230E on 3 cylinders

[markalexander]

Got spark at all 4, Any tricks for unblocking fuel injectors? 250 miles from home. Got all my tools.

 

[Will]

I'd be surprised if it's a blocked injector. Far more likely to be something else at fault - e.g. Fuel distributor or one of the other K-jet items if fuelling is an issue.

You can remove the injectors from the inlet and manually deflect the airflow plate if you want to check fuel delivery from each?

If it's misfiring though I would still want to rule out ignition first - if you don't know what you're doing with the K-jet system you might cause more issues than you can solve

Possibly cheaper and better to see if you have a decent local MB indi or Bosch service centre nearby. Where are you located?

 

[markalexander]

Checked all leads, continuity ok at specified 1K resistance. All other cylinders running spot on

 

[markalexander]

In Wetherby, near Harrogate.

 

[grober]

Other causes of cylinder misfire are unfortunately a bit more drastic - cylinder head gasket being one. Its a known fault on these M102 engines Try running the engine to get it fully warmed up then pull a couple of the plugs to compare them. If no 3 looks black and wet it may signal coolant is getting into cylinder head. Then try looking down the no 3 plug hole- again if the top of piston is black and "oily" looking it may be down to coolant.

 

[Will]

Checked all leads, continuity ok at specified 1K resistance. All other cylinders running spot on

Continuity/resistance check won't tell you if the insulation is breaking down though hence it's possible that one of the leads is shorting to earth (head/cam cover) rather than firing the plug.

Best bet would be to do as Graeme has said above, run it for a bit then once cooled off take all four plugs out and compare them. If one cylinder is not firing you'll notice the difference. Head gasket usually affects cylinder 4 first on the M102 engines and sometime #3 depending on how long they've been leaking (if that is what's wrong of course)

What's the coolant look like? Any mayo in the oil either?

Have you got access to a compression gauge?

It will be simple to diagnose where the fault lies even if the repair is a bit more complex. You only need compression, fuel and a spark to run so you're obvious missing one of those three.

 

[bolide]

If it runs OK under load but misses at idle I think that rules out sparks

Although it's not the first thing you'd suspect I would think it's a fuel-related problem. If you know which cylinder is missing you could try swopping injectors to see if the fault follows the injector. If the fault follows the injector than suspect the injector. If it doesn't, suspect the fuel distibutor

If you pull the ignition leads at idle the one that makes the smallest difference to the idle will be the one to the bad cylinder

Replacing the coil & HT leads just adds more variables. I'd pin down the fault(s) as much as you can before doing that. You may be able to swop HT leads between cylinders to see if the fault follows the lead. If it doesn't it points again at fuel

Nick Froome

 

[markalexander]

Many thanks for taking the time to offer your comments and assistance, It is very much appreciated! I have located an independent garage used to "older" i.e. not plug in cars, who is going to have a look for me, and will report back next week.

As an aside, Auto Discount in Harrogate, tel 01423 562049, did me a distributor cap and rotor arm for £39.90 all in, ordered 10.00 am, ready for collection 4.00p.m. Useful People! (plus a set of plugs for £10.00!)

Thanks again Guys

 

[markalexander]

next problem

Fault was caused by a burnt exhaust valve.( no damage to seat) Next problem is where to get a replacement. Garage are struggling so I am helping to look while the head is waiting to be skimmed. Any suggestions

 

[Will]

Fairly unusual on an M102. Have you tried MB for a price, if it's only one valve I doubt it will be too bad?

Any pictures?

 

[grober]

From this https://en.wikipedia.org/wiki/Mercedes-Benz_M102_engine I would make your engine the M 102.982
exhaust valve no A1020500327
See Original & Neu Mercedes M 102 Auslassventil: A1020500327 | eBay

You might also want to renew/check that hydraulic lifter in case its seized and any other valve components spring collets etc
the lifter is part no A1030500080

ps your first port of call might be your local MB dealer parst counter just to check if they haven't got any of these bits?

 

[John Jones Jr]

Fault was caused by a burnt exhaust valve.( no damage to seat) Next problem is where to get a replacement. Garage are struggling so I am helping to look while the head is waiting to be skimmed. Any suggestions

There's several potential faults that could have caused the burnt valve and one could be it was running lean on that cylinder. I'd strongly advise fitting new injectors as a matter of course, they're past their best if original and they probably are too.

 

[markalexander]

Only one valve, no head damage but some corrosion around one coolant channel, so head getting skimmed

Hope the picture works, never tried this before..

 

[grober]

Only one valve, no head damage but some corrosion around one coolant channel, so head getting skimmed

Hope the picture works, never tried this before..

Your link only works on your own computer -nobody else's unfortunately. You need to use the manage attachments button below the post box , which allows you to upload an image to the forum.
ps there is a restriction on size.