Fuel Sender Test
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Fuel Sender Test
I have a 1996 Jaguar XJS convertible with the AJ16 engine.
I’m back to my flaky fuel gauge. It will not got to full.
I have swapped anti-slosh modules.
I have replaced the sender.
I have replaced the gauge.
I have added grounds to the dash.
When I pull the voltage from the wires at the sender, it never goes below 5v, so the problem is at the sender/anti-slosh module.
What is the best way to bench test the DAC11188 part? Obviously off the car, it gets no voltage. I have a car battery in the basement, is there a safe way to apply 12v without frying anything?
I’m back to my flaky fuel gauge. It will not got to full.
I have swapped anti-slosh modules.
I have replaced the sender.
I have replaced the gauge.
I have added grounds to the dash.
When I pull the voltage from the wires at the sender, it never goes below 5v, so the problem is at the sender/anti-slosh module.
What is the best way to bench test the DAC11188 part? Obviously off the car, it gets no voltage. I have a car battery in the basement, is there a safe way to apply 12v without frying anything?
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The sender? I need that! I want to know how much fuel I have before I go empty.
I have bypassed the anti-slosh, removing the anti-slosh and connecting the green with the green w/ orange stripe on the harness. No difference.
I have bypassed the anti-slosh, removing the anti-slosh and connecting the green with the green w/ orange stripe on the harness. No difference.
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Have you followed the Great palm's instructions about cleaning up the path of the electrical signals to the gauge within the cluster? This is critical and it is what made my gauge go to the top properly.
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Vee,
Nearly all fuel gauge reading problems are one of:
- the sender
- the A/S module
- the instrument cluster wiring integrity
- the gauge
I think that the easiest way to diagnose the problem is:
1. Bypass the A/S module. If the gauge doesn't then rise, it almost definitely isn't the issue
2. Ground the sender to force the gauge to read above Full. If that happens, it probably isn't the gauge
3. Ensure the fuel level is low enough then remove the sender form the tank and manually raise the float to a "full level" position. If the gauge then moves to full, it's probably a sender float that is leaking.
Only after you've done those three simple tests, would I start looking for wiring integrity or sender resistance problems.
As you say that you've now eliminated the A/S module as being the problem, do tests 2 & 3.
Good luck
Paul
Nearly all fuel gauge reading problems are one of:
- the sender
- the A/S module
- the instrument cluster wiring integrity
- the gauge
I think that the easiest way to diagnose the problem is:
1. Bypass the A/S module. If the gauge doesn't then rise, it almost definitely isn't the issue
2. Ground the sender to force the gauge to read above Full. If that happens, it probably isn't the gauge
3. Ensure the fuel level is low enough then remove the sender form the tank and manually raise the float to a "full level" position. If the gauge then moves to full, it's probably a sender float that is leaking.
Only after you've done those three simple tests, would I start looking for wiring integrity or sender resistance problems.
As you say that you've now eliminated the A/S module as being the problem, do tests 2 & 3.
Good luck
Paul
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From: France
Paul
I agree with your advice 100%. I would just add, though, that pushing a full 12v through the gauge as per your point 2, will, almost certainly, make the gauge go to the top. But, it will not rule out the resistance created by the astonishingly gimcrack connections between the blue circuit "board" at the cluster and the gauge itself as a full 12v will overcome it in a manner the normal signal cannot. Fixing this aspect, as per Palm, is what what eventually got the gauge reading correctly in my car. I did not do any mods, just very carefully cleaned up all the four possible resistance places as described by Palm here:"Instruments and Gauges
FLAKY INSTRUMENTS: There are four vertical gauges in the center of the instrument panel on most older XJ‑S’s, and they are unreliable -- not because they quit working altogether, but because they never seem to provide consistent readings. Brian W. Rice writes: “All gauges in my 85 XJ‑S read low by 25% when I acquired the car several years ago. I did some tests by lifting No. 4 fuse and applying a variable voltage to the dead end from a power supply, making sure not to exceed 15 volts. With precisely 12 volts applied the voltmeter showed about 9V. The fuel gauge also only indicated 3/4 with a full tank of petrol.” These problems are because the wiring to these gauges is a disaster, with at least four likely locations for poor connections on each lead to each gauge.
