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Starts When Motor is Cold, Idles for 50 Seconds then Stalls
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walkngdude
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PostPosted: Mon May 17, 2021 5:17 pm    Post subject: Starts When Motor is Cold, Idles for 50 Seconds then Stalls Reply with quote

My son has a 1985 Vanagon 1.9 water cooled that he got from his grandparents. He's been driving it for about 6 months. When his mom got it for him they had it serviced and I'll attach the receipt here that shows what was done. Also in January I broke the "Coolant Hose Flange Connector" and replaced it. Apparently I didn't bleed the system right and that caused the water-pump to fail so I had that replaced for about $800 (ouch!).

=========================

Recently it stalled while he was driving and we've been trying to figure it out in my free time. I was looking for a vacuum leak and found a big rip in the 1/2" hose running to the intake boot and replace it. Then I sprayed (emptied a can of) carburetor cleaner around on anything that looked like a vacuum line and didn't find anything. I would be willing to buy a vacuum gauge and a fuel pressure gauge if I find instructions on how to hook them up.

I pulled 2 spark plugs (one at a time) and checked for spark and it looks good and strong to my untrained eye.

=========================

Right now the symptoms are that when it's been sitting for a while I can turn it over and pumping the gas pedal it will start after maybe 10 seconds. After it starts it will idle nicely without any help for 50 seconds. At that point the idle starts getting rough and will stall unless I help it by giving it some gas and raising the RPM. At this point I have to gradually give it more pedal, raising the RPM continually or it will stall then in a short time it just stalls.

After it stalls it wont start again until it has set for a good long time. We just wait until the next day to try again. Then the same pattern.

=========================

1) I don't think that 50 seconds is enough to make it warm enough to think it has something to do with the choke.
2) Maybe it's still a vacuum line and I need a better way to find it.
3) The vacuum line is fixed and the mechanic had adjusted the idle screw to compensate for it and I need to turn it back.
4) There is a fuel problem. This seems likely to me by how it's acting but what do I know. The mechanic receipt says that he replaced the fuel filter. Maybe the pump, injectors?...
5) A sensor somewhere. This seems very likely.
6) Electric component wiring, connector or ground...

=========================

If anyone would give me some direction here I would be very grateful.
I did buy a Haynes manual for about $70 and didn't find it very helpful. I guess I need the factory service manual.

I did a search and didn't find anything that looked like my problem. I apologize if I missed something obvious.

Thanks
Marc

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brickster
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PostPosted: Mon May 17, 2021 5:55 pm    Post subject: Re: Starts When Motor is Cold, Idles for 50 Seconds then Stalls Reply with quote

If you can return the Haynes, I would, and then pick up a Bentley.

There’s a pdf of the Digijet service manual if you search around that has easy to follow component testing steps similar to the Bentley.

Some observations:
Since you have spark, check fuel pressure on the port near the distributor.
10 seconds to start seems long. Is your battery and its connections in good shape?
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Howesight
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PostPosted: Mon May 17, 2021 5:56 pm    Post subject: Re: Starts When Motor is Cold, Idles for 50 Seconds then Stalls Reply with quote

The problem is most likely caused by the co-axial cable connected to the oxygen sensor. It is likely shorted out.

The Digijet EFI system ignores the oxygen sensor signal until a threshold coolant temperature is sensed by the coolant temperature sensor. At that point, the Engine Control Unit (ECU) begins to adjust the Air/Fuel Ratio (AFR) to what appears to be the correct proportions.

If the oxygen sensor "signal" wire (the centre wire in the coaxial cable) is shorted out to the grounded outer shield wire, then the oxygen sensor signal to the ECU is zero volts. This signal is interpreted as a lean fueling condition, so the ECU adds fueling. This continues in numerous iterations until the fuel mixture is so rich (ie, overfueled) that the engine cannot run. In more modern EFI systems, if this happens, a piece of software interprets the problems and stops adding fuel before the engine stalls out. Not so in the lowly, pre-Cambrian design of the Digifant EFI system.

This is why the engine starts, runs fine, and after the coolant warms up, it runs increasingly poorly until it stops running.

