Itinerant Air-Cooled

I have an air cooled 1980 vanagon. It uses a series resistor to lower the voltage at the injector. When I check the voltage at the injector I get a reading of 12 volts. How can I tell if the injector is getting the correct voltage?

Hi there!

When are you doing the voltage reading? (Under what operation circumstances? Starting? Cranking? Key on only?)

Are you reading across the terminals of the injector plug, or reading one pin to ground?

Have you checked the resistance of the wiring harness and injectors together from the ECU plug? Models with resistor packs like 7-9 ohms. If they’re all high, clean the ground tabs under the intake plenum, and check for corroded/loose wire connectors too. I find it easiest to access while laying on my stomach in the bed, this gives better visuals than working from behind the car, and you can rest easy once you’ve cleaned all the connectors. :)

Good luck,
Robbie

Thanks, All of the above. I did find an answer. You can't use a voltmeter to check for 5 volts at the injector. It will read 12 volts. It would require a special gauge to check for 5 volts at the injector.

If the engine is running, the 5v will be such a rapid pulse that no handheld tools will be able to read voltage with any consistency. A noid light is the home-mechanic's solution to check injector pulse function, while an electronics specialist could use an oscilliscope.

Perhaps describe your car's running issues in one thread, and we can diagnose the general symptoms instead of specific possible non-issues?

Robbie

flyfisher111 wrote: ↑

Fri Sep 13, 2019 5:08 am

Thanks, All of the above. I did find an answer. You can't use a voltmeter to check for 5 volts at the injector. It will read 12 volts. It would require a special gauge to check for 5 volts at the injector.

I want to do a symptom-based diagnosis here, and dispense with some of the arcane tests that seem to obfuscate the issue as often as not.

If you have any voltage at the injector, the series resistors are doing their job. They fail open.
Colin