Subject: Re: [Mgs] Coil for 1980 MGB (was intermittent miss)

From: "PaulHunt73" <[email-masked]>
Date: Wed, 1 Aug 2012 12:28:36 +0100

I think what Richard is trying to say is that the coil and the ballast 
resistance must be carrying a current for you to see the 6v you expect.  Of 
the two wires on the coil +ve one should come from the ignition source via 
the ballast resistance, and the other one should come from the bypass 
contact on the solenoid, both white/light-green.  There should be a third, 
white wire on that terminal which goes to the CEI amplifier, and two 
white/black wires on the coil -ve.  One of these comes from the CEI 
amplifier and the other goes to the tach.

Because the CEI system is variable dwell you may not get a current flowing 
with the ignition on but the engine stopped.  To measure the voltage and 
check that you do have a ballast resistance in circuit and the correct 
resistance coil, remove the white/black from the CEI unit that goes to the 
coil -ve, and connect an earth to the coil -ve instead.  With the ignition 
on measure the coil +ve wrt earth and you should see 6v.  If you see 12v 
there is no ballast in circuit, or the coil is open circuit or not earthed 
properly.  If you see anything else, like 8v, you will have to measure the 
individual coil and ballast resistance with the ignition off and the wires 
disconnected to see where the problem lies (8v is typically caused by trying 
to use a 12v coil, which measure 3 ohms, in series with a ballast).

PaulH.

----- Original Message ----- 
> If the system is ballasted, shouldn't the wire coming from the CEI 
> amplifier
> show 6 volts or is there something different about the CEI ignition 
> system?
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