Simply put, you need to inspect the entirety of the wiring path from the oxygen sensor all the way to the ECU and locate the short.

I will post a link to prior posts on this topic in a minute.
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brickster
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PostPosted: Mon May 17, 2021 5:57 pm    Post subject: Re: Starts When Motor is Cold, Idles for 50 Seconds then Stalls Reply with quote

If you can return the Haynes, I would, and then pick up a Bentley.

There’s a pdf of the Digijet service manual if you search around that has easy to follow component testing steps similar to the Bentley.

Some observations:
Since you have spark, check fuel pressure on the port near the distributor.
10 seconds to start seems long. Is your battery and its connections in good shape?
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Howesight
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PostPosted: Mon May 17, 2021 6:15 pm    Post subject: Re: Starts When Motor is Cold, Idles for 50 Seconds then Stalls Reply with quote

The "ten seconds" described is most likely the cranking duration needed to clear the excess gasoline out of the cylinders.

To the Original Poster (OP): When the engine starts and runs, but dies, is there a lot of smell of raw gasoline in the exhaust gases out the tailpipe? Is there black, sooty smoke? If so, these symptoms confirm my suspicions about the oxygen sensor coaxial cable.
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DanHoug
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PostPosted: Mon May 17, 2021 6:19 pm    Post subject: Re: Starts When Motor is Cold, Idles for 50 Seconds then Stalls Reply with quote

Original Estimate: $500
Pay This Amount: $3,050.63

hope the communication was good in that process. everything looks reasonable for an old vehicle.

it would be good to approach this sequentially. next time it starts and dies, check:
- is spark present?
- pull a spark plug and see if it is wet with fuel. if it is wet that is good info. if it is dry, pull the injector pair (they have new seals, they'll come out easy), ground the ignition coil lead, and crank to see if they spray fuel.

barring a sequential diagnosis, because arm chair guessing is great sport, i'm going to say your spark plugs will be wet when you pull them because the engine is flooding out from a bad ECU coolant sensor that is telling it to pour on the gas.

note that your exhaust manifold was mentioned as cracked. this can introduce air into the exhaust, make the O2 sensor think things are lean, and richen the mixture up. 50 seconds is sorta quick for an O2 sensor to get up to functioning temp but it's sunny California.
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Howesight
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PostPosted: Mon May 17, 2021 6:22 pm    Post subject: Re: Starts When Motor is Cold, Idles for 50 Seconds then Stalls Reply with quote

Here's a link to one of the many threads on this topic with pics of the coaxial cable and the shorting problem:

https://www.thesamba.com/vw/forum/viewtopic.php?p=7283386

Here's another link:

https://www.thesamba.com/vw/forum/viewtopic.php?t=667929
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PostPosted: Mon May 17, 2021 6:28 pm    Post subject: Re: Starts When Motor is Cold, Idles for 50 Seconds then Stalls Reply with quote

Howesight wrote:
Here's a link to one of the many threads on this topic with pics of the coaxial cable and the shorting problem:

https://www.thesamba.com/vw/forum/viewtopic.php?p=7283386

Here's another link:

https://www.thesamba.com/vw/forum/viewtopic.php?t=667929


d'oh! forgot about that!! first place to look!
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PostPosted: Mon May 17, 2021 6:39 pm    Post subject: Re: Starts When Motor is Cold, Idles for 50 Seconds then Stalls Reply with quote

Sounds like it could be a failed or disconnected TSII sensor. The coaxial cable failure shouldn't show itself so fast on a cold engine.
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mikemtnbike
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PostPosted: Mon May 17, 2021 7:00 pm    Post subject: Re: Starts When Motor is Cold, Idles for 50 Seconds then Stalls Reply with quote

Howesight knows his stuff IMO, but so does wildthings I’d try both their suggestions odds are one is right.

Also IMO, pumping the gas has little if any effect on starting a fuel injected engine. The one way it could is if the engine was flooding with gas and you’re clearing it out(I think). So, I’m guessing that points back at the O2 circuit, since it involves fuel. Again, guessing.

Good luck!!
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walkngdude
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PostPosted: Mon May 17, 2021 7:16 pm    Post subject: Re: Starts When Motor is Cold, Idles for 50 Seconds then Stalls Reply with quote

Oh man, you guys are the best!

