L20B No Spark

[slowerthantime]

I'm probably asking dumb questions but I'm stuck, so any help is appreciated.

I have been trying for a first start on a fresh engine with no luck. I have oil pressure, fuel and it cranks over but no spark. I have changed to an IR Alternator and matchbox distributor. The ballast resistor has been removed. The coil is 0.7 ohm for EI. The distributor has had new bushings, cleaned up with new cap, rotor and leads. Spark plugs are new NGK and gapped at 0.030".

I have 12.7 volts at the coil with ignition on and 10.5v while cranking. I have tried 2 coils and both test within spec.

With a spark plug connected to the end of the coil wire and grounded, I get a spark when I ground the negative terminal of the coil. With the distributor turned so that a rotor is lined up with #1, I get a spark at #1 plug when I ground the negative terminal on the coil. This seems to show that there is connectivity between the coil, distributor and spark plug but no signal??

A test light connected to the negative terminal on the coil dims on cranking but I'm not sure if it pulsating enough to indicate a signal.

I did find and repair an exposed and possibly grounded break in the green wire from the magnet. After repairing the wire...still no spark. I have tried 2 ignitors but not sure if either of them were good to start with.

Is there a way to test the ignitor/ switching? Should there be a voltage difference at the negative terminal on the coil between rotor aligned with a post versus in between posts? I am out of my depth with this and appreciate any advice.

[510rob]

I'm probably asking dumb questions but I'm stuck, so any help is appreciated.

1) I have been trying for a first start on a fresh engine with no luck.
2) I have oil pressure, fuel and it cranks over but no spark.
3) I have changed to an IR Alternator and matchbox distributor.
4) The ballast resistor has been removed.
5) The coil is 0.7 ohm for EI.
6) The distributor has had new bushings, cleaned up with new cap, rotor and leads.
7) Spark plugs are new NGK and gapped at 0.030".

8) I have 12.7 volts at the coil with ignition on and 10.5v while cranking.
9) I have tried 2 coils and both test within spec.

10) With a spark plug connected to the end of the coil wire and grounded, I get a spark when I ground the negative terminal of the coil.
11) With the distributor turned so that a rotor is lined up with #1, I get a spark at #1 plug when I ground the negative terminal on the coil.
12) This seems to show that there is connectivity between the coil, distributor and spark plug but no signal??

13) A test light connected to the negative terminal on the coil dims on cranking but I'm not sure if it pulsating enough to indicate a signal.

14) I did find and repair an exposed and possibly grounded break in the green wire from the magnet.
15) After repairing the wire...still no spark.
16) I have tried 2 ignitors but not sure if either of them were good to start with.

17) Is there a way to test the ignitor/switching?
18) Should there be a voltage difference at the negative terminal on the coil between rotor aligned with a post versus in between posts?
19) I am out of my depth with this and appreciate any advice.

I agree that you need to prove (or disprove) that the EI setup works or not.

1) pull the dizzy from the front cover
2) ground out the dizzy to the motor again (use a jumper cable or some other wire that is handy)
3) pull the four plugs, ground them to the head somehow
4) spin the dizzy shaft (spin it the same way it turns on the engine because the reluctor wheel is ramped to give a hard zero crossing to the matchbox!)

you should see the plugs zapping, or not...

For further reading on what exactly the EI box does, the best technical explanation can be found in the Motorola MC3334 datasheet "High Energy Ignition Circuit". That datasheet goes back to 1975, when not surprisingly, Motorola released the chip and GM HEI was born...
(clicking the link will spawn a window to save the datasheet pdf from Future Electronics - don't worry, Future are ok)

[datzenmike]

Igniter? Just to be sure, you have a remote igniter EI? The one with the metal box that is mounted in the cabin of the vehicle. Looks like this...



Make sure distributor is well grounded, igniter box also.


OR

The later matchbox EI with the miniature 'igniter' mounted on the side of the distributor....



See the little brass lug that's for a dedicated ground. Distributor HAS to be well grounded to work.


Any chance the red and green wires are reversed? The induced pulse from the magnet would be negative and the module or igniter on both style distributors may not recognize it

[510rob]

The pickup system in both styles of dizzy is called a "variable reluctance sensor" - it uses a variance in magnetic field to induce a small current into the pickup wires.

The problem with measuring the pickup signal is that the peak-to-peak voltage can vary from <1Vpp down at idle all the way up to >20Vpp at high rpm, so you'll need an oscilloscope to see what is going on.

The 'electronics' part has a zero-crossing detector for detecting the proper triggering point, which connects to an automatic dwell system that ensures that the coil will receive sufficient dwell time to produce each spark, which connects to a power transistor to controls ignition coil current.

It is a neat system of old analog timing circuitry.

[slowerthantime]

Thanks for the direction.

Mike, the distributor is matchbox style with the E12-80 unit. I added a ground to the brass lug with no change. Does the ignitor/er only ground to the distributor housing?

Following Rob's advice, I removed and grounded the distributor and clamped all 4 spark plugs to a grounded bar (tested the pugs for ground). When turning the distributor shaft manually with the ignition on, still no spark.

I tried 3 separate matchbox units, and made sure that the green and red wires were installed in the order indicated on the rubber boot.

