1979 VW Convertible will start but immediately dies

[Sickies Garage]

Had my wife start it while I was at the light….car started on cold start and died. No light at injector wire.

[VW_Jimbo]

NOID light should pulse light during the cranking. Chase that issue down. The question to answer is why do the injectors not trigger? Is a hot side or the ground side or the computer?
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Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[busdaddy]

[Sickies Garage]

I tested the center wire of the resistor pack with a test light and it lit up. (88B at relay is lit as well) I will unplug all of the injectors and test each one with the Noid tonight. Thanks you all for trying to help me with this! On a good note I never worked on a FI bug before and now I have some knowledge of how they work!

[busdaddy]

[Sickies Garage]

Pulled all of the injector wires…. Going across both terminals I’m reading anywhere from 8-11volts depending on which injector I’m at. Guessing the voltage diff is due to the resistor pack? I tested with the Noid lights and still see nothing!

[busdaddy]

Voltage is good, but don't expect any action from the noid light testing static, that only can happen when the distributor is turning.
The system supplies constant positive power to the injectors through the resistors when the key is on, the grounding is done by the ECU when it's time for a squirt of fuel. The trigger to ground the injectors (they all fire at one) comes from the white #1 wire attached to coil terminal #1, it's the same terminal the green points wire is (or should be) on.

You say the grounds on top of the alternator are spiffy clean and securely attached, as well as the single brown wire on the battery negative terminal, that leaves the single wire to the coil. I think it was you who said they tested it for continuity to the big ECU plug and made sure the contact on the board was clean and shiny and the terminal wasn't squished or damaged, there's a few threads I'm involved with and they kind of blur together.
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[Sickies Garage]

Ok so,something didn’t seem right because I went back and tested the Noid light with my 12v battery and it lit up so why didn’t it light up at the injector wire? I went back and looked at my digital V meter and had it set on the wrong setting! I’m not getting any voltage at any of the injector wires…once the meter setting was correct!

[Sickies Garage]

And responding to the coil wire to the ECU, the brown ground wire from the battery to the DR, and the three ground wires by the alternator, and the ECU terminals looking good, yes….I’ve checked the, all several times. The car came with three DR’s and they all test as they are good.

[Sickies Garage]

Question about the trigger wire….I thought that the coil sent the trigger to the ECU as the points fired to send voltage to the injectors? That being said why will there be voltage at the injector wire when the car is not running?

[busdaddy]

There will (should) be voltage on one terminal as long as the key is on, but no ground on the other, that's pulsed by the ECU when the distributor is turning (points opening and closing).
_________________
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[Sickies Garage]

Ok you just clarified the question I had about the injector plug…..where is the ground picked up? That makes perfect sense.
So I just was going over voltages at the resistor connection and I have 12v on each terminal. (Center hot and one for each injector) I’m assuming that’s correct. So does it make sense that I can’t get any injector voltage because rather “trigger”, or ground, from the coil isn’t making it to the injector?

[VW_Jimbo]

[busdaddy]

You can get the injectors to trigger by repeatedly poking the #1 wire at a ground like the engine case while the key is on, on/off/on/off......., watch the noid light.

But if there's an issue in the wiring that test won't do much.
_________________
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[Sickies Garage]

When I purchased the car it had an electronic distributor in it. I pulled it and put the one that came with the car back in it thinking that may have been the problem……way before I started into this efi stuff!

[busdaddy]

Maybe we should go back to square one and consider the ignition system, obviously it's doing something if it runs for a few seconds, but does the action continue after the key is released?, maybe the "quitting" is really an ignition switch problem? And what's the battery voltage while all this is happening?, L-jet doesn't tolerate low voltages very well.

No ignition action means no injector trigger signal, does a test light connected between the coil's primary terminals blink while cranking?, does the blinking continue even during that 1/2 second when it quits and is spooling down?
_________________
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Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
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[VW_Jimbo]

[KKiley]

I sat back and thought this was an ignition switch issue
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1978 Super Beetle convertible

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[Sickies Garage]

Think I may hav ruled out ignition early on by keeping the starter engaged throughout the cold cycle start up…..it still died.

I will go at it again today and physically ground the trigger wire as busdaddy recommended.

[Sickies Garage]

I checked voltages on the injector connectors and I’m getting 12v on both pins??