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CVRT Sabre Electrical Problems


timbo

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Just thought I would post up a thread about an intermittent problem I've had with my Sabre recently. Ran well throughout the summer but just recently had started popping and banging and eventually refused to run completely. I was getting some sparks, but matters were confused by running it low on fuel which I thought might have sucked up some crud from the bottom of the tank.

 

Having checked the fuel filter which had some rubbish in the bowl but was generally pretty clean, I checked the supply to the carb which was clean and clear, so decided it was definitely electrical. I have to say it was a big help that I attended the British Military Tournament last weekend, and one of the Scorpions (the spare one thankfully) had an electrical fault. During the course of the weekend I watched almost the entire ignition system being stripped and overhauled, and although we never found the fault it gave me some good tips.

 

Having got the lid off I decided to start with the rev counter. One thing I learnt is that the CVRT ignition system goes through the rev counter, and I noticed that the rev counter was working intermittently even with the engine turning. There is a wire on the back and apparently it can drop off on occasions leading to loss of ignition. Removed the dash and all wires were solid so no problem there.

 

I then noticed that the plug leading into the ignition junction box was loose ie the socket was spinning in its housing. Not being electrically minded i have no idea what purpose is served by this box, but I do know it contains a couple of ballast resistors. Having removed the lid the problem became obvious - one of the wires (a very short one) had come loose from its connection. I suspect it was never properly seated in the first place, but because it was very short it was able to pass a current most of the time but eventually lost contact. Replaced all the wires and tightened up the plug socket. Lid back on and hey presto away we go!

 

While I had the decks off I tweaked the idle mixture screws which ended up 1 1/4 turns out (compared to the 1 1/2 that you start with), and she's now running crisp and sweet.

 

Next job is to sort the fuel gauge - I'm suspecting a dodgy earth - and then it will be time to put it back together....

 

Cheers

Timbo

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Isn't it a pain when several tons of wonderful hardware are brought to a crashing halt by 1 poxy loose wire.............

 

Mine vehicle wouldn't start because of fuel siphoning back into the tank when stopped. That was after a new battery, new relay, new glowplugs and a lot of swearing.

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Hi Timbo,

 

Let me know how you get on with your fuel gauge. Mine is duff too!

 

I think all the gubbins inside the fuel tank is knackered as I couldn't read any resistance across the sender...

 

Not a fun job and yet another reason to put in a secondary fuel tank!

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Well I sorted my fuel gauge - it had been reading full for at least the last 6 years. A quick inspection showed the earth connector had broken off. Crimped a new one on and bolted it up and Bob's your uncle. It now reads, erm, empty..! It does move a couple of mm when power is switched on, but then I guess 40 litres only just covers the bottom of the fuel bag. In a fit of enthusiasm I also managed to sort out the illumination for the gear indicator, and get the heater working.

 

Back to the ignition junction box. My trusty handbook tells me the purpose of the 2 ballast resistors in the box is to drop the voltage to the coil to 12v, which is what it is rated at. When you push the starter button the resistors are bypassed so that the coil gets 24v to give it a kick up the backside for starting purposes. Release the button and the resistors come back into play so the coil gets 12v in normal running.

 

Cheers

Timbo

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We once had a fault where the engine would run run and drive fine when the main deck was off, but would splutter and cut out with the deck on. Turned out (after much component swapping) to be a faulty coil which would break down under the higher operating temperatures encountered when the deck was on.

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