Author Topic: Fuel Gage Not Working (Read 4877 times)

acbrock · « **on:** May 21, 2024, 18:59:29 »

So I am not getting a reading on the fuel gage. This did work months ago. I replaced the fuel sender and it was great. My wiring mess I assume messed it up. I checked all the wires today they seem good. The wires to the plug at 5 & 6 Black Blue and Blue Black I thought maybe were reversed but so I swapped them and still nothing.

I checked the Plug on the fuel send with a MultiMeter. On the G I am getting 12v on the W something like 5 or 6. So power is making it back to the sender. Is there something I could have fried in the actual Fuel gage or should it have blow the fuse first?

My question is... I am trying to see if there is a way to isolate this problem to either the gage or the Fuel sender. With my Power inverter if I send some power from the plug in the trunk that should engage the Fuel gage if the sender is the issue? Question is how would I do that? My guess would be is to send some power down the W Terminal since the G is producing 12v? Or I could do it at the switch and send some power into the 5 or 6 Terminal? Maybe that is safer? Or am I just crazy and need to pull out the Instrument Cluster to diagnose this?

acbrock · « **Reply #1 on:** May 21, 2024, 19:36:52 »

Or is there a way to test the fuel sender?

I just put my meter on it. So I get NO continuity between the Ground / G or W Pins on the Sender. Only continuity with the Ground Pin and the Copper place holder pin.

When I test from continuity with the wires...

W pin has Continuity with the 4 Pin on the Plug
G pin with the 5 Pin on Plug
Earth Pin to the 6 Pin on the Plug.

acbrock · « **Reply #2 on:** May 21, 2024, 20:00:57 »

Haha. I was doing more searching and found a great post on the Fuel Sender / Gage. Half way down I saw that I posted in it last summer and went thru all this to determine my sender was bad! So I will reread everything and do all the tests that I guess I did last summer. Hopefully I will figure it out and if the sender went bad I hope MB will replace it.

acbrock · « **Reply #3 on:** May 21, 2024, 20:48:44 »

So I looks like if I am not getting any my Fuel Sending is OL then it must be shot. I will pull it and see if I can see anything broken, like the last one I had.

BobH · « **Reply #4 on:** May 21, 2024, 20:54:46 »

Unfortunately, when you transposed the 12 way connectors, you could have accidently sent 12V+e onto pin 6, which would have sent 12V+e onto the blue/black wire, directly onto the resistor wire in the sender, down to earth, which may have burnt the wire out in the sender. You should get a resistance reading between the ground pin and the W pin, (on the sender, not the connector)

You can still prove the gauge by doing the same test you did in the old post, shorting between ground and W on the female sender connector, at least that will prove the gauge is still good

acbrock · « **Reply #5 on:** May 21, 2024, 21:50:16 »

Yep so I Put ground to the Blue/Black and got a full tank.

Ground to Blue/Green no light?

So no resistance on the sender. But when I pulled it out and then tested it I got some resistance. Put it back and and nothing. So sounds like I fried the sender. If so I will head down to MB and get another one. Been wanted to go back anyway. Hope they have Pagoda in the lobby. They rotate the cars and a Pagoda must be coming soon.

acbrock · « **Reply #6 on:** May 23, 2024, 20:06:15 »

So I have a new Fuel Sender. Before I plug it in I wanted to make sure my wires are correct since mine have been moved around!

I am going to double check the colors
Blue/Black goes to the W Pin on Plug to Slot 6 on the 12Slot Connector
Blue/Green goes to the G Pin on Plug to Slot 4 on the 12Slot Connector

But is there a way to confirm that the wires are correct with a MultiMeter?

acbrock · « **Reply #7 on:** May 23, 2024, 20:30:01 »

I just traced all the wires and it is odd. Pin 4 is Correct on Both Female and Male but Blue/Black and Black/Blue are reverse on both Male and Female. And the wires in the plug are reversed too.

