RT number on main board of Bosch ECU D-Jetronic

Interesting. My car is manufactured in September 1971, the first month they were build as my VIN ends on 000101. Volvo 1800ES, model year 1972

Following the instructions:
x21-x31 | 197x | Month is composed of digits 2 and 3 minus 20

The production dates are then:
1972, December
1972, November

The second one (with only the blue dot) is a "loaner". The first one was from my car. This means that it is replaced at a point in time.

Maybe a topic for a new thread, but currently I am struggling to find out why my fuel consumption is so high; 1 on 7, one liter for seven kilometer.
Also why the engine is running irregular or slightly jittering at steady speeds, noticeable at 2000 and 3000 rpm. Probably also the source of high fuel consumption.

After checking any and everything, including replacing the MAP, disconnecting the TPS, replacing the fuel filters, checking if fuel pressure is fluctuating, confirming that the cold start injector is not leaking, measuring the resistance of both the temp sensors both cold and when the engine is warm, confirming that the Aux Valve is completely closed when the engine is warm, new E10 proof fuel hoses and brand new injectors, the only thing remaining is the control module - assuming the trigger signal from the 123 ignition is not the source. Don't know if bad cables can be the source, but the injection system has been checked three times in the last two years with the special Bosch Measure Box.

The Lambda measurements at the Dyno are attached and also look more than OK.

I did borrow a second control module - to no avail. Hence the questions.
Now I need to find one that is absolutely working and maybe have the old one checked to see if that is indeed defective.

Suggestions welcome!

Hi,
the engine is running rich... I wouldn't trust the MPS.

You can't check the MPS using the EFAW-228-testing equipment.

The MPS could leak or could be misadjusted.

New units , especially of late production, can be misadjusted, too.

Do a first checkup following Volker's description and instruction here: jetronic.org/en/d-jetronic/mps

Regards
Norbert

Hi,

well 14l/100 km is a bit high. But depending on how you drive it could happen. You shoudl check whether you have correct MAP sensor, whether it is leaking, what manufacturing date it has (stamped on upper right rivet or on back) and whether it is correctly potted and still has rivets.

I have seen MAP sensors especially from the US which were remanufactured in an incredible way.

Thanks for the suggestions!

Did already look into the MAP sensor and I bought a spare. Noticed on the table in the Control Unit section that both should work with the same Control Unit.

Bosch 0 280 100 035 (B20F, 110hp, US/Canada version, came with the car)
Bosch 0 280 100 015 (B20E, 130hp, European version, from scantrade.ch))

The rivets have been replaced by screws. And sealed with a paint dot.

On the Dyno both MAP sensors have been tried. Not a real measurable difference in engine behavior. See picture below. Unfortunately I did not bring a second Control Unit, as I thought this would do the trick.

Just did a quick measurement of the xx035 per your suggestion. That one must have been repaired in Canada or the US. More than happy to send that one in if you can do some further further checks. Same for the Control Module as I have a loaner.

How about the engine being to rich? Between 2750 rpm and 6000 rpm the Lambda is hovering around 0.9. Should it be different?

Bart

(Excuses for my nails, just have been trying to fix the fuel tank while it was still light)

Hi Bart,
it's quite useless to measure the coil-resistances. This testing makes sense only when the engine doesn't run at all or shows an absolute abnormal behavior. The coils are o.k. - or they are broken <no continuity or a shortcut to ground>.

Please make the vacuum-check Volker describes in the video uand search for the production code that could be stamped into the MPS body, too - maybe downside, not only to be found on a rivet.

Yes, I stated the engine is running rich. The lambda-value is below 0.90 all the time, mostly is around 0.88 or 0.87.
This is a 'rich' value, although engines are being tuned to such values for racing and performance purposes. But you are looking for an fuel-economic setup...

I know the Volvo-engines normally tend to run lean...

How much is the fuel pressure?

Regards
Norbert