Electrical trouble? 1992 2.9 V6

[SteveOS3]

Driving yesterday afternoon I noticed a brief loss of power when I went over some pretty rough surfaces. About ten mins later, on a very smooth bit of new tarmac, all power was lost. I coasted into a side road and tried to restart but nothing happened. While cooling down I checked for obvious loose connections under the bonnet and in the footwellbut none found.

When the AA fellow arrived we checked the fuel pump and coil, both fine but the ECU didn't appear to be 'switching the coil'.

This morning I disconnected the multiplugs on the distributor, ISCV and throttle pot, sprayed with contact cleaner and refitted. Also disconnected the ECU and sprayed there too. Still not starting.

I saw a couple of older threads mention an 8k resistor bestwwen the ECU and coil but I can't see one and the wiring diagram only shows the could connected to the distributor(green) and tacho(white/yellow).

Any advice on what I can check or re-check would be gratefully received.

Thanks,

Steve

[phillpot]

Wasn't there a similar post quite recently, turned out to be a badly soldered spliced connection taped up "somewhere" in the loom?



Do you have an alarm/immobilizer, could that be playing up?



Or the "old favourite", the big yellow connector?


[i] New Search is rubbish! "TVR S Series yellow connector" should bring up loads, it's bringing up bugger all of an relevance

[AndrewS2]

Agree with the new search comment, it's hopeless! To use 'old search', just go to normal google and type in that you're searching for followed by site:www.pistonheads.com

e.g.

"the bloody yellow connector on a TVR S Series site:www.pistonheads.com"

Andrew

[TVRees]

Check that you have a HT voltage at the spark plugs to check the function of coil/dist. Also, check the voltages of ALL of the various sensors which input to the ECU.
Details can be found in the Steve Heath manual/book, where there is also a troubleshooting checklist on "when engine does not start".

"When the AA fellow arrived we checked the fuel pump and coil, both fine" - do you hear the fuel pump priming when you switch on the ignition ?

[Marc C]

this is going to sound daft, but are you sure there's fuel in the tank

[SteveOS3]

Fuel tank is half full. Fuel pressure good when AA tested it.

Just spent an hour poring over it and the situation at the moment is that the coil is not generating a supply down the HT lead to the distributor. Spun the engine and no spark when we tried to earth it.

Tried a different coil, no different.

Disconnected, cleaned and reconnected the multi-plug to the distributor, no different.

Disconnected, cleaned and reconnected all multi-plugs in the footwell and the ecu, no different.

Fuses all ok.

Lights, horn, fan all ok.

Dropped the steering column shroud but couldn't see a melted yellow connector anywhere.....

Gin and tonic and a good read of the Steve Heath troubleshooting guide coming up.

Thanks for the help so far.

Steve

[TVRees]

Remember what

phillpot said:

Do you have an alarm/immobilizer, could that be playing up?

You didn't specifically mention that you'd checked this. The immobiliser can also be set up to intercept the low-voltage ignition circuit, and if your immobiliser is not OK, the engine will not start.

[SteveOS3]

There is an immobiliser. Not sure how to check it fully but the rev counter and speedo both sit around 4-o'clock then rotate to zero when the immobiliser key is inserted. The engine won't turn until this has been done.

[SteveOS3]

Re: Tacho' connections and no power to the coil.

Does anyone have a picture of the back of the tacho or can say which way round they are?

Thanks,

Steve

[Marc C]

Back of my Tacho (S3C) not much to see...



White/Yellow wire comes from coil, into this connector behind dash (at least it would if I had a dash) and connects to the white on the rev counter

[SteveOS3]

Thanks for the photo, it's a great help to visualise things when you're upside down in the footwell...

Steve

[Marc C]

the 2 holes in the back are where the asthmatic glow worms live in their futile attempt to provide illumination

[TVRees]

SteveOS3 said:

Does anyone have a picture of the back of the tacho or can say which way round they are?

I found these on the www a while back, looks like the original site tvrs3.net has now disappeared though
1.

2.

--
In addition to the photos there is a useful schematic.

[SteveOS3]

Superb schematic, many thanks.

Before the immobiliser key is used the speedo is at 40mph and the tacho at about 2000rpm. Both reset to zero when the key is used.

Last night I noticed that the tacho needle is in the zero position before and after the immobiliser key is used.

Not sure if this means the immobiliser is faulty or that there is no feed to the tacho. There is definitely no power form the tacho to the coil.

Steve

[shaun s3c]

Just a thought have you a live to the coil when ignition switch is on if not check ignition fuse which runs speedo as we'llThe problem I had was the speedo cable had dropped down on top of exhaust box melting it and causing a short blowing the fuse,no ignition live!

[SteveOS3]

Thanks for the help and tips gents. Had to leave it for a week but finally got to the bottom of it.

The heater blower/fuel injection fuse was blown. Only found it when I decided to right back to basics and check every fuse. Looking at the wiring diagram in the Steve Heath book I don't think it should be part of the supply to the coil but who knows..... just glad to have it back up and running.

Thanks again,
Steve