I'm wondering how other D-Jet equipped coupes have the knob set on the ECU that adjusts the fuel volume (lean/rich)? I have a D-jet system from a '75 euro transplanted to my '74 CS. The knob on the ECU was set fully clockwise (max volume, I believe) to compensate for a stuck air slide (which I have now replaced.)The car runs fine but is hard to start when hot. I'm thinking the mixture might be too rich and with the new air slide I should lean it out a little. Any advice would be appreciated. Thanks.
D-Jet Adjustment
- Thread starter bill
- Start date
pmansson
Well-Known Member
Somewhere in the middle, without actually checking.
Are there about 17 slots on the knob...?
Not much help I´m afraid...
Are there about 17 slots on the knob...?
Not much help I´m afraid...
JhwShark
Well-Known Member
Mine is a couple of clicks clockwise from factory setting...Clockwise clicks richen the mixture, counter-clockwise clicks lean the mixture. If you are all the way clockwise, as mentioned you are rich.
The factory made a mark on the plastic surround of the knob to indicate the "factory" setting, the correct mixture for proper operation is usually within +/- 3 clicks of this position. I suggest that you use an air/fuel meter to adjust the idle mixture to the factory setting of CO...most have 21 clicks; there are at least three different ECU models.
Jon
The factory made a mark on the plastic surround of the knob to indicate the "factory" setting, the correct mixture for proper operation is usually within +/- 3 clicks of this position. I suggest that you use an air/fuel meter to adjust the idle mixture to the factory setting of CO...most have 21 clicks; there are at least three different ECU models.
Jon
MMercury
Well-Known Member
- Messages
- 481
- Reaction score
- 5
Even if you had two identically fitted engines, there are so many variables introduced - particularly after 35 years - comparable potentiometer settings might not be particularly helpful. I have swapped ECU's (same part number and color coded) on the same engine, yet different adjustments are required to produce similar CO readings. Simply stated no two engines are exactly the same - even on the same test stand.
An apt analogy might be idle (speed and mixture) adjustments on any carburetor. A carburetor set up for use on one engine may still require adjustments on another engine to obtain similar idle characteristics. Even the same engine with something as simple as a plugged air filter might benefit from a different Potentiometer setting than one with a clean or non existent filter. Note below the recommendation that adjustment be made with filter in "good" condition. Same with introducing different spark plugs, spark plug gaps, ambient temperature, humidity, fuel quality, engine mechanical condition (compression and valve adjustment) and so on. Its the reason why even with two identically equipped vehicles - one may be slightly faster than the other.
Modern fuel injection systems and their electronic components may offer better comparisons for each other. Whether that’s the case in 35+ years remains to be seen. :?
13 00 054 - Adjusting idle speed on fuel injection engines:
A) Version with pressure sensor Requirements:
a) correct ignition timing and tappet clearance
b) coil temperature about 60° (140° F)
c) auxiliary air valve closed¹
d) air filter cartridge checked for good condition
Connect tachometer and CO tester.
Adjust idle speed with idle air screw (1).
Europe: 850 to 1000 rpm
USA: 900 to 950 rpm
Adjust fuel volume at idle speed with potentiometer (2).
Turning potentiometer counterclockwise will reduce CO by volume².
If turning potentiometer does not change CO level, check throttle
valve switch or throttle gap - see 13 63 534.
¹ From 70° C 158° F) coolant temperature
² Europe: 1.0 - 2.0; USA: 1.5 2.0
Per Manual: The pressure sensor and control unit are matched for each other.
(If you are a strict adherent to the factory recommendations) "Other combinations are not permissible, or would lead to excessive fuel consumption and poor performance."
Matchings
ressure Sensor Unit - Control Unit:1 without paint dot - without paint dot
2 blue paint dot - blue paint dot
3 red paint dot² - red paint dot¹
¹ Bosch No. 0 280 001 007
² Use a pressure sensor with a green dot, Bosch No. 0 280 100 030,
for fuels with 0.15 grams of lead per litre.