Supercharger woes

JSeaman

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I Need a few ideas now if you can guys and girls, I have an 170 SLK230 which I just bought and it's very under powered. It has 12V to the clutch but no switched ground from the ECU, K40 checked out good and the MOSFET didn't fix it.

Tonight I have put 12V into the clutch connector and it engages the charger but I'm getting no boost, what next? I can't read error codes as there is no OBD socket and the 38 pin adaptor doesn't work so need some old fashioned ideas - bypass valve stuck or other thoughts welcome
 

Uncle Benz

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Without reading the fault codes or looking at the live data I'm afraid you are stabbing in the dark. The supercharger clutch is engaged from an ecu signal, that goes via the K40 module. There is a fuse for it on the k40 too, if memory serves. By the sound of it you have checked most of it out, so it is likely the ecu is not switching it on, probably because of another underlying fault. Plenty of "could be's". Air mass meter not working, bypass flap problems might hold it off too.
Finding someone local with a Star machine would be my advice.
 
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JSeaman

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I am indeed stabbing in the dark but I have no way of getting the codes, this is one of the intermediate years from some reading which means you can only get codes with Carsoft and the 38 pin connector which I don't have.

Correct, the ECU isn't sending the ground signal to the clutch and I agree there is potentially an underlying fault. I've just checked the bypass flap and when you turn the key on it has a small wriggle (doesn't really move) and then sits in the open position but obviously under control. A bit of a rev and you can feel boost out the open air hole so the charger is just boosting into the air box currently.
 
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JSeaman

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Well I managed to fix it. I figured the AFM or cam position sensor were the most likely suspects for causing the ECU to fail to trigger and for £20 I could afford to try it out. The AFM was changed and immediately boost was restored. I even put the clutch back to ECU control and it's all good now
 

Uncle Benz

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Nice work! Did my suggestion swing it? ;)

If there was oil contamination in the air mass meter you need to consider clearing the two brass stubs beneath the intake manifold. They'll likely be blocked up.
 

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