Engine no start condition, possible electrical short?

[rh1231979]

I am working on an 89 Mitsubishi Montero which is experiencing a no start condition. The problem arose all of a sudden with no warning.

When I turn the key in the ignition... all power cuts off to the vehicle. It has to sit for a while with the battery disconnected in order for the vehicle to have power again. This is an intermittent issue and sometimes everything else works (power windows, locks, dome light) but it won't start, and sometimes NOTHING works, even with a fully charged battery.

Any help or ideas would be greatly appreciated.

 

[patprimmer]

Poor connections to the battery including dirty posts, poor fittings or poor connection between wire and fitting.

Internal short in battery that only and quickly occurs as the plates or cells warm from some current flow

Regards
Pat
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[thruthefence]

I'd look for a bad ground on the battery, (both ends of the cable)

Here is a "Southern Engineering" troubleshooting technique, known as "mallatizing":

1) acquire a small hammer (or mallatizer, from the Latin, 'malleus'; "hammer,").

2) next time the problem arises, leaving the key in the ignition, ie "on", not "start". Open the hood.

3) using your hammer (see step 1.) LIGHTLY tap the battery terminals, and the immediate ends of the cables (where they attach to the terminals) By "lightly' I mean don't rare back & wallop the battery, but tap the terminals with some authority, short of destructive force.

use caution that the hammer head doesn't contact the vehicle structure AND the positive terminal at the same time. "Mallatize" the terminals robustly, but carefully.

4) Attempt a start. If successful, it points to a loose, or corroded terminal, or a corroded cable (often inside the insulation where it can't be seen).

5) It's unlikely you will have mallatizing clearance at the ground terminal AWAY from the battery, so you will have to remove it physically & clean it. Also, the positive lead AWAY from the battery often connects to fragile, expensive components. Avoid striking these areas. Checking the fasteners for torque & cleanliness is appropriate.

All this assumes a servicable battery.

 

[LionelHutz]

Geeze, what ever happened to getting out a voltage meter and actually checking the circuits in question?

For example, with key-on, check for voltage on the power wire going to the ignition switch. Then, if power is going to the ignition switch, check for power on the key-on wires leaving the ignition switch.

You can also measure from the vehicle ground wires directly to the negative battery post to see if there is a ground wiring issue. I have found that measuring from the engine block to the negative battery post showed 12V indicating the main negative wire was no longer doing it's job.

If you can't understand electrical circuits well enough to use a meter on them then get help.

 

[thruthefence]

Not everbody got one of them fancy VOM things.

Mos' everbody got a hammer!

 

[MacGyverS2000]

I have the real fancy model... mine goes "Vooom, VoooOOOOMMmmmmm" Mine also starts every time...

Dan - Owner

http://www.Hi-TecDesigns.com

 

[LionelHutz]

Seriously, ever heard of using the right tool for the job? A cheap meter costs about as much as a decent quality hammer....

 

[thruthefence]

"Seriously" is indeed the operative word;

My 'mallatizing' troubleshooting tip was not meant to be, well; taken "Seriously".

sorry for the confusion.

 

[patprimmer]

Very gentle "mallatizing" can work if all else fails in an emergency, BUT an internal open circuit in the battery is also a real possibility with the technique.

Sometimes just wriggling things can fix it for a short time and identify the fault. It works best in very dark environment as you might see the sparks as the contact is re-established.

TTF

Your tongue in cheek post was maybe to subtle as a joke.

Lionel

I agree a voltmeter or even a test pencil can do the job to locate the open circuit or high resistance point.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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for site rules

 

[dicer]

How come every electrical problem is a "short"?

The thing to do is next time it happens don't touch the ignition switch leave it in the on position. Then take the volt meter or test light and see if there is something comming out of the switch. The next thing would be a main power on relay. And yes before checking all that check the battery itself and its connections.
If there is a short there will be either fire / hot wires, blown fuse, tripped circuit breaker.