The W123 Lets me down for the first time!

[jaymanek]

Hi all,

Need a bit of help, was driving back from London at 2am on Sunday morning when my W123 decided to lose power...
I pulled over and the engine was idling fine but it would hesitate if i revved it... So i left it ticking over whilst i checked under the bonnet, couldnt see anything obvious..
anyway, when i got back in the car it was revving perfectly and so carried on.. drove perfectly for around 5 miles then the same thing happened...
to cut a long story short it did this all the way home... i had to stop every few miles and let it idle before setting off again!

Its very strange as i cant see anything out of place..

My dad seems to think it may be a blockage in the exhaust but seems unlikely to me, the middle and back box are newish anyway..

i did service the car last week so i thought it may be something to do with air filter but driving the car with the filter off didnt make a difference...

any ideas?

Thanks

p.s. its a carburettor engine..

 

[Dieselman]

Check the coil for proper output and check the fuel filter for blockage. In addition it could be the fuel pump packing in so the carburettor runs out of fuel under load or the vent into the fuel tank is blocked causing vacuum in the tank, also starving the carburettor of fuel under load.

My best guess would be fuel pump.

 

[jaymanek]

yes thanks Will, how do you check the output of the coil pack? im not sure there really is a fuel filter in it as such, it just has a mesh at the fuel pump... the mechanical fuel pump is clicking away at idle but ill have another look at this too... thanks

 

[Dieselman]

Jay
You can buy a really cheap flash tester here, but especially with the mechanical pump I'd go for the pump.

As a quick check of spark power pull off an HT lead and stick a screwdriver up it. Hold the shaft of the driver near the head and the spark will jump to the head. Start close and increase the gap slowly. The spark should jump about 20-25mm without problem if good.

To check the fuel pressure either use a low pressure guage or just pull the pipe off hte carburettor and crank the engine. If it squirts about 3 to 6 feet then it's probably duff, if it squirts over ten feet then it's good.

Best to have the coil disconnected for this test as a spark can make for some entertainment....

 

[Ian B Walker]

Jay the diaphragms of mechanical pumps split sometimes. I think (not 100% sure) that you can get a refurb kit for them.

 

[jaymanek]

I have changed the pump as it was only £24 from Euro, its not genuine but german made...

Also i found a large air pipe that runs from air filter to carb air intake was off (my fault after i changed the air filter)

The problem is the fault only occurs after a period of driving so will see how it goes now!

 

[jaymanek]

Ok so happy that fuel was pumping to my engine efficiently, i filled up the tank with 60 litres of premium unleaded the other day..

Drove 6 miles home.

gets in this morning and the fuel light is on

look at the ground, huge crater on the tarmac where around 59 litres fuel has leaked out of the tank and onto my 3 year old drive....

so there was nothing wrong with the fuel pump all along, just a perished rubber hose... cost be about 14p to fix!

so ive wasted £55 fuel, £25ish for the fuel pump (and a hole in my drive) when all along all i had to do was to look underneath the car!

oh and by the way, design floor if there is such a thing on a W123... having the rubber section of petrol pipe directly above the exaust pipe.. thoughts of me driving down the M1 with my bum on fire

 

[grober]

I,ve heard of built in obsolescence but that seems a bit extreme! Are you missing a protective metal screen?? http://www.detali.ru/cat/oem_mb2.as...GM=716.005&CT=F&cat=222&SID=49&SGR=300&SGN=05

 

[pammy]

Sounds like early seat warming technology

 

[jaymanek]

Are you missing a protective metal screen?? QUOTE]



No because those plates sit above where the pipes leave the tank... its very bad design. The irony is that i have replaced every single piece of rubber and generally anything perishable over the last few years and cant believe i missed these little pipes that are only a few inches long!

 

[grober]

Fair enough. Maybe you could jury-rig some form of reflective shielding/lagging to protect the pipe in the future??

 

[Dieselman]

oh and by the way, design floor if there is such a thing on a W123... having the rubber section of petrol pipe directly above the exaust pipe.. thoughts of me driving down the M1 with my bum on fire

Just to reassure you Jay, a hot exhaust can't set petrol on fire it needs a spark.