I don't have time for a couple of day to dig into it but I did run out and look at the O2 sensor wire and looked at a video. I have a good multi-meter and can check for 0.4 volts and maybe see if it is changing voltage while running if my meter will react that quickly.

The Temp 2 sensor looks like it's under the water pump? I can go look to see if it's connected after diner. Looks a little hard to get too though. We did have the water pump replaced so maybe something happened to it...

When I had the spark plugs off to check for spark I was looking to see if they looked fouled. They were a little blackish, definitely not coco brown and maybe slightly wet. We didn't smell gas when it was running and no black smoke.

I even tried to run it at relatively high RPM for a bit to try to "blow out" any loaded up carbon or fuel like we used to on 2 strokes but nothing really came out that I could see.

I still have to go read the links that Howesight posted and maybe I'll get the good service manual. It's around $150 but worth it if they are going to keep the van. I'd hate to sell it, it's very cool.

Cool beans guys.

Thanks!
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Howesight
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PostPosted: Mon May 17, 2021 7:47 pm    Post subject: Re: Starts When Motor is Cold, Idles for 50 Seconds then Stalls Reply with quote

Wildthings wrote:
Sounds like it could be a failed or disconnected TSII sensor. The coaxial cable failure shouldn't show itself so fast on a cold engine.


Hi Wildthings:

I agree that the coolant temp sensor or its wiring can also cause these symptoms. The OP writes that the symptoms begin after 50 seconds, (which might not have been measured with a stop watch Wink ) and that throttle is required to keep it going, after which it stops running. That sequence is what stuck out to me. Also, the OP is in Santa Cruz which, as I recall from visits to Carmel, does not get very cold this time of year.

In addition, it is also possible that the AFM is the culprit in causing these symptoms. The Temp 2 sensor and the oxygen sensor wiring short are free to diagnose with a VOM meter. Swapping in a new/rebuilt AFM on a diagnostic lark is expensive, so eliminating the Temp2 sensor and wiring as a cause is a good starting point. The oxygen sensor cable is a tad more effort to rule out.

To the OP:

Here is a link to the VW Digijet Pro-training manual that you may find helpful:

https://redirect.viglink.com/?format=go&jsonp=...jet_FI.pdf

If that link doesn't work, google VW Digijet Pro-training manual.
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PostPosted: Mon May 17, 2021 8:22 pm    Post subject: Re: Starts When Motor is Cold, Idles for 50 Seconds then Stalls Reply with quote

Thanks again. I did time it with my phone "stop watch" haha. So is really seems to start at about 50 seconds. Maybe a little plus or minus..

It doesn't get below 60 degrees here this time of year (much). Weather this week was between 58 and 65.

I found the TSII sensor.
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PostPosted: Tue May 18, 2021 3:56 am    Post subject: Re: Starts When Motor is Cold, Idles for 50 Seconds then Stalls Reply with quote

You are at a crossroads where you have to decide on one of the following paths

1invest the time and resources to learn how this vehicle operates , source parts, and perform maintenance about 4x per year

2 pay a set of repair bills of $3000-5000 each year

3 sell it

Note that driving it until there is a problem, then calling the appliance repair man, aka the Samba, is conspicuously absent as long term strategy. This will cost you a major repair bill of $10,000 and up.
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PostPosted: Tue May 18, 2021 4:29 am    Post subject: Re: Starts When Motor is Cold, Idles for 50 Seconds then Stalls Reply with quote

Am I out of touch with reality?
$350 for front calipers, and another $300 to install?
$300 for coolant
Replace battery for $50, cost of battery is extra.
Lube CVs for $50

I'll change 20 batteries before I feel like disassembling and repacking one CV joint.
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PostPosted: Tue May 18, 2021 7:18 am    Post subject: Re: Starts When Motor is Cold, Idles for 50 Seconds then Stalls Reply with quote

Wellington wrote:
Am I out of touch with reality?
$350 for front calipers, and another $300 to install?
$300 for coolant
Replace battery for $50, cost of battery is extra.
Lube CVs for $50

