C200 (W202) ECU problems, Ignition Coils test, Guide and help

[Rai]

Hi all, I got a replacement PMS unit for my C180 1995. I was going to put it in the car when i remembered somewhere, its recommended to replace the coil packs before plugging in the PMS unit. is this true? I mean the coil packs themselves are fine.

Thanks

 

[grober]

Replacing the coil packs is not necessary unless they are faulty. In which case they can blow the 2 switching transistors in the replacment PMS ECU --- Its a "fail safe" suggestion because more often than not its what caused the ECU to fail in the first place and some owners don't clock this. But you have checked yours right?
That said if they are the coil type that's under the cover plate on top of the cam cover then these are prone to failure with age as they and their associated low tension wiring gets "cooked" by the engine heat. Price up replacements--taking into account the price of a PMS unit and make what is a judgement call.
cost versus risk.

 

[Rai]

Replacing the coil packs is not necessary unless they are faulty. In which case they can blow the 2 switching transistors in the replacement PMS ECU --- Its a "fail safe" suggestion because more often than not its what caused the ECU to fail in the first place and some owners don't clock this. But you have checked yours right?
That said if they are the coil type that's under the cover plate on top of the cam cover then these are prone to failure with age as they and their associated low tension wiring gets "cooked" by the engine heat. Price up replacements--taking into account the price of a PMS unit and make what is a judgement call.
cost versus risk.

Hi Grober, I have checked the coil packs by testing the resistance which is in the range given in the Haynes manual. Haynes say 5.2 to 8.5 Kohms, the coils are 7.44 and 7.45 Kohms.
Well my coils are on the inlet manifold. Another question regarding the coils, is the tension wires, there are no indication where + and - goes. will that cause an issue?

Kind regards

 

[190]

Sounds like you measured the secondary resistance of the coils on the HT side. It's the primary resistance that would impact on the power transistors. If Haynes lists the primary values it's likely to be in the region of 1 ohm or less.

Where each coil fires two cylinders at the same time it normally doesn't matter about polarity of the primary side connections as whatever you do one plug will fire centre electrode to earth strap and the other earth strap to centre electrode. It's called a wasted spark system.

 

[Rai]

Sounds like you measured the secondary resistance of the coils on the HT side. It's the primary resistance that would impact on the power transistors. If Haynes lists the primary values it's likely to be in the region of 1 ohm or less.

Where each coil fires two cylinders at the same time it normally doesn't matter about polarity of the primary side connections as whatever you do one plug will fire centre electrode to earth strap and the other earth strap to centre electrode. It's called a wasted spark system.

In the Book it says 0.3 to 0.6 ohms, how do I check the primary resistance?

 

[Rai]

Well the PMS Unit failed. Made no difference and still firing on cylinder 2 and 3.

Do not know what to do now. HELP!

 

[neilrr]

Do you know for a fact that the replacement PMS unit, the one that failed, was ever working as it should have been?

What's the part # on it?

 

[Rai]

Do you know for a fact that the replacement PMS unit, the one that failed, was ever working as it should have been?

What's the part # on it?

Original is 018 545 02 32

A garage specialist in MB said it's the pms after getting no led flash from one of the injector leads

Another specialist told me a 018 545 03 32 will work after sending it to me

 

[Rai]

Here is the original

 

[neilrr]

Do you know for a fact that the replacement PMS unit, the one that failed, was ever working as it should have been?

What's the part # on it?

Original is 018 545 02 32

A garage specialist in MB said it's the pms after getting no led flash from one of the injector leads

Another specialist told me a 018 545 03 32 will work after sending it to me

Yeah, I understand the original was dead, what I'm trying to establish is whether you know the second (the replacement unit) ever worked properly.

What's your car's VIN?

 

[grober]

Your coils should look like this. See the two low voltage connections underneath? the resistance across them [ disconnected ] should be 0.3 to 0.6 ohms measured with a digital multimeter as said previously. That said the test uses low voltage which doesn't test insulation breakthrough! To do the next test you have to understand the principle of operation. The coils are live on ignition switch on----in other words one of those 2 terminals on the coil base should have 12volts on it with the ignition switch on. What the ECU does is provide a path to earth via a switching power transistor- this causes the the coil to fire when the field in the primary collapses and induces a current in the HT coil.

At this point if the coil is getting a 12volts supply with the ignition on [ no need to start the engine ] I would be inclined to change the suspect coil.
coil part no is A0001580480

 

[grober]

Sorry that should read a 0001500480 for the coil part no.

 

[Rai]

Ah okay. Thank you Grober

My Vin is WDB2020182F188498 Neil

I've been looking at other forums. Checked the spark plugs HT Leads Coil Packs. Worst case it could be the PMS. Only thing that hasn't been ruled out.

 

[neilrr]

Yeah, I understand the original was dead, what I'm trying to establish is whether you know the second (the replacement unit) ever worked properly.

Bump.

 

[Rai]

Hi Neil and Grober. Sorry for the late reply but i got my car working now. The injected leads was short circuiting but manage to fixed it.

Thank you for your help guys

 

[Rai]

Running much better now lol

 

[grober]

Hi Neil and Grober. Sorry for the late reply but i got my car working now. The injected leads was short circuiting but manage to fixed it.

Thank you for your help guys

Are you saying the cause of the misfire was a short in one of the fuel injector leads? whatever- glad its sorted now.