Hi all,
I have read through previous threads and can't see an answer to my particular problem so hopefully someone can help...
I have a 3.5 efi flapper which I transplanted into my trialer 90 some 2 years or so ago. The motor came from a RR classic and has been running well ish since it was fitted. A few weeks ago I broke down in it on my way home from work. Engine coughed and spluttered a bit then died altogether. Nice AA bloke put his plug tester on no 1 and found no spark when cranked. Told me the coild had gone and dragged me home.
On replacing the coil, dizzy cap and rotor arm I still have no spark at the plugs. I have checked the supply and there is 12v at the coil+ and the resistor is fitted to the - side. I replaced the whole distributor unit about 6 months ago. All I can think is that something electronic in the dizzy has packed up. But before I go and exchange it is there anything else I should be checking first?
Any suggestions would be appreciated
Thanks
She won't start!
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ramon alban
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Hello Bob, I'm taking a pot shot here that your ignition system is similar what follows, but just to clarify, what you call a resistor on the side of the dizzy is more likely to be an amplifier:
With no spark anywhere, its almost certainly a Low Tension circuit problems, so:
IGNITION TESTING - BACK TO BASICS
The circuit represents BOTH the system where the amplifier is mounted behind the coil AND where it is mounted on the side of the dizzy. The effective electrics are the same, just the physical locations of components differ. The circuit is also good for most later systems where Carbs were used for fuelling, in which case ignore any Efi references.
Be sure the wiring and earths from the ignition switch, through to the coil, dizzy and amplifier module is pretty much the same as shown.
o Remove the king lead from the distributor, connect it to a spark plug and lay the plug on the engine somewhere.
o Switch on the ignition and use a multimeter to verify there are 12 volts at coil positive.
o If No - find out why by checking further back in the circuit between coil positive and the ignition switch and beyond to the battery.
o If Yes - crank the engine.
o Is there a spark at the spark plug.
o If Yes - then the problems are downstream from the king lead at the dizzy cap, rotor arm, plug leads, plugs, or ignition timing so that is where to look - choose the suspects and fix.
o If No - change the king lead and - If still No - then the problems are upstream from the king lead at the coil, amplifier, distributor innards or their local connections.
Test the coil
o Disconnect the amplifier.
o Strike coil neg to earth with a flying lead and see how good is the king lead spark.
o If sparks are poor/weak the input voltage and coil are candidates for inspection/replacement.
o If sparks are fat/healthy look for amplifier/pickup coil problemss.
Test the Amplifier and Dissy Pickup Coil.
o Remove distributor cap.
o Disconnect ECU trigger wire so no spurious signal go thataway.
o Disconnect coil negative wire from amplifier.
o Wire a 12v 21W bulb from amplifier to coil positive (12 volt supply).
o The 21W bulb acts as a substitute load.
o Turn ignition on.
o Rotate distributor rotor back and forward against the vacuum advance springs.
o As the rotor triggers the pickup coil, the amplifier should flash the bulb.
o If the bulb flashing is positive and consistent the amplifier/pickup coil are working correctly.
o If inconsistent or weak either the amplifier or pickup coil is faulty.
Check the pickup coil
o Remove the amplifier and measure the resistance of the dissy pickup coil for a steady value between 500 ohms to 1500 ohms on the ohm-meter. Flex the wires at the same time to test their integrity.
o Outside the above range, short or open circuit indicates a duff pickup coil.
o By process of elimination, if the pickup coil is OK, one might conclude the amplifier is faulty but to be sure, consider the following elegant (but slightly more complex) test process.
Test the Amplifier
o Use a 1.5 volt pen-cell battery connected in series with a (say} 2700 ohm resistor and two flying leads to simulate the pickup coil.
o With the coil and amplifier connected normally and the dissy pickup coil disconnected from the amplifier, connect one flying lead to one of the amplifier input connectors and stroke the other flying lead intermittantly across the second amplifier input connector'
o This emulated pulsed input thereby activates the amplifier in sympathy to generate sparks from the coil?
o Polarity of this simulation is non-critical as neither flying lead is connected to earth, only to the amplifier input connectors, and the pulsing voltage from the pen-cell acts similar to the pickup coil input.
o The same test could be performed with the 21 watt bulb as the coil substitute as previously described.
