Cluster & fuel pump issue

[Roffa230]

Hi, I am a proud owner of a 1999 polo 6n1. How ever I am experiencing a issue with my fuel gauge. It does intermittently and is just moving either very fast or just showing a full tank and seconds later a empty tank. I have all removed the fuel pump and floater and tested it. It works correctly. Now I have removed the cluster, and I can see some dark brown to black lines on the print board. Can this cause these issues?

Different problem, the car stutters a lot when lightly pressing the gas pedal. I also noticed that the fuel pump won't stop priming when turning the key but not starting the car. After some research I understood that this could be cause by the key slot. And here is the funny part, to start the car I have to push a button. It seems that at some point one of the previous owners pulled 2 wires from the key slot. 1 connected to the red wire and 1 to the yellow wire. Turning they key to start won't start the car either. S it possible that the start position of the key slot is broken, which would explain why such a system has been added?

I have to add that I am living in Mauritius, a country where they are amongst world champs of modification how it shouldn't

[alexperkins]

Yes the cluster could have a damaged board. A bad earth on these is also often a cause

Id also be removing that button and replacing the ignition switch to get it back to how it should be originally

[Roffa230]

Hi ALexperkins,

Thank you, do you have an idea where i should be looking for the earth connection?

concerning the ignition switch, when turning the key the car doesn't do anything. So i guess the ignition is broken, and that is why they put in a start button. I guess apart from buying a new ignition chance are rare to get this ignition switch in shape again.

[alexperkins]

Normally it’s the earth into the gearbox

The ignition switch cannot be repaired. It’s cheap to replace in any case.

[Roffa230]

Hi alexperkins,

I checked the earth connection, it's good. I guess I'll be dropping the cluster with a electrician so he can take a look at it. Concerning the fuel pump it's a bit more complicated.

When I turn the key without starting I can hear the fuel pump priming non stop. It continues to prime until I get the key out. The car stutters when applying light pressure on the gas pedal, and the engine somehow loses power when driving on the highway. I get the feeling the the pump is just sending fuel to the engine, regardless of the accelerator input. Also the fuel consumption is incredibly high.

I am really wondering if the key could cause this, and if so if there is a correct way to connect the start button. As buying a new key mechanism is incredible expensive over here. Or could there be an other reason for this?

[alexperkins]

Id replace the fuel pump relay first as it could be sticking in permanent prime mode

[Roffa230]

Ok I will try to look for one. Also where can I find this relay? As I tried to look for it, but no-one is really able to tell where this relay is.

While lifting the hood and removing the air filter I noticed a loose wire, like a ground wire. I reconnected it to some ground. You know the purpose of this wire?

[alexperkins]

Thats a pretty important earth wire - Have you tried it since?

The relay is above the fuse board inside the car. Its relay 410

[Roffa230]

I did, I drove for like 1 hour but no significant improvement. Could you tell me what this earth wire is for? Since I has been loose since I have the car.

My fuse box looks a bit different.

[Roffa230]

The stuttering car issue got solved. It was the temp sensor. Cursed myself for not checking this earlier. However now a other issue arise. When applying light pressure to the gas pedal the car still stutters like it received too much fuel, and the gas pedal vibrates briefly.

[alexperkins]

Clean the throttle body and align it. It’s probably getting too much air and too little fuel

[Roffa230]

So after a period of radio silence i have news.

Temp sensor has been changed. Throttle body cleaned and released. But the car started heavily stuttering and making backfire after the relearn.

Diagnostics shows code:
00525 oxygen sensor
00561 mixture adaptation

I brought it to 2 different garages of which 1 is a volkswagen specialist. The first one told me it's the lambdasensor as the specialist told me he tested the car without sensors, and no difference. The car is visibly running lean, and lacks power.

You have any ideas what could cause these sudden issues?

[alexperkins]

Check the wiring on the front of the gearbox for the lambda sensor for breaks. It’s very fragile and tends to break up over time. That will cause the issues

The two codes you are seeing is related

[Roffa230]

SO this would also explain that there is no difference between connecting and disconnecting the lambdasensor, and why there is no signal even when connected

[alexperkins]

yes quite likely. Check the wiring 6 inches back from the plug