Printable Version of Topic

Posted by: BIGKAT_83 Oct 2 2015, 12:54 PM

I've got a 25k mile 1979 VW Bug convertible. It starts up fine and runs for just a couple of seconds and then quits.
It does not matter if its hot or cold.
Any ideas on where to start?

Thanks in advance Bob

Posted by: Jeffs9146 Oct 2 2015, 01:13 PM

QUOTE(BIGKAT_83 @ Oct 2 2015, 11:54 AM)

Posted by: Tom Oct 2 2015, 01:14 PM

Put a fuel pressure gage on it and monitor. I bet the fuel pump run after start circuit is not working properly. I believe the old VW's had something close to L-jet injection, so some of the troubleshooting methods would be the same.
Tom

Posted by: hcdmueller Oct 2 2015, 01:49 PM

Definitely L-jet. I retrofitted the same setup onto a Euro Baywindow bus I used to have. Your double relay might be bad or the wiring to the air flow sensor. You can check the fuel pump by pushing the air flow flap on the intake. If the key is on the pump should run. The pump only runs on the double relay while starting. Obviously check for vacuum leaks. The entire alternator stand is part of the intake. You may have some leaks there if the rubber parts of your intake are good.

Posted by: Mark Henry Oct 2 2015, 03:30 PM

All of the above, plus Bug FI is famous for cooking the wire harness, it's why so many backyard wrenches would rip off the FI and stick a carb on. Check the condition of the wires and connectors.
Also in your hunt replace the injector seals, while the injector is out take a pin and press on the pintle, you should hear/feel a slight click.

Posted by: Jake Raby Oct 2 2015, 05:07 PM

Could be a dozen things. Verify fuel pressure, and pull an injector to check the spray pattern for starters.

Hook up with the Athens VW Club guys, they are awesome, and have tech days all the time. Sometimes they hang out at my garage.

Posted by: aircooledtechguy Oct 2 2015, 06:21 PM

I've seen more than just a couple of these where one of the hoses coming off the large rubber elbow between the MAF and the TB popped loose. It will do the very thing you describe.

Posted by: rgalla9146 Oct 2 2015, 06:39 PM

The big hose on top is not just a connector to the air filter.
It must be clamped and vacuum leak proof from flapper box to throttle and beyond.

Posted by: rgalla9146 Oct 2 2015, 06:40 PM

The big hose on top is not just a connector to the air filter.
It must be clamped and vacuum leak proof from flapper box to throttle and beyond.

Posted by: Jake Raby Oct 2 2015, 08:01 PM

That hose will bite you!

Posted by: Jeff Bowlsby Oct 2 2015, 09:42 PM

Go through the test protocol, check every thing:

http://bowlsby.net/914/Classic/zTN_Man12.pdf

Posted by: BIGKAT_83 Oct 8 2015, 08:25 AM

Thanks everyone got a chance to work on it today. You guys nailed it a vacuum leak.


Bob

Posted by: Chris H. Oct 8 2015, 10:14 AM

So you bought a Beetle or what ???

Posted by: Jeffs9146 Oct 8 2015, 09:21 PM

I had the same problem on my 3.0L FI six when I first fired it up so it just made sense!