiring (mymopar.com) but found notne. But it was free and I've already got my money's worth out of it.

Remember: While the engine/forward lamp (only where they're the same harness) and dash wiring are in the CSM, the rest of the wiring is in the body service manual. The rear wiring for your car is on page 5-81 in the '71 BSM, which is actual page 190 in the mymopar .pdf download.

Dang son, that's a lot of typing.

It is. I definitely could've diagnosed the car more quickly than I typed it. I'm also sure it takes longer to read than it does to perform the tests described therein.

 

[Dr.Jass]

BTW I found the other B-body fender strut and it fits the A-body. Don't let anybody tell you otherwise. This one came right off the bumper bracket so I am certain it's a b-body part.

Damn it. I knew I was forgetting something!

 

[69.5CUDA]

there was a time i ran across a rash of piss poor pin to board connections that led to "it works on the bench not in the car", my solve was a permanent one and is probably one of the single best electrical system mods for almost any old car

find brass/copper "nails" that fit into the OE pins on the PCB, cut them to length and stuff them in from the back, then soilder ALL OF THEM, what your left with is a PCB that has 110% solid connection and the pins wont just snap off..with this method you can fix old boards with missing pins

 

[b-body-bob]

Ok I grounded the sender wire, gauge went to full, so wiring and gauge are OK.

I checked the ground at the sender, all is well. It's hard to find something independent under there to test against because it's all painted, surface rusted, or mounted in rubber. I had continuity between the sender and the parking brake cable so it's grounded.

Now for the suck - siphoning gas (pun intended). I removed the fuel line, gas gushed out of the sender. So then I got all the fuel I could out of the filler neck. Removed the line to the sender again, nothing gushed out, so I thought I was good. Then I knocked the sender ring off, and gas poured out. I only took a small bath before I got it stopped by putting it back on.

I guess I have to start the damned thing up and let it idle until it runs out of gas, I wonder how long that will take if it's got gas all the way up to the sender seal.

It also means I have to add more ATF because a quart or more came out yesterday when I checked the speedo gear and I don't want to run the car with the ATF low for fear of something going dry and galling.

Have you priced ATF lately? I'll be dumping what I caught yesterday back in through a paper cone filter in the funnel.

 

[69.5CUDA]

best way to drain the tank is pop the hose off at the fuel pump and let it drain......useualy gravity will siphon down a long ways, but i keep a couple of electric pumps around so i dont have to deal with getting it all over the place LOL

but hey atleast you know its just the sender, before you go replacing it tho, see if you can open up the "cage" around the wiper and resistor, sometimes they can simply be cleaned up, other times youll find the wiper has simply slid out of place

 

[b-body-bob]

Yeah I was trying to save the gas but am going to try to fit a homer bucket in there to catch what's left. With my luck there's more than a drain pan (1 gal or so) left in it.

I pumped a little bit more out last night but not much. There can't be a lot left in it, but it seems like a river when it's gushing in your face. It sure seems like there has to be more in it than I think there is for it to reach the sender, but the hose makes it seem like there's only an inch or so left.

If I wasn't afraid of being under an unbalanced car I'd raise the front/lower the rear to get it to slosh away from the sender. It's not worth the risk IMO. I ran out of time yesterday but will pop the cork on it soon and try to figure out the problem before replacing the sender.

 

[Dr.Jass]

Be careful with the bucket. Some of those don't react well to gasoline.

There's probably more left in it than you suspect. I mean, how much can an oil-furnace combustion chamber possibly hold, right? Several gallons, as it turns out. Each gallon is only going to remove maybe 1/2" of fuel level from that tank, so you could be further out than you think.

It almost has to be the sender at this point. If you replace it, I'd suggest going up a size from stock to 3/8". The cost is negligible, but any reduction in restriction on the suction side saves wear on the pump. I ran a 1/2" pickup and the same size line all the way to my electric pump, because it's a bitch to change.

 

[69.5CUDA]

are senders cheep and easy to get now?, last one i couldnt fix/replace with a good used one was the one for my 58 ford

 

[Dr.Jass]

I think I paid around $50 for mine with the sewer-pipe 1/2" pickup. I haven't had the tank full to swear on accuracy, but when it says it's empty the car's definitely empty... which is really the most critical bit, isn't it?

A quick check of eBay shows 3/8" stainless units bringing around $40 w/free shipping, so they've actually come down from when I bought mine. The '58 Ford units seem to be in a similar price neighborhood.