So regardless of Color G -> Pin 4 and W -> Pin 6.

I am going to pull the wires and reverse them so they are in the right slots and then double check it all and then fire it up.

acbrock · « **Reply #8 on:** May 23, 2024, 20:59:25 »

Ok so I guess the wires were probably reversed Color-wize in the beginning because swapping them took a bit of pulling and tucking to get them to fit. I know there also might be slight differences in all the models of these cars over the years. But I decided to make everything match these diagrams because this is what I will use in the future if I have to pull things out and now they match! So all colors are in the correct spots in both sides of the 12 Pin Connector and in the Plug.
G goes to 4
W goes to 6
5 Not sure where its journey begins or ends, must be picking up power somewhere along the long.
Test 4 and 6 with the wires in the plug to make sure they were still the same with the meter. All good.

When I attach the battery and turn it on...
I get

Nothing at 4 and 6 but 12v at Pin 5.

At the plug I get nothing on G but about 5-6v on (I think on the schematic Pin 5 hooks up with wire 6 somewhere...

Does this all sound about right? Should I plug it in and see if the gage comes to life?

acbrock · « **Reply #9 on:** May 24, 2024, 16:49:34 »

So I think I have all the wiring correct...
Can anyone confirm the meter readings I am getting from the plug at the Fuel Sender. If these wires are wrong or sending the wrong current will it fry the Fuel Sender again? Nervous I am going to kill it again...

acbrock · « **Reply #10 on:** May 24, 2024, 17:44:55 »

Just did some more MultiMeter tests....

Tested the Plug Ground to the ground at the Rear Right Light and that is good.

Multimeter test on the new Fuel Sender I get about 47 (200ohm) when I connect the Ground to the G Pin.
When I Jump the W to the Ground with a wire on the Plug the Fuel gage goes Full.

BobH · « **Reply #11 on:** May 24, 2024, 18:00:00 »

It's difficult measuring voltage at the sender plug, there's a ground there, but the +ve will be coming through the resistance of the gauge on pin W and through the low fuel lamp on pin G, so won't read the full 12v+e, 5 odd volts may be correct, but not an accurate way of measuring

Your colours are going to the correct pins, they always should have, so a bit worrying if you've had to change them, perhaps you put them on the incorrect pins when you took the connector apart, could that have happened?

Easiest test is as before, link ground to W = gauge should show full
Link ground to G - low fuel lamp should illuminate, if it doesn't perhaps the bulb has blown, might be worth checking before you go any further

lpeterssen · « **Reply #12 on:** May 24, 2024, 18:17:31 »

Dear Aaron:

Here attached the position of cables at fuel sender connector

Looking connector from
Behind:

Bottom left = ground feed brown

Top left = blue/black = variable ground signal for fuel meter

Top right = blue/green = fixed ground signal for low fuel bulb

Best regards
L.Peterssen
Www.wiredoktor.com

acbrock · « **Reply #13 on:** May 24, 2024, 18:36:30 »

ok thanks. So I think it is all wired right. I am not getting then Reserve light so I will check that bulb if I take it out.
I will see if I can jump the pins on the 12pin connector to see if I can get that Reserve to light up. If not I plan on taking the instruments out so that I can fix the damn speedo anyway. Once I confirm all this I will plug it in and test...
Thanks!

acbrock · « **Reply #14 on:** May 24, 2024, 18:43:29 »

oh boy. I am confused now. From the diagram below from the tech manual doesn't it show the Blue/Green wire going to the G Pin? And that pin would be under the Ground so where you have Blue Black in your connector?

acbrock · « **Reply #15 on:** May 24, 2024, 19:21:56 »

ok I will give that a go. I have all the instruments out again so I am going to text the bulbs too. Hopefully I can figure it all out before I put it back in.

acbrock · « **Reply #16 on:** May 24, 2024, 21:24:34 »