I have messed around with this distributor quite a bit. The breaker plate assembly has been apart and has a modified bearing holder. New bushings, and replaced a section of the green wire on the magnet (soldered and tested for connectivity). Is it possible that I have damaged the reluctor/ stator? Maybe its time to try a different distributor.

[510rob]

Wait... Waaaaaaaait...

Please tell me that you already connected together the [black + blue_stripe] wire and the [black + white_stripe] wire...

When cranking with the key in "START" position, ignition current comes from the key directly to the coil via the [black + blue_stripe] wire.

When running with the key in "RUN" position, ignition current comes from the key to the ballast resistor [black + white_stripe] wire, then over to the coil with a little jump of wire from the ballast resistor.

These needed to be discrete circuits back in the day, which means that the [black + white_stripe] wire ("RUN" position ) LOSES power during cranking...

If you don't tie the [black + blue_stripe] wire to the [black + white_stripe] wires together, you will be measuring 12V at the coil in "RUN" thinking everything is great while standing there with the meter, but then you lose 12V power to the ignition bits during "START" when you are sitting in the driver's seat scratching your head.

Could this be it?

[slowerthantime]

Yes, those wires were joined and connected to the +ve terminal on the coil. I have 12.7v (give or take) at the coil in the ignition "om" position. When cranking, this drops to approx 10.5 v volts. Is that drop OK or too much?

[datzenmike]

If you don't tie the [black + blue_stripe] wire to the [black + white_stripe] wires together, you will be measuring 12V at the coil in "RUN" thinking everything is great while standing there with the meter, but then you lose 12V power to the ignition bits during "START" when you are sitting in the driver's seat scratching your head.

Rob I'm pretty sure that there is 12v on the Black/White during ON and START as well as 12v on the Black/Blue on START. I have a wire diagram showing the Black/White powered in the On position, and on START, it's the same but two more outputs are added one to the starter solenoid and the other to go around the coil ballast. When I wired a matchbox to my 710 I didn't use the Black/Blue START wire.

[510rob]

Turn off the power, gently pull off one of the two spade connectors for either the red or green wire of the pickup coil, then measure the series resistance of the pickup coil. (and report back)

[slowerthantime]

Rob, homework is done. Resistance measured between the magnet wire (red or green) and its post on the ignitor is 103,000 ohm.

Mike, I measured voltage on the individual wires at the coil. BW has 12v at the on position and at the start position. BL only has power at the start position.

[510rob]

I am hoping that Mike might be able to measure a pickup coil, or someone else who has one handy, so we can get another measurement to compare your 100K measurement with.

At this point, I'd say scrounge up an old GM 4-pin HEI ignition module

https://forums.hybridz.org/topic/129542 ... e-problem/

https://www.youtube.com/watch?v=4lxoUvwgZ54

Then hook it up to the pickup coil to see if the pickup coil works. If yes, then the matchbox doesn't work.

1) You have shown that the ignition coil works, gives spark
2) You need to prove that the pickup coil works, GM HEI module can show this.
3) You need to prove that the matchbox works.

[datzenmike]

For what it's worth... I have a '78 FSM and '78 was the year the remote igniter was used, NOT the matchbox, and the pick up coil resistance is 750 ohms or less. I can only assume the matchbox coil will be similar.

103,000 ohms is awfully high. I don't know on the matchbox 103k may be normal. If it's not correct, changing to an HEI module won't fix the problem.


I know the HEI module works on either type of EI distributor.



Two thing about this diagram. Ignore the 'non matchbox type' and the '1.6 ohm 12v coil'

Connect the red and green wires as shown.

[slowerthantime]

Mike, I just measured resistance across the pick up coil (disconnected, measured at the terminals on red and green wire) and it is 370 ohms.

Hoping to get my hands on a GM module this afternoon.

[510rob]

14) I did find and repair an exposed and possibly grounded break in the green wire from the magnet.
15) After repairing the wire...still no spark.
16) I have tried 2 ignitors but not sure if either of them were good to start with.

I removed and grounded the distributor and clamped all 4 spark plugs to a grounded bar (tested the pugs for ground). When turning the distributor shaft manually with the ignition on, still no spark.

I tried 3 separate matchbox units, and made sure that the green and red wires were installed in the order indicated on the rubber boot.

Resistance measured between the magnet wire (red or green) and its post on the ignitor is 103,000 ohm.

For what it's worth... I have a '78 FSM and '78 was the year the remote igniter was used, NOT the matchbox, and the pick up coil resistance is 750 ohms or less. I can only assume the matchbox coil will be similar.

103,000 ohms is awfully high. I don't know on the matchbox 103k may be normal. If it's not correct, changing to an HEI module won't fix the problem.

At this point, I would say the existing pickup coil was damaged somehow.

That part can be transplanted from another dizzy if you have another one.

Don't fret. The EI dizzys are rock-solid when sorted so this will all be worth it once you are zooming up the hilly corners from Kaleden to Keremeos!

[510rob]

The 200SX manual had no data, but the 280ZX manual said the pickup coil should read 400 ohms, so your pickup coil is likely no good

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I should have thought to check the old manuals, but totally forgot. Oops.

The Clymer manual also says the 280ZX Matchbox EI coil should have:
Pri Resistance: 0.84Ω-1.02Ω
Sec Resistance: 8,200Ω-12,400Ω