[240] another starter question

I'm driving home today and the starter kicks in. Ugly sound.
Glad I wasn't on the freeway.
Turned the motor off and coasted to the shoulder.
If I turn the motor over and it doesn't start, everything acts as it should.
If the motor starts, the starter stays engaged.

I'm off to google some solutions. Any ideas from the gallery appreciated.

'83 245 automatic. Bazillion miles. Original crumbly engine harness...

 

Sounds like the ignition switch (the electrical part) is falling apart inside.
Or, it's your "crumbly engine harness" shorting wires together.

If you can get at the starter, disconnect the small "push-on" wire, hook it to
a test light or voltmeter, and make sure it ONLY has voltage when the key
in the "Start" position. It should be dead in any other position. Try it several
times, bang on the steering column, shake and twist the harnesses, etc...

 

Well the obvious place to start is replacing or rebuilding the engine
wiring harness. That's almost certainly the cause. It's shocking that
the car still runs at all with the original harness.

 

For sure the harness needs to be (will be) replaced.
I milked it way too long as it is.
Won't be able to get to it for two weeks though.
Barton is pretty much out of stock on replacement stuff. Maybe we can
piece together enough bits so I don't have to run every wire.
Until then, I need to figure which wires to mess with to get it running
(without the starter turning)

 

Don't think it's the switch. the starter behaves as it should as long
as the motor doesn't start.
Only when it starts, the starter continues to spin engaged.
James is right. The harness is the likely culprit.
Now to figure which wires to replace...

 

If you are pretty confident as a mechanic and have a bit of patience,
I'd suggets removing the intake manifold and then removing the harness
completely, put it on the floor and inspect it closely.

Use a razor to cut open and explore sheathed / covered areas.

Odds are pretty good you will find lots of crumbled insulation and
shorted wires.

Rewrap all affected areas with electrical tape, then reinstall.

Worked for me on a couple of cars.

 

Ability is not an issue... I've been wrenching all my life. Not as much
fun as it used to be though. *g*
The challenge will be finding enough good wire to work with. All the
wires from the connector at the firewall was bare when I got the car. I
sealed the wires with liquid electrical tape.
Fairly sure the wires will crumble when I remove the harness.
Making a new harness is straight forward. Salvaging the connector(s) may
not be so easy.

 

I've rebuilt several harnesses from scratch, it's a lot cheaper than a
new one. You'll need a bunch of wire, heatshrink tubing and electrical
tape, as well as a soldering iron, rosin core solder and a heat gun.
Best way is to remove the harness, lay it out on the ground or a sheet
of cardboard or something, and tape it so it stays put. Cut off the
outer sheath and then cut pieces of new wire of the correct size from
spools and lay them out. Solder joints where required and cover with
heatshrink, then slip heatshrink over the large sections of the new
harness to protect and contain the wires. Snip the connectors off the
old harness one at a time and splice them onto the ends of the new
harness by soldering and heatshrink over those too. Usually the big
connector to the ECU has a couple feet of good wire on it that is inside
the passenger compartment, I like to stagger the joints here to reduce
the chance of a sharp bit poking through the heatshrink and shorting. It
should also be mentioned that you do NOT want to cut the wires to the
knock sensor and O2 sensor connector, they are shielded coaxial cables.

Don't try to patch up and keep going on what you've got, it's just
asking for a fried ECU, as well as it's dangerous, your car could stall
while pulling out into traffic or have an engine compartment fire which
can quickly spread to the entire car.

 

Salvaging the connectors is not hard, just snip them off with about an
inch of wire remaining, strip off the insulation, slip a small piece of
heatshrink over the new wire, strip about an inch and twist them tightly
together then solder.

Often the old wire will be heavily oxidized in which case I've used some
fine sandpaper to scrub the strands of old wire until enough clean
copper is visible to make a nice tight soldered connection.

The larger connectors at the firewall are nice because the pins can be
individually removed, I sometimes snip connectors from damaged harnesses
at junkyards so I have spare bits for this sort of thing.

 

About what I figured...
Thanks for the tip on the O² and knock sensor wires.
16, 18, or 20 ga wire?
Do you mess with color coding or just run a bunch of the same color wires?

 

Good idea. A trip to the pick a part is in order to get some spare
connectors, pins, and stuff.
fun... fun...

 

IIRC there's a few #10, some #16 and some #18. I use a variety of
colors, I haven't found a good place to get wire in the variety of
striped colors the original harnesses use so I try to pick a color
that's close and stick to it for that purpose. Makes it a whole lot
easier to keep track of and troubleshoot.

Another thing worth mentioning is make careful note of which connector
goes to the throttle switch and the idle speed motor, I found out the
hard way they're interchangeable, and at least on a 740 if you get them
swapped it blows the transistor in the ECU that drives the idle valve.

 

Big wires then. I wouldn't have guessed, looking at what's hanging out
of the firewall plug.
Troubleshoot? If it doesn't run when I finish, it's off to the boneyard
with it!
.... not really. *g*

Good to know, thanks!

 

Some of them may be smaller, for the sensors and such, but #18 is common
and cheap, no reason to go smaller.

 

Agreed. Wire is cheap. Just don't want to end up with a harness that's
too fat to bend.
12 ga is ~1/8" in diameter. Doesn't take too many of those before the
harness becomes a python.
Anyway... I have several links to look at with pictures and info on
doing harnesses. Should be no problem getting it sorted.

 

There's only a couple of big fat ones, and they're all stranded, I never
had any trouble with flexibility and I use heatshrink since it's easy to
find big pieces of that in all different diameters and I was never able
to find a source for the sheathing they use from the factory, so the
harness ends up thinner than original.

 

How much (if any) of the wiring has to be accessed from under the car?
I'm debating putting the car up on ramps before I start... much easier
to do while it's still running.
Sure, I could jack it up later and put it on stands if I have to.

 

Just the wire for the oil pressure switch and/or sender and the wires to
the alternator. Most of the work you can do from up above, and that will
be much easier with the car on the ground. I suppose you could put it up
on ramps, disconnect that wiring, then lower it down. You could start
the car with that stuff disconnected so long as you insulate the big red
wire since it goes straight to the battery. 700 series is easier since
the alternator is in a different spot so only the oil pressure wire goes
down under the front.

You'll probably want a new gasket for the intake manifold so you can
pull that off. With that out of the way it's much easier to work with
the old brittle harness and it's a good excuse to thoroughly scrub out
the throttle body and all the vacuum nipples. One other tip, anywhere I
use crimp connectors I solder them too and put heatshrink over the
connection, helps prevent corrosion from ever lurking.

 

Had that problem once years ago. The return spring in the starter motor was gunked up and stopped retracting. I replaced starter and solenoid. Fine.