An Electrical Conundrum
Discussion
Technical Electrical Conundrum
Guys I need some help. My Spark has Died and I can not find the source of the problem. Long Chats with PB3 and Tuxman (thanks Guys) and I still can not solve the problem….
The start of the Story….
Returning from a far away trip (second star on the left) the car just died… on investigation by myself I had fuel but no spark. No electrical test equipment in the car so called recovery. Everything works, lights, wiper, heater, left and right fuel pumps, indicators etc. etc. except no spark.
Mechanic arrived and deduced that the MSD unit was at fault. He said Power in but none out. Took him at his word and ordered a new one from the USA. Fitted, drained the battery trying to start the car. Went through all the tests, I’ll come to these later. Read on the net about the coil and the Ohm resistances. It failed. Internet said +ve to –ve should be 9,000 to 11,000 Ohms and HT to LT should be 75,000 to 85,000. Results were LT +ve to –ve 500 and HT to LT 2000. So ordered new coil. Coil arrived and completed same tests again on the coil. The new matched the old. So I fitted the new coil anyway to see where we were. Still no Spark.
In summary
There are 8 wires from the MSD ignition unit.
2 to the Magnetic pick up in the distributor
1 to Earth (connected to the cylinder head)
1 to Battery Connected to the back of the alternator (This only gives 5 volts with ignition on and may be a source of the problem???)
2 to the coil +ve & -ve There is no voltage at the positive with the ignition on. I assumed that this is due to the magnetic pick up in the distributor
1 red to the ignition switch giving 11.98 v
1 white (not used and blanked)
All fuses show 1 Ohm of resistance (they are all Ok)
There is 2 Ohm’s of resistance from the cylinder head to the fuel tank sender on the passenger side. To test this I then connected a Jumper lead from the cylinder head to the Battery –ve. There is still 2 Ohm’s of resistance. It may be that the jumper lead is meant for big engine cars and has a hefty cable that this would not help much with the resistance. I don’t know?
I have tried the MSD test of disconnecting the magnetic pick up in the distributor and shorting this. At the time I had the HT lead from the coil touching the cylinder head with a spark plug attached. No spark I then tried with the park plug connected to a grounding wire which was bolted to the cylinder head. To no avail. Still no spark. THe manual suggests that the MSD unit is at fault. I struggle to believe that the new one is also at fault.
I am left with the 5v from the alternator, surly this should be 12 and what would cause this not to be? I guess also that this is a permanent 12v? Has the alternator failed. Is this the ballast resistor that is causing the 5V? How would I know if one is fitted?
Additionally I have the car up on axle stands and can not find the engine earth strap. It must be there somewhere. What does it look like and where is it likely to be?
Please help I am stuck and on the point of calling an Auto electrics engineer. The wife is going nuts as I have spent every night in the garage with this conundrum and will not quit. I get back into the house smelling of a grease Monkey, much to her disgust.
What is the problem? My fellow Ultimainians can you help me
Guys I need some help. My Spark has Died and I can not find the source of the problem. Long Chats with PB3 and Tuxman (thanks Guys) and I still can not solve the problem….
The start of the Story….
Returning from a far away trip (second star on the left) the car just died… on investigation by myself I had fuel but no spark. No electrical test equipment in the car so called recovery. Everything works, lights, wiper, heater, left and right fuel pumps, indicators etc. etc. except no spark.
Mechanic arrived and deduced that the MSD unit was at fault. He said Power in but none out. Took him at his word and ordered a new one from the USA. Fitted, drained the battery trying to start the car. Went through all the tests, I’ll come to these later. Read on the net about the coil and the Ohm resistances. It failed. Internet said +ve to –ve should be 9,000 to 11,000 Ohms and HT to LT should be 75,000 to 85,000. Results were LT +ve to –ve 500 and HT to LT 2000. So ordered new coil. Coil arrived and completed same tests again on the coil. The new matched the old. So I fitted the new coil anyway to see where we were. Still no Spark.
In summary
There are 8 wires from the MSD ignition unit.
2 to the Magnetic pick up in the distributor
1 to Earth (connected to the cylinder head)
1 to Battery Connected to the back of the alternator (This only gives 5 volts with ignition on and may be a source of the problem???)
