Haven't been on the 700 forum for a while because, as a Brit, I tend to visit the UK forum. Nothing personal! However, the 700 knowledge here is more extensive and I'd like to share some thoughts with you on Hall Sensor replacement, inside the dist. that is. I first "discovered" BB in 2002 when my 740GLE (B230E, UK spec) died, due it transpired, to hall failure. At the time I happened to obtain another distributor from a scrap vehicle at a good price and this stayed on the car until last week when I had a no-start issue that turned out to be the hall sensor again.

So I thought I'd bite the bullet and attempt to replace it. I read the FAQ here which has excellent advice from John Sargent and others. Firstly, as John says, the dowel pin can be difficult to remove. I had two distributors to work on, one as practice in case I messed up. The first pin came out fairly easily but not the second - tight as hell. I started it with a centre punch then ended up using a 4" masonry nail (US description??) which is pretty hard and withstood the pounding required. However I may have slightly bent the dogs - I did this in the vice jaws and probably had insufficient support for the round part of the drive. I stripped the rotor assembly being careful with the washers. Then came the really difficult part - removal and replacement of hall. IMO, this is HARD even if you have reasonable workshop skills, which I think I have. You have to be EXTREMELY precise drilling out the rivets or you enlarge the holes - this I did on my first attempt with the "practice" dist. So the second time I was very careful with centre-punching the rivets and drilling them on the drill-press. Now for the hall replacement. I was working alone and it's almost impossible. I supported the first rivet underneath with a piece of bar in the vice. I should probably have drilled a depression into a bar of the right size so the rivet head just sat in it. Those rivets are as hard as hell. Like the FAQ says, it's like attaching a horse-shoe to a hard-boiled egg. I simply couldn't get the rivet to preen over enough to tighten in the hole. Then I realised the rivet head (underneath) was also compressing to the point where my supporting bar caught the plastic of the hall sensor and it split it a little. I thought I'd wrecked it (30 pounds down the pan, it was a Scan-Tech replacement) but I managed to superglue it back together. So I thought, to hell with this, I'll glue it in. So I used a two-pack epoxy resin (Araldite in the UK) which seems OK. The rest was easy. Re-assembled, pressed pin in using vice, put back on car. What a difference! Fired up like a dream.

The new hall seemed to have a stronger magnet, so I'm convinced that contributes to failure. They don't seem to stop working altogether, it's the voltage that drops below a critical level (around 3.5v I think). If you have a signal generator and scope you can connect up to the car and measure the minimum square wave value that drives a spark. I think the fuel pumps come on at a lower hall voltage than what is required for a spark. I'd have to know more about the ICU circuit to verify this.

I'm not sure I'd attempt this again. Maybe. There's the satisfaction of doing it, isn't there. Also, I didn't replace the bearing oil seal as I don't know what's available here - hadn't time to check it out. Hope it doesn't leak too much - I don't mind the odd drip. Well, I hope that's of interest / use to someone. I'm posting pictures on the UK forum if you're interested. Regards and thanks to all who contributed to the FAQ - it's invaluable.
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BillB