Hi

I have a '81 manual car with CIS injection (UK car).

I have just fitted a new set of injectors because I couldn't get the car to idle nicely. (Mercedes 0 437 502 010)

I have set up the injection system as per the book, correct pump pressure and flow rates, correct control pressures Cold and Hot.

Mixture is 1.8% CO at idle with the air pump disconnected.

Idle is now nice and smooth, the engine revs cleanly with a very sharp throttle response.

Car has had new NGK plugs, a new set of BERU leads and a rotor arm, the distributor cap looks good and clean.

As soon as I try and drive the car, ie apply any load to the engine it drops out 1 or maybe 2 cylinders and runs lumpy.

It happily returns to a smooth idle, and will revs cleanly off load.

I have checked all the vacuum hoses, and replaced any dodgy looking ones.

Also blown Propane over the engine to check for vacuum leaks - none found.

Not sure where to go from here.

John

 

Sounds like it is running too rich higher up the load range ? i.e "lumpy"...

 

Hi John

The WUR has a vacuum input which I have tested and it is working as specified. Feels like an ignition problem.......just not convinced.

The rev counter has never worked on this car, I have checked the wiring from the ignition control module right thro' to the pod. I wonder if here could be a problem with this ignition control module?

John

 

Paul Anderson would be able to help, I've no real experience with K-jet although I can repair the igntion boxes.

Paul and Richard Armstrong have had misfire problems on their race cars which I think were due to falling 12v supply volts.

The coil primary signal is the same signal sent to the rev counter. It has lots of high voltage inductive spikes on it, so be careful. If you have a 'scope you could confirm that signal is reaching the dash\tach.

If signalis there then the tach itself orwiring is te problem, probably not related to the misfire issue.

 

Could be a bad green wire. Check for abrasions and route it so it's not touching the block.

Could also be a problem in the fuel distributor, but I'm doubting that.

If it seems like it's electrical, it probably is.

 

The volt meter was only reading 10V, I put that down to being a very hot day. It was about 26 deg C.

I know the gauge is accurate because I have fed it with a digital power supply and it was spot on.

Maybe these cars have a problem with low volts?

The car starts OK, flies over on the starter, so I don't think the battery is an issue. Although I do have a brand new one here I could try.

 

Try geting in touch with Richard...