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Repairing the Fuel Tank Sending Unit
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Pelican Technical Article:

Repairing the Fuel Tank Sending Unit

Terry Steer


2 hours2 hrs






Rags, fire extinguisher, 8mm, 4mm socket or wrench, ratchet, needle nose pliers, emery cloth, fine glass paper, WD-40

Applicable Models:

Porsche 911 (1965-89)
Porsche 912 (1965-69)
Porsche 930 Turbo (1976-89)

Parts Required:

Fuel sending unit, Pelican Part # 901.741.801.00

Performance Gain:

A 911 that gets the correct supply of fuel

Complementary Modification:

Replace the fuel pump
Originally posted to the PorscheFans mailing list, and written with the 911 in mind, this procedure can be used on other cars as well.

     You may remember I posted last week about my fuel gauge which was stuck at the half way point no matter how much fuel was in the tank.  Judging from the amount of mail I received this is a really common problem.

     Today I removed the unit, disassembled it and gave it a clean, as well as cleaned the electrical connections and it now works perfectly. These were the steps I took:

Removing the sender unit.

1. Remove carpet from trunk. This is needed as the fuel can leak from the sender during removal. Place fire extinguisher within easy reach. Also, be sure to carry this procedure out in a well ventilated area.

2. Place towels inside trunk around sending unit to soak up any leaked fuel.

3. Unplug electrical system plug.

4. Remove filler cap to let pressure out of the system. (I don't know if this is required but I felt better about relieving the pressure at the filler cap rather than when undoing the bolts holding the sender in)

5. Remove the five 8mm nuts securing the sending unit.

6. Gently lift sending unit up from its position. I made sure to lift very slowly to allow the fuel to drain from the unit back into the tank rather than into the trunk.

7. Stuff a rag in the now empty spot where the unit was to stop the fuel vapors escaping and to insure against any dirt or pesky type rodents entering the fuel cell.

8. Check sending unit gasket to see if it's in good enough condition to use again. Mine was.


     The sender is a long cylinder, about 300mm in length and 40mm in diameter with electrical connectors at the top and pin holes to allow the fuel to enter the unit at the bottom. It's secured by a 4mm nut and locking washer at the bottom.

9. With needle nose pliers, bend the small locking washer flat so you can access the nut to remove it.

10. Slide the float assembly from the housing.

Cleaning the Unit:

     It has one thin wire which runs the length of the unit and then back up the other side, as well as a copper earth wire. In fact, the long thin wire looks like two different wires but it crosses from one side of the assembly to the other. This wire supports a cork like float with two electrical contacts that touch each side of the wire. The unit measures the resistance of the electrical circuit depending on the location of the float. There is also a contact at the bottom of the unit that the sender closes to activate the low fuel warning light.

11. Check the integrity of the active wire. The float should move freely up and down the wire. Also check the solders at each end where the wire connects for both the active wire and the earth. My earth was very dirty with what looked like some type of corrosion. If the float or the wires are damaged, you could try to fix them or maybe the easier path would be to order a new sender unit (p/n 901.741.801.00) as it's quite delicate in there.

12. Lightly sand the active wire and all the contacts with some emery cloth or fine glass paper, being careful not to rub too hard.

13. I then lightly sprayed the wires and contacts, as well as the outer electrical contacts where the lug connects with some WD-40 then left it to dry.


14. As per disassembly. The float assembly is keyed to the housing by a notch at the top so you can't assemble it incorrectly, though I can't see what difference it would make. I guess it's there for a stronger join. Remember the locking washer before fastening the nut.

15. Reinsert into fuel tank and tighten the five 8mm nuts.

16. Clean the connection points on the plug. I used a cotton bud (I think they're called q-tips in the US) dipped in WD40 and pushed it into the three connector holes. It came out filthy dirty so I think this was quite worthwhile.

17. Attach plug to connector on sender unit.

18. Reinstall trunk carpet

19. Turn on ignition and see the fuel gauge jump to the correct reading!

This process is not going to be the panacea for every fuel gauge problem, but it's probably something you should do to at least get a better idea of what might be causing your problem

Terry Steer 
1980 911SC Petrol Blue 

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Comments and Suggestions:
Vashil T Comments: When i Fill my fuel tank at the station. The needle suck on 3/4 indication and does not goes up to full and goes down as and when I drive. Please help.
October 11, 2016
  Followup from the Pelican Staff: Sounds like your fuel level sender is faulty.

Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
rj Comments: I have a 78 924 it starts first thing but after its warmed up it will not start again without starter fluid my gauge is also stuck at empty is his possibly connected to the sending unit or air flow censor
December 19, 2014
  Followup from the Pelican Staff: You may have a failing fuel pump. I would perform a fuel delivery system test. Check fuel pressure, volume and quality.
- Nick at Pelican Parts
Felix Reyes Comments: i have a motorcycle with faulty sending unit. Is there any possibility that sending unit can ignite and catches fire? thanks... and regards.
December 15, 2014
  Followup from the Pelican Staff: You never know. Anything is possible. - Nick at Pelican Parts  
Al Comments: My 1999 Buick Park Avenue fuel gauge needle keeps jumping from empty to full while driving, especially while turning. Do you think this is the fuel sending unit? Is the process for replacing the fuel sending unit very different from the process shown above???
August 14, 2014
  Followup from the Pelican Staff: Your vehicle is very different. The fuel tank has to be removed. It could be the sending unit or a broken baffle inside the fuel tank. - Nick at Pelican Parts  
Alfy Comments: My 996 C4 sending unit head gives annoying rattling noise on road humps despite it works properly. Is that normal?
July 4, 2014
  Followup from the Pelican Staff: No. There may be a broken piece rattling around. - Nick at Pelican Parts  
Jim Comments: ALL PARTS ACCOUNTED FOR.The float was broken horizontally. I epoxied it without improvement. I re-cleaned it, found a thin high resistance wire out of its channel which keeps it touching two thin copper tabs. Still no improvement. Out of the tank it will register the expected gauge reading of full and empty with the warning light on when I turn the tube up or down. But not in the tank! It works intermittently, drops suddenly to the off position and sometimes returns to a proper reading. I tested all ohm measurements, off, on and sliding it along. The float moves freely. The ground is OK. The meter sometimes works It did before the float broke how did this occur? but hung up at 3/8 full. Now I do not even get this accuracy. Any hintsa t cheaper replacement than the $150-200 I see?
June 9, 2014
  Followup from the Pelican Staff: No fix except to replace the sending unit. - Nick at Pelican Parts  
Jim Comments: After removing and cleaning the fuel level sender of my 300TD Mercedes 1985 the needle sticking problem at 3/8 ceased. But now the needle either reads accurately or pins itself to below the R site which I deduce is loss of power. It will then jump back and forth from a normal read to off and again on, off, etc.. Ground is OK, a closed circuit and the ohm readings are all appropriate. R light low level warning works. What gives?
June 7, 2014
  Followup from the Pelican Staff: Did you leave a part out of the tank? Fuel movement can cause that is the baffle is broken. - Nick at Pelican Parts  
JK Comments: I have 2002 996 with fuel gauge problems. It is very erratic and never makes it to E. frustrating on trips! The digital read out is incorrect too miles to empty. Does this sound like the sending unit or should I be looking elsewhere?
May 18, 2014
  Followup from the Pelican Staff: It does. I would test it before replacing, as it is easy to access. - Nick at Pelican Parts  
JB Comments: What voltage should be if any at the sending unit ? Thanks JB
April 10, 2014
  Followup from the Pelican Staff: Likely battery volts for the sensor, pulled to ground through the sending unit resistor. - Nick at Pelican Parts  
Cece Comments: My sending unit on my 04 Grand Prix is not working. The gas gauge sweeps when you turn the car on and then stays on E. I had the whole fuel pump changed and the gas gauge is still not working. I dont know what else to do.
April 9, 2014
  Followup from the Pelican Staff: I suggest checking the fuel level signal to the instrument cluster using a GM scan tool. It may be a faulty cluster or bad connection. - Nick at Pelican Parts  
gordonmacwillia Comments: To determine whether the sensor or the indicator is at fault, remove the female plug from the sensor and jump the closest two of the three conductors an alligator clip works well. If the indicator reads full, then the sensor is the problem. If the reading is less than full, the indicator is the problem. Indicator repair can be found here: http://forums.rennlist.com/rennforums/924-931-944-951-968-forum/618247-fuel-gauge-accuracy-late-model-944-a.html
February 23, 2013
  Followup from the Pelican Staff: Thanks for the additional Info. We appreciate it.
- Nick at Pelican Parts
Bob Comments: Good how to article. I have repaired a few by doing this. The one step I would add is to bench test the sender with a multimeter attached. As you move the float the resistance on the meter should increase or decrease smoothly. I have encountered ones with dead spots that couldnt be repaired. Bob.
December 14, 2011
  Followup from the Pelican Staff: Thanks for the additional Info. We appreciate it.
- Nick at Pelican Parts
Davey Cracker Comments: Thank you, Terry!

