Good info ^^ but I'll add the aux air reg has a heating element that closes the air passage as the engine heats up. It allows extra air whilst cold and over a few minutes (depnding on ambient) closes it off.
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the aux air valve from my understanding is to allow more air during cold idle? its pretty old tech.
the resistor pack is there not to fry the injector drivers int he ECU as they are used on some older systems in conjunction with low Z injectors. Pretty much all cars use high Z injectors and don't need the resistors.
If there is no injector pulse you might want to check the trigger input from the coil to the ECU. That is how the ECU knows the engine speed and when to fire the injectors. Without that the ECU does nothing.
also there is no TPS, weird system ! the D jet does and its older. I wonder how it calculates engine load?
71 notchback,
Past owner of, 70 NB, 73 SB and 72 FB TLE
The ecu does get the 'trigger pulse' from the coil just no pulse at the injectors. That's why I'm thinking the ECU.
was the injector plugs constantly on or off? when you tested them
71 notchback,
Past owner of, 70 NB, 73 SB and 72 FB TLE
Well if all the relevant inputs are working and power is getting thru the dual relay where it needs to go then gotta be the ECU.
Oh, thinking about it. Does the relay output for the ECU power work?
madness is in the eye of the beholder 👍
The injector plugs were live (on) and the relay...I can't remember ,when I put the loom back in I'll check😊
So where the injectors fully open and spraying without the engine turning? Considering it was live?
71 notchback,
Past owner of, 70 NB, 73 SB and 72 FB TLE
No silly Vlad 😂
The multimeter will just show 12v at the injector but without the ECU grounding the injector they won't be on. Well, least ways they shouldn't 🤪
madness is in the eye of the beholder 👍
The way he explained it, it sounded like 12v across the plug. He didn't mention testing against ground hence why I asked if the injectors were stuck on or not. If they are, then it indicates the drivers int he ECU are dead. When transistor or fets die they usually go short circuit resulting injectors being on all the time. Seen it happen, not often but it can if something is wired wrong.
71 notchback,
Past owner of, 70 NB, 73 SB and 72 FB TLE
Both contacts in the plug were live and when plugged onto the injector it was closed i.e. not spraying.
ok? current leakage though the drivers maybe? or maybe they are switched high in the off mode then switched low when firing?
sounds like a weird setup for sure.
So when cranking they don't fire?
71 notchback,
Past owner of, 70 NB, 73 SB and 72 FB TLE
Obviously not as the spark plugs are sparking but no fuel to the cylinders and when a spark plug is removed it is not wet and no smell of fuel.
If you put a bulb inline with the no1 ECU input you can see it flash when cranking?
madness is in the eye of the beholder 👍
psimitar wrote:If you put a bulb inline with the no1 ECU input you can see it flash when cranking?
that is the normal way to test them.
I had a thought about how both pins in the plug are high. The ECU side could well be floating high because there is power but can't be switched low due to missing ECU ground/s.
I would go over and check the ECU grounds, even make new ones to be sure. To me this is what is staring to sound like.
71 notchback,
Past owner of, 70 NB, 73 SB and 72 FB TLE
Well all the loom checked out fine including the earth cables so I'm going run an extra earth wire to the car body as the loom earths connect to the body of the alternator so maybe that could be it. If that doesn't work then the Ecu is going to be given a bloody serious talking to!
Well fitted new earth to body, all loom back in place ,spark plugs sparking but still nothing....anyone got an ecu?! Or better a carb😬
according to the diagram, there is 3 grounds. did you confirm each of them?
Can you confirm you are getting trigger pulse at the actual ECU? you will need a silly scope to see it its there.
71 notchback,
Past owner of, 70 NB, 73 SB and 72 FB TLE
All the earths checked out, there were in fact 4 earth wires in the loom and the pulse from the coil is getting to the ecu.
Reckon it's time to try and borrow a working ECU, unless you had any luck finding a Bosch specialist repairers.
madness is in the eye of the beholder 👍
Methinks the same, I'll try taking the ecu to a place in Noosa during the week to see if they can at least check it then replace it if it's cactus.
was going to say, always good to have a spare ECU to confirm with.
let us know how you go.
71 notchback,
Past owner of, 70 NB, 73 SB and 72 FB TLE
If anyone has a spare ECU it would be handy as I've been told to just send it down to Melbourne (Injectronics) .
71 notchback,
Past owner of, 70 NB, 73 SB and 72 FB TLE
Thats a 2L Kombi one, bug ones are different
Bug ECU is 0 280 000 105
Bosch number for the beetle ECU is 0 280 000 115 according to the number on mine. Maybe they're interchangeable?
Do you have a manual or semi auto gearbox?
They stopped making semi autos in 74.
The reason there is probably two different model ECUs for Beetles is only some US models ran a cat.
what did bugs use? was it L jet or D jet?
71 notchback,
Past owner of, 70 NB, 73 SB and 72 FB TLE
L-jet, just the early ones didnt run a catalitic converter which Im sure would have called for a different ECU.
it may, but if it doesn't have an O2 sensor i would assume it be the same.
71 notchback,
Past owner of, 70 NB, 73 SB and 72 FB TLE
