Help with MS1 v2.2?.

[keithmac]

Hello all, I converted my Golf Mk2 over to Megasquirt 15 years ago. It gave great service for 5 years then due to a gearbox failure I stood the car up (that was 10 years ago!).

I've come to get the car going again, and to be fair after 10 years it wasn't going to be easy..

The fuel pumps were sized (run through a dedicated relay) but I also had no spark.

Looking at the wiring I noticed the "magic smoke" smell near my MS1 ECU, after stripping I've noticed that C? 30 which I presume is a ceramic capacitor has burnt out.

Could anybody hazard a guess as to why this has happened and how I can prevent it again?, will it be related to the pump issue?.

Could I replace with a different capaitor or does it have to be exactly the same?.

Any help greatly appreciated as electronics isn't my strong point!.

Cheers, Keith.

[DaveEFI]

Always replace components with ones to the same spec. You'll get the spec in the BOM in the manual. Very few parts in MS are solely MS - they are generic components which can be obtained from a variety of sources. Sadly Maplin shops in the UK seem not so interested in components as once. For a very small order value, Ebay may be the best best. Larger companies like CPC may have a minimum order value or P&P charges - and that cap is likely only a few pennies.

Not uncommon to have a failure after a long period of no use. Just like your fuel pump.

[keithmac]

Is it just one of those things then?, the board looks fine.

I've read it's part of the tacho circuit.

To be honest I was expecting the fuel pumps to be siezed solid!.

[keithmac]

I've got it to connect to the laptop off the car now (on a 12v battery)

I remeber wiring the MS to the Hall Sender in "pull up resistor" mode, will this capacitor have anything to do with that? (running ms-extra with spark control).

[keithmac]

I take it this wouldn't be suitable 4.7uf 50v film capacitor?.

Struggling to find the same as fitted to the board, found the BOM but the link for the part was dead.

[DaveEFI]

If it is C30, that is an electrolytic cap. Not familiar with the V2.2, but think it is a tantalum. Note they are polarity sensitive.

[keithmac]

Managed to find some in the UK on ebay, they are tantalum as you say.

I take it the + printed on the case denotes the +ve leg..

[DaveEFI]

Managed to find some in the UK on ebay, they are tantalum as you say.

I take it the + printed on the case denotes the +ve leg..

Correct. Tantalum are known for self destructing for no apparent reason, but are used because they have a very good performance.

[keithmac]

Oddly enough I managed to get the car running today with the burnt capacitor. I had a poor 12v positive feed to the Megasquirt so maybe the voltage has fed backwards some how and caused the capacitor to burn out?.

Won't be running it again until I've replaced the cap though.