 

[69.5CUDA]

holy hell i had to MAKE my 1/2 inch for the cuda

 

[b-body-bob]

I got this 3/8 sender from Herb's. It was a big order and I had problems, so tread carefully if you shop there. I didn't notice it was owned by the Frank Mitchell consortium until the order was in process. Slow to ship was the problem I had with them. I would get a box with some of the parts in it, then a week later, a few more would show up. It took like a month to get the last few bumper bolts of the full set I had ordered.

I have a diesel sized drain pain because of my CTD so I just put it under there and let er rip. I backed out until it had stopped splashing, and stuck the transfer hose/bulb in there and finished filling up my 5 gallon can. Using my finger it seems to be about at the bottom of the circular stamping mark around the sender hole.

Before I start with this, I want to say that the stupid sender had to come out anyway because it had a small leak. This is not a thing you can just loosen up and check the gasket maybe fixing it without a lot of hassle. So, no matter what, draining the tank was happening.

Once I fished the sender on the bench, I rang it out and it ranged from 11-85 ohms. So if I understand it correctly, it is high on the low side but otherwise working. It seems like it should have worked but maybe not gone all the way to full. When I bench tested it, I connected ground to the wire I had clamped to the vent then screwed to the body as well as to the sender itself with little difference noted.

I couldn't figure out how to get the float off and don't have anything that I could dunk the whole thing in to see if it sinks or floats, but since it's brand new it seems like it should be OK. I will come back to this before I put it back in the tank and refill.

For right now anyway, the sender is exonerated.

Then I remembered the voltage limiter and how that affects both the temp and fuel gauges, and realized that yes I do have a working temp gauge but it isn't the one in the dash because there's no sending unit installed for it – just the one for the underdash gauge. Could the limiter could be the problem even if the gauge went Full when the wire was grounded? I haven't read Jass' instructions yet, but I think I'll have to unscrew and pull back the cluster to get to it anyway so that is my next likely move. I'm already half way there with the column dropped down so I could get to the speedo cable.

 

[b-body-bob]

I haven't read Jass' instructions yet, but I think I'll have to unscrew and pull back the cluster to get to it anyway so that is my next likely move.

But now I have -

If your temperature gauge works and seems approximately accurate (mine actually reads exactly mid-gauge at 180° engine temp--and it was NOS) you can perform the pulse-voltage test for the ICL (limiter) at the tank wire. Same deal: ground the negative lead of your DMM and connect positive to the disconnected sender wire, looking for pulsed 12V. That would verify your wiring; if the temp gauge works chances are the limiter's OK. I'd still install the RTE limiter, personally... if the one in there fails, it's taking at least one gauge and probably the PCB with it when it goes.

That is definitely easier than taking things further apart to get to the limiter but I was also thinking along the lines of it might be a good thing to replace it anyway since "I'm already half way there with the column dropped down so I could get to the speedo cable."

No doubt you can get to the back side of the cluster from beneath too, and I will have a look before doing anything else. But given my night blindness and general old eyes I figure it might just be easier to go ahead and take the cluster out instead of fumbling around under the dash and then pulling it out anyway.

 

[Dr.Jass]

I got this 3/8 sender from Herb's. It was a big order and I had problems, so tread carefully if you shop there. I didn't notice it was owned by the Frank Mitchell consortium until the order was in process.

Frank Mitchell is no longer affiliated with Mitchell Motor Parts, and hasn't been for quite some time. The consortium that bought his place also bought Herb's and possibly a couple of others. I've only bought one item from MMP, just recently, and not surprisingly there was horsefuckery involved (late-model Jeep antenna mast in an NOS Mopar antenna kit). Luckily, I expected exactly that and was able to source a real-deal, not-superseded, 1973-number-and-packaging antenna mast prior to the arrival of the MMP kit.

I've had pretty good luck with Van's Auto out of WI. They sell through both eBay (their eBay guy is the dude that bought my '73 Challenger back in '89), and through their website. They're pretty good about customer service if there's an issue, too

No doubt you can get to the back side of the cluster from beneath too, and I will have a look before doing anything else. But given my night blindness and general old eyes I figure it might just be easier to go ahead and take the cluster out instead of fumbling around under the dash and then pulling it out anyway.

Maybe it's better with the column down, but I want no part of trying to install shit in the cluster with it in the car. I had to change two bulbs in mine last year and it was several miles south of fun.

 

[b-body-bob]

Frank Mitchell is no longer affiliated with Mitchell Motor Parts, and hasn't been for quite some time. The consortium that bought his place also bought Herb's and possibly a couple of others. I've only bought one item from MMP, just recently, and not surprisingly there was horsefuckery involved (late-model Jeep antenna mast in an NOS Mopar antenna kit). Luckily, I expected exactly that and was able to source a real-deal, not-superseded, 1973-number-and-packaging antenna mast prior to the arrival of the MMP kit.

