Loosing spark randomly on rear rotor
05-29-18, 10:15 PM
#1
Loosing spark randomly on rear rotor
Hello all,
Here are the specs of the car
12A bridgeport
Stock electronic distributor
MSD Blaster 2 coils
Original ignitors
New spark plugs- NGK racing plugs
New wire
I start the car and i see the wideband reading about 11 AFR on both rotors, i have the DLG guage with the LC2.
The car sounds ok, smokes some since its a fresh rebuild, irons lapped and all newish parts.
Once its started, it maybe takes about 10 to 15 seconds and then you can hear the exhaust change how it stops firing the on the rear rotor and i see the wideband on rotor 2 read 22 afr.
I checked spark on all wires and i get spark.
WHat would be my next step to check?
Check igniters? Would they get warm so fast to stop firing?
WHen it stops firing, what could i check? see if i am getting 12V to the coil and if i see the field drop?
Here are the specs of the car
12A bridgeport
Stock electronic distributor
MSD Blaster 2 coils
Original ignitors
New spark plugs- NGK racing plugs
New wire
I start the car and i see the wideband reading about 11 AFR on both rotors, i have the DLG guage with the LC2.
The car sounds ok, smokes some since its a fresh rebuild, irons lapped and all newish parts.
Once its started, it maybe takes about 10 to 15 seconds and then you can hear the exhaust change how it stops firing the on the rear rotor and i see the wideband on rotor 2 read 22 afr.
I checked spark on all wires and i get spark.
WHat would be my next step to check?
Check igniters? Would they get warm so fast to stop firing?
WHen it stops firing, what could i check? see if i am getting 12V to the coil and if i see the field drop?
05-31-18, 12:28 PM
#4
Wouldn’t a bad igniter effect both rotors at the same time as one is leading and the other is trailing? If it only effects the rear rotor I would suspect a problem in the distributor, wires, or spark plugs on that rotor. Try spritzing water on the plug wires while running to see if it changes how it runs. Swap to a know good distributor and see how it acts. Hook up a timing light on every wire and watch the flashes and see if you can find where it loses spark. Swap spark plugs and see if the misfire moves. Swap coils and see if it moves.
Last edited by NCross; 05-31-18 at 12:34 PM.
05-31-18, 09:57 PM
#5
Alright, so swapped igniters and it stays on the rear rotor. The igniter ground backing looked rough so i sanded it a bit and dielectric grease. This time it lasted about a minute then it lost spark again and i could hear how it was intermittently firing. Wiggled some wires hoping to see if it was a faulty wire, but nothing.
NCross, thanks for the advice. I just bought new rotor and cap. Ill plug my timing light tomorrow and see whats going on. Like you said, not sure why swapping coils would make a difference since its one coil for leading and one for trailing. Ill try the water spray thing and ill swap spark plugs as well and come back and update.
thanks.
NCross, thanks for the advice. I just bought new rotor and cap. Ill plug my timing light tomorrow and see whats going on. Like you said, not sure why swapping coils would make a difference since its one coil for leading and one for trailing. Ill try the water spray thing and ill swap spark plugs as well and come back and update.
thanks.
06-01-18, 02:22 PM
#6
The only reason I can see for swapping leading and trailing coils is that maybe... the leading coil is weak and only has enough power to fire one rotor? Not likely, but worth a shot. Thats just a diagnostic step most of us technicians use when there is a misfire code present, clear the codes, and see if the misfire travels to a different cylinder. I'm thinking something within the dizzy (cap, rotor, or internal) is bad.
06-01-18, 03:29 PM
#7
The only reason I can see for swapping leading and trailing coils is that maybe... the leading coil is weak and only has enough power to fire one rotor? Not likely, but worth a shot. Thats just a diagnostic step most of us technicians use when there is a misfire code present, clear the codes, and see if the misfire travels to a different cylinder. I'm thinking something within the dizzy (cap, rotor, or internal) is bad.
Thanks.
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06-01-18, 10:53 PM
#8
ok, update.
Swapped coils, still did it.
Put a whole other set of coils, still did it.
Checked with the timing light and even when i saw that the wideband said 22 and it sounded like no combustion from rotor 2, the timing light still flashed.
Swapped spark plug the trailing for the leading on the rear rotor and still did it
Then i thought since i am getting spark, the only other thing could be fuel and i swapped the injector plugs and then everything just ran fine. I am not sure why this would make a difference since my MS is set up for simultaneous injection and i swore i had injector 1 in the front and 2 in rear.
Swapped coils, still did it.
Put a whole other set of coils, still did it.