o Going one step further, construct a small test box complete with switch, 21 watt bulb/holder, pen-cell battery, 2700 ohm resistor, 12 volt pos/neg power connections (from a car battery), spade connectors to the amplifier, etc. (Anyone care to draw up the circuit, pro-tem? [8D])
o Connect up the 12 volts power and the amplifier. Now flick the switch to emulate the pulsed input from a pickup coil and watch the 21 watt bulb flash in sympathy. Seemples!
o Another possible component failure will be the suppressing condenser breaking down under the back-EMF from the coil.
o Remove capacitor from circuit to see if the problem disappears.
o If yes, replace the capacitor.
o Almost finally, for all the above components check the LT wiring is not corroded, broken, dodgy or otherwise failing.
o When all the above upstream components from the king lead check out OK. Time to review the downstream components to see if they are intermittently dragging down the Hi-tension energy.
o Rotor arm - inspect for carbon tracking, clean with WD40, smear with a trace of silicon grease to prevent moisture ingress.
o Dizzy cap - inside and outside - inspect for carbon tracking, clean with WD40, smear with a trace of silicon grease to prevent moisture ingress. Wipe completely clean and shiny, especially between the turrets.
o Plug Leads and Hi-tension connectors - inspect for breaks and contact damage, clean with WD40, smear with a trace of silicon grease to prevent moisture ingress. Wipe completely clean and shiny.
o Spark Plugs - Check for recommended type, clean and gap to correct spec, inspect for insulator damage externally and whiskering/crud between central contact and body. Clean externally to a shine.
o The above four items are "zero cost" actions. Many owners replace them all never knowing whether they are faulty, only to find no difference.
o Given the availability of some known good spares, checking by swapping is an easy process and looking for spark tracking on a dark night generally reveals faulty hi-tension parts.
Back to basics, indeed, but it also goes a long way to illuminate the way the ignition system works and adds enlightenment to the fault finding routine. One step at a time!
With no spark anywhere, its almost certainly a Low Tension circuit problems, so:
IGNITION TESTING - BACK TO BASICS
The circuit represents BOTH the system where the amplifier is mounted behind the coil AND where it is mounted on the side of the dizzy. The effective electrics are the same, just the physical locations of components differ. The circuit is also good for most later systems where Carbs were used for fuelling, in which case ignore any Efi references.
Be sure the wiring and earths from the ignition switch, through to the coil, dizzy and amplifier module is pretty much the same as shown.
o Remove the king lead from the distributor, connect it to a spark plug and lay the plug on the engine somewhere.
o Switch on the ignition and use a multimeter to verify there are 12 volts at coil positive.
o If No - find out why by checking further back in the circuit between coil positive and the ignition switch and beyond to the battery.
o If Yes - crank the engine.
o Is there a spark at the spark plug.
o If Yes - then the problems are downstream from the king lead at the dizzy cap, rotor arm, plug leads, plugs, or ignition timing so that is where to look - choose the suspects and fix.
o If No - change the king lead and - If still No - then the problems are upstream from the king lead at the coil, amplifier, distributor innards or their local connections.
Test the coil
o Disconnect the amplifier.
o Strike coil neg to earth with a flying lead and see how good is the king lead spark.
o If sparks are poor/weak the input voltage and coil are candidates for inspection/replacement.
o If sparks are fat/healthy look for amplifier/pickup coil problemss.
Test the Amplifier and Dissy Pickup Coil.
o Remove distributor cap.
o Disconnect ECU trigger wire so no spurious signal go thataway.
o Disconnect coil negative wire from amplifier.
o Wire a 12v 21W bulb from amplifier to coil positive (12 volt supply).
o The 21W bulb acts as a substitute load.
o Turn ignition on.
o Rotate distributor rotor back and forward against the vacuum advance springs.
o As the rotor triggers the pickup coil, the amplifier should flash the bulb.
o If the bulb flashing is positive and consistent the amplifier/pickup coil are working correctly.
o If inconsistent or weak either the amplifier or pickup coil is faulty.
Check the pickup coil
o Remove the amplifier and measure the resistance of the dissy pickup coil for a steady value between 500 ohms to 1500 ohms on the ohm-meter. Flex the wires at the same time to test their integrity.
o Outside the above range, short or open circuit indicates a duff pickup coil.
o By process of elimination, if the pickup coil is OK, one might conclude the amplifier is faulty but to be sure, consider the following elegant (but slightly more complex) test process.
