w123 230E - Keeps cutting out - totally random...

[mezza]

1985 230E Auto

Sorry for the long post

I have a problem with this old lady. Other than this problem she is magnificent. If I manage to solve this problem I will reward her with an underbody seal! Can anyone help me get there?

She starts straight away, idles at about 750-850rpm and runs quietly and smoothly. She accelerates well, steers fine and stops when I press the brake. The electrics work fine, the heater works fine and the vacuum locks also work perfectly.

Problem is that she cuts out from time to time.

I cannot predict when it will happen. I can be driving at 70 mph or just at idle. I could be going up a hill or freewheeling down one. I can be on a smooth road or a bumpy road. It can be wet or dry, hot or cold - there seems to be no pattern to it.

When she conks out she does the following (when driving):-

quietly and without warning the power goes and the revs start to drop. The ignition light comes on and I put her in neutral. Almost always I can restart her (after waiting about 5 seconds) whilst I am still coasting along, and continue my journey. It may happen again within the next minute or not happen for the rest of the afternoon.

My confusion is that the problem is so transient and intermittent. The radio does not cut out when the engine does. She is always available for restart almost immediately and she runs so bleeding good in the meantime. Sometimes when I stall whilst doing, say, 70mph there will be a backfire which indicates to me that it is not a case of fuel starvation.

Understandably it is a little embarrassing when I show her off to people!

I am not a mechanic but have checked a few things that I think may be responsible:-

The battery is fine and the -ve ground terminals seems fine
The HT leads have previously been replaced with the correctly rated leads
The ignition amplifier was also replaced with s/h part
The fuel pump relay has very recently been replaced with a new part
I am running on 98ron unleaded which shouldn't be a problem
(a previous owner has indicated that it was previously run on 4star)

Only thoughts I have are some sort of airlock, an electrical fault, a problem with the injector

I would be grateful if people could give me pointers of things to test and check (I have a test meter if you tell me how) to help me diagnose the fault without having to pay a garage for a whole day's diagnosis!

Remember - we get this sorted and its me and her, a wire brush, a tin of underseal and rust in the eye!

Since drafting the above (for http://www.w123.net/) I have done a couple of more tests: fuel pump voltage and current are within normal limits. I also witnessed a stall when I was by the fuel pump today and noticed that it ran for a second after the engine had cut out - so I don't think it is the fuel pump

:? :?

thanks for all your help

mezza

 

[njpumphrey]

A recent problem someone had with random cut outs was finally resolved by replacing the rotor arm on the distributer...

 

[mezza]

thanks for this - on my list this week:

new in-line fuel filter
rotor arm

do you know if there is a way to test the ignition amplifier with a multimeter?

 

[Russel Weston]

Mezza, I have a 230E as well and about a year ago, mine developed the identical problem. I went throught the motions of Dist cap and Rotor. I replaced the Fuel pump relay, and that worked for a while. Then the problem came back. I then ran a bypass for the fuel pump, missing out the relay and the problem has never re-occured. If you need details on the fix I used let me know and I will send you a breakdown.
Regards

 

[mezza]

thanks for that - I will give it a go (pins 7 & 8 isn't it?)

I am taking the car out tomorrow so will check if it does it more when cold or when hot

 

[mezza]

No joy
She cuts out no more in the dry than the wet
I have tested the coil
primary winding resistance is 1.2 ohms
Book says it should be less than 1 ohm
I will replace coil and report back

 

[mezza]

Book was wrong - my new coil tests the same - I will leave the original in.

I read some post about the ignition amplifier/ECU and how it requires good heat sink. I have cleaned the back and re-bedded it on conductive paste. I think things may be improved a little

I looked everywhere for a OVP relay but I can't find one - did they fit them to my 1985 230E Auto?

Thanks for your help

p.s. I am now undertaking petrol treatment as well - I will get this sucker running spot on eventually!

mezza

 

[mezza]

I have not managed to crack this one yet

To date I replaced:-

HT leads
Distributor cap
Rotor arm
Ignition amplifier (with s/h unit)
Fuel pump relay

car still running excellent, until it stalls. It then restarts easily. There is no spluttering so I'm sure it is an electrical ceasing of the engine. The fule pump can be heard running continually right up until a second after the stall. I have tested the existing coil with a new one (same results) but have not replaced it (I don't see the need).

I'm in need of a new direction on this one...very weak now...

mezza :cry:

I am very confused

 

[talbir]

Your OVP relay should be behind your battery - remove the plastic cover and you'll see the silver relay with a red top.

Check that pins are not corroded and good tight contact is formed when relay is connected.

Also check integrity of contacts on ignition coil, and the battery/starter terminal block connector, next to the battery.

Given you've changed/checked most things in the ignition system, it might just be your ignition ECU playing up. Try tapping it when the cars at idle, to see if anything happens.

 

[TimN]

I have a 230TE 1981. I had a problem with it starting once which lead me to question the fuel pump. I then wondered how the power was supplied to the fuel pump because when you turn the key to the run position you do not hear the pump like you might do on other cars. I do not have an electrical wiring diagram for the vehicle but I wondered if either of the two vacuum operated switches were in line. So when the engine was cranked over the vacuum switch would operate and power supplied to the pump either directly or via a relay. One vacuum switch is underneath the self levelling fluid reservoir on the estate or just behind the left habd headlamp unit as you look oat the car from the front. The other one is attached to the inner wing just below the air intake. Perhaps someone might know what these switches do. It would be simple to override them an see if that cures the problem.

 

[wagamama]

Hi there,

i had a problem with my diesel car cutting out randomly just like yours. It took the garage nearly 3 weeks to figure out what was wrong, replacing loads of things (spark plugs, filters etc). In the end it turned out to be a blocked fuel line. They promptly replaced it with clear fuel pipes and charged me almost £900 for labour and parts(!)

 

[mezza]

Thanks for the tips gentlemen

I have a replacement fuel filter, but havn't fitted it yet

I am going to have that changed and also the in-line filter to see if there is an improvement

Watch this space

 

[DVF]

Just came across this today.

I see you considered the coil, did you try the new coil in there?

I and a friend both had the exact same problem on our cars, a Ford Focus and a Renault Laguna. Both times the coil was to blame. The spark plugs on both cars were severely damaged by this so you could check the condition of them too for a clue. Also the resistance you measured might well be within limits of the coil was worrking at the time. Like you say the engine only cut out occasionally.

 

[mezza]

Update. This problem is now solved - but not before I changed the coil and the plugs!

It turned out that a ignition amp which was replaced by another garage with a 2nd hand part, was faulty

It was impossible to diagnose until the car got really bad - even then the window for diagnosis (by the excellent AA) was about 10-15 seconds every 5 minutes or so

Replaced the ig amp with another 2nd hand part (budget too tight) and have not looked back since - I learnt a lot in the 3 months of plight!

 

[LukeHayler]

mezza, you dont know what a breath of freshair your reply brought to this gloomy sense of hopelessness i am feeling with the same cutout problem i have with my 190E.

my latest waste of money attempt was to change the air flow sensor for £320 (second hand - didnt work). i hadnt tried the OVP or fuel pump yet.

would you say that changing the ignition amplifier would be the problem fixer then? (ie anything else needs to be change eg: the coil and plugs?)how much was the second hand part? and how much did your mechanic charge you to change it? is it based in london?

regards,
luke