Ok Speedo back in. Testing the Instrument Gage. All lights are now good. One was blown but for the Oil Pressure. Not sure how to test this thing but just went with the OHM. So I tested the 3 areas under the Gas Light. 1 had Continuity with Pin 4 Ground, 2 had continuity with Pin 6 and 3 Had continuity with Pin5 and Pin6 ---0.6 on Pin 5 and 8.0 on Pin 6. I am guessing if I am getting readings then this part of it is ok so I am going to put it back in.

lpeterssen · « **Reply #17 on:** May 24, 2024, 21:45:17 »

Quote from: acbrock on May 24, 2024, 18:43:29

oh boy. I am confused now. From the diagram below from the tech manual doesn't it show the Blue/Green wire going to the G Pin? And that pin would be under the Ground so where you have Blue Black in your connector?

That drawing is definitely mistaken

Looked for another book with MB wiring diagrams and confirmed that what I posted is correct

Fuel sender terminal

Pin 1= blue/black
Pin 2 = blue/green
Pin 3= ground

Best regards
Eng. Leonardo Peterssen
Www.wiredoktor.com

acbrock · « **Reply #18 on:** May 25, 2024, 01:26:25 »

Yikes! But ok! That is how mine was ( I think) and I switched it around to match that diagram on the Tech Site. I will flop things back in the morning. I think that will make my pins fit better in the connector too. Ok so regardless of COLOR...

W ->Goes to Pin 4
G -> Goes to Pin 6

Pin 4 I got no continuity or Ohm on the Instrument cluster when I test the 3 connections below the bulb
The first connection connected to the 3 Pin Ground
The 2nd to Pin 6
The 3rd to Pin 5 and Pin 6 (Pin 5: 0.4ohm Pin 6: 8.0ohm)

Which is reverse of what I have. So if I correct Fingers crossed I get a fuel gage again.

Thanks for all the help on this crazyiness but it seems like I am one instrument away from having it all sorted out!

acbrock · « **Reply #19 on:** May 25, 2024, 15:10:03 »

Wow crazy to figure this out. I can edit the images and repost them

BobH · « **Reply #20 on:** May 25, 2024, 15:23:36 »

Best to get this confirmed before changing the tech manual, every picture i've seen of the 12 way connector is the same, they can't all be wrong!

Need someone experienced to chime in, in case we're missing something

lpeterssen · « **Reply #21 on:** May 25, 2024, 15:34:41 »

Dear Bobh

Send to my personal email the pictures you have on hands for the 12 pin female connector for the instrumentation cluster. I will compare with mine

Best regards
Lp
Www.wiredoktor.com

acbrock · « **Reply #22 on:** May 25, 2024, 15:40:07 »

Funny I got out the manual that came with my car and the wiring diagram does not show colors! So if both of you confirm the wires in the plug I am going to fix those this morning and the wires in the plug then maybe fire it up...

Also to clear up one other thing when I had the Instrument Cluster out. I am not sure where my brain was but the blown Bulb was the reserve light. So that should be good now too...

acbrock · « **Reply #23 on:** May 25, 2024, 16:46:56 »

Man I have so many pages now with so many options. I think this is correct if I start at the plug and put the wires like Leo's Plug.

W =>Blue / Green => Pin 4 (Fuel Reserve Light)
=> Black / Blue => Pin 5 (Fuel Gauge, +12V from Fuse)
G => Blue / Black => Pin 6 (Fuel Gauge, Fuel Sender)

acbrock · « **Reply #24 on:** May 25, 2024, 17:12:59 »

Ok so I put all the wires like I posted. Put everything back together. Not the Fuel Sender Yet but when to attach the battery the ground on the battery and it sparked. This is the first time it has done that... Does that mean I have have some wires shorting each other out. Maybe getting pinched in the connector?

Unplugged the connector and tried to connect the battery. Spark and a little smoke as soon as it touched. Oh boy.

I matched all the colors to this diagram and then the plug like Leos on the Sender

News:

Author Topic: Fuel Gage Not Working (Read 4877 times)