Test the Amplifier
o Use a 1.5 volt pen-cell battery connected in series with a (say} 2700 ohm resistor and two flying leads to simulate the pickup coil.
o With the coil and amplifier connected normally and the dissy pickup coil disconnected from the amplifier, connect one flying lead to one of the amplifier input connectors and stroke the other flying lead intermittantly across the second amplifier input connector'
o This emulated pulsed input thereby activates the amplifier in sympathy to generate sparks from the coil?
o Polarity of this simulation is non-critical as neither flying lead is connected to earth, only to the amplifier input connectors, and the pulsing voltage from the pen-cell acts similar to the pickup coil input.
o The same test could be performed with the 21 watt bulb as the coil substitute as previously described.
o Going one step further, construct a small test box complete with switch, 21 watt bulb/holder, pen-cell battery, 2700 ohm resistor, 12 volt pos/neg power connections (from a car battery), spade connectors to the amplifier, etc. (Anyone care to draw up the circuit, pro-tem? [8D])
o Connect up the 12 volts power and the amplifier. Now flick the switch to emulate the pulsed input from a pickup coil and watch the 21 watt bulb flash in sympathy. Seemples!
o Another possible component failure will be the suppressing condenser breaking down under the back-EMF from the coil.
o Remove capacitor from circuit to see if the problem disappears.
o If yes, replace the capacitor.
o Almost finally, for all the above components check the LT wiring is not corroded, broken, dodgy or otherwise failing.
o When all the above upstream components from the king lead check out OK. Time to review the downstream components to see if they are intermittently dragging down the Hi-tension energy.
o Rotor arm - inspect for carbon tracking, clean with WD40, smear with a trace of silicon grease to prevent moisture ingress.
o Dizzy cap - inside and outside - inspect for carbon tracking, clean with WD40, smear with a trace of silicon grease to prevent moisture ingress. Wipe completely clean and shiny, especially between the turrets.
o Plug Leads and Hi-tension connectors - inspect for breaks and contact damage, clean with WD40, smear with a trace of silicon grease to prevent moisture ingress. Wipe completely clean and shiny.
o Spark Plugs - Check for recommended type, clean and gap to correct spec, inspect for insulator damage externally and whiskering/crud between central contact and body. Clean externally to a shine.
o The above four items are "zero cost" actions. Many owners replace them all never knowing whether they are faulty, only to find no difference.
o Given the availability of some known good spares, checking by swapping is an easy process and looking for spark tracking on a dark night generally reveals faulty hi-tension parts.
Back to basics, indeed, but it also goes a long way to illuminate the way the ignition system works and adds enlightenment to the fault finding routine. One step at a time!
Re: She won't start!
Which dizzy? Most common on EFI engines is the DLM - it has an amp mounted on the side. That fails. The pick-up coil rarely.90Bob wrote:Hi all,
I have read through previous threads and can't see an answer to my particular problem so hopefully someone can help...
I have a 3.5 efi flapper which I transplanted into my trialer 90 some 2 years or so ago. The motor came from a RR classic and has been running well ish since it was fitted. A few weeks ago I broke down in it on my way home from work. Engine coughed and spluttered a bit then died altogether. Nice AA bloke put his plug tester on no 1 and found no spark when cranked. Told me the coild had gone and dragged me home.
On replacing the coil, dizzy cap and rotor arm I still have no spark at the plugs. I have checked the supply and there is 12v at the coil+ and the resistor is fitted to the - side. I replaced the whole distributor unit about 6 months ago. All I can think is that something electronic in the dizzy has packed up. But before I go and exchange it is there anything else I should be checking first?
Any suggestions would be appreciated
Thanks
Dave
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y
If you have a dwell meter lying around from points days - or a DVM with this function - it will show the LT side is switching. Ie do a basic test on the amp.90Bob wrote:Thanks guys,
This is all extremely helpful.
I will keep you informed.
Dave
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y
Doesn't say much for the 'AA man' if he diagnosed the coil. He should have test equipment to show if the LT side is working.ChrisJC wrote:Almost certainly the ignition amplifier, which is the small black box on the side of the distributor.
Chris.
Dave
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y
Perhaps he was an 'expert', used to distributorless systems.....DaveEFI wrote:Doesn't say much for the 'AA man' if he diagnosed the coil. He should have test equipment to show if the LT side is working.ChrisJC wrote:Almost certainly the ignition amplifier, which is the small black box on the side of the distributor.
Chris.
Chris.
--
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Series IIA 4.6 V8
R/R P38 4.6 V8
R/R L405 4.4 SDV8
