I would check a few things [not ness. in this order]
- Check your alternator with a meter and make sure it's putting out enough voltage should be somewheres up around 13.5 or 14 under RPM load.
- Check all your ground wires, remove the connections and clean them really good replace the wire if it feels stiff at any point. You should have 4 if I remember correctly. The grounds on these trucks can cause all sorts of issues.
- Check your ignition applifier, on later Disco's its relocated next to the radiator on the drivers side early it's on the side of the dizzy. Sometimes a dodgy connection at the ig. amp or from the ig. amp to the coil can be a problem for staying running. On the dizzy mounted ones p/s fluid can leak from the pump and belt throws it perfectly on the ig. amp module. It's almost like the bastards planned it that way.
- Check to make sure your coil lead to your distributor has a good connection. I always pull the boot back an inch or so take some needle nose pliers and push the connecter in deep [covered in di-electric grease] and then slip the boot back over. Some times the grease causes a bit of a suction so when you slide the boot back take a small pick and stick it into the boot to release the presure then it creates a small suction and helps hold that bugger on there.
Hope this helps, email me if you have any more problems.
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