I've had pretty good luck with Van's Auto out of WI. They sell through both eBay (their eBay guy is the dude that bought my '73 Challenger back in '89), and through their website. They're pretty good about customer service if there's an issue, too


Maybe it's better with the column down, but I want no part of trying to install shit in the cluster with it in the car. I had to change two bulbs in mine last year and it was several miles south of fun.

I've bought from Vans recently. I've never had an experience like the one with Herb's. It was just odd. Covid might have played a part I guess. They were also in the middle of that bumper deal where I ended up with two damaged ones and one good one.

IIRC the cluster will come right on out without too much trouble. Right now even the dash pad is unbolted and just laying there so I have some room in that direction too if I need it If the pulse test shows it's good I won't need to do that, but I'm running out of things that could be wrong.

 

[b-body-bob]

I did a pulse test under the hood at the temp gauge and at the tank and it worked as expected on both ends. The IVR seems OK.

Double checked the "ground the sender wire and it goes Full" test. Wiring and gauge are OK.

Ohms on the sender were 11-85. That seems OK.

I realized I could just pop the float off and toss it in a little water to test that, and it is OK.

Also, the ground I used to do the pulse and the ground the sender wire test was the same one used to ground the sender. I put the screw in and connected my jumper to it. The screw gives a good ground.

I also verified the ground wire for that screw that I clamped to the vent has continuity with the sender itself. The grounding should have been OK.

The only thing I haven't done is hook the sender up under the car and move the float while somebody watches the gauge.

 

[69.5CUDA]

honestly just prop it up in such a way that it would read "full" as well as 1/2 tank, since the whole setup moves "slow" its not like you can have someone moving it around and actualy watch it move...hell you could go move it from empty to half get in sit down and watch the guage creep up LOL

 

[Dr.Jass]

Make sure the metal part of the sender's connector is a tight fit on the stud. If it's been on and off several times over its life--and we have no way of knowing whether it was--it could be a poor fit causing intermittent connection. It has to be something simple at this point.

If you can't convince B-body-Babe to spend some quality time in the garage, disconnect the plug shown in my hand way up yonder, and install a jumper wire from the sender terminal to the dark blue wire. Grounded the sender with another jumper (the door switch is handy for this), you can sit in the driver's seat and watch the gauge whilst you move the float arm to and fro... but as 69.5 said, it's a slow mover anyhow.

 

[b-body-bob]

honestly just prop it up in such a way that it would read "full" as well as 1/2 tank, since the whole setup moves "slow" its not like you can have someone moving it around and actualy watch it move...hell you could go move it from empty to half get in sit down and watch the guage creep up LOL

Another thing is I don't need to see it move, I just need to see that it has moved. So far it has never budged off E. So even if it's moved all the way or is still in process, if it's off E, it's going to work.

Make sure the metal part of the sender's connector is a tight fit on the stud. If it's been on and off several times over its life--and we have no way of knowing whether it was--it could be a poor fit causing intermittent connection. It has to be something simple at this point.

If you can't convince B-body-Babe to spend some quality time in the garage, disconnect the plug shown in my hand way up yonder, and install a jumper wire from the sender terminal to the dark blue wire. Grounded the sender with another jumper (the door switch is handy for this), you can sit in the driver's seat and watch the gauge whilst you move the float arm to and fro... but as 69.5 said, it's a slow mover anyhow.

Phones/cameras are handy too. When I was figuring out the speedo problem, I couldn't tell if it was plugged up or not, so I propped my phone up to record it while I spun the cable from below with a drill.

One benefit of doing it with a helper or phone is it saves me one get down get up cycle, and I need all of that I can get.

 

[b-body-bob]

I hooked the sender up outside the tank and the gauge worked. I put it in the tank, and it doesn't work. I used a jumper between the wiring and the sender and ditto for the ground to be sure. There is continuity between the sender and the rear bumper. I did the grounded wire test and that still works. But the gauge won't move.

I did find that the wiring doesn't fit on the stud at all so I will need to change the terminal to a ring connector. Maybe the fuel is low enough that registering E is right? The gauge does not move at all. I did not start the car to see if it was too low to pick up fuel. I'm trying to avoid putting gas back in it just to spill it back out again.

 

[Dr.Jass]

No need to change the terminal. Try mildly deforming it with a pair of pliers. It doesn't have to touch all the way around, it just has to touch consistently.