QUOTE(kiloman @ Sep 3 2006, 04:54 PM) [snapback]31331[/snapback]
Folks,
One by one I am knocking problems off my repair list. A big thanks to John at JOMO for sorting some issues, thanks again John.

My fuel gauge is reading 1/2 when the tank is full. John looked at the wiring and this seems fine so now it looks like the cluster. Everything else with the cluster is fine,except for a legendary fuel efficient 99.9mpg on the MFA(related ?).

Is there anything that can be done with this fuel gauge (or MFA mpg even)?

Thanks
Gavin


Hmmm... Does it seem to read 1/2 until the tank is half empty and then read as normal? Or does it gradually drop off, so it's reading half of what it should the whole time? It could be the sender unit either - try disconnect the sender unit and short the connection to the chassis, if the gauge reads full then it's the sender at fault.

I don't think they're related as my understanding of the MFA is that it uses the vacuum strength as an indication of engine load coupled with the trip meter to calculate mpg as the gauge is far too coarse a reading to be used over a few minutes. With really high efficiency there's a really low vacuum load and so with 99.9mpg I'd guess the vacuum connection is blocked or disconnected altogether.

 

Think you have hit a few nails on the head there Rob!!

 

The fuel gauge works on a float that moves a contact on a metal resistor track on the in tank unit (you can get to it by removing the circular cover under the boot carpet). Sometimes the contacts get corroded and it won;t read properly so would be worth checking it and giving ita clean.

 

Thanks for the replies.

I replaced the sender as I thought that this was the problem. Unfortunately this did not solve it. I have not tried to run it down low as I bought the car with the issue and am afraid that the car will run out. When it was being looked at, by manlipuating the float it could read 0 when empty but when full only read half.

Where are these magical vacuum connections?

Thanks again.

 

The MFA vacuum lead goes from the end (passenger side) of the intake manifold, through the bukhead to a connector at the back of the clocks.

 

QUOTE(kiloman @ Sep 5 2006, 06:37 PM) [snapback]31560[/snapback]
Thanks for the replies.

I replaced the sender as I thought that this was the problem. Unfortunately this did not solve it. I have not tried to run it down low as I bought the car with the issue and am afraid that the car will run out. When it was being looked at, by manlipuating the float it could read 0 when empty but when full only read half.

Where are these magical vacuum connections?

Thanks again.


So, if you push the float down it reads empty, and when it's full it reads half full... What about when the tank is half full? what does it read then? Still half full, quarter full or something else? Like I said, try disconnect the lead from the sender and connect it to the chassis with a bit of wire and see if the gauge reads full. If it does, then the problem is with the sender (though it being a new sender I'd say it'd more likely me a mechanical fault with the float linkage). If it doesn't read full then, it's the gauge at fault.

 

is the sender fitted wrong? ive seen cars where the sender was fitted 90 or 180 degrees out and the float was hitting against something in the tank and not allowing it to read full

 

I had a similar problem in a MK4 Golf but it turned out the needle in the clock was sticking. I had to have the clocks replaced. I'd fill the tank and the needle would only go up half way. The next time I started the car it might work alright. The car was covered under a warranty at the time. The garage checked the tank the first day but had to get a contractor in to fit the clocks. I think the whole cluster was replaced I don't know what work is involved. I just know how to use the pedals, steering wheel and gear stick.