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Happyfolk
Samba Member
Joined: May 26, 2014
Posts: 183
Location: Madison, WI
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 Posted: Sat Sep 16, 2017 7:41 pm Post subject: Re: '79 CA FI bus ran fine then suddenly won't start |
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The schematic doesn't show a ground at pin 85 on the dual relay. Why not?
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'79 Westfalia Deluxe Campmobile, 2.0L CA FI, Mexico Beige |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50338
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| Posted: Sat Sep 16, 2017 8:06 pm Post subject: Re: '79 CA FI bus ran fine then suddenly won't start |
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| Happyfolk wrote: |
| The schematic doesn't show a ground at pin 85 on the dual relay. Why not? |
The schematics shows pin 85 being grounded via pin 28 on the ECU, which is internally connected to one of the three ground wires coming off the ECU. Your original problem likely lies within the ECU, but it is probably fine to connect pin 85 directly to ground instead of tearing in to the ECU. |
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Happyfolk
Samba Member
Joined: May 26, 2014
Posts: 183
Location: Madison, WI
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| Posted: Sun Sep 17, 2017 5:17 am Post subject: Re: '79 CA FI bus ran fine then suddenly won't start |
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| Wildthings wrote: |
| The schematics shows pin 85 being grounded via pin 28 on the ECU, which is internally connected to one of the three ground wires coming off the ECU. Your original problem likely lies within the ECU, but it is probably fine to connect pin 85 directly to ground instead of tearing in to the ECU. |
I have no reason yet to think my ECU is bad. I redid the relay ground connections because the AFM manual said I was supposed to get 12v at ECU pin 10 with the ECU unplugged and the ignition key ON. If that's not true and relay pin 85 is supposed to get ground from ECU pin 28 once it is plugged into the ECU then it was correct before I changed it, but what I did should only improve the ground connection.
I found this schematic for the ECU and it looks like ECU pin 28 doesn't connect to any grounds, only relay pin 85.
Maybe cleaning up all of the connections for ECU & Hall Ignition Control grounds and the coil + to relay pin 86c caused the improvement?
I still need to determine if the problem is totally fixed.
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'79 Westfalia Deluxe Campmobile, 2.0L CA FI, Mexico Beige |
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BayCreamPuff
Samba Member
Joined: August 10, 2015
Posts: 769
Location: Oakland, CA
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| Posted: Sun Sep 17, 2017 7:28 am Post subject: Re: '79 CA FI bus ran fine then suddenly won't start |
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| Happyfolk wrote: |
I found this schematic for the ECU and it looks like ECU pin 28 doesn't connect to any grounds, only relay pin 85.
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That's just an l-jet diagram. If you want to see where 28 is grounded you need to find the schematic for the ECU.
If you are curious which of the 3 ECU grounds it grounds to you can pull all 3 from the spade under the plenum and test for continuity between them and 85 on the double relay.
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Cream Puff
'79 CA Stock FI Deluxe Campmobile
Earl Grey
'87 GoWesty 2.2 Westfalia
Marsha Mellow
'00 Eurovan VR6 Full Camper |
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furgo
Samba Member
Joined: September 06, 2016
Posts: 944
Location: Southern Germany
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| Posted: Sun Sep 17, 2017 8:20 am Post subject: Re: '79 CA FI bus ran fine then suddenly won't start |
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| Happyfolk wrote: |
Curious that the pin 28 connection isn't listed on this:
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Note that there is no mention that this connector pinout diagram was for the bus, or even for which year. L-Jetronic was used on a multitude of other vehicles. Also, I don't think the source from the diagram comes from either Bosch or VW.
L-Jetronic had a base standard, but there were some slight modifications or additions to accommodate new features over the years (e.g. O2 sensors on '79 CA buses, dropping the injector series resistors in favour of internal ECU current control, etc.)
