Misfire - Change Coils - 2,3 ?? what to get..

[crammy69]

I want to change my coils as a pre-requisite to getting my ECU looked at / fixed, but wanted to confirm a couple of things before I try and order anything

1. Can anyone confirm whether I need 2 or 3? coils as per this diagram item no 29 which shows on top of the engine.
http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=124051&A=00069&M=104980&GA=722501&VIN=1240512B189721&CT=F&cat=15T&SID=54&SGR=255&SGN=07

2. I've seen various prices but as they differ so much wondered wether this things are sold separately or as a set? Does anyone know?

Inchcape £92.53

Euro Car Parts £52.50

3. If they are priced separately and I need 3, then looks like its going to cost at least £157, is there a way or telling which if any are damaged or is it one of those things whereby its best just to replace them all?..

All advise most welcome, cheers!

 

[Ian B Walker]

If you are talking about your 300CE -24 you will only need 1 coil. The 280 and 320's have 3 coil packs on top of the engine. The 300-24 series don't have this option (thank God)

Item 29 in the drawing above.

 

[crammy69]

Thats great , many thanks Ian!

Cheers!

 

[OzC36]

According to the quoted Detali diagram/table and Autohaus, you need only one:

This one:
http://www.autohausaz.com/search/product.aspx?sid=rzhholvd5dncihmpsuo4lp45&partnumber=0001586403

Or this one is interchangeable:
http://catalog.autohausaz.com/autoh...uo4lp45&partner=autohausaz&product=0001585803

 

[crammy69]

Thanks OzC36, so that's what one actually looks like! cant wait to get it Im going to call Eurocarparts / Local Motor factors on Monday and get one Ive got a good feeling that Im on the right track now for curing the misfire (famous last words..)

Cheers

 

[Dieselman]

Buy a cheap spark tester before spending money on new parts. It may not be the coil and more likely the distributor/rotor arm, etc.

 

[kth286]

The ECU repair people are NOT refering to your car when they say that the coils blow and can ruin the ecu.

They are refering to the later cars with all electronic engine with both fueling and ignition control all combined in one computer/ECU. Your's is not that design.

So unless the coil is obviously gone do not buy another one.

 

[bolide]

^^^ What he said

You have an early M104 engine with a distributor, points, coil and CIS injection, not the later AFM M104 with 3 coils and no distributor

Nick Froome
www.w124.co.uk

 

[crammy69]

Thanks gents. I did have a brand new genuine Mercedes Dizzy cap, HT leads rotor arm etc. fitted shortly after buying the car in February and the misfire/rough running remained. Its not terrible by any means, hence just tinkering around for so long.

I had a little look around the engine bay with haynes in hand and couldnt see the coil, I know the later engines (with 3 coils) are under the engine cover, is mine behind the Dizzy cap? any guesses?, the haynes says I should see it on the left side of the engine, but I could'nt see it unless its really small I should have a look at it before buying one I suppose, but at £50 I though if I have to take lots of bits apart to check it I may as well change it whilst Im there ( the cars has done between 120-140k miles so much be due one?)

Dieselman, I'm ashamed to say I still have not bought a spark tester despite it clearly being good advice!.

 

[Ian B Walker]

Coil is situated on the passengers side of the car, under the bonnet, below the ABS pump. Or follow the King lead back from the Dissi cap

 

[crammy69]

Thanks Ian, I was looking actually on the engine block (Doh), right then Im off out for a fag and a quick look then, cheers!

 

[crammy69]

Found it ! cheers. Its a bit dark but looks 'ok' how do you tell if its shot or not?

 

[crammy69]

Any ideas? I've been told today that a coil either works or it does'nt, would you guys agree with this?

 

[Dieselman]

Any ideas? I've been told today that a coil either works or it does'nt, would you guys agree with this?

No.
It can produce a reduced voltage under load.

Buy a cheap spark tester to see.

http://cgi.ebay.co.uk/NEW-IGNITION-...14&_trkparms=72:1301|66:2|65:12|39:2|240:1318

or

http://www.limora.com/index/lang-2/...sult_zoom.tpl,kat-,actmenu-,search-303508.htm

 

[crammy69]

Ok I give in Ill buy one ( it is cheaper than the coil after all ).

For my curiosity how exactly does it work though? It looks like you connect it to the spark plug itself, crank the engine and then --- what exactly? and how does this tell you if the coil is faulty? it looks like a simple device.

Cheers!

 

[Dieselman]

It is a simple device.
Connect to the HT contact and the other end to the engine block then crank/run the engine.
It measures the voltage output by causing it to jump across an air gap. It takes about 25Kv to jump an inch.

Page 35 gives the stock code.

 

[crammy69]

Ok my tester arrived from Ebay today so going to give it a go tommorrow, however it doesnt appear to give any reading, its juts lights up / or not. I guess if there is no spark at all that will be very telling...

 

[Dieselman]

It's a shame you bought a simple spark tester as opposed to a voltage tester. I'm sure you will see the spark, but that's not a real test as it only takes a few Kv to jump the small gap.
The caliper or screw type tester will test at what voltage the spark fails. More is better.

 

[crammy69]

The thing is I was going to get the Gunson one, but whilst showing in their catalogue I could'nt find it online anywhere for sale so just bought the simple one. Of course unless this one shows no spark at all, its not going to tell me much at all, so Ill have to find one (trawl the shops I guess!).

Cheers

 

[daveuj]

Plugs ?