No spark, no ground to coil?

[Nordin]

You need power, AND you need the module to ground the coil in pulses. Grounding the coil permits current flow, which creates magnetism. When the module breaks the ground connection, the magnetic field collapses, and you get a spark. The ground is not continuous.


A meter cannot tell you that the coil is good. A meter can tell you that the coil is bad.

Coil testing for most of us involves the meter, AND a spark-tester calibrated for HEI ignition systems.

This is the kind of spark-tester I favor:
www.amazon.com/dp/B003WZXAWK/?coliid=I3S98D7T1J0RLJ&colid=2VLYZKC3HBBDO&psc=1&ref_=lv_ov_lig_dp_it


"New" doesn't mean "good". What parts did you replace?

If you connect a test light to battery +, then probe the ground wire on that two-wire connector you pictured earlier, the test light should flicker when someone turns the key to "crank".

It's unlikely to be a fuse or relay.

Thanks for the input! I have checked the ground to coil from the 3-leaded connector and I got 12V and ground in pulses.

I just tested the coil with a meter (ohm) and I think that Ive done it correct, and it should be good according to the readings. But I still have no spark from the coil (tested with a spark-plug tester) I might have done it all wrong .

New cap, rotor, wires and all the plugs. I removed the cap and the rotor seems fine, doesnt spin around and aint loose.

 

[Schurkey]

Thanks for the input! I have checked the ground to coil from the 3-leaded connector and I got 12V and ground in pulses.

What vehicle is this? I blew-up your photo, now I see that there's three wires in that connector body, not just the two like I expected.

I obviously need to do some research. The harness will connect to both ends of the primary windings of the coil--battery power, and pulsed ground. The third wire could be a ground for the secondary winding, with the other end of the secondary winding being connected to the "coil wire" leading to the distributor cap. But I've never seen that on a freestanding HEI coil. I've seen it on the older, "coil-in-cap" HEIs.

I just tested the coil with a meter (ohm) and I think that Ive done it correct, and it should be good according to the readings. But I still have no spark from the coil (tested with a spark-plug tester) I might have done it all wrong .

New cap, rotor, wires and all the plugs. I removed the cap and the rotor seems fine, doesnt spin around and aint loose.

Do you have another coil to try? I get extras from the Treasure Yard for very low cost, but maybe that's tough in Sweden.

Does the vehicle have a pickup coil? Or is the ignition triggered via a crank sensor?

 

[Nordin]

What vehicle is this? I blew-up your photo, now I see that there's three wires in that connector body, not just the two like I expected.

I obviously need to do some research. The harness will connect to both ends of the primary windings of the coil--battery power, and pulsed ground. The third wire could be a ground for the secondary winding, with the other end of the secondary winding being connected to the "coil wire" leading to the distributor cap. But I've never seen that on a freestanding HEI coil. I've seen it on the older, "coil-in-cap" HEIs.

Do you have another coil to try? I get extras from the Treasure Yard for very low cost, but maybe that's tough in Sweden.

Does the vehicle have a pickup coil? Or is the ignition triggered via a crank sensor?

This is a 1999 chevy suburban. 5.7L.

I attach a half-bad picture of the wiring to the coil if that helps.

I ordered a new coil yesterday and it should arrive today so I hope thats the issue.

No pickup coil as far as I know, there is a crank sensor and I got 12V and ground on that one and should be fine according to the ohm reading I did. Tried to look at the voltage with my obd2 reader aswell but the app didnt support that and my laptop is at my brothers house.

 

[Schurkey]

Thanks for that. "A" is the power input to the coil; B and C are essentially the same thing, but wired to different devices. The module would control the ground on C, which is connected to B, which is connected to the dashboard tach.

Therefore, A--C is the coil primary winding, B is a tach output, electrically identical to C.

It's not wired like the old coil-in-cap coils where the "extra" wire was the other end of the secondary winding, independent of the primary winding.

You're correct, no pickup coil on Vortec engines. Ignition is via crank sensor and computer trickery.

 

[Nordin]

Thanks for that. "A" is the power input to the coil; B and C are essentially the same thing, but wired to different devices. The module would control the ground on C, which is connected to B, which is connected to the dashboard tach.

Therefore, A--C is the coil primary winding, B is a tach output, electrically identical to C.

It's not wired like the old coil-in-cap coils where the "extra" wire was the other end of the secondary winding, independent of the primary winding.

You're correct, no pickup coil on Vortec engines. Ignition is via crank sensor and computer trickery.

Thanks for the explanation! I'm no good at reading these schemes

Well, the next step if the problem persists after I changed to the new coil, I must change the crank sensor. I dont know if it can read wrong even if the ohm reading where good?

I dont really know how to explain it in english but look at it as a wave with 12v at the top and 0 at the bottom ~ If the sensor doesnt drop all the way down to 0, I dont think it gives a correct signal to the computer/ignition and causes a no spark situation?

 

[Nordin]

Well brand new coil, no start... this starts to makes me real mad...

 

[Nordin]

After charging the battery for a while I had a start and run for a couple of second but then just dies right away.
Now this is what happends.
(I think the starter is about to give up aswell)

Hope the video works.

xc_hide_links_from_guests_guests_error_hide_media

 

[Schurkey]

Based on the abruptness with which the tach drops to "0", I'm fairly sure the ECM isn't getting a crank sensor signal; or the ECM is faulty.

Could be crank sensor, ECM, or the wire harness between them. Maybe the ignition module.

Outside chance: intermittent short to ground on the Tach wire; which would also disable the ignition--it would act like the module is grounding the coil, so there's never an open circuit causing the magnetic field of the coil to collapse and induce the spark voltage into the secondary windings.

I'd be looking over the wire harness carefully before replacing any parts.

A crank sensor can't be reliably tested with an ohmmeter.

 

[Nordin]

Based on the abruptness with which the tach drops to "0", I'm fairly sure the ECM isn't getting a crank sensor signal; or the ECM is faulty.

Could be crank sensor, ECM, or the wire harness between them. Maybe the ignition module.

Outside chance: intermittent short to ground on the Tach wire; which would also disable the ignition--it would act like the module is grounding the coil, so there's never an open circuit causing the magnetic field of the coil to collapse and induce the spark voltage into the secondary windings.

I'd be looking over the wire harness carefully before replacing any parts.

A crank sensor can't be reliably tested with an ohmmeter.

I kinda felt the same thing when it happened so I wanted to get it on film to show you guys.

I’ve checked the harness both two and three times but nothing, cant find any damage at all. I havent looked the tach-wire tho, will do that tomorrow.
Either the wires are OK or its well hidden, even removed all the wire protection

ordered a crank sensor just in case, it takes a day or two so I want to be prepared

(The ignition module (ICM) is a day old, no guarantee its working properly but its not from 1999.)

 

[HotWheelsBurban]

could be the crankshaft position sensor. Could also be the Passlock system, if you have a known good ICM and CPS. This happened to my 99 Burb a couple years ago, only sure cure was to have the function deleted in the computer. $250 but he starts when he's supposed to!