Griffith V8 ECU Fault.
Discussion
I have a fault with mt 1996 Griifith 5L. Would turn over but not start and no fuel pump running.
I thought I had tracked this to the Fuel pump relay but now I am not so sure.
I was able to start the car but direct wiring the fuel pump to run. It did take a few tries to get it started.
I changed the relay but the car would not run still. I changed it for one with the diode reverse accross the coil rather than in line with it. (All that was available locally) The car still would not run.
I put my fuel pump bypass wire back on and the car would run again but after a couple of minutes the ECU began to smoke.
So inside the ECU R49 has been very hot although it seems OK when tested with a meter. Obviously there are other components around it that have got hot too but I am unable to test without identifying them (eg transistor T6, Zenner diode Z25)
Two questions:
Could using the wrong relay have damaged the ECU? That was my first idea but I can't see why it would. The diode is backwards accross the coil so it only acts to stop transient voltage from switching off the coil.
Is it likely that the ECU was the original fault or is there something else I should be looking for?
I thought I had tracked this to the Fuel pump relay but now I am not so sure.
I was able to start the car but direct wiring the fuel pump to run. It did take a few tries to get it started.
I changed the relay but the car would not run still. I changed it for one with the diode reverse accross the coil rather than in line with it. (All that was available locally) The car still would not run.
I put my fuel pump bypass wire back on and the car would run again but after a couple of minutes the ECU began to smoke.
So inside the ECU R49 has been very hot although it seems OK when tested with a meter. Obviously there are other components around it that have got hot too but I am unable to test without identifying them (eg transistor T6, Zenner diode Z25)
Two questions:
Could using the wrong relay have damaged the ECU? That was my first idea but I can't see why it would. The diode is backwards accross the coil so it only acts to stop transient voltage from switching off the coil.
Is it likely that the ECU was the original fault or is there something else I should be looking for?
There are relays with different pin positions. So using the wrong one could damage the ecu. Although the fact there was smoke coming from the ecu...does clearly suggest something went badly wrong !!!
It would have made more sense to actually test the operation of the relay instead of trying to bypass or use a different one.
Its impossible to say what the original fault was...and with the damage now seems to be done, its going to be hard to carry out any diagnosis.
It would have made more sense to actually test the operation of the relay instead of trying to bypass or use a different one.
Its impossible to say what the original fault was...and with the damage now seems to be done, its going to be hard to carry out any diagnosis.
If the smoke has escaped from your ECU then the best bet is to get it tested/repaired before you go any further.
I have used http://www.carelect.demon.co.uk/ in the past for my ECU repair and was very pleased with both the results and the service. I posted my ECU to them and had it back fixed in 1.5 days.
They will also make some changes to the ECU while they have it and if it is anything like mine the car was much more responsive when back on the road.
Steve
I have used http://www.carelect.demon.co.uk/ in the past for my ECU repair and was very pleased with both the results and the service. I posted my ECU to them and had it back fixed in 1.5 days.
They will also make some changes to the ECU while they have it and if it is anything like mine the car was much more responsive when back on the road.
Steve
I have been working on this today.
Firstly a bit of good luck, I was able to source from a local independant Land Rover guy a brand new sealed in the box Lucas ECU. Not only that it has all the very same part numbers as the original. And at a BARGAIN price !!
I have re-tested the fuel pump relay that I removed and yes it is faulty. There is some mechanical missalignment in the spring copper hinge that stops the contacts closing together. The coil brings it in about 1/2 way. So I am now confident of my original diagnosis. Just for the record the resistance accross pins 86-85 is ~2Mohm one way and 'OL' the other (due to the diode)When tested with the diode function of a meter it gives 'OL' one way and 0.6V the correct way. (so the diode is a-ok) From inside the casing the coil resistance is 63 ohm. The coil operates at around 200mA.
Now I tested the replacement. This has the same PIN configuration but the diode is reversed accross the coil to kill the back EMF when the coil is switched off (instead of in series which blocks it) It is a HELLA 4RA 940010-67. Bought new yesterday from a motor factor in Ireland.
Resistance across coil 0.0 Ohm both ways. Diode test shows 0V accross. On my bench power supply I can give it a full (current limited) 1 Amp without any sign of movement in the coil. Prediction - the diode is faulty @ short circuit. Now I cant test this independent from the coil without deconstructing the relay; and I don't want to do that because I am going to be laying into Hella next week
So progress with the old ECU. I have desoldered the resistor on the output to the fuel pump relay (via ECU pin 16). Below it are 5 PCB tracks. One from the resistor itself and four tiny ones passing innocently by!! The board is well charred. And we all know from school that carbon conducts electricity. I tested the resistance across the charred board and got ~400kOhm. Maybe enough to send some spurious signal?? So I have cut away the tracks and cleaned off the carbon/ash.
Next plan - wake up in the morning with a very steady hand and a roll of fuse wire to repair the tracks.I have a new resistor, this time a 7 Watt rather than the ??2W?? original and its a 15 Ohm rather than 13 but I reckon it will be ok. If I don't get to it tomorrow I might go to RS for the correct replacement.
Whether any other component has been fried will remain to be seen. But still I have my new ECU and I have to hope the EPROM is good.
Photos to follow!
Firstly a bit of good luck, I was able to source from a local independant Land Rover guy a brand new sealed in the box Lucas ECU. Not only that it has all the very same part numbers as the original. And at a BARGAIN price !!
I have re-tested the fuel pump relay that I removed and yes it is faulty. There is some mechanical missalignment in the spring copper hinge that stops the contacts closing together. The coil brings it in about 1/2 way. So I am now confident of my original diagnosis. Just for the record the resistance accross pins 86-85 is ~2Mohm one way and 'OL' the other (due to the diode)When tested with the diode function of a meter it gives 'OL' one way and 0.6V the correct way. (so the diode is a-ok) From inside the casing the coil resistance is 63 ohm. The coil operates at around 200mA.
Now I tested the replacement. This has the same PIN configuration but the diode is reversed accross the coil to kill the back EMF when the coil is switched off (instead of in series which blocks it) It is a HELLA 4RA 940010-67. Bought new yesterday from a motor factor in Ireland.
Resistance across coil 0.0 Ohm both ways. Diode test shows 0V accross. On my bench power supply I can give it a full (current limited) 1 Amp without any sign of movement in the coil. Prediction - the diode is faulty @ short circuit. Now I cant test this independent from the coil without deconstructing the relay; and I don't want to do that because I am going to be laying into Hella next week
So progress with the old ECU. I have desoldered the resistor on the output to the fuel pump relay (via ECU pin 16). Below it are 5 PCB tracks. One from the resistor itself and four tiny ones passing innocently by!! The board is well charred. And we all know from school that carbon conducts electricity. I tested the resistance across the charred board and got ~400kOhm. Maybe enough to send some spurious signal?? So I have cut away the tracks and cleaned off the carbon/ash.
Next plan - wake up in the morning with a very steady hand and a roll of fuse wire to repair the tracks.I have a new resistor, this time a 7 Watt rather than the ??2W?? original and its a 15 Ohm rather than 13 but I reckon it will be ok. If I don't get to it tomorrow I might go to RS for the correct replacement.
Whether any other component has been fried will remain to be seen. But still I have my new ECU and I have to hope the EPROM is good.
Photos to follow!
Edited by markgreen on Monday 5th July 22:31
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