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Discussion Starter #1
I posted this in the Milano / 75 forum, but not much response so I thought I'd try here: It's been a while since I was on this forum; so long that I've been forgotten and had to re-register!

Anyway, I'm in the process of resurrecting my old hillclimb 75, and I'm having some problems which appear to be the injection system.

Briefly, the car is a 1990 UK model 3.0L V6 (no Cat or Lamba sensor), and must be about the last of the L-Jetronic models; electrically and engine - wise it's completely stock and un - modified.

The issue is that, while car will start and run, it only runs on 3 cylinders: 1, 4 and 6 don't run.

So far, as I have gone through the process of elimination, I have checked that the fuel pump runs and delivers ok, fuel pressure is fine; ignition sparks are ok on all cylinders, as is compression pressure and ignition timing. I have swapped the double relay with another, also the ECU, ignition module, coil assembly, and nothing makes any difference. All fuses are ok, and I've been round every earth / ground I can find in the the engine compartment and cleaned them all.
All the injector plugs show + 12V with the ignition on, the battery is good, and everything else electrical works ok.

I suspected stuck / clogged injectors, but they have now been serviced and I bench tested them and they open / close and pass fuel ok; however, on the car, 1,4 and 6 don't produce anything, although the other injectors happily spray away..........

So I suspect that somewhere there's another bad earth or similar, but I haven't managed to find it yet!

Does this ring any bells with anybody, has anyone else seen anything like this? It's becoming a bit frustrating.....
 

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The injectors are turned on when the L-Jet computer grounds the low side of the injector. All of them are turned on and off together so you problem is specific to those injectors or the associated wiring and connections. The L-Jet computer has a number of ground wires that are usually all connected to the engine under one of the valve cover bolts. It is likely that one of them is for 1, 4 & 6 and it is either loose missing or broken. If they are all good then check the condition of the Bosch connectors to the injectors.
 

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Discussion Starter #3
Thanks, I think you have confirmed what I was already thinking; I have already been over the wires connected to the valve cover bolt, including re-making the connections, so I guess it's not them, but further back into the wiring: this should be fun!
 

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How do you know that injectors 1, 4 & 6 aren't firing? Have you established this with a NOID light ? or some other way? Also when you say 1, 4 & 6, you are referring to the numbers marked on the valve covers, right?

Anyway assuming that 1, 4 & 6 aren't firing, then the ground wires going to those injectors are bad.

Unfortunately I don't have my wiring diagrams with me, but what I recall is this. All six injectors are fired at the same time. They are fired by the ECU turning on a ground. There are two pins on the ECU that ground the injectors. Each pin grounds three injectors.

In the harness, a single wire connects to the grounding pin on the ECU, that wire splits into three wires, one for each injector. If that wire is broken in the harness before it splits into three, then none of the three injectors it serves will get a ground.

The injectors always have 12V positive supplied to them from the combo relay. However that current can't flow into the injector until the ECU provides a ground. When the ECU does provide a ground, the current flows and the injector fires. It continues firing until the ECU turns off the ground.

Please let us know how this develops .
 
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