A 1980 may have one of two types of electronic ignition if it is original,
or an aftermarket electronic system or straight points and a coil. What do
you have?. And from the info I have either factory electronic system should
be using a 6v coil with external ballast (a length of resistance wire
contained within the loom). A 6v system should also have a
white/light-green wire going to the coil +ve from the solenoid which boosts
coil voltage to 12v while cranking. If connecting a jumper lead from
fusebox to coil allows it to start then possibly the white/light-green
between solenoid and coil is broken, since that wire effectively does
exactly what your jumper does. Check at the solenoid for a
white/light-green, and check the voltage on it wioth the key in the run
position. If you see 0v then the wire is broken between there and the coil
and not feeding boost voltage up to the coil. If you see the same voltage
as at the coil positive then remove the white/light-green from the solenoid
and with the voltmeter connected to the solenoid spade check the voltage
while cranking. If you don't see 10-12v then the solenoid is faulty and not
putting out the boost voltage. Don't know what you are measuring the
voltage with but there should be some difference between the key in the run
position but the engine stationary and cranking. If there really is no
difference (and it is not just a case of not being able to measure the
difference) then the trigger in the distributor, whatever it is, is not
causing the voltage to the coil to be switched and hence no spark will be
generated.
PaulH.
----- Original Message -----
From: Phil Farmer <swimmer@seark.net>
To: <mgs@autox.team.net>
Cc: <farmer.phil@burlington.com>
Sent: Friday, June 23, 2000 3:55 AM
Subject: 80 MGB runs but won't start
> I am back again needing help on my 1980 MGB that will run but will not
> start. (Can pull to start). Starter turns over fine and fast.
>
> I ask for some help back in March (slow to work out problems and covered
> with other priorities). I feel like I have a bad connection some where.
> While checking connections and occasionally trying to start engine, it
> started once but not since. Again my working on it has not been
consistent.
>
> I had one suggestion to check the voltage at the positive connection on
the
> coil; Should be high (10-12V) both just with the key on and while
cranking.
> If the voltage was low (or none) while cranking I should have a bad
> connection from the starter solenoid. This could be verified by using a
> jumper wire from the fuse box to the positive terminal on the coil, which
> should cause it to start.
>
> My voltage at the positive on the coil is high both while cranking and
just
> with the key on. However, using a jumper wire to the fuse box causes it
to
> start. Removing the wire it continues to run just fine.
>
> I am still trying to clean up and chase all the connections, as I feel it
is
> a poor connection somewhere.
>
>
> However, while I am working on the problem I am still open to any and all
> suggestions. I also have some questions:
>
>
>
>
> What is the best way to clean the female part of the type connecters that
> slip over a spade terminal (such as on the starter solenoid relay)?
>
>
> Also, How can you bend / tighten the tang to tighten the connection?
>
>
>
> My distributor has a vacuum advance but has never had a vacuum hose to it.
> Normally runs just fine and accelerates good. See below for my coil and
> electronic ignition set up. Should I change this?
>
>
>
> My wiring doesn't match any of the diagrams I can fine. I have John
Twist's
> book, Haynes, The Complete Official MGB (Bentley), Porters, Chilton and
> Clymer.
>
>
> Coming from the Distributor, I have 3 "small wires" to a plug. Black,
> White and Grey.
>
> Coming out of the plug: There are 3 "normal size" wires. Black, White
and
> Grey.
>
> These go into the Electronic Ignition Module. Gold colored - Crane
ams -
> XR700 Ignition - CARB D-47-2&3 Daytona Beach, Florida. I have no
> papers for this.
>
> Coming out of the module is a "large" black wire to the screw mounting the
> module to the fender. Has a label: Ground see Instructions for Positive
> Ground.
>
> Also coming out of the module is a "large" Yellow wire to the negative
post
> on the coil. Has a label: - Coil Bosch 1.
>
> Also coming out of the module is a "large" Red wire to the positive post
on
> the coil. Has a label (very faded but I think says): + Coil Bosch 15.
>
> Coil is an Intermotor 11050.
>
> Coming off the negative terminal on the coil (in addition to Yellow above)
> is a Brown wire that is not connected to anything.
>
> Also coming off the negative terminal on the coil is a White wire with
Black
> strip that goes into the harness and I think goes to tachometer.
>
>
> Coming off the positive terminal of the coil is a White wire (no stripe)
> that goes into harness. I have not been able to determine where this
goes.
> ????
>
>
>
> Mounted on the fender below the fuse box is what I think is a resistor
> (Mounted by being stuck in a clip on fender). It has plastic base on top
> site with two posts. Sides are metal. Size is approximately 1 1/8" tall
x
> ¾" wide x ¾" thick. The bottom terminal has a "big" Green wire going into
> harness and the top terminal has a "big" White wire with Brown strip going
> into harness. What is this and is it needed in my set up.
>
>
> The harness looks original and unmodified.
>
>
> The colors of wires on what I think is the starter solenoid relay (mounted
> on the left fender even with the fuse box and between the fuse box and the
> fire wall) match the wiring diagrams and seem to be wired to match
> diagrams.
>
>
> On the starter solenoid I have:
>
> The "big" black cable from the battery.
>
> 3 "large" Brown wires that go into a harness and up (have not completely
> traced yet). These are on same post with the battery cable.
>
> On a spade connector I have a White wire with Brown strip that goes to
> harness and I think to the starter solenoid relay. There is a small spade
> terminal on the solenoid with nothing attached.
>
> I don't think I have the connection from the solenoid to the positive
> terminal on the coil, which is shown on the diagrams as a White wire with
> Light Green stripe.
>
>
>
>
> I apologize for the many questions and length, but any and all input is
> appreciated.
>
>
>
>
>
>
> Phil Farmer
> http://www.seark.net/~swimmer - Arkansas Swimming Home Page
> Monticello Marlins (Arkansas Swimming - USS)
> Monticello Billies High School Swim Team
> Burlington Ind.
>
>
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