It’s suddenly gone very rich.

ChrisB

ChrisB

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Hey all, any thoughts on why my 72 CSL is suddenly running very rich? Was fine when I parked it up, but on starting the following day she’s running v poor, barely maintains a misfirey idle, plugs black and all sorts of oily crap being thrown from the exhaust.
I’ve had a brief look and found nothing obvious.
The only thing worth mentioning is that in trying to start prior to it running rough it didn’t quite catch the first time and coughed back thru the inlet quite violently.
Thoughts appreciated.
Thanks.
 
Over rich condition could be caused by many things.

What is line fuel pressure? If it is above normal, ~28psi/2bar, this could upset normal air/rule ratio. Hint: fuel pressure can be adjusted via fuel pressure regulator.

Is vacuum hose securely connected to Manifold Pressure Sensor? How about the electrical connection to the Manifold Pressure Sensor? A problem with either of these two inputs can cause extremely rough/erratic running that mimics over rich condition. Manifold Pressure Sensor could also be faulty.

Electrical connection to manifold-log sensor? Is it secure and corrosion free?

Retarded ignition timing? Has something, i.e., distributor, been bumped/moved?

Ignition coil condition? Is it possible that ignition coil has been overheated and fritz’ing?

https://jetronic.org/en/d-jetronic/72-troubleshooting


fuel pressure regulator
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manifold pressure sender
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No info on this curious mockup
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ChrisB said:
Hey all, any thoughts on why my 72 CSL is suddenly running very rich? Was fine when I parked it up, but on starting the following day she’s running v poor, barely maintains a misfirey idle, plugs black and all sorts of oily crap being thrown from the exhaust.
I’ve had a brief look and found nothing obvious.
The only thing worth mentioning is that in trying to start prior to it running rough it didn’t quite catch the first time and coughed back thru the inlet quite violently.
Thoughts appreciated.
Thanks.
Click to expand...
disconnect the wires from the cold start injector AND put a visegrip on the hose.

Any different?
 
ChrisB said:
No change unfortunately.
I did check fuel pressure at the same time, seems to be a steady 29 psi.
Click to expand...
It’s also fitted with a 123 dizzy if that’s of any relevance, maybe a problem with the triggers?
Also, I do have a complete spare set of d jet parts including ecu. I’ll try the ecu this evening
 
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Not too familiar with D-Jet, but 29 PSI seems low. L-Jet runs 3 Bar, which is about 40 PSI. One source of sudden poor running is the voltage reg. Try pulling the field wire off the alternator. Long shot, but that was the issue with TJ Noto’s CSL back in the day.

But this sure sounds like a leaking CSV. If not that, the only other source of fuel is the injectors, so that points to the MAP sensor, or (unlikely) the ECU
 
And pull your plugs

Look to see if all are wet or just some.

If it’s not too much of a bother, disconnect, the cold start injector cover the hole with rag start the engine with the injector facing into a plastic jug and count how many seconds it fires and that it stops

By now your spark plugs are probably all fuel fouled and you might want to start with a fresh set. They’re only two bucks apiece.

Do you still have the original Distributor with the original trigger points available?
 
I'm sure I read somewhere that the pressure sensors were sensitive to pressure spikes - is it possible that the backfire on initial starting has ruptured the diaphragm in the manifold pressure sensor? I've no idea just how fragile (or not) these are and it might be an odd failure mode, but perhaps something else to look into after the cold start system and sensors?
 
The e9 forum does have a library of djet spare parts that we loan out.
You pay shipping.


Ecu
TPS
MPS
Trigger points
Distributor
IAT
CLT sensor
Temp/time switch.
 
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