Oh Dear... I got a problem :(

[Sp!ke]

Driving into work today and was fine for the first 20 miles or so and then I went to pull away and the car stalled.

Tried to restart it and it reluctantly started after about ten seconds on the key. Normally its immediate.

Anyway, tried to pull away and its lumpy as hell, I found that if I am very gentle on the gas it would pull away OK but if I put more than a little pressure on the pedal, it would misfire and try to die. Once moving and the revs up a little, the car ran normally with little or no signs of problems.

I limped to work and parked up I've just been out now and looked for anything obvious but couldnt see anything but the car now refuses to start and the battery is showing signs of being on the low side as after only a few seconds on the key, it started turning over more slowly.

Does anybody have any ideas on this one? It feels like fuel starvation but I can hear the fuel pump turning. I was thinking mebbe alternator/battery (no lights to indicate this mind). I also thought mebbe my cat has finally collapsed and is blocking the exhaust or something unded certain conditions.

If the car had a carb I'd say it was the idle jets that were blocked - is there similar on a injection system?

 

[Steve_Perry]

Noooo Sorry to hear the car is playing up Sp!ke.

When my dad had a similar problem with his W124 200 it turned out that the engine (pistons /cylinders) was badly coked and it needed a complete clean out... strip, clean & reassembly. Symptoms were lumpy idling, stalling and refusal to start in extreme cases. The problem seemed most prevalent as the engine was making the transition from cold to warm running and an inability to drive the car up even the shallowest of hills / slopes.

The MB dealer at the time were useless at diagnosing the fault plus wanted loads of money to look at the problem without giving any guarantees that any corrective work that they did perform would actually cure the fault.

George Fraser found the problem and fixed it after methodically testing each part of the engine and its ancilliaries, eg. carb, auto choke, etc. He only charged for the engine clean and not any of the investigative work. :bannana:

Hope you get yours sorted soon.

S.

 

[marc777]

Spike, I had a BMW 325i that did exactly this and it turned out to be the ECU - the car's control for ignition, etc etc

New one was expensive and subsequently learnt that 2nd hand would have done - was no time alas and it cost me £700.

Does yours have an ECU?


Good luck
Marc

 

[GrahamC230K]

Air Flow Meter (NOT MAS)?

 

[Howard]

Sp!ke, i had almost exactly the same symptoms as you describe, mine i found in the end was a carcked distibutor cap (split in half but held in place with the bolts). It was arcing everywhere.

As you say once the revs are up and your moving its ok, but pulling away and too much throttle and its spluttering all over the place. It was more prevalent when it was damp too ( like this morning). Found it took ages to start, and if you did stall it ages to re-start which then pulled down the battery.

I don't know too much about the engine itself, but i hope this is of some use to you. I expect you have probably checked the dist. cap already (being the font of MB knowldege you are ) but if not perhaps this could be the cause, my cap was hidden under a protective rubber sheath (oo err missus) and at first glance appeared ok.

H

 

[Robby]

Check the battery first - a cooked battery may well give those symptoms, enough charge in it to just about run the ignition system - about 8 or 9 volts, but not charging because its knackered.

On the bike forum that I frequent a surprising amount of problems, particularly at this time of year, come down to a sick battery. Bear in mind that a car won't run at all with a totally dead battery, even if its started off a healthy one.

Otherwise, could be ECU, could be wiring if it passes close to the block and can get hot/cooked like on my ford scorpio. Crank position sensor is a possibility too.

 

[Sp!ke]

Hmmm thanks for your ideas... I doubt it is coked up since it was all checked when the head was off 12k miles ago.

Battery? Well it wont start when on Jump leads.

Distributer? Will double check now, sounds a likely candidate.

ECU? I hope not

Gonna get my hands dirty now, in the dark with a torch

 

[Howard]

Brrrrrrrrrr......

Checking engines in the dark, and the cold , just the thought of it is making me shiver. I'll stick another log on the fire for you mate !!

Seriously though, i hope its nothing serious, fingers crossed on the dizzy cap!!!


Let us know how you get on !

 

[league67]

I'd bet on Air Flow Meter.

 

[bazza]

I have the same problem now and again with my 190. I was thinking fuel or timing but I am now positive it is the distributor cap. Just need to get time to prove my theory but let us know how you get on


Bazza

 

[jgevers]

Hi,

If the car runs KE jectronic, the first thing I would check is the overvoltage protection relay. From memory, it sits on the passenger side scuttle. It is the one with the fuse in the top.

regards,

Job

 

[Will]

Spike,

Try and locate the fuel pump relay. Not sure about the 124 CEs, but on the W201s it is next to the OVP (over-voltage protection relay).