That connector schematic might be correct for a Federal bus that does not have pin 28 connected, but you have a CA bus, so it does not apply for that particular pin. What I mean is simply take that diagram as orientation, but with a pinch of salt 
A while ago, I started tracing and the pinout for my bus and putting it all together in a diagram, with notes for other bus years. At some point, I'm planning to make it more generic and useful for all years, but for now, if that helps as WIP, here it is:
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'79 Westy, P22 interior, FI 2.0 l Federal, GE engine (hydraulic lifters)
Decode your M-Plate
Last edited by furgo on Sun Sep 17, 2017 8:21 am; edited 1 time in total |
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Happyfolk
Samba Member
Joined: May 26, 2014
Posts: 183
Location: Madison, WI
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| Posted: Sun Sep 17, 2017 8:21 am Post subject: Re: '79 CA FI bus ran fine then suddenly won't start |
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Look at this thread. It seems the actual schematic for the ECU hasn't been found, at least not as of four years ago: https://www.thesamba.com/vw/forum/viewtopic.php?p=6929629
From the diagram above it doesn't look like ECU pin 28 is attached to ground pins 5, 16, or 17.
I checked those three grounds and they are good now. A couple of them were reading 3-4 ohms but I cleaned up the connections and got them down to .3 or .4 ohms.
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'79 Westfalia Deluxe Campmobile, 2.0L CA FI, Mexico Beige |
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furgo
Samba Member
Joined: September 06, 2016
Posts: 944
Location: Southern Germany
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| Posted: Sun Sep 17, 2017 8:29 am Post subject: Re: '79 CA FI bus ran fine then suddenly won't start |
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And it probably won't be, unless someone reverse-engineers the ECU PCB. The internal ECU diagrams were never published (as far as I'm aware a least).
| Happyfolk wrote: |
| From the diagram above it doesn't look like ECU pin 28 is attached to 5, 16, or 17. |
Not externally, but it might be hardwired to GND inside the ECU box. You can measure the resistance between pin 28 and any of the three GND pins (5, 16 or 17), or perhaps someone with a spare California ECU can open up the box and confirm it by looking at the PCB trace from pin 28.
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'79 Westy, P22 interior, FI 2.0 l Federal, GE engine (hydraulic lifters)
Decode your M-Plate |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50338
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| Posted: Sun Sep 17, 2017 8:34 am Post subject: Re: '79 CA FI bus ran fine then suddenly won't start |
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| Happyfolk wrote: |
I found this schematic for the ECU and it looks like ECU pin 28 doesn't connect to any grounds, only relay pin 85.
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Your diagram doesn't show any of the internal wiring of the ECU only a different view of the external wiring. Pin 28 is going to be connected to one of the grounds (probably pin 5) internally.
You have already found that VW shows two different ways that pin 85 is grounded. Accept that VW diagrams don't always reflect how the wiring ended up when the vehicles were actually produced. I usually look at diagrams for additional years, both a few years before and a few years after, when I have a question about how something is wired. Sometimes a particular diagram will lead a production change by a year or two, other times it will lag. By making the change to ground pin 85 internally, VW probably saved a $100,000 over the aircooled Vanagon run, as there was one less wire to attach on the assembly line. |
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Happyfolk
Samba Member
Joined: May 26, 2014
Posts: 183
Location: Madison, WI
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| Posted: Sun Sep 17, 2017 12:03 pm Post subject: Re: '79 CA FI bus ran fine then suddenly won't start |
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Well, I took it for a drive today. I drove it for an hour and went about 40 miles. I started out staying very close to home. After about a half hour staying within a couple miles of home I ventured out farther. It ran great like it had up until I went to start it a couple of weeks ago and it wouldn't. Had it up to highway speed a couple of stretches.
Still going to be a bit cautious with trip distance for a while but the problem seems to be resolved. Must've been the bad electrical connections that were cleaned up.
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'79 Westfalia Deluxe Campmobile, 2.0L CA FI, Mexico Beige |
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Happyfolk
Samba Member
Joined: May 26, 2014
Posts: 183
Location: Madison, WI
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| Posted: Sun Sep 17, 2017 6:03 pm Post subject: Re: '79 CA FI bus ran fine then suddenly won't start |
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Took the wife to town in the bus tonight for dinner. She was reluctant to say the least. She was with me when we broke down Thursday night.
She said "If we break down I will be pissed"! I didn't think we'd break down. We didn't. Ran great! Knock on wood!
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'79 Westfalia Deluxe Campmobile, 2.0L CA FI, Mexico Beige |
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