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Discussion Starter #1
Vehicle - RB30 Patrol/carby

Hey Guys,
It took me some good time to work out the reason behind the auto choke failure.
For a while now, the auto choke flaps weren't opening when the engine's warm enough, obviously costing me
extra fuel every time I drive it, as well as performance issues.
I checked the power the to the socket that takes the +12V to the auto choke heater unit, and it was fine. I checked the auto choke relay prior to that, and it was fine as well.

The real culprit was as in the pictures.
I has been eluding me for a while.
I wonder how many dodgy wires/connectors in the old wiring of the vehicle like that, giving me all sort of trouble.

I gota similar problem with the Fuel Pump Control Unit which appears to be working only intermittently. I'm guessing it's a similar kinda issue.
 

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Make sure the fuel pump has a good earth.
 
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Discussion Starter #3 (Edited)
Make sure the fuel pump has a good earth.
Thanx mate. I haven't actually done that yet.
Should've checked it earlier. Many problems are caused by poor earth connections.
The earth is a separate black wire goes to the fuel pump, from the back end of the Fuel Pump Control Unit(by the looks of it).

I'm thinking of creating a dedicated earth from rear chassis to important units like fuel pump.
Do you think that's a good idea or an overkill?


It's not possible to check the quality of the connections to the fuel pump without lowering the tank(Long Range tank, pump connectors can't be accessed from the access point inside the back of the car), hence the reason for my slackness with correctly diagnosing the problem.
But, I think he Fuel Pump Control Unit is not at fault. I think it's a weak connection in the wire somewhere, either the earth or the +12V wire. ATM, I have wire directly connected to the fuel pump +12V that goes out of the Fuel Pump Control Unit to keep the pump going reliably.

One of the benefits of the Fuel Pump Control Unit is to prime the carby with a bit of petrol to get it started when we first turn on the ignition(really handy when dual fuel with carby) and more importantly to cut power to the fuel pump when the engine suddenly stops while the ignition is on(as it happens in an accident) This is done by piggybacking the connection to pump(or rather receiving an deactivation/activation signal) via Oil Pressure Switch on the engine block. Electronic switching circuitry inside the Fuel Pump Control Unit does that. So, when the oil pressure drops(as in engine's stopping while the ignition is on), the Fuel Pump Control Unit cuts the power to fuel pump(Dark Green wire with a res stripe that comes out of the Fuel Pump Control Unit).

See the circuit diagram I posted.

Use the zoom function of Google Photos to enlarge the circuit diagram.

https://photos.google.com/share/AF1QipM7ZT2F5ddwNbvAmY0TOlKVEdKx6czfdJgGv1giK5pbhwipFixzvX9ZOwBiQhpJNA/photo/AF1QipNJWWR45QL2LFrX94DyRSzfrXZLqtXjzw1qJdgD?key=RjBDMHY4V3NxZTJzZkJFcWloWWR4ekpsdmlwZUZn

Cheers
 

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