This was on the passenger side, behind the battery. There should be a plastic panel to remove, and as Job mentioned, the OVP relay should be an aluminium cased relay, about an inch square and 2 inches tall with a blade fuse on the top.

The fuel pump relay may be about the size of a cigarette packet, normally with a black plastic casing.

If you suspect the fuel pump relay, PM me and I can describe a way of testing it to eliminate this.

P.S, with a faulty fuel pump relay, the fuel pump may still 'prime'.

What happens is that when you turn the ignition on, it runs the pump for a couple of seconds to 'pressurise' the system. It then stops the pump to prevent it from overheating (no fuel flow through it whilst the engine is not running).

You then turn the ignition key and start the engine as normal, and the fuel pump relay will switch the pump on to run more continuously.

How did you get on tonight?

Good Luck,

Will

 

[Sp!ke]

Car is sparking but dizzy cap & rotor all look like they havnt been changed in 20k - god I hate mechanics.... so much for getting it regularly serviced.

Gonna leave the car at work, buy new plugs, rotor and cap and mebbe leads if I have to & try again tomorrow.

Fuel pump primes but as you say it could be fuel, could be electrics. Will have to dig out the test for the fuel pump and bring tools and multimeter tomorrow.

 

[Will]

Can you smell unburnt fuel getting through the exhaust?

Does it backfire?

Before you go through all the hassle/cost of fitting new plug/cap/leads why not eliminate the FPR and OVP?

You can by-pass the fuel pump relay very, very easily and therefore rule this out. I would certainly spend 2 minutes to eliminate this before going in feet first!

Good Luck,

Will

 

[Sp!ke]

I cant really smell unburnt fuel so you sound like you're right and should check the FPR.

How do I bypass it? I know you bridge some of the terminals but dont know which ones.

 

[Roy]

re the limp to work.

As Robby stated in his reply, check the battery thoroughly..
During my working life I worked for one of the country's leading battery manufacturers for over quarter of a century....
We picked up from F..d Motor Co. that when a battery was geting low and towards the end of it's life the performance of the engine went off..

We regularly changed batteries on our Company cars ( all experimental of course) and found the engine performance increased immediately and the engine performance became much smoother... All down to the voltage at the ECU... Worth a try.
Any other comments on this would be most welcome. My original battery on my E300TD is now about 7 years old. :bannana: I keep wondering about investing in a new one (retired now so I have to pay ?). From the info I have to hand the best battery for a Merc is definitely a VARTA heavy duty. This was the OE spec on my older model and is the main battery fitted in Germany to BMW's.
Be careful of the imported Far Eastern batteries.... well, well below the German specs. I would not consider them.
Roy

 

[Will]

Spike - PM Sent

Roy - I can see your logic, but just slightly dubious in this particular case as I am sure that the older Bosch KE Jetronic fuel injection system is very primative. Ie, IIRC you can actually unplug the entire ECU and the engine should still run in a basic operation mode. It is a 'mechanical' injection system, but elecronically 'fine tuned'

Therefore, if the engine's main components are functioning (ie, compression, fuel, ignition) it should still run!

Any 'experts' out there able to elaborate/confirm/correct?

Cheers,

Will

 

[Ian B Walker]

Sp!ke if you need a fuel pump relay I have one spare. Cost £80 last time I asked, but yours for the postage.

If its ECU V12 is "THE" man, yeah ok, I am advertising but I believe good service deserves recognition.

 

[jgevers]

Spike - PM Sent

Roy - I can see your logic, but just slightly dubious in this particular case as I am sure that the older Bosch KE Jetronic fuel injection system is very primative. Ie, IIRC you can actually unplug the entire ECU and the engine should still run in a basic operation mode. It is a 'mechanical' injection system, but elecronically 'fine tuned'

Therefore, if the engine's main components are functioning (ie, compression, fuel, ignition) it should still run!

Any 'experts' out there able to elaborate/confirm/correct?

Cheers,

Will

Hi Will,

You are correct. KE Jectronic should still run with computer unplugged. It is essentially a K jectronic with an electric fuel pressure regulator instead of a 'warm up regulator'. This is what happens when the over voltage protection relay stops working (normally due to dry joints - easily repaired) or if the fuse on top pops. This cuts the battery voltage to the KE control unit. The symptoms tend to show hard starting, bad idle but ok-ish at higher revs.

regards,

Job

 

[Will]

As I thought - cheers!

Will