Not starting...
Discussion
Oh dear - I have a(nother) problem!
A bit of background...
Decided to go for a spin a week ago - fired the car up but was running very, very rough - car shaking all over the place. I had to hold the revs a bit higher in order to stop it from cutting out. After a few mins of doing this on the drive it settled down a bit, but was still rough.
I then drove it away, it was hesitant and rough but not cutting out with no throttle anymore. After it reached temperature, it ran fine and as normal, and continued to do so for the rest of the journey.
Fast forward to today, just gone to start the car and had the same issue - very, very rough running. So I hold the revs for a bit again to see if I can get it to stabilise, but it cuts out.
Open up the bonnet, the offside exhaust manifold is very hot, but the nearside is stone cold - looks like it's only firing on the offside bank, which would explain the shaking car!
Try and fire it up again but it's now just cranking and not catching. I've just removed one plug on the nearside and it was very black and damp. I've left it out for the time being.
So what are my steps for fault finding on this one?
A bit of background...
Decided to go for a spin a week ago - fired the car up but was running very, very rough - car shaking all over the place. I had to hold the revs a bit higher in order to stop it from cutting out. After a few mins of doing this on the drive it settled down a bit, but was still rough.
I then drove it away, it was hesitant and rough but not cutting out with no throttle anymore. After it reached temperature, it ran fine and as normal, and continued to do so for the rest of the journey.
Fast forward to today, just gone to start the car and had the same issue - very, very rough running. So I hold the revs for a bit again to see if I can get it to stabilise, but it cuts out.
Open up the bonnet, the offside exhaust manifold is very hot, but the nearside is stone cold - looks like it's only firing on the offside bank, which would explain the shaking car!
Try and fire it up again but it's now just cranking and not catching. I've just removed one plug on the nearside and it was very black and damp. I've left it out for the time being.
So what are my steps for fault finding on this one?
I will give your post a bump, because someone will know what the issue is even though I don’t. I even went out in the dark last night with my torch to check the plug numbers attached to each of my coil packs, only to find that wasn’t the answer.
Just to check - was the nearside exhaust manifold utterly stone cold, or just not very warm?
I am guessing your issue has been getting worse for some time. One thing I had major issues with until 12 months ago was my plug extenders. My kindly TVR guy thought mine looked scruffy at a regular service in March 2016, so fitted a new set. Unfortunately even though they were sourced from an unimpeachable source, they were bin-fodder, and six failed over the next 4 months.
Can I suggest you remove all the nearside extenders, reattach the leads making sure they aren’t touching the engine, and try starting it again?
Just to check - was the nearside exhaust manifold utterly stone cold, or just not very warm?
I am guessing your issue has been getting worse for some time. One thing I had major issues with until 12 months ago was my plug extenders. My kindly TVR guy thought mine looked scruffy at a regular service in March 2016, so fitted a new set. Unfortunately even though they were sourced from an unimpeachable source, they were bin-fodder, and six failed over the next 4 months.
Can I suggest you remove all the nearside extenders, reattach the leads making sure they aren’t touching the engine, and try starting it again?
The positive supply to the nearside bank of injectors, the signal cable from the ECU to the nearside bank of injectors or the ECU are very likely going to be the cause of the problem
Due to you finding a wet spark plug in the nearside bank this points to the injectors are opening and letting fuel in, there is a possibility that the fuel that is getting in is not enough or that the fuel getting in is doing so when it should't be, it would have been good to know if all the nearside plugs were wet
if all the plugs in the nearside bank are wet, there is a very good chance that the signal wire from the ECU to the nearside bank injectors is shorting to earth and keeping the injectors open***or***there is a problem with the wiring to those injectors and not enough fuel is getting in and that problem could be at the supply or signal cables
On the other hand, if the plugs are hardly wet at all, you should be looking for open circuit wiring rather than a short to earth
All the above can be checked once you have proven that the nearside bank of spark plugs are working ok as mentioned above about HT leads....
Due to you finding a wet spark plug in the nearside bank this points to the injectors are opening and letting fuel in, there is a possibility that the fuel that is getting in is not enough or that the fuel getting in is doing so when it should't be, it would have been good to know if all the nearside plugs were wet
if all the plugs in the nearside bank are wet, there is a very good chance that the signal wire from the ECU to the nearside bank injectors is shorting to earth and keeping the injectors open***or***there is a problem with the wiring to those injectors and not enough fuel is getting in and that problem could be at the supply or signal cables
On the other hand, if the plugs are hardly wet at all, you should be looking for open circuit wiring rather than a short to earth
All the above can be checked once you have proven that the nearside bank of spark plugs are working ok as mentioned above about HT leads....
If you have a multimeter, disconnect the injectors. With the meter connected to a harness plug, crank the engine. You should get a battery voltage on and off. Compare with the other side.
If you don't have a multimeter or voltmeter you can use a type 501 car bulb. Available at any garage.
Unravel the wires of the bulb and simply insert them into the wiring harness plug. Crank the engine and if you have a signal the bulb will flash. Bear in mind there are 8 cylinders so there will be a delay between the flashes. This will confirm if you are getting a signal to the injectors.
