Main beam kills engine.

[Nick Heppinstall]

Hi guys. Just got in after episode you can read about in general gassing if interested. Anyway. Flick lights onto mainbeam and engine stops. Cool way to turn engine off but not what I really want ! Any ideas ?

[wedg1e]

Do the lamps actually light? If not, one of them may have a short that is pulling down the +12v rail and killing the sparks. Alternatively (pun intended) the battery has seen better days, and the alternator is struggling to cope with the demand of your 400W lamps - the RV8 has no idle speed compensation so the drag of the alternator stalls the engine.

Ian

[nick heppinstall]

wedg1e said: Do the lamps actually light? If not, one of them may have a short that is pulling down the +12v rail and killing the sparks. Alternatively (pun intended) the battery has seen better days, and the alternator is struggling to cope with the demand of your 400W lamps - the RV8 has no idle speed compensation so the drag of the alternator stalls the engine.

Ian

Hi Ian. Yeah both lights work ok on dip and the battery's a big Varta thats only a yeard old. I also keep it topped up. It's strange that after I lost all power there was nothing for a few mins then suddenly everything came back on. Could this be a relay overheating ? Could there be a dead short somewhere in the mainbeam circuit ?

[andymadmak]

What does your battery guage show when you put main beam on? If it drops straight to red it might be a big short. Otherwise, my moneys on a bad main connection to the fuse box that makes it unable to cope with the extra load from the MB lights

Andy 400se

[nick heppinstall]

andymadmak said: What does your battery guage show when you put main beam on? If it drops straight to red it might be a big short. Otherwise, my moneys on a bad main connection to the fuse box that makes it unable to cope with the extra load from the MB lights

Andy 400se

Morning Andy. When I put main beam on evreything dies. Just like I pulled the battery terminal off !

[2 sheds]

Hold the revs at around 1500 rpm and turn the lights on, to see what happens, it could just need fuelling / idle adjustments, if for example running too rich can reduce engine torque at idle by 50%, then the reduced spark can upset the idle or as you've found kill the engine.
Tim

>> Edited by 2 sheds on Friday 16th May 11:13

[andymadmak]

Morning Nick!
If the battery is good then total electrical death can only be a bad connection, a bad relay or a massive short.
If it was down to poor sparks etc the engine death would still leave other lights on etc, even if only dimly. Are your battery terminals tight and free from corrosion? I did once have a situation where corrosion had built up under the battery terminals. they looked fine from above but when I took them off they were cacked up and were breaking the contact under load.
If not there, then something must be interrupting the flow from the battery/alternator when the extra load kicks in of the full beam.
Suggest you trace everything through and tighten/clean etc.
Cheers
Andy 400se

[danny hoffman]

It might be worth checking the thick earth wire that goes to the ECU

[G-Man]

Had the same problem on my 89 350 - whack the beams on and the car almost falls over itself trying to stall.

Couldn't find the problem, though it went away on its own. I let you know if it re-occurs again.

Right now it with Dave Batty's having a service & MOT.

[andymadmak]

Have you sorted it yet Nick? You'll want to be back on the road for when it stops raining!!

Andy 400se

[nick heppinstall]

Andy. Would you believe it ! ( bet you would !! ) It's fine now. Not done owt !! Going to do all the earths and connections this week like you suggested. Been about a year since I did them last. Just ordered my new Manifolds from Mr Thorpe. Should be here in a week or so. Went for the mild steel.

[andymadmak]

Ahhh! The "onlyhappensattheworstpossiblemomentandisotherwiseunrepeatableinallothersituations" type fault.

Aren't they just the BEST type!

Andy 400se

[danny hoffman]

Don't you love TVRs - self fixing! If you leave the problem long enough it is bound to go away eventually.

Well sometimes......

[wedg1e]

In that case, could be water in the headlamp connectors. Water is quite a good conductor of electricity: my cousin had a Fiat that used to blow fuses 'cos the condensation on the inside of the tailgate used to short-circuit the demister (itself already a very low resistance!).

Worth some silicone grease in the connectors methinks.

Ian