No voltage or spray at injectors and testing ECU

[winddude]

I found this schematic of the pin connectors, but nothing of the ECU.

So the pins seem to be 23, 24, 11 and 12. The middle leg on the injector is connected to the pins. The number on the transistor is PH ON823, a google search isn't giving much...

Should I be worried about the burnt portion on the printing of the circuit board?

[morymob]

If someone has an old ecu with 'good' pwr transistors and remove one. Do a resistance test using all 3 legs ,both ways & all combos, write it down and then u can determine if they R NPN or PNP types, NOT interchangeable.Take this info 2 an electronic supply not necessarly R Shack as they don't have a clue how to test 1 even if they have a sub.There R a lot of this style driver packs that sub & don't have to be exact only don't use 1 with less current rating. My '88 , digifant did this once/ ecu cable conn came unlatched & plug moved out enuf so injectors wouldn't fire, u probably have checked yours??

[crazyvwvanman]

It looks like the part is an ON823 . Google shows other people have used certain generic electronic store replacements to fix their Bosch ECUs that have the same part in them.

TIP120 is one such generic replacement part reported to work.

They cost under $1 in quantity.
Here, I just ordered 5 for $3 including shipping.

http://www.ebay.com/sch/i.html?_sacat=0&_nkw=tip120+transistor&_sop=15&_frs=1

RadioShack carries them too.

Mark

[winddude]

Thanks you, how on earth did you find that, I tried for quite awhile. Unfortunately there's no Radio Shack in Canada so I'll have to find another components store.

The other transistor is ON946, any idea?

[winddude]

So after getting the transistors it seems my transistor is fine... so back to trouble shooting.

[winddude]

After getting the noid tester, and finding no pulse at the injector plugs, I did some more trouble shooting per http://www.vanagonauts.com/files/Digijet_FI.pdf.

-air flow sensor is good.
-injector wiring, no noid light, continuity on circuit is good except cylinder 4
-both grounds going to ecu are good. Continuity between pins 7 and 25 on connector.

So it still seems like the ecu is shot, plus one set of wires to the injector.


I ran into two issues:
1) No continuity between terminal 23 and 7 on the ecu connector.

So I'm guessing there's a issue with the wiring somewhere on the wire to cylinder 4. Any advice to trouble shoot this?

[Steve M.]

Terminal 23 at the connector is going to be one of the wires in the plug for the injector. See if you have continuity from terminal 23 to one of the terminals in the injector plug. I think the other terminal in the injector plug is going to be the ground to terminal #7.
Okay so if none of your injectors are firing then what is common to each injector? Terminal #7 is common to each one.
So check the continuity from terminals 11, 12, 23 and 24 to each of the respective connectors that go to the injectors. I kinda think your going to find that it is a bad #7 since the odds of all four of the injector wires going bad at once unlikely...
It might be a bad ground or maybe the connection inside the ECU connector for Terminal #7.
Check continuity from Terminal 7 to ground. wait you did that in checking 25 and 7. Check it again from #7 to a point on the engine just to see what it is. (I may be wrong in thinking that 7 is a ground, I checked mine a month ago and I can't even remember something from yesterday!)
If the continuity to the the 11, 12, 23, and 24 is good and the continuity from #7 to the other terminal in the injector plugs is good then I would start thinking the ECU.

My Bentley manual had Terminals 23 and 24 being Cylinders 1 & 2, Terminals 11 & 12 being Cylinders 4 & 3.

[winddude]

[Vanagon Nut]

I hate to ask, and I bet you did, but did you remove all plugs from injectors before testing?

My first thought was "short". You should for sure see individual continuity between the neg. connection at each injector plug and it's corresponding pin on ECU connector.

I recall on my Jetta harness that all three wires to hall had cracked casings and exposed copper. Theses wires were twisted together within the loom.

Some of the fuel injector wires could be shorting to each other within loom?

[Steve M.]

Have you got someone there to turn the key on while your back there at the engine?
With the brakes "ON" try doing this in total darkness.
You might see a spark from something that you cannot see in daylight.
Open the fuel relay box if you do this to see inside it as well.
At this point it couldn't hurt to try this.

[winddude]

[Vanagon Nut]

I'd have to look at my Bentley but there should be wire resistance test values shown. eg. between a given negative terminal at a fuel injector plug, and corresponding terminal on ECU connector, you should see a very low resistance. Like several Ohms. But for sure. There should be continuity.

Double check what range you have your VOM set to.

The other part is that each wire to each connector is likely white. Looking at the diagram here, one terminal of each injector plug connects to 87 of fuel pump relay.

[winddude]

Ordered an ECU from a wrecker that was supposedly good. Still no pulse at the injectors. Starting to get a bit frustrated.

[winddude]

Just to wrap up, it was the ECU, van is now starting and idling ...ok... for the most part. Now on to other issues, it looks like I have a leaking head gasket and exhaust issues

[mrcool]

[winddude]

[mtjade8384]

This is an old thread but I ran into the same problem and did the troubleshooting recently. I thought to share what I did so that anyone who come across the issue can try.

Keep in mind that the 4 pairs of wiring of the 4 injectors are in parallel, meaning all 4 injectors are driving altogether as one. You will need to check one pair of wiring only. All other 3 are in parallel.

What I did was to unplug 3 of the 4 injector plugs leaving one still plugged in. I had my wife sitting in the driver seat to crank the engine (center coil connector disconnected). While the engine is cranking I checked one of the unplugged injector connector. So this will reveal if the injector gets the 12 volt in one wire and if the ECU driving signal (grounding signal actually) is present in the other wire. If all 4 connectors are unplugged the ECU signal is disconnected as well so it can not be checked at the injector connectors. I also had all 4 spark plugs removed so it was easier for the starter to crank the engine. I did not have to troubleshoot the ECU which is just about impossible.

There is still a problem though. The ECU pulsation driving signal was very short. A multimeter will not be able to see if the pulsation exists. I ended up using an oscilloscope and the pulsation was nowhere to hide.

It turned out my problem was caused by incorrect distributor driving shaft alignment. Once it was correctly aligned the engine was started successfully. My old timing gun was very dim so I could not find the distributor problem in the beginning.