Quote:
Originally Posted by Vakito
Hi all, I own a 1988 240 Saloon with the 2.0L K-Jetronic engine.
Once started the engine runs perfectly, pulls a strong 20"Hg vacuum at 1000rpm idle and eats up thousands upon thousands of miles without a care in the world. However all my time owning it I have had troubles starting it and to make things worse this is an intermittent fault. This really puts a lot of stress on my recently replaced engine mounts. Here's what I've observed:
- When starting the engine feels like it's firing on 3 and sometimes 2 cylinders, the throttle feels slightly more delayed and you have to rev it to about ~1500rpm for a few seconds before everything smooths out
- Sometimes it will start and immediately stall, sometimes it will start and run down over a few seconds until it stalls.
- It it stalls, the engine takes a bit of cranking to get it going again, unless you anticipate this quick enough and turn the key back to zero before it stalls, in which case it will very often surprisingly start back up immediately with no issues.
- This whole starting issue affects probably 20% of cold starts and 90% of warm/hot starts.
- I have not noticed any correlation between this problem and weather conditions
- Once started like I said, engine runs perfectly with no issues whatsoever.
Here's what I have currently done, with no success in curing the problem.
- New plugs, leads, distributor cap and fixed type rotor arm.
- New fuel pump relay
- New fuel filter
- Thorough cleaning of fuel injectors with new O-rings
- Cleaned throttle body
- Polishing of distributor and rotor arm contacts every few thousand miles
- Replacement of all cracked vacuum lines
I believe the problem may lie with either the fuel accumulator, the one way valve on the fuel pump, the ignition coil or god forbid the K-Jet metering unit but before I go throwing more money at the problem has anybody else had this experience and any success in curing it?
Thanks
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Right then, My money is on a faulty warm up regulator or auxiliary air valve.
Assuming you have checked and sorted out ignition problems,( you have) and the relay is not faulty(replaced with a new one)
The first thing to do is check all the pipes for vacuum leaks you can snip off the end of the vacuum lines lines and refit them
if the lines are long enough and a push fit just cut off the tip that is wider than the rest of the pipe
secondly check all the pipes that feed air from the metering unit for splits cracks etc and are not leaking between the metering unit and the throttle body,leaks here will reduce the pull on the metering plate screwing up the mixture for starting and once running will cause a weaker mixture when these leaks open up to atmosphere
from your description I think you have the following problems these are caused by the control pressure regulator being faulty or there is a leak in the lines to it, check fuel and vacuum if you have vacuum depending on which one you have.
The control pressure is managed by the control pressure regulator during warm up and also acceleration if a vacuum connection is present
Behind the larger of the 2 unions is a metal gauze filter. If this gets blocked, it causes the warm up regulator to remain closed, causing very bad flat spots and poor acceleration during the warm up, its like driving with the choke in. It can be cleaned using clean petrol. It also has a vacuum connection to it.This is for full load enrichment.
At full load,the engine vacuum is low, which opens the valve slightly, reducing the pressure on the control plunger and giving a slightly richer mixture exactly like an accelerator pump in a carburettor
Inside the main fuel feed line to the metering head is a small mesh type filter which you should remove and either clean thoroughly or replace it, see a manual how to do this
they are cheap and available on ebay but be careful replacing it as you may need new seals for the banjo bolts etc
check the smoothness of the air flow sensor plate it should not be jerky just smooth and easy.
Also sometimes the Auxiliary air valve sticks closed and does not open test this as follows
Cold Operation.
Test the auxiliary air valve first with the engine cold (not run for several hours, preferably overnight).
Disconnect the electric plug from the auxiliary air valve and from the control pressure regulator.
Remove both air hoses from the auxiliary air valve.Using a torch and a mirror, look through the valve When the engine is cold, the valve must be open. If not, the auxiliary air valve is knackered also check the voltage at the plug should be 11.5 volts minimum
Warm Operation.
Disconnect the electrical connection plug to the auxiliary air valve. feed 12v to the auxiliary air valve pins observing the correct polarity, you will know which way around it is from the previous test, the valve must be completely closed within about 10 minutes.
If the auxiliary air valve does not completely close within about 10 minutes, it's knackered.
The cold start injector is only squirting fuel when the starter motor is active but a dribbling injector will cause a rich mixture
some of the faults you describe make me think its these listed below
Engine stalls immediately after starting(warm)
1)Warm control pressure
If the warm control pressure is too high,the
air-fuel ratio will be very lean,causing the engine
to die.
2)System pressure
If the system pressure is too high or too low,the
air-fuel ratio will be incorrect.Incorrect fuel
pressure can result in either a rich or lean running
engine.Either one can cause the engine to stall
after start up.
Engine stalls immediately after starting(warm)
1)Warm control pressure
If the warm control pressure is too high,the
air-fuel ratio will be very lean,causing the engine
to die.
2)System pressure
If the system pressure is too high or too low,the
air-fuel ratio will be incorrect.Incorrect fuel
pressure can result in either a rich or lean running
engine.Either one can cause the engine to stall
after start up.
for those who don't know ....
The Auxiliary air valve looks like this
http://www.bosch-classic.com/media/b...ll_gb_w734.jpg
The warm-up regulator, also called the control pressure regulator, looks like this
http://www.bosch-classic.com/media/b...er_gb_w734.jpg
hope this helps