I'll change 20 batteries before I feel like disassembling and repacking one CV joint.
I have to think that for $50, you could only squirt CV grease through a loosened boot end on the shaft, into the CV joint.
Not the same as removal and repacking.... Think Think
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PostPosted: Tue May 18, 2021 7:40 am    Post subject: Re: Starts When Motor is Cold, Idles for 50 Seconds then Stalls Reply with quote

Car was up on a lift, do CV removal with an impact takes about 5 minutes. 30 minutes to clean and repack

it’s a short bill , but not crazy.
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PostPosted: Tue May 18, 2021 12:28 pm    Post subject: Re: Starts When Motor is Cold, Idles for 50 Seconds then Stalls Reply with quote

Abscate wrote:
Car was up on a lift, do CV removal with an impact takes about 5 minutes. 30 minutes to clean and repack

it’s a short bill , but not crazy.
Not enough labor charge to get them clean and repacked. And I wouldn't bet on a' Racetrack' 5 minutes to impact all those CV bolts without one or more needed special attention due to crud stuck in the way , inside the bolt head. Razz Razz Razz
But, that's the least of the OPs problem right now... Sad Sad Think
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PostPosted: Tue May 18, 2021 2:00 pm    Post subject: Re: Starts When Motor is Cold, Idles for 50 Seconds then Stalls Reply with quote

jlrftype7 wrote:
Abscate wrote:
Car was up on a lift, do CV removal with an impact takes about 5 minutes. 30 minutes to clean and repack

it’s a short bill , but not crazy.
Not enough labor charge to get them clean and repacked. And I wouldn't bet on a' Racetrack' 5 minutes to impact all those CV bolts without one or more needed special attention due to crud stuck in the way , inside the bolt head. Razz Razz Razz
But, that's the least of the OPs problem right now... Sad Sad Think


When it’s up,in the air , a spray and a pick are really quick. It’s amazing how fast stuff is on a lift

I’d want an hour and $100 in shop supplies, agreed.
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PostPosted: Sun May 23, 2021 3:42 pm    Post subject: Re: Starts When Motor is Cold, Idles for 50 Seconds then Stalls Reply with quote

OK, we worked on it today.
We took the connector for the O2 sensor apart and read resistance with my Fluke multi-meter.
With engine cold (not running) I got 143k ohms to ground (practically open) for the O2 sensor wire (coming from the ECU).

Then with the O2 sensor still disconnected we started it (cold).
Reading voltage from the ECU on the green O2 sensor wire I got 0.47 volts.

I timed it from start and the engine idled smoothly for 58 seconds before stalling.

We started it again and tried to keep it alive with gas pedal and it acted like before.

We then took off the temperature 2 sensor wires (connector) and read resistance to ground toward the ECU and got 8k ohms.

We tried to start it with the temp 2 sensor disconnected and it did start and ran poorly for a bit with help for the throttle pedal then stalled.

We then disconnected the harness/connector from the air flow meter and tried to start it with all three disconnected (AFM, O2
& Temp2 sensors) and didn't notice any change. (Ran poorly then stalled).

=======================

Am I taking these steps correctly?
Seems like no ground fault on the o2 sensor wire and no noticeable point of failure and that I read 0.4 volts make it pass. Also from what I've read if it was the o2 sensor itself the van should have idled when we disconnected it. (Is this right?)

I read (on the multi-meter) no major short on the temp 2 wire and I believe that I read (on a forum thread) that if the sensor had failed that it would run disconnected, (I think that when we ran this disconnected we also had the 02 sensor disconnected).

We then disconnected the Air Flow Meter and it still didnt go away.

Also there are a couple of bundles of ground wires under bolts that we took apart and cleaned with contact cleaner and a wire brush. We wiggled and moved all the connectors that we could see.

We do see a green wire sitting close by the o2 sensor connector that is not connected to anything. I've looked around closely and can't see anything that it might go to. There is a empty terminal on the coil that it looks like it might connect to. Last week I put it on there and it made no difference. This wire goes into a loom that then goes into a black box (splice box) with a vacuum hose diagram on it. It appears to go through the firewall and out of the engine compartment inside another loom of wire.

I'll include photos.

Any ideas?

Thanks
Marc
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