If you do not on one side - check all 4 on each bank - then connect the multimeter to the positive on the harness plug and the other to the engine block. If you now get a signal then the earth wire to/from the ECU is broken.
If you still do not get a signal (12 volts) on one bank then check the connector at the ECU.
Another possibility is the coolant temperature sensor. If it fails the ECU will think the temperature is -20c or colder and so the ECU will over-fuel. If one or more plugs catch and fire the heat from the adjacent cylinders will help to overcome the over-fuelling and so why you may be getting one side to run. Once the engine is running, the heat and higher revs will overcome the excess fuel. Result is black plugs which you need to clean before refitting and after finding the fault.
If you don't have a multimeter or voltmeter you can use a type 501 car bulb. Available at any garage.
Unravel the wires of the bulb and simply insert them into the wiring harness plug. Crank the engine and if you have a signal the bulb will flash. Bear in mind there are 8 cylinders so there will be a delay between the flashes. This will confirm if you are getting a signal to the injectors.
If you do not on one side - check all 4 on each bank - then connect the multimeter to the positive on the harness plug and the other to the engine block. If you now get a signal then the earth wire to/from the ECU is broken.
If you still do not get a signal (12 volts) on one bank then check the connector at the ECU.
Another possibility is the coolant temperature sensor. If it fails the ECU will think the temperature is -20c or colder and so the ECU will over-fuel. If one or more plugs catch and fire the heat from the adjacent cylinders will help to overcome the over-fuelling and so why you may be getting one side to run. Once the engine is running, the heat and higher revs will overcome the excess fuel. Result is black plugs which you need to clean before refitting and after finding the fault.
Edited by N7GTX on Sunday 14th January 14:00
Many thanks for all your replies.
A bit of an update...first thing this morning I removed all the plugs, which were wet and black. I cleaned them up and put them back in.
I checked the dizzy, rotor arm, HT leads and ignition coil connections for security. I then also reset the ECU by disconnecting the battery.
I'd already removed the plug extenders last year.
After fitting everything back together I figured I'd try firing it up, and...it fired up straight away. Slightly rough for a few seconds but was then fine. I took it out for a good drive to blow out the cobwebs, and it didn't miss a beat.
So I'm not actually sure what the problem was/is...I'd like to get to the bottom of it since it may still be present and come back to bite me again.
I suspect it may be something to do with the ECU or a connection as suggested, so I will probably investigate this avenue first.
Thanks again!
A bit of an update...first thing this morning I removed all the plugs, which were wet and black. I cleaned them up and put them back in.
I checked the dizzy, rotor arm, HT leads and ignition coil connections for security. I then also reset the ECU by disconnecting the battery.
I'd already removed the plug extenders last year.
After fitting everything back together I figured I'd try firing it up, and...it fired up straight away. Slightly rough for a few seconds but was then fine. I took it out for a good drive to blow out the cobwebs, and it didn't miss a beat.
So I'm not actually sure what the problem was/is...I'd like to get to the bottom of it since it may still be present and come back to bite me again.
I suspect it may be something to do with the ECU or a connection as suggested, so I will probably investigate this avenue first.
Thanks again!
GR_TVR said:
Many thanks for all your replies.
A bit of an update...first thing this morning I removed all the plugs, which were wet and black. I cleaned them up and put them back in.
I checked the dizzy, rotor arm, HT leads and ignition coil connections for security. I then also reset the ECU by disconnecting the battery.
I'd already removed the plug extenders last year.
After fitting everything back together I figured I'd try firing it up, and...it fired up straight away. Slightly rough for a few seconds but was then fine. I took it out for a good drive to blow out the cobwebs, and it didn't miss a beat.
So I'm not actually sure what the problem was/is...I'd like to get to the bottom of it since it may still be present and come back to bite me again.
I suspect it may be something to do with the ECU or a connection as suggested, so I will probably investigate this avenue first.
Thanks again!
There is always the possibility that you have disturbed the short circuit or bad connectionA bit of an update...first thing this morning I removed all the plugs, which were wet and black. I cleaned them up and put them back in.
I checked the dizzy, rotor arm, HT leads and ignition coil connections for security. I then also reset the ECU by disconnecting the battery.
I'd already removed the plug extenders last year.
After fitting everything back together I figured I'd try firing it up, and...it fired up straight away. Slightly rough for a few seconds but was then fine. I took it out for a good drive to blow out the cobwebs, and it didn't miss a beat.
So I'm not actually sure what the problem was/is...I'd like to get to the bottom of it since it may still be present and come back to bite me again.
I suspect it may be something to do with the ECU or a connection as suggested, so I will probably investigate this avenue first.
Thanks again!
I would like to investigate my injector circuit and wonder if someone could just explain the circuit as i feel that i may sometimes also loose the nearside bank of cylinders.
Is it just a pulsed 12v from the ECU for each bank, ie 2 pulsed outputs and then downto earth on the other side of the injector?
Is the feed for this to the ECU common to both sides?
Any pin numbers or colour codes for a 95 500 would be greatly appreciated.
Is it just a pulsed 12v from the ECU for each bank, ie 2 pulsed outputs and then downto earth on the other side of the injector?
Is the feed for this to the ECU common to both sides?
Any pin numbers or colour codes for a 95 500 would be greatly appreciated.
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