Even if you don’t think you have a problem with the gauges, it is suggested you do a minor overhaul and cleanup of the instrument cluster anyway. It’s really easy, anyone can do it, and it’ll only take a couple hours even if you’re really milkin’ the job.
First, remove the instrument cluster from the dash -- see notes above. Second, remove five screws from the back side and separate the front cover from the rear housing of the instrument cluster. This will give you access to all the innards.
Now, if you have a VOM, you should be using it. Check the ohmage of each circuit from the socket where the wiring harness plugs in all the way to the brass nuts on the screw posts on the side of the gauge itself. Of course, these circuits should read zero ohms, or maybe some really small amount like 0.1Ω if you have a sensitive digital VOM. Basically, they should read pretty much the same thing you read if you just connect the leads of the VOM together.
You’re likely to find some poor connections indeed. This author found circuits with more than 2Ω. That may not sound like much, but it’s a lot for a circuit that isn’t supposed to have any measurable resistance. Of course, if you don’t have a VOM, just dive in and fix all the connections described below as though they are all bad.
The first likely source of trouble is the harness connectors themselves. The entire panel is wired with a clever flexible printed circuit, and the harness sockets are formed by folding portions of this flexible circuit into a hole and pushing the plugs in; the connections on the sides of the plug make contact with the bare copper on the flexible sheet. There’s not a whole lot you can do here other than clean up the connections a bit (rub with fine sandpaper or the like) and perhaps apply some Ox-Gard to prevent further corrosion, but if some of the circuits are really messed up, here’s a tip: places that do stained glass work use thin copper foil tape, and some of this tape might be usable to fix a damaged connection on that flexible circuit. Another idea is a hobby shop; places that sell stuff for model trains and the like sometimes sell copper foil conductors for sticking down on a surface and then painting over so there are no wires visible.
Each of the four vertical gauges is connected to the flexible circuit with screws with stainless steel wavy washers under the heads. Here’s the second likely spot for a bad connection. If you’re in a hurry, you might just loosen the screws a bit and retighten, since that will usually make a good connection for a while. For a more permanent solution, there are several suggestions. Besides polishing up the copper surface, you might consider replacing that wavy washer with something with a little more “bite”. Basic steel is not recommended, though; this is one place you don’t need rust. Some hardware stores sell bronze lock washers; if you find some in a suitable size, they’d probably work well. You’ll need at least 29 of them. Alternatively, you might just take a pair of pliers to those wavy washers and make them more wavy. "
I agree with your advice 100%. I would just add, though, that pushing a full 12v through the gauge as per your point 2, will, almost certainly, make the gauge go to the top. But, it will not rule out the resistance created by the astonishingly gimcrack connections between the blue circuit "board" at the cluster and the gauge itself as a full 12v will overcome it in a manner the normal signal cannot. Fixing this aspect, as per Palm, is what what eventually got the gauge reading correctly in my car. I did not do any mods, just very carefully cleaned up all the four possible resistance places as described by Palm here:"Instruments and Gauges
FLAKY INSTRUMENTS: There are four vertical gauges in the center of the instrument panel on most older XJ‑S’s, and they are unreliable -- not because they quit working altogether, but because they never seem to provide consistent readings. Brian W. Rice writes: “All gauges in my 85 XJ‑S read low by 25% when I acquired the car several years ago. I did some tests by lifting No. 4 fuse and applying a variable voltage to the dead end from a power supply, making sure not to exceed 15 volts. With precisely 12 volts applied the voltmeter showed about 9V. The fuel gauge also only indicated 3/4 with a full tank of petrol.” These problems are because the wiring to these gauges is a disaster, with at least four likely locations for poor connections on each lead to each gauge.
