Fuel gauge and speedo cable

#1
Hi guys..a couple of issues to get sorted.

I have had the BW35 reconditioned. However my speedor and trip meter does not work. I had tried to loosen the cable at the gearbox
but not sure if I have to loosen is alot of if I am doing it correctly. The other issue is the fuel gauge shows slightly more than empty although
I have filled her up and she's full of petrol. I checked the cable and she's attached. She goes empty when you turn her off and when you turn
her on, needle moves to just above empty. Any idea why?
 
#2
Hi, sounds like an earthing issue if your getting different readings by switching off and back on again (assuming u are waiting long enough for the gauge to move fully). have u tried taking the wire off the sender and seeing if it reads full. I believe the other possible issue is the voltage regulator on the pcb behind the instruments.

hope this helps
Coop
 

colnerov

Well-Known Member
#3
Fuel gauge. Is the temp gauge working OK? If yes then it's not the voltage regulator. Try earthing
the wire on the sender, does the gauge go to max? If yes, then it's the sender at fault, if no, then
it's the gauge.

Speedo. Undo the speedo cable from the speedo and pull it away so that you can see the end. When
you drive forward does it turn? If yes, then its the speedo or its angle drive the latter more likely.
If no, then its the cable or the angle drive at the gearbox end. If you pull the inner cable out does it
have a squared off end? If yes, its the angle drive. If no, then its the cable having twisted off part
way along.

Colin
 
#4
colnerov said:
Fuel gauge. Is the temp gauge working OK? If yes then it's not the voltage regulator. Try earthing
the wire on the sender, does the gauge go to max? If yes, then it's the sender at fault, if no, then
it's the gauge.

Speedo. Undo the speedo cable from the speedo and pull it away so that you can see the end. When
you drive forward does it turn? If yes, then its the speedo or its angle drive the latter more likely.
If no, then its the cable or the angle drive at the gearbox end. If you pull the inner cable out does it
have a squared off end? If yes, its the angle drive. If no, then its the cable having twisted off part
way along.

Colin
Hi both..this is great tips...the temp works..so perhaps not the PCB...I took both wires out and the needle is not
moving at all. can you tell me more on what you mean by earthing?

The speedo only stopped working when the transmission specialist rebuilt the box. He did tell me to loosen the knob
near the end of the box which I did but nothing happened. So are you saying I should loosen it all the way and take
the cable out?
 

colnerov

Well-Known Member
#5
Hi, underneath the back of the car over the right hand drive shaft is the tank sender,
there should be two wires one is black, this is the sender earth wire make sure that
is OK. The other wire is colour coded, pull that of its terminal and touch it to the body
earth. Have a lovely assistant to tell you if the gauge goes to max, if it does the sender
is at fault. As far as the gearbox 'knob' is concerned I think he is referring to the angle
drive. But you need to prove whether there is any drive coming out of it, so either try
and follow as before or remove from the back of the box and check it, it may appear OK
but fail under the load of driving the cable and speedo.

Colin
 
#6
colnerov said:
Hi, underneath the back of the car over the right hand drive shaft is the tank sender,
there should be two wires one is black, this is the sender earth wire make sure that
is OK. The other wire is colour coded, pull that of its terminal and touch it to the body
earth. Have a lovely assistant to tell you if the gauge goes to max, if it does the sender
is at fault. As far as the gearbox 'knob' is concerned I think he is referring to the angle
drive. But you need to prove whether there is any drive coming out of it, so either try
and follow as before or remove from the back of the box and check it, it may appear OK
but fail under the load of driving the cable and speedo.

Colin
Thanks Colin, did what you said and seems like the sender inside the tank is the culprit after all. Probably need to wait for the tank to be empty before I remedy that, and I just filled her up...all 68ltr two days ago.

I will look at the speedo soon.
Have you got much experience with the infamous reserve tap? My electrical pump does not seem to get much fuel out of it. Is it simply just replacing the famous 'O' ring and it will work? I just replaced the reserve with a 3mtr new fuel line and go straight to the pump. Works fine after 5km of driving today. Previously when I went all original from the tank to the tap and to the electrical pump, the car keeps dying due when it gets really hot due to lack of petrol going to the carbs. I had to cool her down several times before nursing her back home. So today I decided to use a new line and put it right to the pump. So all is good. I'd love to use the reserve tap though.

The other thing keeping me up is the mechanical pump. Is there a way I can determine if its working at all? It's alot quieter than an electrical pump. I'd love to go all original. I did take the new fuel line and attached it to the brass pipe above the trans and tried started the car. No fuel is being pump out from the pump. How many starts do I need to make before it can suck the fuel out? Also if I take a compressor and blow from the brass pipe will unclog it? Cause I dont know if it's the pump or the pipe to the pump that is not the culprit.

Anyhow, is the mechanical pump even worthwhile to save or stick to the electrical one? Lastly is low pressure pump the right pump for our car? What PSI is best?
 

colnerov

Well-Known Member
#7
Hi, as you have, from what I gather, bypassed all or most of the original pipework, then you
can remove and check the old stuff. Yes, do the reserve tap, there are available service kits
to rebuild the mechanical pump. But be aware there are two sizes of one way valves fitted to
the pumps, one size come in the kit the other has to be obtained separately. You wont know
which is fitted until it's stripped. As the fuel line have been cut about it would be a good idea
to rerun them, either in plastic or copper, I would suggest using compression fittings as I have
not had success sweating plastic onto the metal ends.

Colin
 
#8
Hi Colin, thanks for your input. I, for now, have took out the reserve line and put a stopper at the tank end to eliminate any overflow from main line which tend to drip back into the reserve line. I have put a new and proper fuel line from the tank straight to the electrical pump and the pump seems happier and a bit less noisier compared to when I was running another hose before. This fuel line is also slightly larger. However what I don't understand is that is that whilst the new fuel line bypasses the reserve tap completely and go straight to the electrical pump, the fuel filter, which is attached after the pump and before the carb, is not always full. The car runs and never gave me problems though. But I am always very worried that the carbs are not getting enough fuel which happened many times when I was using all the original lines and feeding to the reserve tap. Is it normal for the fuel filter not to be always full?

On the speedo cable, I sent the car back to the trans workshop to check on the speedo cable and the mechanic said it is turning. He can't find any issue. He suspects that the issue is coming from behind the dash although before I had the gearbox recon, the everything on the dash works. After the recon, the speedo and trip meter are not working, but RPM, temperature and clock work fine. What can I do to get to the bottom of it?

thanks again.
 
#9
Oh by the way, my elect pump is the low pressure sort, 12V and about 3-6PSI. I wonder if it's strong enough to pull from the tank cause it times it is full but sometime it is not but the engine runs well.
 
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