89 Jeep Cherokee 4L Weird starting problem

My Cherokee starts fine but as soon as I touch the brake pedal it kills the
engine. If I keep my foot on the brake pedal it won't start. I tried
disconnecting the wire to the brake light switch but if I do this it won't
start. The brake lights work fine and the hazard lights work so I don't
think the switch is the problem. Does anybody know what this problem is?
Glen

I could see a short in the brake light circuit sucking so much
power that your computer wouldn't work, but disconnecting the line to
that switch, and the engine won't run makes no sense, the line is
terminated there. I once had a similar problem where is would hit the
brakes and engine would die, but actually my knee was hitting the column
where the ignition switch was coming apart. The only thing I could
suggest is double check every connection, looking for hot spots where a
couple of wire could have melted together.
God Bless America, ßill O|||||||O
http://www.billhughes.com/

Glen Hudgin wrote:
>
> My Cherokee starts fine but as soon as I touch the brake pedal it kills the
> engine. If I keep my foot on the brake pedal it won't start. I tried
> disconnecting the wire to the brake light switch but if I do this it won't
> start. The brake lights work fine and the hazard lights work so I don't
> think the switch is the problem. Does anybody know what this problem is?
> Glen

Glen Hudgin did pass the time by typing:
> My Cherokee starts fine but as soon as I touch the brake pedal it kills the
> engine. If I keep my foot on the brake pedal it won't start. I tried
> disconnecting the wire to the brake light switch but if I do this it won't
> start. The brake lights work fine and the hazard lights work so I don't
> think the switch is the problem. Does anybody know what this problem is?
> Glen


Without a wiring schematic I can't give you more than suggestions.

First the basics:
Do you have an aftermarket alarm system on your Jeep?

Go through and check every fuse.

Assuming you have an automatic transmission, try starting the Jeep
in Neutral. (possibly the park safety/interlock switch) But that
usually results in a no-start.

<wild guess>
Something in the ignition circuit has lost its ground and is finding
one through the brake lamp system. (actually if something is, the lamps
should glow) When you press the brakes that puts 12v to the lamp and
interferes with the engine operation. Try putting a jumpercable between
the engine block and the frame. If that works then it's your engine
ground strap that has rotted.
</wild guess>


--
-- DougW -- 93 ZJ 4.0 http://members.cox.net/wilsond
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
Banks Header - and BEER, in the fridge!

That should be a dead mesh ground strap from the rear of the engine head
to the firewall.

There is a 99% chance your vehicle is stealing the ground through the
brake pedal and light circuit.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

Glen Hudgin wrote:
>
> My Cherokee starts fine but as soon as I touch the brake pedal it kills the
> engine. If I keep my foot on the brake pedal it won't start. I tried
> disconnecting the wire to the brake light switch but if I do this it won't
> start. The brake lights work fine and the hazard lights work so I don't
> think the switch is the problem. Does anybody know what this problem is?
> Glen

I believe there was a recall on the shift interlock switch not sure why but
you might want to check that you are up to date on recalls.

"Glen Hudgin" > wrote in message
. ..
> My Cherokee starts fine but as soon as I touch the brake pedal it kills
> the
> engine. If I keep my foot on the brake pedal it won't start. I tried
> disconnecting the wire to the brake light switch but if I do this it won't
> start. The brake lights work fine and the hazard lights work so I don't
> think the switch is the problem. Does anybody know what this problem is?
> Glen
>
>

Also see if the bake pedal hits some wiring for the ECM.
When you hit the Brakes, does the tach drop dead instantly like the power
was cut off? If so then I agree with ("ßill")
--
later,
dave AKA vwdoc1
88 XJ 4.0 auto


"L.W. ("ßill") Hughes III" > wrote in message
...
> I could see a short in the brake light circuit sucking so much
> power that your computer wouldn't work, but disconnecting the line to
> that switch, and the engine won't run makes no sense, the line is
> terminated there. I once had a similar problem where is would hit the
> brakes and engine would die, but actually my knee was hitting the column
> where the ignition switch was coming apart. The only thing I could
> suggest is double check every connection, looking for hot spots where a
> couple of wire could have melted together.
> God Bless America, ßill O|||||||O
> http://www.billhughes.com/

Ok seeing as you have new ground straps, (everyone should know this), I
would take a booster cable and run it from the battery negative to the
firewall and see what happens.

If no change, I would then turn on the emergency flashers and see if a)
it starts with them on or b) it dies when they come on or c) they have
no effect.

There is one other place to check for a broken ground as well. Look on
the passenger side of the engine near the back for a bolt with 2 or 3
small black wires coming off it. This is the ground for the computer
harness.

Have you had any wiring issues or melts or bad electrical smells?
Anything like the 4x4 light stuck on or anything else unusual?

Mike

Mike Romain wrote:
>
> That should be a dead mesh ground strap from the rear of the engine head
> to the firewall.
>
> There is a 99% chance your vehicle is stealing the ground through the
> brake pedal and light circuit.
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 88 Cherokee 235 BFG AT's
>
> Glen Hudgin wrote:
> >
> > My Cherokee starts fine but as soon as I touch the brake pedal it kills the
> > engine. If I keep my foot on the brake pedal it won't start. I tried
> > disconnecting the wire to the brake light switch but if I do this it won't
> > start. The brake lights work fine and the hazard lights work so I don't
> > think the switch is the problem. Does anybody know what this problem is?
> > Glen

Problem solved. It was a bad ground wire, apparently for the computer or
control unit.
Thanks for all the input.

"mike92105" > wrote in message
news:XRYXd.58092$%U2.49331@lakeread01...
>I believe there was a recall on the shift interlock switch not sure why but
>you might want to check that you are up to date on recalls.
>
> "Glen Hudgin" > wrote in message
> . ..
>> My Cherokee starts fine but as soon as I touch the brake pedal it kills
>> the
>> engine. If I keep my foot on the brake pedal it won't start. I tried
>> disconnecting the wire to the brake light switch but if I do this it
>> won't
>> start. The brake lights work fine and the hazard lights work so I don't
>> think the switch is the problem. Does anybody know what this problem is?
>> Glen
>>
>>
>
>

Hi Glen,
Thanks for telling us. It's unbelievable how many times it's Mike's
infamous engine ground strap.
God Bless America, ßill O|||||||O
http://www.billhughes.com/

Glen Hudgin wrote:
>
> Problem solved. It was a bad ground wire, apparently for the computer or
> control unit.
> Thanks for all the input.