My fuel gauge now works. ;
October 23, 2011
  Followup from the Pelican Staff: Glad it worked out! - Nick at Pelican Parts  
silverstorm Comments: Hi There..My car has a problem where the fuel gauge sometimes gets stuck on empty and even after shes been re-fuelled so would this proceedure be the same on my car too ? Its a 2003 911 C2..
September 26, 2011
  Followup from the Pelican Staff: No, the procedure would be different for your late model. You can access the sending unit and test the wiring to see if the sending unit is faulty.

Unplug the sending unit. The violet wire and the brown/violet wire are for the sending unit. Disconnecting them should send the fuel gauge to empty, connecting them should send the fuel gauge to full.You will have cycle the key and give it some time to react.- Nick at Pelican Parts
johnstahl Comments: I remove my sending unit and the fine wire was broken. So I have 3 questions what is the size of that very thin wire and what it is made of. Last question is how is the wire routed at the oposite end of the solder points? I assume it should not touch the threaded rod that holds the casing on, correct?
June 29, 2011
  Followup from the Pelican Staff: I would assume it is copper. I do not know the wire gauge, you can measure it since you have it. Keep in mind, you will need special wires rated for use in fuel. I would suggest replacing the sending unit. I would not rewire it myself. - Nick at Pelican Parts  
Hollywood D Comments: I tried to replace the gasket on my sender '83 but it's stuck inside the tank. I pull it all the way out and theres somethig on the end thats catching. Not sure what it would be. I don't want to force it out because it works fine, I just need to put a new gasket on.
March 2, 2011
  Followup from the Pelican Staff: The only thing that could be on the end of the sender is some corrosion - the sender should be a straight fit into the tank. Pulling it out might release that corrosion into the tank though - I would run the tank down as low as possible, and then pull the sender - then clean out whatever is left behind. - Wayne at Pelican Parts  
chuck Comments: I am installing a fuel pump on a 1988 944porsche. I got the old unit out without any problems but upon reinstalling i found out the the wires are color coded. I have a brown and also a black and green. Which wire goes on the positive and negative?
June 16, 2010
  Followup from the Pelican Staff: I'm not 100% sure, but on almost all Porsches, the brown wires are connected to the battery ground. - Wayne at Pelican Parts  
redbaron3d Comments: don't forget to replace the cork gasket whenever removing the sender, our host has them cheap. a little gas smell vapour leak can really stink. Also I think the outer shell may be aluminum . mine was super light , if so will not be able to grab it with a magnet.
May 16, 2010
  Followup from the Pelican Staff: Thanks for the input on this one. We appreciate the help.
- Nick at Pelican Parts
Sonny Comments: My fuel sending unit was not working,when I removed it the outer housing was no where to found. I assume it's somewhere in the tank,
any segestions on how to get it out, I'm hoping it's a metal casing that can be grabbed by a flex magnate
February 6, 2010
  Followup from the Pelican Staff: You could use a flexible pickup tool with expanding jaws, or long needle nose pliers. If that doesn't work, you will have to remove the fuel tank so you can position it in a way that the part falls out. - Nick at Pelican Parts  
justforfun Comments: Good suggestions. My gauge was stuck @ 1/4 , but by removing the sending unit and cleaning it fixed the problem. The only other thing I did was to test the unit prior to reinstalling it into the car to confirm it was not the gauge.One way to test is to plug the unit in turn on the ignition, check at full, empty and a position inbetween not really a good idea since gas vapors are involved. The other is to use a volt ohom meter and check the resistance change across the unit as the float moves.
October 29, 2009
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
JJ 911SC Comments: Had the same problem when I got the car 3 months ago.

The previous owner was using Esso Gas. I switch to Shell V Power with Nitrogen Cleaning agent and sure enough a month ago the needle went all the way up.


September 15, 2009
  Followup from the Pelican Staff: Thanks for the additional Info. We appreciate it.
- Nick at Pelican Parts
Harry Comments: my 1985,1 944 turns over great and begin's to start but will not start all the way. Do you think that the fuel sender might be the cause of this?
July 23, 2009
  Followup from the Pelican Staff: Nope, the fuel sender has nothing to do with the starter circuit. Try replacing the battery and/or the starter as a first step. - Wayne at Pelican Parts  

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