Even if you don’t think you have a problem with the gauges, it is suggested you do a minor overhaul and cleanup of the instrument cluster anyway. It’s really easy, anyone can do it, and it’ll only take a couple hours even if you’re really milkin’ the job.
First, remove the instrument cluster from the dash -- see notes above. Second, remove five screws from the back side and separate the front cover from the rear housing of the instrument cluster. This will give you access to all the innards.
Now, if you have a VOM, you should be using it. Check the ohmage of each circuit from the socket where the wiring harness plugs in all the way to the brass nuts on the screw posts on the side of the gauge itself. Of course, these circuits should read zero ohms, or maybe some really small amount like 0.1Ω if you have a sensitive digital VOM. Basically, they should read pretty much the same thing you read if you just connect the leads of the VOM together.
You’re likely to find some poor connections indeed. This author found circuits with more than 2Ω. That may not sound like much, but it’s a lot for a circuit that isn’t supposed to have any measurable resistance. Of course, if you don’t have a VOM, just dive in and fix all the connections described below as though they are all bad.
The first likely source of trouble is the harness connectors themselves. The entire panel is wired with a clever flexible printed circuit, and the harness sockets are formed by folding portions of this flexible circuit into a hole and pushing the plugs in; the connections on the sides of the plug make contact with the bare copper on the flexible sheet. There’s not a whole lot you can do here other than clean up the connections a bit (rub with fine sandpaper or the like) and perhaps apply some Ox-Gard to prevent further corrosion, but if some of the circuits are really messed up, here’s a tip: places that do stained glass work use thin copper foil tape, and some of this tape might be usable to fix a damaged connection on that flexible circuit. Another idea is a hobby shop; places that sell stuff for model trains and the like sometimes sell copper foil conductors for sticking down on a surface and then painting over so there are no wires visible.
Each of the four vertical gauges is connected to the flexible circuit with screws with stainless steel wavy washers under the heads. Here’s the second likely spot for a bad connection. If you’re in a hurry, you might just loosen the screws a bit and retighten, since that will usually make a good connection for a while. For a more permanent solution, there are several suggestions. Besides polishing up the copper surface, you might consider replacing that wavy washer with something with a little more “bite”. Basic steel is not recommended, though; this is one place you don’t need rust. Some hardware stores sell bronze lock washers; if you find some in a suitable size, they’d probably work well. You’ll need at least 29 of them. Alternatively, you might just take a pair of pliers to those wavy washers and make them more wavy. "
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From: Kent, UK
Good point Greg. You're right, it could still be the resistance in the gauge, even it can read above Full with full voltage.
Maybe once the basic 3 tests are done, throwing in some resistors at the wiring connections at the sender would be a valid test?
Paul
Maybe once the basic 3 tests are done, throwing in some resistors at the wiring connections at the sender would be a valid test?
Paul
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From: Arlington, VA
I think that the easiest way to diagnose the problem is:
1. Bypass the A/S module. If the gauge doesn't then rise, it almost definitely isn't the issue
Done. I removed the A/S module and jumped the green and green with orange stripe female terminals and had no difference. I think we can cross off a flaky A/S module.
2. Ground the sender to force the gauge to read above Full. If that happens, it probably isn't the gauge
Done, I think? I ran a wire from the negative battery post to one of the two sender male terminals. No change.
3. Ensure the fuel level is low enough then remove the sender form the tank and manually raise the float to a "full level" position. If the gauge then moves to full, it's probably a sender float that is leaking.
Not sure why I haven't tried this. Will do this next week, when I am back home. I did get a replacement (aftermarket) sender a few months ago which didn't change anything, so I didn't think I'd have a leaky float, but I do need to test that thing out of the car.
Only after you've done those three simple tests, would I start looking for wiring integrity or sender resistance problems.
1. Bypass the A/S module. If the gauge doesn't then rise, it almost definitely isn't the issue
Done. I removed the A/S module and jumped the green and green with orange stripe female terminals and had no difference. I think we can cross off a flaky A/S module.
