84 350i wiring diagram

[Markymark21]

Hi All,
I’ve just bought an early TVR 350i. I bought it as a non runner and finally got an mot today. The last problem was the EFI ECU which fixed chronic overfuelling. Problem is that after less than one day of good running it has failed to start this afternoon. Welcome to the world of TVRs!

I have a spark and I have a smell of fuel. The fuel pump is new and is getting 9v when cranking. When I look at the fuse box I have a melted 30A fuse. I’ve replaced it but unsure of good contact as the fuse box itself has melted around that fuse. Not sure if this is related, but wanted to understand which fuse is which. I have looked for wiring diagrams on search but links are broken. Can anyone help?

Thanks,
Mark

[Markymark21]

Hi Adam,
The CTS is new as it was replaced before the ecu repair.
I found an image online and fuse ratings seem the same with exception of the melted fuse - heated rear screen



So seems to not be related to the non starting.

[Markymark21]

Hi Adam,
The car was running well but idle was too high. I adjusted the idle screw on the plenum (turned anti clockwise) to lower rpm then switched the engine off. When I went to restart the car it fired and died. Then it wouldn’t fire again. Could the idle adjustment have something to do with it?

Btw this is the car:-

[Markymark21]

Adam - thanks a million. I’ll work through it....

[Markymark21]

Hi All,
The plug for the CTS came away in my hands. One of the internal connectors is broken too. Does anyone know where I can purchase a replacement?
Thanks,
Mark

[Markymark21]

Thanks both.
I went to a local garage yesterday and managed to get a connector like shown in the pick/link. Unfortunately the CTS is very close to a pipe and the larger locking mechanism meant it won’t go on.
If you do have a scrap loom and can help, I’d appreciate it!

[Markymark21]

Brilliant Penelope. I have ordered a new connector.

As an update, the TVR is still not running. I plan to return the previously repaired ECU under warranty for testing as I think that is where the fault lies.
Observations are:-

Cold start injector disconnected.
CTS feed to ECU tested and continuity is good.
CTS ground wire is getting a good earth.
CTS is bridged to simulate a hot engine. This means terminal 13 on ECU is direct to earth.
Flapper observed to be smooth moving - not difinitive in any way but gives some confidence
Throttle pot tested and good (per vintage model airplane)
Fuel pump and regulator are new. Previous owner tells me fuel pressure is within tolerance.

If I put clean plugs into a cold engine with this configuration it fires up and idles no problem. As it warms up there is black/grey smoke starting to come from exhaust and idle speed drops. After 1-2 mins the engine stops altogether and won’t restart. Plugs are black and stinking of fuel.

To me the ECU is overfuelling again. I had the same observations before and an ECU repair fixed it but not for long it seems....

[Markymark21]

Hi All,
I am in Bromley, so I guess Essex is doable at a push. Thanks for the offer. Where abouts in Essex?

Hi Adam,
I have measured the CTS several times and appears good. I have also bridged it out to remove it from the picture and it still overfuels. I’m convinced the CTS and wiring is ok.

Thanks!
Mark

[Markymark21]

Hi Adam,
I’m going to come back to the 30A fuse. No evidence of PAS but has some cooling fans fitted with override switch. My investigation will start there.

Hi Bluewedgy,
Seems you’ve had fun too. The earths looked sound but I still took them off, cleaned them and put back. I don’t think that’s a source of the problem. The AFM hose is old looking and I plan to replace, but doesn’t have any obvious holes or leaks. I’ve not looked at the injectors but I’m getting the same on all cylinders from inspection of the plugs so I’m not thinking the problem lies there....

Regarding the kind offer to borrow an ECU, I’m going to see what the repair shop say when I contact them tomorrow. They’re only in Greenwich so maybe I can go there and get them to look at it. If they don’t play ball, I may be back in touch.

Thanks all for your help....Mark

[Markymark21]

Hi All,
I just wanted to let you know that it was the ECU that caused the problem. I now have a running TVR.

I’ve started investigating the electric fans that are fitted. There are two of them behind the rad (between engine and radiator). Label on one says Smiths Industries. Could these have been an original fitment? They are old, but seem to work. Only trouble is that when they are running the idle speed drops a lot. If I set the idle where I want (900rpm) the car stalls. Hmmm....

Thanks,
Mark

[Markymark21]

Thanks. I’ve managed to download this one...

[Markymark21]

Another question - sorry - at the fuel pump with the engine running I have 12.8v. At the battery I have 14v. Is a voltage like that to be expected or could I have a dirty connection somewhere? Thanks...

[Markymark21]

Hi Adam,
I will check that. It looked to me that the earths typically come out of the loom. I’m guessing the chassis is grounded to the battery negative. Where would I find that earth point out of interest?
Thanks
Mark

[Markymark21]

Hi All,
I had a good look without getting the car on a lift and cannot see the earth to the chassis from the engine. I found an earthing point on the near side chassis suspension upright that has an earth connection into the loom (lots of black wires) and to the AFM. I fitted another earthstrap from that point to a bolt on the water pump as I figured it wouldn’t do any harm.
Having done that the car seems happier. It doesn’t stall when the fans cut in now, so I guess it’s made a difference.
Next thing is to get the car out and do some miles to shake it down.
Thank you all for your help to get to this point....

Mark

[Markymark21]

Thanks. I have an earth to the bonnet catch. Will look further. I need to get under the car again soon so will look for earths there too.