Some engine ground straps run between the block and chassis at the LH engine
mount, and if it missing cranking will cause the accellerator and heater
cables to get hot and smoke. But the coil is on the inner wing, so unless
the voltage was measured between coil terminal and engine ground instead of
coil terminal and coil body you wouild not see the effect of a bad engine
ground.
If it goes from 4v with the plugs in to 9v with them out then a bad battery
or bad connections in the heavy current circuit *is* indicated. If you
connect your meter from the hot post of the battery (the post, not the
connector) to the hot terminal on the solenoid and crank with the plugs in,
you should ideally only see 0.2v The same from the ground post to the
starter body. If you see more than 0.5v on either test you have bad
connections, you can use the same technique to break down where the bad
connections are.
PaulH.
----- Original Message -----
From: J MILLER <road1978@hotmail.com>
To: <FJ40Jim@aol.com>; <Wake074@aol.com>; <mgb-v8@autox.team.net>
Sent: Wednesday, May 10, 2000 1:56 AM
Subject: Re: More info, but still won't start
> That brings up a good point. Make sure you have a good ground connection
to
> your motor. The original MG system used a ground cable between the
> transmission and the transmission cross member. I was able to reuse my
> cable. If you don't have this cable you engine won't have a good ground
and
> will result in slow cranking. The engine and transmission are sitting on
> three rubber mounts.
>
>
>
> ----Original Message Follows----
> From: FJ40Jim@aol.com
> Reply-To: FJ40Jim@aol.com
> To: Wake074@aol.com, mgb-v8@autox.team.net
> Subject: Re: More info, but still won't start
> Date: Tue, 9 May 2000 07:41:11 EDT
>
> In a message dated 5/7/00, Wake074@aol.com writes:
> > I seem to be getting consistent spark, although not very strong. When
I
> > crank the starter, the voltage at the coil drops considerable down to
> around
> > 4 volts. This is certainly causing the weak spark.
>
> Glenn,
> This is not normal. A healthy battery and starter system should not drop
> below 9 volts during cranking. A normal, modern car will not go below 10
> volts. Possible culprits include: weak battery, weak cabling &
connections,
> dying starter motor(draws too much current, but doesn't turn over the
> engine), mechanical problem inside the engine causing excessive load for
> starter.
>
> > I pulled all the spark plugs and tried rolling the engine over that
way.
> It
> > spun at a better speed (closer to normal), and the voltage at the coil
> > dropped to only 9 volts. The engine seems to be free, ie. it mores
with
> a
> > wrench on the crankshaft sprocket.
>
> If you can turn it over fairly easy w/ a wrench, then it is not a bad
> engine.
> Also, the dropping to 9 volts when cranking w/ no plugs sounds suspect.
> An
> engine w/ no plugs will crank real easy and real fast. There isn't enough
> load to drop chassis voltage below 11V.
>
> I'd say you have a starter or cable problem. Have a helper turn the key
and
> crank the engine while you check for voltage drop along the positive lead
> and
> the ground path.
>
> Thanks,
> Jim Chenoweth
> Lancaster, Ohio, USA
> Mailto: fj40jim@aol.com
> Ph. 740.862.2604
>
>
|