Ignition cuts out when brake pedal pressed

[goldiloxgirl]

I have searched the archives and can't find a precedent for this problem, so thought I'd ask if we have an exorcist here...or even a few ideas? My p38 had been sitting unused for a few months with the battery disconnected (brand new), but it started ok. After driving it a few miles it developed the usual ghost in the machine symptoms of radio turning itself on and refusing to turn off, gearbox fault, and eventually the instruments and ignition cut out whenever I used any electrical item such as blinker, brake pedal cabin light, headlights etc.

Alright, I know that the P38 loves voltage, and lots of it, so I put the battery on a charger overnight. Next day I could start her up but pressing the brake pedal caused the ignition and instruments to cut out. Other electrical items had no ill effect. By removing the brake switch fuse, I was able to restore normal function and drive home (a little cautiously with my eye on the rear view mirror) without brake lights.

Any ideas guys?

[Keithy P38]

I'd say that your alternator is kaput.

It doesn't explain the problem, but I think it'll go a long way towards fixing it.

Cheers
Keithy

[mtb_gary]

A quick test to see if your voltage is the problem. Try turning on the headlights. If it stops or hiccups I'd be looking potentially at another battery. Then of course there are the multiple earth connections. Definitely worth a check up.

[goldiloxgirl]

Thanks Keith and Gary. The alternator was putting in 13.3 volts when I checked and the ghost in the machine symptoms disappeared after I fully charged the battery. All that remained was the ignition and instruments going dead only when the brake was pressed. No other electrical items including headlights caused a problem, only the brakes. If there was a dead short in the brake light circuit, I would've thought the fuse would blow but perhaps it's only shorting enough to trip a relay? Or maybe there is a ghost inside the BeCM.

But I know one thing...brakes are suppose to stop the car _ not the engine! :confused:

[TheTree]

Hi

I would suspect an earth connection, the one behind the side panel where the bonnet release is.

Also worth checking the under bonnet ones

Steve

[Rupert Prior]

if you are around the area of Bexley or up to Padstow, i can have a quick free look at it (rover electrics is what i do for a living) ring me 0421509083 regards Rupert

[d2dave]

(rover electrics is what i do for a living

You must be a very busy person:twisted:

[Rupert Prior]

not so much now, values are low, parts are expensive, even some sports are beyond economic repair.

[Ghind]

Now that you've fully charged the battery, start the car, turn the rear window heater on, high beam headlights on and heater fan in max. Hold the engine at 2000rpm. What voltage are you getting across the battery then?

Is it ok to post a link to a post I wrote on another Range Rover site about how to diagnose this?

[glenhendry]

Is it ok to post a link to a post I wrote on another Range Rover site about how to diagnose this?

Your electrical sticky has helped so many over the years, I certainly hope it is ok to link to from here...

[daf11e]

That sticky on RRNet is excellent, I also would hope it's ok.

[Ghind]

Range Rover Mark II / P38 (http://www.rangerovers.net/forum/7-range-rover-mark-ii-p38/#/forumsite/20563/topics/28663)

Post your results here and we will help interpret them for you

[goldiloxgirl]

Hi all, just a quick update. I've checked the charging system; Alternator output at 2000 rpm is 14.4 volts no load. Across battery terminals; 14.38 no load and 13.8 with full load. I'm still to attribute the loses to the various leads etc but its only 200 milli volts in total. Battery voltage after load test is 12.59 volts. All in all, it seems ok here.

Rupert has zeroed in on the BeCM and I kinda agree my problem does lie within this mischievous piece of English electronic engineering. He suggested I remove it for inspection...which I am about to do.

Sigh, am I crazy or is this a perfectly good way to spend a lovely winter afternoon? Nope, there is no joy like one receives after successfully mastering a mystery, nor can any other car fill one with such contentment whilst purring through the country. On the other hand, I could be crazy.:confused:;)

Regards,

Lani







Range Rover Mark II / P38 (http://www.rangerovers.net/forum/7-range-rover-mark-ii-p38/#/forumsite/20563/topics/28663)

Post your results here and we will help interpret them for you

[Scouse]

not so much now, values are low, parts are expensive, even some sports are beyond economic repair.You haven't been called in to look at the blinged up P38 sitting at the Metro servo on Bexley Rd ?
I noticed it while filling up & wandered over for a look. On the dash was a few engine wiring schematic pages :D.

[goldiloxgirl]

Okay, the sun's gone done, I've a beer in my hand...and the problem is solved.

[goldiloxgirl]

Okay, the sun's gone done, I've a beer in my hand...and the problem is solved. The trouble lay not so much in the BeCM, but more so on it. Took the seat trim off, removed the seat and started undoing the BeCM. Began undoing one of its earth connections and guess what? It was already loose!

Full kudos to Gary and Steve, you both suggested checking the earths. Thank you. Thank you also to everyone else who offered some insight, it was most appreciated. :)

Regards,

Lani

[Keithy P38]

Great work, I'll join you in celebrating (well, I began earlier than you I do believe).

Awesome!

Cheers
Keithy

[mtb_gary]

Good find goldiloxgirl and a great result. Is still has me stumped how they can come loose after close on 20 years of being untouched.

[Pete38]

Don't you love it when you start expecting the worst and it turns out to be such a little thing. Had a few of those, not that I am paranoid about the P38 ha ha

[mtb_gary]

Don't you love it when you start expecting the worst and it turns out to be such a little thing. Had a few of those, not that I am paranoid about the P38 ha ha

Peter, I think the paranoia is a pre requisite to p38 ownership. In reality they are a pretty solid car when maintained correctly.