Too rich / too lean

[scudderfish]

Fortunately his website was archived here https://web.archive.org/web/20220525185 ... plane.com/ before the domain name registration lapsed.

[jeesee]

thanks

[ChrisJC]

If you have not got this already, here is the factory manual for diagnosis:

www.cowdery.org.uk/downloads/FlapperManual.zip

Are you taking all of your readings from the ECU connector? (that eliminates any wiring problems).

The system is 'open loop', so if the sensors are correct, it will run OK.

It does sound like a problem with the water temperature sensor to me if it's running very rich. Or the AFM is defective.

I guess another explanation may be a leaking fuel injector, possibly the cold-start one. You can unplug the cold-start injector once the engine is started. Maybe clamp the pipe off as well in case it is leaking.

And unplug fuel injectors one by one to see if one makes a bigger difference than the others.

Or take them out and get them tested.

Chris.

[jeesee]

hello, thanks for the feedback and the link

of course, the measurements are taken directly on the ECU socket... and on the components to compare
I know that the harness can be a victim of breakage in its wires......
I tested all the wires under load with a 21w lamp
all connectors have been checked and replaced or cleaned
the cold start injector is disconnected (electrical and fuel)

I am used to the L-jetronic fuel injection system (installed on many sports cars of the time)
and I also directly thought of a problem on the CST
open circuit = too rich
closed circuit (short circuit) too lean

but it gives the right measurements
same thing on AST (air temp) gently heated with a hot air gun) value varies within the standards

AFM also gives fluid values without shock when you move the flapper and also in the norm.....

the 8 injectors (new) but have been dismantled and tested, the power pack resistor tested and correct

TPS replaced and set to 0.325V

plenum dismantled and seals restored all the depression sockets sealed for test does not change)
fuel pump flow rate (new) gives 4L/minute
fuel regulator replaced by an adjustable one (set at 2.5 bar)
at cut-off returns to 2.2 bar to decrease gently to 1 bar after more than 2 hours
and pressure indicator mounted in place of the cold start injector
AFM air screw was set to 2.5 turns before jamming

I don't have a scope to measure the opening time and voltage of the injectors
I read somewhere that the tachometer can disturb the ignition signal on line 1 of the ECU
tomorrow I place a direct wire from the resistor (6.8Kohms) on the coil to line 1 of the ECU for testing

the car has no O2 sensor and catalyst
does not have a fuel gas recuperator
and no pollution control system
..........
I don't understand why with an ECU it is too lean (delay on acceleration and no power like a lack of fuel!!!! .....fuel pressure increased to 3.0 Bar does not change)

and with another bought second hand and guaranteed good (cost me a kidney!!!)
it is too rich (a lot!!!!) dies in slow motion and smokes black like a steam locomotive
fuel pressure lowered to 1 bar runs a little better but no longer accelerates)
I would have two faulty ECUs
I dream of having a functional car to compare but it's rare like fresh water in the sea

thanks you

[stevieturbo]

The main load metering parameter of the system is the airflow meter.

If this voltage output relative to airflow is incorrect, then fueling will be wrong, and it only takes millivolts in error.

So first port of call would be scoping voltages from this ( although you'd need a reference to compare to ) vs rpm etc.

[ChrisJC]

Does the tachometer appear to work correctly?, i.e. stable, and an accurate representation of engine speed?

The AFM does not need to be calibrated to the ECU.

Chris.

[jeesee]

Hello
@stevieturbo

I have the values on the ECU connector (connected)
-between pin 6 and 9= 4.3V (Vref)
-between pin 6 and 7= 3.7V
-between pin 7 and 9= 3.7V which decreases properly (without shocks or jumps) down to 1.6V when the valve is opened
to know if the AFM is correctly adjusted I must have a comparison table V (AFM) / RPM / position TP
if the AFM is not well adjusted (ea: loose spring-----> rich mixture or spring too tight-----> lean mixture) I must have the same fault with the 2 ECUs except that on is lean and the other rich

@chrisJC
first!!!!!! thanks for the link to factory manual
the tachometer works correctly and gives approximately the same value as the stroboscope
I had already had a breakdown on an MGB which gave misfire at high revs because of the faulty tachometer.
today I removed the wire on neg coil to eliminate the risk does not change anything
I saw on another forum problems with a bad coil which gives parasites, but does not change my thinking why too lean with 1 ECU and too rich with the other
....... To be continued

Thank you for your support

[ChrisJC]

I think you have two problems:
1. Bad ECU
2. Bad AFM

Can you get one more of each??

Chris.

[jeesee]

Hello everyone
As a reminder, I had a 1986 RRC 3.5 EFI with a 4CU ECU # 84477B suspected bad----> lean mixture and retarded acceleration + lack of power.
bought second hand a 4CU 84941B sold as the same which gives too rich and black smoke (spark plug destroyed after one day)
received another 4CU 84941B today for testing with the same result....
put back the 84477B and removed the cover of the AFM which had been rebuilt by a "specialist", I turned the toothed wheel as explained here: https://www.club4ag.com/forums/viewtopic.php?t=21407
clockwise and got good results

the engine runs very smooth without shock or delay in acceleration, the CO is located at 2%

Why the 2 4CU #84941B gives too rich???? mystery!!!!!!
date code 2489 and 1989 I assume intended for engine with lambda probe or calibrated for the 3.9 motor.
Finally!!! it's solved
thank you all for the assistance received

[ChrisJC]

Good news!

Chris.

[GDCobra]

Good news indeed, that link was a good find.

Why the 2 4CU #84941B gives too rich???? mystery!!!!!!
date code 2489 and 1989 I assume intended for engine with lambda probe or calibrated for the 3.9 motor.

I suspect the alternate part number works to a different specification, maybe uses different injectors or AFM.
Didn't think flapper was used on 3.9, thought 3.9 coincided with move to Hotwire, could be wrong.
Also didn't think flapper was used with lambda's but again there's a good chance of error on my part. I'd be interested if anyone knows for sure though.

[ChrisJC]

There was a 3.5 Hotwire used on early DIscos's, presumably also used in Range Rovers, but I'm not sure.

I also agree that the 3.9 was not Flapper, but Hotwire.

I am not aware of any Flapper that uses lambda sensors, but I also would be interested to know of something that did.

Chris.

[GDCobra]

There was a 3.5 Hotwire used on early DIscos's, presumably also used in Range Rovers, but I'm not sure.

I also agree that the 3.9 was not Flapper, but Hotwire.

I am not aware of any Flapper that uses lambda sensors, but I also would be interested to know of something that did.

Chris.

That all agrees with my thinking. Flapper was 3.5 only and pre-cats.
As I understand it the flapper is an analogue system, more or less an electrical version of the previous mechanical systmes offerend by Bosch, as such I don't think it would/could have the capability for closed loop required when running O2 sensors. I've been wrong before though!