Hi All, I'm in awe of the wisdom here!
I hope someone can help because I?ve run out of knowledge! I've got an M10 engined 1776cc BMW E21(love it and the rust it came with for free) and have got a gremlin.
Since I bought it it's stuttered (loss of power) under moderate/ hard acceleration but I can get it to higher rpms (though not max) if I let the revs build gently (slamming my right foot down makes it stutter a hell of a lot and i slow down). I changed the distributor cap and plugs about a year ago I thought it was a carb or fuelling issue - recently bought a weber to fit.
Recently it stuttered much more than usual and I noticed that a spark from one of the ht leads on the distributor cap was arcing across to the metal surround of the cap. Took off ht lead to see the copper socket that goes onto the cap wrecked and with green residue on both it and in the cap (another was also a bit green). Replaced leads and it now runs much better but still the stuttering on moderate/ hard accel and I also noticed (in the dark) arcing again, but less so. I also noticed that the distributor cap has scoring in the plastic around the contact diametrically opposite to the one that?s arcing noticeably.
I?ve also noticed that the metal surround that goes over the distributor cap is a very tight fit/ doesn?t really fit and also stands prouder than the picture of it in my Haynes manual ? do you think it?s possible that this closeness (probably only 5mm) between the metal surround of the cap and the leads is leading to the bad running?
Any thoughts at all would be really appreciated ? I?m deeply confused?
Many thanks!
James
{Subject header amended to include car details - DD}
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If it's a Bosch with a Bosch metal surround,take the surround off and throw it away(part of a suppression kit).However a new cap and leads would probably be a good idea.
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Another thing to check is that the fitting on the ends of the leads and the fitting in the cap are compatible. There are some leads that are designed to grip a pin in the distributor cap, and some leads which are designed to push into a metal cup in the cap.
Clearly, the coil can produce good sparks, so, check coil lead to distributor, the rotor arm, the distributor cap, and the plug leads themselves. If you open the bonnet in the dark with the engine ticking over, you will soon see if there's a problem with arcing to earth. To test for continuity, you will need an Ohmeter.
Number_Cruncher
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New cap and HT leads, make sure everything fits correctly. Change the plugs too if they're old.
Bad HT leads can be the very devil, and aren't always obvious.
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>>Bad HT leads can be the very devil and aren't always obvious.
To illustrate: I once bought a low-mileage Skoda that, when hot, shunted abominably, could only be driven at full throttle and did about 10mpg. With new HT leads it behaved impeccably, considering the carburettor was a porous casting that wouldn't idle when properly adjusted... An old but good carb solved that one.
Of course I shouldn't mention a Skoda in a thread about a BMW. My apologies :o)
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Cheers gents,
Good stuff - got new leads, getting new cap and rotor arm at the weekend - plugs in good nick and a year old.
Question: my distributor cap's Beru if i remember right and there's an earth from the metal body/guard thing that sits on the cap - what does it do? will i be OK to chuck the metal guard thing because the spark's arcing to it. this can't be good for running!
J
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The metal shield is there for suppression of radio interference. You can temporarily do away with it for testing purposes. But, your distibutor cap and leads should be able to cope with the shield. The fact that you have arcing suggests that the cap isn't working properly.
You are using genuine parts aren't you? I would suggest that you should be. Spurious non-genuine HT parts aren't really worth bothering with.
Number_Cruncher
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Cheers,
I got parts from eurocarparts - it's a Beru Distributor Cap and Hansa leads - German. No more arcing across to the supressor! That's a win. Running much better now (although carb still not running right) although I did run it with the suppressor off and noticed that the distributir cap was wobbling slightly (checked distributor and it was secure) this leads me to believe that the shaft that the rotor arm goes on of the distributor is a bit out of whack. Pretty gutted as distributors cost a bomb.
J
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believe that the shaft that the rotor arm goes on of the distributor is a bit out of whack. Pretty gutted as distributors cost a bomb. J
I thought the scoring you mentioned in the OP sounded a bit sinister...
Second-hand one shouldn't be impossible to find though.
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>>distributir cap was wobbling slightly
Yes, if the shaft is bent enough to allow the rotor to hit the segments in the distributor cap, neither the cap or rotor will last long. As suggested by Lud, get a S/H distributor.
Number_Cruncher
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Hmm. . have had a quick look on the net and haven't spotted a s/h one yet - sure i will, though and as mine is a v.late E21 316 and hopefully I'll have E30 316s to choose from too - might be worth a trip down the scrap yard.
Funnily enought I spotted one for a 318i (320i in US) for $100- am going to dig and see if it'll fit (probably not!).
Cheers all,
J
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There's an outfit, perhaps several, called 'Find Parts' or something of the sort. You enter the part you want and the message goes out to a syndicate of breakers' yards. Those who have the thing you want then email you, you ring them up, and you make a choice on that basis. Got a good gearbox for my Ford for £100 or so delivered. No complaints at all, and better than rolling around in the toxic slime under a tottering pile of wrecks.
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try www.247spares.co.uk, I've used them before and the service was great. If you Google ' 24 7 motor spares ' a whole list of similar websites come up.
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Thanks chaps - will do. not got the money this month though!
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has the condensor that bridges the contacts in the points been checked, this is a very long shot but a very cheap solution if its found to be faulty, its there to prevent arcing when the points open and close
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