Damp weather, hard to start classic.

shawnee

My friend's merc estate, normally starts and drives very well. However when we get damp weather , it splutters and he finds it hard to start, also runs univenly and cuts out. When it warms up it is fine. He has replaced plugs and distributor looks okay. Any ideas !!:o:o

mike65

Fuel injection or carb fed?

MercMad

I would take another look at both the cap and rotor, make sure they are correct, clean and in good shape. Check the HT leads and ensure he has used the correct grade of plug, and that its not a cheap brand.

Some of these cars uses seperate coils for each plug and the cable harness breaks down over time causing random misfiring ! You will need to remove the cover on top of the cam cover and closely inspect the wiring.

If possible, you could start the car in the darkness and observe and arching which will show where the fault is

Good luck.

MercMad

Sorry for some reason I assumed it was a W124 !

What year/model etc.. is it ?

shawnee

Car is a 1982 merc 123 series.;) and is fuel injected.

MercMad

Then ignore my first answer and concetrate on the HT leads, cap and rotor.

Are you sure its the damp that affects it, or is it the drop in temperature. The later could be caused by malfunctioning cold start system.

Dades

shawnee wrote: »

My friend's merc estate, normally starts and drives very well. However when we get damp weather , it splutters and he finds it hard to start, also runs univenly and cuts out. When it warms up it is fine. He has replaced plugs and distributor looks okay. Any ideas !!:o:o

I had one or two starting issues with my SL this winter. Would regularly take a lot of turning over, and a couple of times she wouldn't start at all. (Once she did get going all was fine). I had figured since it was turning over, the battery was fine, when in fact it was labouring.

It may seem obvious now - but I gave the battery a full charge and since then she's started up first turn every time. Even with 5 inches of snow cover last week!

shawnee

It's definitely the damp weather, car started fine in the colder frostier weather. Thanks for advice will check quality of plugs and try that starting it in the dark and see if spark is escaping.

mustang68

If the HT leads are old they get porous and in damp conditions the insulation of the leads gets wet right to the core that carries the spark, which give the spark a path out to the damp air.

MercMad

mustang68 wrote: »

If the HT leads are old they get porous and in damp conditions the insulation of the leads gets wet right to the core that carries the spark, which give the spark a path out to the damp air.

.......yeah thats exactly what happens and why spraying WD40 or some such will cure it ......................for a while. But it may be enough to get it started.

You can ensure the leads have a healthy smooth appearance and texture. Any hardness or strange marks indicate tracking.

Good one Dades about the battery. The V8 on the 350 is quite smooth and silent whilst cranking and it can be hard to tell if the motor is actually turning that bit slower, unlike in a 4 cylinder car where each compression stroke nearly stops a weak battery.

The clue on this W123 is that it does start, but still runs poorly.

Luke Crowley

I had similar problems with my W201 a couple of years ago. You should definitely replace the distributor cap straightaway, these are often the most troublesome part of the HT system. Your HT leads could also be causing trouble. Take one off and, if you can't tie a knot in it, replace all five.

shawnee

We just started the car tonight and can see spark jumping from distributor cap and also half way up the plug leads. Anyone know what is best type of replacement equipment to get and where I might get it. :o

MercMad

shawnee wrote: »

We just started the car tonight and can see spark jumping from distributor cap and also half way up the plug leads. Anyone know what is best type of replacement equipment to get and where I might get it. :o

Get Bosch or Beru, thats what the OEM parts are. You could try GSF or OTTO.

shawnee

Thanks for that, Will treat her to a new discributor cap and leads.;)

corktina

WD40 the solution to and the cause of all automotive problems...or is that Duff beer....anyway...WD40 water dipersant.