Strange starting problem..

[LadVR 0]

Been scratching my head with this one....hope someone on here can help, I found a few threads in the search with similar problems but they turned out to be alarm/immobilser which I havent got.

Im running a late OBD2 aaa in my mk2 road/track toy which up until now has been fine until about a week a go. It has no immobs/alarms/transponder as i've got the United Motorsports transponder bypass reprogram.

Basically it will start with the first turn of the key, run and drives fine, if I turn it off again it wont start. It fires up for a second then dies. However, if I disconnect the battery for a few seconds, reconnect, then it will start fine again. Hot or cold engine makes no difference.

I have done the ususal, checked all earths, connections, fusebox, tried bypassing various parts of the loom, getting voltages etc... Havnt been able to get it on a laptop as mine has packed up..

When it does run im getting a healthy charge from the alternator and the battery is the 3rd brand new one i've tried of known working cars.

I can use a battery cut-off switch but this is curing the sympton rather than the problem, also wouldnt want to be half way across a busy road and stall!

Any suggestions would be most appreciated!

LadVR

[russj249 2]

When you say its runs for a second then cuts out.. do you mean exactly 1 second or as a rough term? Also in this second, will the car rev up if started with throttle on, but still cut out?

[LadVR 0]

It wil run for roughly around a second, sometimes 2. You can open the throttle and the car will rev briefly but only for the duration of that second before cutting out. It will continue to do this however many times you do this until you disconnect the battery for a couple of seconds and then it will start fine!?!?!

[russj249 2]

Ok.. i have to say it does sound exactly like immobiliser.. ideally there's a couple of things you could do. I know you say its broke, but really need to get the car on VCDS.. click on 'immobiliser' then into measuring blocks. On there press the 'up' button, and it says if transponder is recognised. Now in theory it should say yes, but turn the engine off so it plays up and try it again. See what the results show and if it is the immobilized kicking in.

Also I'm not sure how the United Motorsport immob delete works, but I am just thinking if the ecu needs to power down when the car is turned off, so it resets when the car is started again, so what I'm thinking is that maybe the ignition switch isn't allowing the ecu to power down so not resetting it.. obviously taking the battery off will then reset it so it starts up again after that.

You noticed anything weird about the ignition switch or radio staying on or anything? And how does the switch feel? I might be completely wrong, but just a thought.

Without a doubt I'm get in contact with United Motorsports, they're always on here so can either wait cor them to reply or drop them a PM.

[LadVR 0]

Yes it does sound just like the immob, I had this problem last year so had it decoded and binned the transponder.

The ignition switch feels ok, and works as it should, as does (whats left) of the electrical items - wipers, lights, horn, engine fans, I havent a radio, its an empty shell with 2 seats and a cage...oh and a boat anchor! I'll have another look tommorow at that..

Interesting point about the ecu maybe needing to shut down, would make sense...

Thanks for the advise, i'll get my laptop up and running again (they dont bounce too well!!)

[LadVR 0]

Well sent the ECU off to United Motorsport, looks like a voltage spike had erased some memory. All sorted now, starts everytime (It did till I took the engine out yesterday!!)

Big thanks to United Motorsports for fixing it and the quick turn around!