VW Wasserboxer nerds, assemble!

"RamblinRover Luxury-Yacht" (ramblininexile)
07/19/2018 at 20:25 • Filed to: None

A friend’s Wasserboxer Ve Wanagon with Digifant (‘90) is being a poo and running very rich. So rich, in fact, that it’s running around with the vacuum line to the fuel regulator disconnected for extra air (!), and if connected, it chokes itself out. It also chokes itself out when the hole is merely blocked, and the regulator being connected doesn’t help at all .

I have checked to see what it does with the low idle enrichment switch disconnected, with the idle air control disconnected* , and the temp sending unit is new, as is the fuel regulator.

I have tasked the owner with doing an O2 sensor, and multimeter-checking the (new) temp sensor and the airflow and air temp sensor unit, since he has specs for it. We will also check the hall effect sensor on the dizzy and its connections, because they have been spliced(!) dodgily in the past, other than ground . Can’t see why that would be it, but it’s there...

Any other ideas?

*Yeah, with running rich at high throttle as well as low, wasn’t going to be it, but a boy can dream.

DISCUSSION (13)

sony1492 > RamblinRover Luxury-Yacht
07/19/2018 at 20:37

The fpr will have the least fuel pressure at idle under vacuum and the greatest under atmospheric. ( because you want the most pressure at wot)

So running that vacuum line disconnected is actually increasing fuel pressure and adding more fuel.(I’m not familiar with vw’s system but in general that’s how they work )

LOREM IPSUM > RamblinRover Luxury-Yacht
07/19/2018 at 20:51

Welp, wildly guessing, but perhaps leaking injector, bad 02 sensor, unmetered air leak, bad whatever it uses to meter intake air or temp, bad temp sensor, wiring issues, low on farfegnugen fluid...

RamblinRover Luxury-Yacht > sony1492
07/19/2018 at 20:57

That’s what I would have thought, but connected vs. disconnected doesn’t seem to have a great effect - the overdelivery is substantial enough due to some other cause that it overfuels worst with the vacuum tap blocked, less bad with the regulator connected(?), and least with the tap open to air.

RamblinRover Luxury-Yacht > LOREM IPSUM
07/19/2018 at 20:59

low on farfegnugen fluid...

Well, other than that...

I think this is a bigger act-up than one leaking injector, since it has four. Every one would have to be FUBAR. Can’t be unmetered air leak if it runs *better* when leaking more air, bad o2 definitely possible/likely, and I’ve told him to check both the air temp and water temp sensing, so.

LOREM IPSUM > RamblinRover Luxury-Yacht
07/19/2018 at 21:03

It was all really just a lead up to the farfegnugen gag, but ya never know when a bullshit shot in the dark might hit the mark anyway.

sony1492 > RamblinRover Luxury-Yacht
07/19/2018 at 21:21

Does unplugging the water temp sensor effect anything?

RamblinRover Luxury-Yacht > sony1492
07/19/2018 at 21:33

Seen some notes that that's a thing, haven't done it.

vicali > RamblinRover Luxury-Yacht
07/19/2018 at 23:14

Our v an ran rich too, dealership unplugged the O2 and gave it back as fixed.. lol. I plugged it back in and got the digi set screw adjusted to where it wouldn’t die at idle but wouldn’t rpm up either. I always thought I had an air leak after the air flow sensor..

Might be helpful;

http://www.gowesty.com/tech-article-details.php?id=85

sony1492 > RamblinRover Luxury-Yacht
07/20/2018 at 14:14

If the ect is faulty, the sensor will act as an open circuit so unplugging the sensor will do nothing if the ect is already faulty(depending on how it broke but it will most likely be an open circuit). If it effects anything when you unplug it you know the car is getting a reading from it. Usually an open will make the car think it’s-40F and run accordingly rich(negative temperature coefficient thermistor which increases resistance the lower the temp, hence the name. So infinite resistance is a very low temp)

RamblinRover Luxury-Yacht > sony1492
07/20/2018 at 15:04

The trouble is this - it is already running so incredibly rich that I don’t know if I would be able to tell a difference. It is running so rich that it chokes out very quickly if there is not an *active leak* into the manifold.

It could all be something idiotic like the airflow sensor having been monkeyed with by somebody who didn’t know that the regulator vacuum line was off. But. I don’t know. I could possibly test unplugging the sensor after babooning the airflow sensor, but that’s as far as my imagination stretches at present.

sony1492 > RamblinRover Luxury-Yacht
07/20/2018 at 16:20

At this point unplugging stuff to see if anything changes is a solid plan.

RamblinRover Luxury-Yacht > sony1492
07/20/2018 at 16:26

Yeah - there’s an O2 sensor override thing I’ve read. If an O2 sensor replacement doesn’t work and the O2 sensor override doesn’t do anything and the results from the air sensor and dizzy sensor checks are inconclusive, I will probably monkey with the air flow sensor, apply suction to the regulator, and then disconnect the temp sensor.

Since I already tried disconnecting the idle air control, the low idle enrichment sensor, and a couple of other things. Haven’t tried disconnecting the dodgy electric connections to the hall sensor - don’t know if it’ll even run that way. I know it won’t without the air sensor.

I have heard that these old Digifants and Digijets will sometimes run infinitely rich because they never hit their index temp to switch off warmup mode. Low temp thermostat = temp just a few degrees too low = choke forever. The mind reels.

sony1492 > RamblinRover Luxury-Yacht
07/20/2018 at 18:11

I have doubts that the o2 sensor can affect fuel trim enough to richen as much as your describing, then again I know nothing of how vw does things