2 to the coil +ve & -ve There is no voltage at the positive with the ignition on. I assumed that this is due to the magnetic pick up in the distributor
1 red to the ignition switch giving 11.98 v
1 white (not used and blanked)
All fuses show 1 Ohm of resistance (they are all Ok)
There is 2 Ohm’s of resistance from the cylinder head to the fuel tank sender on the passenger side. To test this I then connected a Jumper lead from the cylinder head to the Battery –ve. There is still 2 Ohm’s of resistance. It may be that the jumper lead is meant for big engine cars and has a hefty cable that this would not help much with the resistance. I don’t know?
I have tried the MSD test of disconnecting the magnetic pick up in the distributor and shorting this. At the time I had the HT lead from the coil touching the cylinder head with a spark plug attached. No spark I then tried with the park plug connected to a grounding wire which was bolted to the cylinder head. To no avail. Still no spark. THe manual suggests that the MSD unit is at fault. I struggle to believe that the new one is also at fault.
I am left with the 5v from the alternator, surly this should be 12 and what would cause this not to be? I guess also that this is a permanent 12v? Has the alternator failed. Is this the ballast resistor that is causing the 5V? How would I know if one is fitted?
Additionally I have the car up on axle stands and can not find the engine earth strap. It must be there somewhere. What does it look like and where is it likely to be?
Please help I am stuck and on the point of calling an Auto electrics engineer. The wife is going nuts as I have spent every night in the garage with this conundrum and will not quit. I get back into the house smelling of a grease Monkey, much to her disgust.
What is the problem? My fellow Ultimainians can you help me
I have a spare distributor and coil at home you can borrow, I can drop them off and take alook if you like??
If you short the two wires that go to the dizzy (green and purple) with the ignition on the msd unit should make a noise, also check your msd earth.
just read your post again, try a 12v feed direct from the battery rather than via the alternator, low voltage could be because of this, or a bad earth, or even a flat battery after all that cranking!! I know what your going through, I had the same thing!!
If you short the two wires that go to the dizzy (green and purple) with the ignition on the msd unit should make a noise, also check your msd earth.
just read your post again, try a 12v feed direct from the battery rather than via the alternator, low voltage could be because of this, or a bad earth, or even a flat battery after all that cranking!! I know what your going through, I had the same thing!!
Edited by dilley on Saturday 7th July 22:37
Take a heavy duty wire from the battery to the main red input wire. If this is the wire you are saying goes to the alternator then you could try connecting it to the starter as the lead from there to the battery does not come any fatter. Again check the voltage on that when cranking as I believe the MSD shuts down if the voltage is below 9V.
Going back to your static spark test. With the king lead close to an earth and all relevant electrics connected and turned on flash the white lead to earth and see if you get a spark. The white is used for contact breakers so works in the same way.
My engine earth comes from the side of the adaptor plate and onto the chassis just below the upper suspension mounts and either loops over or under the gear link rod. Doubt it's that if the engine is turning over OK.
You don't have to answer this but do you have an immobiliser that may be killing the circuit.
Come back for more thoughts if none of this gets you anywhere.
Steve
Going back to your static spark test. With the king lead close to an earth and all relevant electrics connected and turned on flash the white lead to earth and see if you get a spark. The white is used for contact breakers so works in the same way.
My engine earth comes from the side of the adaptor plate and onto the chassis just below the upper suspension mounts and either loops over or under the gear link rod. Doubt it's that if the engine is turning over OK.
You don't have to answer this but do you have an immobiliser that may be killing the circuit.
Come back for more thoughts if none of this gets you anywhere.
Steve
Echo what steve says, remove the alternator from the circuit, get good 12v supplies to the msd, make sure resistance from the -ve to chassis is minimal, couple of ohms at most. had a similar prob on a friends car (msd box) a shorted 12v blew the box. i am engineer and it is not uncommon for me to see 'new' parts that are faulty on install. its a fairly simple circuit but you must have the good supplies to start with. good luck.
Well, Well, well. The beast has roared and I am left with a large financial hole in my pocket for a 12p connector.
The answer is...after wiring round the feed from the alternator to the MSD Unit, I had a spark and had the engine running. I then decided that it must be the alternator and took it off. In the doing so there were two brown wires, terminated, that brushed the alternator as I was removing the bolts. It flashed (shorted). The ends of the brown wires ended in a termination and were wrapped in red electrical tape. The size of the hole in the rubber boot for the MSD +ve wire entry was vastly oversized for the MSD wire, and I think that the two brown wires must have been in there at some point. At the time I guessed that they were put there to keep them out of the way (there is no where else to put them and that they just needed connecting together as part if the loom, hence the terminator connector and the red electrical tape) I had assumed (incorrectly) that the tape had just been worn away, as not all the end of the terminator was exposed.