Checked with the timing light and even when i saw that the wideband said 22 and it sounded like no combustion from rotor 2, the timing light still flashed.
Swapped spark plug the trailing for the leading on the rear rotor and still did it
Then i thought since i am getting spark, the only other thing could be fuel and i swapped the injector plugs and then everything just ran fine. I am not sure why this would make a difference since my MS is set up for simultaneous injection and i swore i had injector 1 in the front and 2 in rear.
06-02-18, 10:54 AM
#9
Junior Member
The metal surface of the ignitors needs to b smeared with ceramic paste, before installing. Ignitors get hot, they use the dizzy as a heat sink, drawing heat away from them. Not doing so will cause premature ignitors failure.
06-02-18, 11:27 AM
#10
did not know that was the heat sink, thanks. I put dielectric grease thinking it was just the ground. I’ll get some ceramic paste and put some. Also, any input from my last post? Somehow swapping the injectors seems to have solved the problem, but I am not sure as to why that would have solved the problem. I also confirmed spark with the timing light even when the wideband showed a lean condition which is what lead me to believe it was fuel.
06-02-18, 07:00 PM
#12
I am sorry. I happen to forget to say that in the original post. Yes, it’s 12a running ms2 with 48ida style itb with 900cc injector per rotor. I started it today again and it stayed on and no issues. Did not get a chance to swap back to see if it would do it again. I was fighting my efan not turning with the ms.
thank you all for the help.
thank you all for the help.
06-03-18, 10:56 AM
#14
Junior Member
did not know that was the heat sink, thanks. I put dielectric grease thinking it was just the ground. I’ll get some ceramic paste and put some. Also, any input from my last post? Somehow swapping the injectors seems to have solved the problem, but I am not sure as to why that would have solved the problem. I also confirmed spark with the timing light even when the wideband showed a lean condition which is what lead me to believe it was fuel.
06-03-18, 04:13 PM
#15
I did the same thing with my ignitors the 1st time also, then someone here pointed me in the right direction. As for the injectors, n lean conditions. I couldn't say for sure. What I can say is, on the SE, the fuel pump, injectors, n tachometer all get there signal from the trailing side of the ignition. I.E. if your running and the tach dropped to 0, a split second before stalling, the trailing ignitor failed. Or something on the trailing side. Another scenario, motor cranks but not starting. If the tachometer is not moving, while cranking, trailing side of ignition has a fault.
06-04-18, 01:08 AM
#16
84SE-EGI helpy-helperton
By switching your Tach Lead (also your Fuel Injection trigger on an -SE) to the Leading Coil, you're using the trigger from the Leading Ignitor to determine when to fire the injection system - in a stock -SE fuel injection setup. What you're running is somewhat unique, and you'll have to figure out where your electronic fuel injection controller is taking the signal. For conventional wisdom, the fuel injection system should be triggered from Trailing Ignition.
In a pinch, if you have a bad Ignitor, you can switch your trigger wire from the Trailing to Leading Coil and get the car running with EFI. This should only be used as a temporary fix, though, as I've done it as a diagnostic measure - and to get me to where I was going so I could look at it further.
In a pinch, if you have a bad Ignitor, you can switch your trigger wire from the Trailing to Leading Coil and get the car running with EFI. This should only be used as a temporary fix, though, as I've done it as a diagnostic measure - and to get me to where I was going so I could look at it further.
06-04-18, 07:28 PM
#17
By switching your Tach Lead (also your Fuel Injection trigger on an -SE) to the Leading Coil, you're using the trigger from the Leading Ignitor to determine when to fire the injection system - in a stock -SE fuel injection setup. What you're running is somewhat unique, and you'll have to figure out where your electronic fuel injection controller is taking the signal. For conventional wisdom, the fuel injection system should be triggered from Trailing Ignition.
In a pinch, if you have a bad Ignitor, you can switch your trigger wire from the Trailing to Leading Coil and get the car running with EFI. This should only be used as a temporary fix, though, as I've done it as a diagnostic measure - and to get me to where I was going so I could look at it further.
In a pinch, if you have a bad Ignitor, you can switch your trigger wire from the Trailing to Leading Coil and get the car running with EFI. This should only be used as a temporary fix, though, as I've done it as a diagnostic measure - and to get me to where I was going so I could look at it further.
thanks. I seem to have gotten a more stable idle after switching to trailing. I am still fighting a bit to lean out my idle a bit more. The best I seem to get is 12.7 and I am at the point that if I bring down my VE value at idle just one more from 17 to 16 then it starts stumbling and dies. I have 900cc injectors (1x per rotor) so maybe the injector is not very stable below 2.5 ms.
Thank you all for the help.