2. Ground the sender to force the gauge to read above Full. If that happens, it probably isn't the gauge
Done, I think? I ran a wire from the negative battery post to one of the two sender male terminals. No change.
3. Ensure the fuel level is low enough then remove the sender form the tank and manually raise the float to a "full level" position. If the gauge then moves to full, it's probably a sender float that is leaking.
Not sure why I haven't tried this. Will do this next week, when I am back home. I did get a replacement (aftermarket) sender a few months ago which didn't change anything, so I didn't think I'd have a leaky float, but I do need to test that thing out of the car.
Only after you've done those three simple tests, would I start looking for wiring integrity or sender resistance problems.
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From: Arlington, VA
Vee,
Nearly all fuel gauge reading problems are one of:
- the sender
- the A/S module
- the instrument cluster wiring integrity
- the gauge
I think that the easiest way to diagnose the problem is:
1. Bypass the A/S module. If the gauge doesn't then rise, it almost definitely isn't the issue
2. Ground the sender to force the gauge to read above Full. If that happens, it probably isn't the gauge
3. Ensure the fuel level is low enough then remove the sender form the tank and manually raise the float to a "full level" position. If the gauge then moves to full, it's probably a sender float that is leaking.
Only after you've done those three simple tests, would I start looking for wiring integrity or sender resistance problems.
As you say that you've now eliminated the A/S module as being the problem, do tests 2 & 3.
Good luck
Paul
Nearly all fuel gauge reading problems are one of:
- the sender
- the A/S module
- the instrument cluster wiring integrity
- the gauge
I think that the easiest way to diagnose the problem is:
1. Bypass the A/S module. If the gauge doesn't then rise, it almost definitely isn't the issue
2. Ground the sender to force the gauge to read above Full. If that happens, it probably isn't the gauge
3. Ensure the fuel level is low enough then remove the sender form the tank and manually raise the float to a "full level" position. If the gauge then moves to full, it's probably a sender float that is leaking.
Only after you've done those three simple tests, would I start looking for wiring integrity or sender resistance problems.
As you say that you've now eliminated the A/S module as being the problem, do tests 2 & 3.
Good luck
Paul
(a) ran a wire from the battery post to the other male terminal on the sender
(b) ran a wire from the battery post to the female terminal on the wire.
I both cases, the gauge is reading low.
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From: France
Vee
Have you hot wired the sender direct to (a) the guage and then (b) cluster and gauge, by running a wire out of the boot and round into the door bypassing the in-car loom completely? The results of this should show if (a) the gauge is OK, (b) the cluster flexible is OK, and (c) if the loom is OK. Or, which of them is the problem.
Have you hot wired the sender direct to (a) the guage and then (b) cluster and gauge, by running a wire out of the boot and round into the door bypassing the in-car loom completely? The results of this should show if (a) the gauge is OK, (b) the cluster flexible is OK, and (c) if the loom is OK. Or, which of them is the problem.
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Yes. That was done. I ran a looooong set of wires, bypassing the AS module, and getting it directly to the gauge. No difference.
I also performed continuity tests between points on the flexible sheet, with no outliers.
I also performed continuity tests between points on the flexible sheet, with no outliers.
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I did try an aftermarket gauge (Eurospare). No change. I bit the bullet and ordered one from JDHT. I have to wait until I burn through more fuel before I install it.
I did not wire 12V from the battery, but I did connect the green wire all the way to the gauge.
There is 12v on the green wire when I take it off the sender. It drops to the low reading when I put it back on the sender. In this case it’s in the 5v range, but the tank is mostly full.
I did not wire 12V from the battery, but I did connect the green wire all the way to the gauge.
There is 12v on the green wire when I take it off the sender. It drops to the low reading when I put it back on the sender. In this case it’s in the 5v range, but the tank is mostly full.
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OK.
I took the previous sender that I replaced, and I plugged it in, outside of the tank. Gauge went to F! Haven't seen it there in ages!
