84 350i wiring diagram
Discussion
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
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
Hi Mark, welcome.
You might want to get the "Wedge Bible" it's got some diagrams in there.
Overfuelling quite often is caused by a faulty Coolant Temperature Sensor (CTS) they are only around 12 quid and easy to change. Probably best to start with that.
I'll have a look for some diagrams online.
This one looks right vintage but poor quality (possibly faxed):
https://ww2-secure.justanswer.com/uploads/350matt/...
Looks like I posted some back in the day but directupload deleted them! I'll have another look...
In the mean time try this thread and the ones leading off it:
https://www.pistonheads.com/gassing/topic.asp?h=0&...
You might want to get the "Wedge Bible" it's got some diagrams in there.
Overfuelling quite often is caused by a faulty Coolant Temperature Sensor (CTS) they are only around 12 quid and easy to change. Probably best to start with that.
I'll have a look for some diagrams online.
This one looks right vintage but poor quality (possibly faxed):
https://ww2-secure.justanswer.com/uploads/350matt/...
Looks like I posted some back in the day but directupload deleted them! I'll have another look...
In the mean time try this thread and the ones leading off it:
https://www.pistonheads.com/gassing/topic.asp?h=0&...
Edited by adam quantrill on Wednesday 31st March 17:31
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:-
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:-
Nice - yeah no "heated rear screen" there! Most likely for an addition. Does it have a big stereo installation?
OK CTS done (though these can also fail early so do double-check it with a meter).
Also worth checking the wiring to the CTS from the ECU multiplug as this can give similar symptoms. Use a meter on the ECU multiplug to check CTS resistance again. Wiggle the wiring too in case the connection is loose.
unlikely the idle screw will cause your problem as you can defeat this by putting your foot on the pedal.
I have mine set for 800 rpm normally, and 950 for the MoT...
Next up is to check the throttle butterfly opening and also the throttle pot voltage swing.
So I guess you need to follow the diagnostics in the http://www.vintagemodelairplane.com/ website next, and work your way through.
OK CTS done (though these can also fail early so do double-check it with a meter).
Also worth checking the wiring to the CTS from the ECU multiplug as this can give similar symptoms. Use a meter on the ECU multiplug to check CTS resistance again. Wiggle the wiring too in case the connection is loose.
unlikely the idle screw will cause your problem as you can defeat this by putting your foot on the pedal.
I have mine set for 800 rpm normally, and 950 for the MoT...
Next up is to check the throttle butterfly opening and also the throttle pot voltage swing.
So I guess you need to follow the diagnostics in the http://www.vintagemodelairplane.com/ website next, and work your way through.
Something in the back of my mind is telling me that a junior timer plug will fit
https://www.autoelectricsupplies.co.uk/product/680...
https://www.autoelectricsupplies.co.uk/product/680...
Edited by Penelope Stopit on Thursday 1st April 22:04
30A fuse is a high current circuit. If that fuse has blown then it should be very obvious which bits of the car aren't working, without the need for a wiring diagram. High current is often things like headlamps, cigarette lighter, blower motor or heated rear window (if fitted). And always be suspicious of any aftermarket accessories that have been fitted. (Electric radiator fan?) Fundamentally if you're getting a spark and can also see voltage at the fuel pump and fuel injection you know they're not affected.
You mentioned 9v when cranking. That's not a lot of voltage. How old's the battery and what's its condition? I'd get it down to a battery specialist and have it checked. https://www.trawlerforum.com/forums/s4/acceptable-...
Just because a battery can turn the starter (which relies mainly on current, not voltage) doesn't necessarily mean it's able to deliver enough voltage during cranking to run the rest of the car's electronics. This is usually a problem on more modern cars with fancy computers but it's possible EFi or electronic ignition could be affected.
You mentioned 9v when cranking. That's not a lot of voltage. How old's the battery and what's its condition? I'd get it down to a battery specialist and have it checked. https://www.trawlerforum.com/forums/s4/acceptable-...
Just because a battery can turn the starter (which relies mainly on current, not voltage) doesn't necessarily mean it's able to deliver enough voltage during cranking to run the rest of the car's electronics. This is usually a problem on more modern cars with fancy computers but it's possible EFi or electronic ignition could be affected.
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....
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....
Does sound like classic CTS symptoms it is worth removing it and trying it at different temperatures with an ohmmeter, just in case before sending off the ECU.
I had one that failed open circuit during warm-up, but hot is was OK. So it was overfuel badly when warming up.
I would recommend putting it in a mug/glass of boiling water and taking readings, then tip in a little cold, and repeat.
You should get a gradual curve from low resistance back to high. If there's a sudden jump to high/infinite in the middle, that's your problem, get (yet) another CTS.
But the ECU can also give rise to these symptoms with dry solder joints inside, so if under warranty yes send it back and tell them what you've already checked.
I had one that failed open circuit during warm-up, but hot is was OK. So it was overfuel badly when warming up.
I would recommend putting it in a mug/glass of boiling water and taking readings, then tip in a little cold, and repeat.
You should get a gradual curve from low resistance back to high. If there's a sudden jump to high/infinite in the middle, that's your problem, get (yet) another CTS.
But the ECU can also give rise to these symptoms with dry solder joints inside, so if under warranty yes send it back and tell them what you've already checked.
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