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Sun Feb 28, 2010 7:07 pm

My ECU does not have one. According to Bentley and the AFC manual, #20 on the ECU connects to 86b on the double relay (resistor pack side) then on to 36 on the Air Intake Sensor (AFM). I have continuity from the ECU plug #20 to 86b on the Double Relay. OK so 86a in the DBR closes a switch in the AFM to 39, that goes to 88a on the DBR to 88b on the resistor pack. With key on I have power at 88b from a signal of #10 on the ECU.

Correct part number for year. 1977 manual transmission 022 906 021 S

There are spots on the ECU board that have gotten too hot (most likely the problem).

I have done all the continuity/voltage tests per Bentley & AFC manual. All check good.

Current symptom:
Crankcase flooding.
Fuel pressure on rail, all 1-4 injectors plugged in, key on and pressure dissipates to 0 very fast. Tells me that the ECU grounds the injectors once power is available at the ECU. ECU unplugged and the rail holds pressure with the key on. CSV removed, as it was the first thing I checked for leaking/stuck open. CSV checks good BTW.

So is having a physical pin 20 on the ECU required? I'm thinking no as there are no checks in the Bentley or the AFC for 86b on the DBR. There is sufficient voltage at pin 20 on the ECU plug with the key on (But no ECU pin 20).

And I am not sure why the ECU is like it is. Bus did run before the motor pull for #3 exhaust time-sert install and trans nosecone refresh.

So my assumption of the cause is the ECU is bad. Do you agree?

Sun Feb 28, 2010 7:12 pm

* fine print in my Bosch book says California Vehicles use pin 28 instead of pin 20. Maybe that is it.

There are also different harnesses. I went through a whole bus full at Interstate VW looking for one that would match ours so we would have a spare.

Sun Feb 28, 2010 7:19 pm

I have no wire 28 in the ECU plug or on the ECU itself. Not a CA vehicle.

Sun Feb 28, 2010 7:29 pm

did you test the injector plugs to see if they were constantly grounded? test light should flash when you crank the engine.

sounds like a stuck injector or CSV.

Sun Feb 28, 2010 7:39 pm

the book clearly shows a wire between pin 20 or 28 and 86b. 86b also goes to 36 on the intake air sensor which is the contact points inside. When the AFM flap is closed it opens that set of points. It looks like to me that the real test is that 86b should not have 12v volts on it except when the bus is running (flap is open).

Sun Feb 28, 2010 8:00 pm

borninabus wrote: did you test the injector plugs to see if they were constantly grounded? test light should flash when you crank the engine.

sounds like a stuck injector or CSV.

Yes, I did every test in the Bentley and the AFC which included testing each injector for grounding. They are not doing that with all injector plugs disconnected and ohm'ng from the injector case to each of its pins. Test light dims, doesn't flash. No pulse from ECU.

Sun Feb 28, 2010 8:12 pm

SGKent wrote: the book clearly shows a wire between pin 20 or 28 and 86b. 86b also goes to 36 on the intake air sensor which is the contact points inside. When the AFM flap is closed it opens that set of points. It looks like to me that the real test is that 86b should not have 12v volts on it except when the bus is running (flap is open).

It does that.

Damage on the ECU looks to be on 10 (all 4 injectors ground circuit I believe), 13 (TS II) & 5 (ground).

Sun Feb 28, 2010 8:41 pm

if the board shows heat that is caused by too much current in that part of the board. The usual culprit is a failed transistor or diode. I think all but the 1979 model have ballast resistor in the injector circuit to lower current. That module has to be in the circuit or current will be too high. Other possible causes - if this is a Westy someone could have accidently gotten 110V into the system if the built in inverter/charger failed. A failed diode in the alternator could have put alternating current into the system.

The easiest solution is to find a good used ECU. I have 2 from 1977 and neither shows heat damage so it is not a common problem.

Sun Feb 28, 2010 10:17 pm

Not a Westy, transporter. There is a resistor pack in the circuit, and it measures within limits. The 2 diodes are on the starter circuit (86a) to 86b and from the ignition (86c) to 88b. Both of those tests passed per Bentley Chapter 8, section 4.1 (current supply and relay function)

Because of the damage to the ECU, it is not possible to determine the cause of the damage. The result is clear however, injectors grounded with key on and engine not running.

Sun Feb 28, 2010 10:52 pm

diodes I was refering to are in the Alternator. They change AC to pulsing DC. The battery acts as a giant capacitor to even out the pulses. If a diode shorts then AC gets into things. It frys electronics, cooks batteries etc. I would think that Bosch would have built the system to handle other flaws. Someone recently had a bad ECU from a reversed battery. Was there ever a time when fuel didn't puddle into the crankcase? Is this a new bus to you?

Mon Mar 01, 2010 6:26 am

Actually only the 79CA model is the only one that had no series resister mounted to the firewall. The 79 Federal version does.

Clean the FI ground block under the air plenum on the left side. Looks sort of like this....

I think your problem is a fuel delivery issue. Likely a leaking fuel line, fuel pressure regulator, or a fuel pump check valve problem.

Been here?

http://www.itinerant-air-cooled.com/viewtopic.php?t=213

Mon Mar 01, 2010 6:49 am

SGK- New bus to me. I've only driven it for about 200 miles. It wasn't running well when I bought it and the first thing I did was pull the motor and trans to clean them up and re-seal everything without splitting the case. Got that done and she ran, but shifting was getting harder to find a gear. Ball in the nosecone completely gone. Never noticed fuel increasing the oil capacity. This time she would not start. So after many attempts to start, and the smell of too much fuel I got the Bentley and AFC out and started troubleshooting the system. Thats when I found that with fuel pressure on the rail, then just the key on, fuel pressure get released at the injectors. They were sent out to Witchhunter for cleaning the first time I pulled the motor.

Randy the FPR and fuel pump check valve tests passed. The ground block under the plenum is new and connections bright and shinny. They also passed the check from the ECU plug pins 5, 16 &17. Thanks for that link, I'll read it.

Mon Mar 01, 2010 1:57 pm

I would look for a spare ECU that matches what SHOULD be there. Use Ratwell for the ECU numbers. A spare won't hurt you and usually they are cheap. I keep one around as a troubleshooting tool just in case. And if reolacing it solves the problem then you get another as a spare.

Mon Mar 01, 2010 2:16 pm

SGKent wrote: I would look for a spare ECU that matches what SHOULD be there. Use Ratwell for the ECU numbers. A spare won't hurt you and usually they are cheap. I keep one around as a troubleshooting tool just in case. And if reolacing it solves the problem then you get another as a spare.

My last problem with injector grounds was no ground. Constant ground after a harness check rules a short-to-ground out of the picture, leads directly to the ECU, do not pass go.
Colin

Mon Mar 01, 2010 3:56 pm

Thanks Colin that is exactly what I thought. Seeing it controls the injector ground. Found one cheap too! I just choked on the Busdepot price, way too much for my wallet. A little leary of electronics that they say are rebuilt. AFM with scored card still, and all pins heavily corroded. Must of set on a shelf for years.