Injector power supply

PugMonkey

PugMonkey

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I'm struggling with an issue of power supply to injectors 2 & 4.

All of a sudden car is coughing and running really bad. I have spark on all four cylinders and when I disconnect injector plugs to cylinder 2 and cylinder 4 the rough idle does not change with no voltage or pulse with to the fuel injectors.

I'm thinking it's a damaged wire as I think I remember they are wired in pairs.

Any other input as to what I look for?
 
At least with the XU9JA/Z (DKZ) Motronic the injectors were feed in pairs from the ECU via two outputs although I believe these outputs were fired simultaneously like the Jetronic and not 'banked'.

So it would appear to be either a wiring issue with one pair or the respective output of the ECU.

PugMonkey said:
Aahh yeah... Lol 1.9l mi16 xu9j4
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The four injectors and the ICV (M9) are fed from the same 12+ supply (relay M743), thus it's unlikely to be that. Enjoy your trouble shooting.
 

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PeterT said:
The four injectors and the ICV (M9) are fed from the same 12+ supply (relay M743), thus it's unlikely to be that. Enjoy your trouble shooting.
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Thanks guys. I have the +12v at the injector but no negative signal either by reverse test lamp or cro. Somehow today I have to winch the car back into the garage to investigate.
 
PugMonkey said:
Thanks guys. I have the +12v at the injector but no negative signal either by reverse test lamp or cro. Somehow today I have to winch the car back into the garage to investigate.
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The negative signal is fed to the injectors in pairs by pin 16 & 17 so it's out with the ecu to see what I measure at that end.

So didn't want to do this today....
 
That'l do it I suspect, need to talk re cabriolet 306's!
 
robmac said:
Time to fit some corrugated loom tube. :wink2:
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Hhmm fixed cables replaced fuse and still have no two or four cylinder. +12v and pulsing earth at all four injectors now which means ecu is ok. Maybe blocked injectors or head gasket issue. I'll do a compression test and clean injectors tommorow.

Good night for this one.
 
PugMonkey said:
Hhmm fixed cables replaced fuse and still have no two or four cylinder. +12v and pulsing earth at all four injectors now which means ecu is ok. Maybe blocked injectors or head gasket issue. I'll do a compression test and clean injectors tommorow.

Good night for this one.
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Correction - pulsing zero volts...

May swap the crank angle sensor too.
 
Have you considered that the injectors may be faulty electrically, what I mean is that they may be open circuit (easy to check with a multi-meter) Seeing as they have been shorted to earth and have had current running through them longer than they were designed (been energised longer than the designed duty cycle).

This is just my :2cents: worth and is easier to check than the other things that you have planned.
 
COL said:
Have you considered that the injectors may be faulty electrically, what I mean is that they may be open circuit (easy to check with a multi-meter) Seeing as they have been shorted to earth and have had current running through them longer than they were designed (been energised longer than the designed duty cycle).

This is just my :2cents: worth and is easier to check than the other things that you have planned.
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Hi Col, I'm getting 15.9 ohms across the terminals on each injectors and a "click" upon applying voltage to them. I will do some mote checkswhen I remove them for cleaning.
 
PugMonkey said:
Hi Col, I'm getting 15.9 ohms across the terminals on each injectors and a "click" upon applying voltage to them. I will do some mote checkswhen I remove them for cleaning.
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Sounds like the injector is working then, like you said may be a fuel delivery problem.
 
Are injectors 2 and 4 paired ? Can you see a square wave on your cro for 2 and 4 whilst the engine is running? And does that wave match what's happening on 1 and 3 at the same revs?
 
Yes I had square waves across all for injectors now although I wasn't looking for any difference between them. Charged the fuel line then applied power to injector to see fuel pressure gauge drop - same for all four injectors. So by fixing the shorted wiring issue I now have a full bank of injectors.

But this did not fix the really bad idle and running so I did a compression test. Not good.

1 - 110
2 - 160
3 - 130
4 - 160

So petert now is the time to have my cam done send me a pm with address again and I will post it over Christmas break.
 
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