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Erratic fuel gauge

Kermit4

Enthusiast
Messages
31
Location
Algarve,Portugal
#1
I picked up a 1987 R4 in Porto, Portugal a few weeks ago. All is well except the speedo and fuel gauge did not work. I got hold of a replacement instrument cluster which is now fitted and works fine. The fuel gauge in the new unit also does not work so I guess I am looking at the float mechanism or some other issue.
Sorry about the preamble but I am getting there!
The old fuel gauge moved from registering nothing to registering almost empty with ignition on. The new gauge also registers nearly empty BUT higher up the gauge than the previous one. Then when driving the gauge registers 1/2 full when tank is completely full.
So I am a bit confused. If it was the float mechanism I would have expected no movement or at least the same movement in the 2 gauges. Before removing the tank and float mechanism can anyone point to another explanation? I don't want to take the tank out unless I have tried any other possibilities.
Any suggestions gratefully received.
Many thanks Ian
 

reidalpine

Enthusiast
Messages
1,443
#2
my guess would be the rheostat thet gets a signal from the floater in the tank..might be gunk or bad connection. have no clue as to what values it should read from full to empty,someone here will no doubt know,Have it checked and measured..-Reid
 
Messages
287
#4
My suggestion to confirm that the gauge itself is working properly would be to earth the feed to the sender unit in the tank. With the ignition on the gauge should then read full & when it's not earthed it should read empty. If this is so you know the gauge and associated wiring is all working properly and the problem lies in the sender unit itself. As already said, cleaning up any contacts would be a good suggestion, too.
 
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