1999 D1, 161000km. I've just about got everything running on this SOB, The PO has burned out the fuel pump & melted the connectors. I sourced a used harness and connected it onto the remaining good wiring of the truck. I have a problem Houston. The fuel gauge doesn't work and the low fuel light is on. I have checked all my values with my meter. The replacement pump has similar ohm readings as old and is within spec, I ran an extra ground just in case. I am now convinced it is in the wiring or the dash. I can not find what voltage the dash gauge sends to the back, I'm reading 1.9 volts. Can anyone help-what voltage should I read on the power wire for the fuel gauge?? If I can get this sorted I can start wheeling on the street.

 

RAVE set of manuals has an electrical section, under Instruments :


will illuminate to warn the driver .

See attached pages for wiring. Unplug connector at fuel tank. Pin 1 should be "GB" or green & black in Roverspeak. Pin 2 should be "B" or black, and must go to ground. Using test meter, read ohms between pin 1 and 2 looking toward pump assembly. Should be around 19 - 20 ohms when full. You really can't do a good test at the gauge, becuase the voltage there is influenced by the instrument pod and the ECU connection. Can't tell you an exact reading at the gauge.

However, to test wiring and gauge, you could purchase a couple of ten ohm resistors at Radio Shack, put them in series and attach them to pin 1 and ground and gauge should read pretty close to full.

You'll see from schematic that + battery volts has to go thru the coil of the MFR (multi function relay, near ECU), to the ECU, and then to the sender. Because your pump was burnt up, the MFR may also have issues. Should be able to meter that at the MFR connector. I suspect that the ECU supplies switched ground to turn pump relay on/off; and supplies some sort of plus voltage toward the fuel level sensor.

 

Is it just me or am I tick in duh hed. I have also read the passage you quoted and it doesn't make sense. "When the fuel tank level is low, the resistance of the fuel gauge sender is approximately 245 ohms.As the fuel level increses, the resistance of the sender decreases". I would then say that when full the R is low- which would mean that it can't be even lower when empty. Do they have their numbers reversed? There is only 6 ohms R from full to warning light - but 220 ohms from from low fuel at 245 ohms. It doesn't make sense to me.

 

Yup, seems backwards.

 

It be Roverspeak. But my point would be, you can sub a known el cheapo resistor there, and see if gauge moves, before going into the harness. This must be a translation error from the original Klingon.

 

We have visitors today so I can get back to garage tomorrow. I still have a bunch of variable resistors left from my previous life before retirement. I'll play and see what happens.Thanks for the help.

 

After much trial & error I have narrowed the problem down to some where between the fuel tank side of the connector plug over the rear left wheel. The chassis/dasah side of the plug indicates 5.6 volts at the Green with Black stripe wire. While my meter shows continuity on the Green/black stripe on the tank side of the plug-I am not getting anything but 1.2 volts at tank for fuel level. I tapped into 5.6 volt at dash side of plug over the wheel and ran that through the old fuel gauge & voila-the dash gauge worked and the low fuel light went out. Tomorrow I'll determine if that one pin is dead at the plug or if some wires got fried in the loom between the tank and the connector over the wheel. If I have to I'll remove that plug and solder connect each of the wires- I may have to run a new set of wires altogether. Tomorrow will tell. At least I'm down to the last 2 feet of wire. By Monday I should be rolling up main street. Thanks for the help.

 

Take a look above the rear muffler. IIRC the harness runs above it and
can melt when muffler rots out and the exhaust melts it.

 

We have lift off. I bought some heavy truck 6/14 wire and replaced the plug connector at the frame above left rear wheel-all the way to fuel tank. I have fuel gauge and light working as it should, fuel pump and all is well. Clean up time and ready to drive this truck.