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Fri Feb 13, 2009 2:27 pm

I recently (3 weeks ago) bought a 1988 2.1 bus with a Digijet fuel injection system. I noticed some silicone sealant on top of the engine and removed the fuel injection system (pulled out all the connectors, loosened the bolts at the heads) to take a better look at the engine. After putting everything back as it was before, I could not get the engine to start and keep on running.

I noticed that the air flow sensor does not open when the engine is cranked after I rmoved the cover on top. When holding it nearly all the way open while someone else turns the key, the engine does start and keeps on running, but dies again when I let it close. Everything else that I tested seems fine except the switch underneath the throttle control and one of the wires connected to the air flow sensor. I could not get a reading (resistance) from the switch and the wire was broken somewhere (temporarily bypassed it)

Can someone please help.

Fri Feb 13, 2009 6:26 pm

You seem most likely to have some kind of wiring issues. In the list below get the wiring diagram as it has a complete system on one page so you can trace it. Now you said you have a Digijet installed. I hope not, then you have a form of miscongenation going on and the system is some kind of weird hybrid. Hopefully, it is a stock Digifant system as it should be, cause then the following will get you started.

You need to gain a better understanding of the system. The VW Protraining manuals will get you up to speed on how it works and how to troubleshoot. To get you own electronic versions of the ProTraining Manuals, go to my public folder and get:

86 Vanagon Protraining.pdf
Vanagon Protraining 86-91 Fuel Systems.pdf
Vanagon Protraining Digifant I 86-91.pdf
Vanagon Wiring Diagram.pdf

http://homepage.mac.com/WebObjects/FileSharing.woa...mp;lang=en

Specifically run these tests:

Sat Feb 14, 2009 1:09 am

I checked again and the system is definately a Digijet according to what is printed on the ECU cover. The plug attaching to the ECU has connections in different locations from the ones in the Digifant documentation: 1, 2, 4, 6, 7,11, 12, 13, 14, 15, 19, 20, 21, 23, 24, 25.

I went to the nearest Volkswagen branch this morning to ask advice and was told to tow the vehicle in and that they would take a look at it for R475-00 per hour. On a twenty year old vehicle that is not an option for me.

Should the air flow meter open (stays closed as far as I can see) when the engine is turning fast enough to start? After the starter stops it sounds as if the engine keeps on running for a second or two before stopping again. Sometimes it backfires. Meter not opening looks as if it could be mechanical, backfiring sounds like electrical?

Sat Feb 14, 2009 2:36 am

Make sure you have all the vacuum hoses reinstalled correctly, and the clamps on the S boot are tightened down properly. Are your manifolds seated against your heads well? You should get enough air flow at idle to move the flapper in the AFM. Assuming that something has not happened inside your engine then air must be bypassing around instead of going through your AFM.

Sat Feb 14, 2009 5:10 am

:D I checked all the places again where air might be able to enter the system and found that the two pipes going to the right head had partially slipped off from where they are tightened to the manifold (clamps not very tight, could push them back on without loosening the clamps). The must have moved when I put everything back. Next time I will know where to start looking.

The switch underneath the throttle valve was not being switched when the throttle was fully open or closed, adjusted it and can now hear a click in both positions.

Thank you Wildthings and Dogpilot, I appreciate the advice that you gave me.