No spark @ plugs on 2.1. Update: Spark, still no start [Solved]

[wehrbüchse]

using a jumper wire to ground the center wire of the Hall sensor connector produces a spark at the wire coming from the coil (detached from dist cap and lying on block). In theory, this should mean the ECU and coil are good, indicating a bad Hall sender.

This Hall sensor is exceptionally new looking. Nevertheless, I swapped in the distributor from a running van. Still no spark at the plugs.

I have tried four sets of caps & rotors, and three sets of cables just to make my kid shut up about the cables. Still no spark at the plugs.

To understand how simple the Hall sender is = understanding that this simply makes no sense. The spark from the coil wire should be mechanically distributed to the cables via the cap and rotor. Unless I'm simply spacing out from tunnel vision, the only way for this to make sense is that the coil is putting out *insufficient* spark or somehow BOTH Hall senders are suddenly bad. They don't go bad that often.

I swapped in a good coil just to be sure. And then a good ECU. Still no spark.

I'm at my wit's end.

Any ideas?

[xoo00oox]

Did you check the power AND the ground at the hall sensor?

[DanHoug]

first, you can definitively test your Hall sensor:
https://www.thesamba.com/vw/forum/viewtopic.php?t=701391&highlight=

then go to basic troubleshooting:
https://www.thesamba.com/vw/forum/viewtopic.php?t=349429

between these two things, you can pinpoint your problem.
_________________
-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[wehrbüchse]

[xoo00oox]

[wehrbüchse]

[Wildthings]

The wires in the Hall circuitry are tiny and subject to breakage. Wiggling them around to test the Hall pickup can make the system work momentarily.

[MarkWard]

Have you visually watched the distributor shaft turn while the engine cranks?
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[wehrbüchse]

wow i love you guys. i was about to keel over when i posted and ive spent the last 18hrs doing like 7 convoluted tax returns, I majorly appreciate your brainpower injections and feedback. I’ll be done w this stupid desk crap in a bit!

[wehrbüchse]

[Wildthings]

Check the voltage at the Hall Unit when cranking to both the engine block and to the body/frame. If the engine/starter has a wacky ground to the body it might still crank, but the Hall unit might not see enough volts to fire.

[wehrbüchse]

when you say check voltage at the hall unit, you mean at the connector? i measured 12V between the outer two contacts last night. but the power to the plugs comes from the coil anyway, such that it shouldn't matter right?

[wehrbüchse]

the hall sender tested fine using Dan’s unit. i have spark at the plugs as evidenced by a spark tester from napa. i just sprayed starter fluid *vapor* into the S boot where it attaches to the MAF sensor. engine cranks but absolutely will not start.

do I understand correctly that if there were a bad ground somewhere, the ECU simply won’t send the signal to the hall sender to create the spark? in other words doesn’t the presence of spark confirm that grounds are fine? I guess I already know the answer to this but maybe someone can help it make sense for me. this van has been broken down now for a solid YEAR.

[crazyvwvanman]

I think you are misunderstanding how the ignition spark works in your Digifant van.

The Hall unit doesn't make the spark.
The Hall unit tells the ECU that the engine is turning.
The Hall unit tells the ECU when the engine is in a certain position as it is turning.
So the Hall unit is the base timing source for the ECU.
Once the Hall has sent its small timing pulse to the ECU the Hall has no further role in the spark creation and distribution.
The ECU uses these small base timing pulses from the Hall to determine when the ECU should trigger the ignition coil to make Sparks.
The sparks go from the ignition coil to the center of the distributor cap.
The spinning rotor points to one of the 4 spark plug wires to direct the spark from the center of the cap to a given cylinder plug wire.

The Hall unit has nothing to do with the spark itself.
It merely is the INITIAL source of the small TIMING pulse used by the ECU to trigger the ignition coil to make the spark.
Then the distributor cap and rotor direct the spark to a given cylinder plug wire.
The low voltage Hall lives a quiet life in the lower part of the distributor while the high voltage spark activity passes through the upper part where the rotor and cap steer the spark to a given plug wire.

Mark

[djkeev]

[DuncanS]

I have heard of them referred to as a Mass Air Flow unit.

Great post by Mark, as always. Sometimes we need to be reminded of the obvious, which we already knew, and or learn something new we didn't before.

Duncan

[djkeev]

[DanHoug]

[wehrbüchse]

[DanHoug]

ok, we gotta get you going. you're still at no spark, correct?

Knowns, correct if wrong:
- Hall sensor good
- spark test grounding center connector on dist results in spark coming out *coil* lead.

Info needed:
- using a remote switch or an assistant, connect the Hall tester to the dist and have someone crank the engine. does the tester flash? this test tells you the distributor is rotating with the engine.

if the tester flashes, next eliminate the cap and rotor as a spark interrupter. pull the coil lead out of the dist and using your remote starter switch (see how handy that'll be now?!), hold the coil lead close to the block. spark? if yes, your problem is in wrong cap/rotor combinations. if no, report back! well, report back anyway.
_________________
-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com