I then filled up a bucket with water and threw the damn thing in there. The float floats. I've left it in there for awhile and manually tried to get the float to take water in, or submerge without getting to the stop on the sender indicating full...no dice. That float is good and is not the problem.
I'm gonna need to find a way to see whats going on in the tank with the sender in to see what's preventing it from showing full! Any ideas?
I took the previous sender that I replaced, and I plugged it in, outside of the tank. Gauge went to F! Haven't seen it there in ages!
I then filled up a bucket with water and threw the damn thing in there. The float floats. I've left it in there for awhile and manually tried to get the float to take water in, or submerge without getting to the stop on the sender indicating full...no dice. That float is good and is not the problem.
I'm gonna need to find a way to see whats going on in the tank with the sender in to see what's preventing it from showing full! Any ideas?
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From: France
Vee
is the sender in the same (more or less) position in the tank as pre-facelifts, that is centre (up and sideways) of the rear of the tank, and of the same type - ie float on a long bent wire? If it is, then what can happen is that the float wire does not have to be bent out of shape much to foul on the baffles in the tank. Maybe try stringing up the float to its top position and seeing if it will go into the tank like that. If it will not, take a look through the hole and see what is preventing it.
is the sender in the same (more or less) position in the tank as pre-facelifts, that is centre (up and sideways) of the rear of the tank, and of the same type - ie float on a long bent wire? If it is, then what can happen is that the float wire does not have to be bent out of shape much to foul on the baffles in the tank. Maybe try stringing up the float to its top position and seeing if it will go into the tank like that. If it will not, take a look through the hole and see what is preventing it.
Last edited by Greg in France; Mar 12, 2021 at 04:09 AM.
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Thanks Greg. It is the same as you describe.
I will add some kind of spring that will force the bent rod to it’s top position inside so when I install it, it should show me what inside the tank that is preventing it from getting to F.
I have a borescope that I am considering shoving in the tank as well, but I’d have to send it in through the fill port, and I’m not sure I can position it well enough to make this worth its while.
I will keep you posted though
I will add some kind of spring that will force the bent rod to it’s top position inside so when I install it, it should show me what inside the tank that is preventing it from getting to F.
I have a borescope that I am considering shoving in the tank as well, but I’d have to send it in through the fill port, and I’m not sure I can position it well enough to make this worth its while.
I will keep you posted though
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Well I cut up one of my old fuel senders… it seems the top of the tank is preventing the fuel float from maxing out its sweep. I can still pull the arm, forcing it to bend to get to a full reading.
I took one of my other spares (the eurospare branded one) and I bent the arm approximately 20 degrees, That’s about how much bend it needed to max out. Now I’ll go tank up and take notes…
I will keep you posted. I have my OEM sender, direct from JDHT, which I have not modified. It is now the spare…for now.
I took one of my other spares (the eurospare branded one) and I bent the arm approximately 20 degrees, That’s about how much bend it needed to max out. Now I’ll go tank up and take notes…
I will keep you posted. I have my OEM sender, direct from JDHT, which I have not modified. It is now the spare…for now.
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Googling reveals 20.7 gallons, but I'm not sure I have ever gotten that far...
My "Vehicle Care" book that came with the car says
a. Indicated Amount between E and F : 19.5 gallons
b. Unindicated Amount : 1.3 gallons
c. Total Refill Capacity : 20.8 gallons
Lastly, the fuel light is supposed to come on when the remaining fuel capacity reaches approximately 2.9 gallons.... not sure whether that's "indicated capacity" or not.
If that's the case, and I really can drive the car for 20 gallons, then I'm happy as a clam.
My "Vehicle Care" book that came with the car says
a. Indicated Amount between E and F : 19.5 gallons
b. Unindicated Amount : 1.3 gallons
c. Total Refill Capacity : 20.8 gallons
Lastly, the fuel light is supposed to come on when the remaining fuel capacity reaches approximately 2.9 gallons.... not sure whether that's "indicated capacity" or not.
If that's the case, and I really can drive the car for 20 gallons, then I'm happy as a clam.