Anyway, I re-wrapped the ends and took the alternator out. Having slept on the conundrum of these wires, I was out at the car this morning with the Multi-meter and there is 12 volts at the termination. I took the alternator to work with the intention of nipping out to the motor factors at lunch to replace it.
Can you guess what is coming....
A quick call to Ultima to discuss these two brown wires and it turns out that they should be on the back of the alternator along with the MSD wire. In checking the Alternator again, what I thought was a washer is in actual fact the end of the ring connector from these two brown wires. The red electrical tape had been a bit over the end of the shroud so had covered all but a small part of what I thought was a terminator connector.
So in the end...
1 x new MSD unit
1 x New coil
1 x New Distributor Cap
And the fault is a broken ring connector. I swore for 10 minutes and did not repeat myself.
The moral of the storey, Do not always take expert people at their word. This is aimed at the mechanic who I took at his word and told me that the MSD unit was at Fault. Check for yourself and talk to colleagues and friends.
Finally.
A Big thanks to Simon (Tuxman) and Phil (PB3) as they have been on the phone for hours walking through the problem with me on several occasions, making suggestions and generally being very supportive.
Hopefully I will see you at 09.00 at Brampton Hut on Sunday ready for the ride to Kimbolton. I think I owe you both a beer.
Lets hope when I get home and put it all back together that this is the end of the storey.
Scuff
The answer is...after wiring round the feed from the alternator to the MSD Unit, I had a spark and had the engine running. I then decided that it must be the alternator and took it off. In the doing so there were two brown wires, terminated, that brushed the alternator as I was removing the bolts. It flashed (shorted). The ends of the brown wires ended in a termination and were wrapped in red electrical tape. The size of the hole in the rubber boot for the MSD +ve wire entry was vastly oversized for the MSD wire, and I think that the two brown wires must have been in there at some point. At the time I guessed that they were put there to keep them out of the way (there is no where else to put them and that they just needed connecting together as part if the loom, hence the terminator connector and the red electrical tape) I had assumed (incorrectly) that the tape had just been worn away, as not all the end of the terminator was exposed.
Anyway, I re-wrapped the ends and took the alternator out. Having slept on the conundrum of these wires, I was out at the car this morning with the Multi-meter and there is 12 volts at the termination. I took the alternator to work with the intention of nipping out to the motor factors at lunch to replace it.
Can you guess what is coming....
A quick call to Ultima to discuss these two brown wires and it turns out that they should be on the back of the alternator along with the MSD wire. In checking the Alternator again, what I thought was a washer is in actual fact the end of the ring connector from these two brown wires. The red electrical tape had been a bit over the end of the shroud so had covered all but a small part of what I thought was a terminator connector.
So in the end...
1 x new MSD unit
1 x New coil
1 x New Distributor Cap
And the fault is a broken ring connector. I swore for 10 minutes and did not repeat myself.
The moral of the storey, Do not always take expert people at their word. This is aimed at the mechanic who I took at his word and told me that the MSD unit was at Fault. Check for yourself and talk to colleagues and friends.
Finally.
A Big thanks to Simon (Tuxman) and Phil (PB3) as they have been on the phone for hours walking through the problem with me on several occasions, making suggestions and generally being very supportive.
Hopefully I will see you at 09.00 at Brampton Hut on Sunday ready for the ride to Kimbolton. I think I owe you both a beer.
Lets hope when I get home and put it all back together that this is the end of the storey.
Scuff
Edited by Scuff on Tuesday 10th July 13:32
Scuff sorry to hear of problem. I have been kicking myself as had same problem but did not see it to be a cause of your trouble. I had this connection ring go twice on my car in the early days which caused 2 breakdowns. In the end I chopped the ring off and replaced with a much heavier duty version which has been fine for years. The only electrical trouble I have ever had with the car has been associated with the alternator. Without the use of a serpentine belt arrangement the stresses seam to shake brackets etc loose. Watch out for any movement you have in the support backets and attachments as fatigue will break both brackets and connectors.
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