Volvo 1800ES D-Jetronic MY73

Hi Pierre,

congrats for having found the fault !

4.05% CO seems too high. I would drive a bit and then adjust to workshop manual values. At a quick glance I saw 1-2% as normal value.

I received all the parts to build a fuel pressure manometer, as Dr-Djet suggested.
I just have chosen the "cheap" version of reader, without glycerin inside.

So I tested it on the 1800ES. It works fine and is very accurate, either because of construction and thanks to the big diameter of the reader. A great tool, which can be used for any other injection system with small adaptation.

One point on the 1800ES : the fuel pressure is not constant as the engine temperature rises. If I adjust the fuel pressure to 2.1 bar when engine is hot, I am not far from 2.5 bar at engine start around 0°C. What can be the cause of this ?

Hi Pierre,

normaly that means an issue with pressure regulator. In rare cases it could be too little fuel volume from pump or blockage on return line to tank.

I will measure with another fuel pressure regulator.
If the problem remains, it will be an interesting point.

Some information about work done on this car :
- engine oil drain revealed dark oil, sign of excessive enrichment, probably linked with bad electrical connections... 
- fuel pressure is well stabilised when engine is hot, but remains higher when engine is cold (2.3 bar). As a consequence, warm-up phase is a bit erratic. Unfortunately, as fuel pressure regulator is not available in new condition, it is a bit tricky to find a reliable one.
- throttle sensor has been carefully opened :





PCB was dusty (means some risks of erosion), so I carefully cleaned it with a small and soft pencil, some brake cleaner fluid, dried it with low pressure compressed air, then cleaned it again with a electrical contact cleaner and a thin piece of soft paper inside the contacts.
Then I adjusted and checked the right positioning of the sensor to obtain the resistance change when leaving idle position and the 10 resistance changes when accelerating and nothing at decelerating. Everything is ok.

Finally, I replaced the thin foam barrier around the sensor, hoping to improve the sealing of the housing.

This throttle sensor is the first version, right ? Is it the right one for '73 Volvo 1800ES ? Not sure...

...

Hi Pierre,

yes Throttle switch is an early version with scres and soldered wires inside.

Hi Pierre,
you could use an alternative pressure regulator like this one: www.ebay.de/itm/233599329216 or this one: www.ebay.de/itm/272270476505
This cheap item could work, too: www.ebay.de/itm/373722429530?hash=item57...tkp%3ABk9SR_yr-KGtYw

Regards
Norbert

Vielen dank Norbert !

the first one seems perfect !

Today I took some time to have a 30 km ride with the ES.
The car is now fine to drive, fuel consumption seems reasonable. Thank you to you all for help and assistance !

One point is still not perfect : when the car quits its place, during clutch coupling and just after, the car hesitates, just one second. It was worse before cleaning and adjusting throttle sensor, but it still hesitates. I can't say if mixture is too lean or too rich just at this moment. I know that ECU enriches mixture at this specific moment, and the engien runs smooth. So I would say that it's a bit too rich...

I will test again tomorrow with the ECU enrichment knob fully turned anti-clockwise to lean the mixture. Unfortunately I can't measure any more CO level so I'm blind about that for the moment.

Any advices ?

Hi Pierre,

rheostat is only active when throttle switch idle contact closes. Is that properly adjusted? And of course you should measure exhaust gas.

yes it is properly adjusted. Idle contact closes immediately when throttle opens.

Hi Pierre,
I think you mean it closes when the throttle closes?

Regards
Norbert

Yes Norbert, but now I have a doubt... I'll check again 

So I can confirm that the idle contact closes at idle. Thank you Norbert for your correction.

About the engine hesitation, I can detect it just by opening the throttle : the engine revs with a small delay (a fraction of second). I tried to increase slightly the fuel pressure (2.15 bar instead of 2.05), it is better. So I was wrong : this hesitation was due to a slightly lean mixture. Maybe a very little more fuel pressure (2.2 bar) and it will be perfect. The accurate manometer is very useful in this case, to adjust precisely fuel pressure.

But even without this ultimate adjustment, the engine runs smooth and noise is low.

Another point : fuel consumption is now very acceptable. This is due to throttle sensor right adjustment and correct wiring of cold start loop. And as a consequence, cold start occurs quickly, just by turning ignition key, in roughly 1.5 second. 

I may be not too far from a very satisfactory tuning 

Hi Pierre,

if your car runs too lean (which you do not know as you do not measure exhaust) it is not the correct way to play with fuel pressure. You should find the real problem starting from engine mechanics and ignition.

So...
Following your advices, I set fuel pressure to 2 bar. This is not a adjustment lever for mixture.
I have found the reason of engine hesitation : on B20E, engine vacuum adds a negative advance. It seems that the negative advance was too high, although initial advance setting was correct. So, instead of trying to make the Bosch vacuum device work properly, I installed a 123ignition distributor. Works like a charm. Advance initial setting is 10 deg, with vacuum "advance" unplugged.
Good news : the gas analyzer works fine again. So I measured exhaust gas : 2.2% CO and 5.9% O2. Bad news, it's too lean.

On previous measurement, before tracking every and each problem, O2 rate was 0.8%. As I did not touch exhaust system nor intake system, I do not believe it is a false air leak that explain this 02 rate. It may be a mixture issue.

As far as I understood D-Jetronic, the devices that influence mixture are water temp sensor, air temp sensor and MPS. But those three devices work as enrichment devices. Am I right if I assume that those three devices can not explain a lean mixture ? Does a poor injection harness can explain a lean mixture ? I thought about ignition vacuum hose, so I installed a plug where the vacuum hose leaves the intake manifold : no effect on exhaust gases.

I also checked the injectors grommets, they are all fine. Engine compressions are ok, all above 10 bar. Valve clearance are all ok, checked twice, on cold and hot engine.

I'm a bit lost now... I can't understand how the mixture can be lean. The only explanation is that there is a false air leak that was hidden by an important enrichment. Now that I solved the enrichment issue, the false air leak is more visible. Or fuel flow is restricted ? I'll change fuel filter, to eliminate this possibility.

Any idea ?


 

Hi Pierre,

well I cannot confirm that engine and air temp sensor plus MPS only work as enrichment device. There is also an rpm influence via trigger contacts and acceleration pulses.

All sensors have the task to adjust the mixture. Both leaner and richer.

Finally, I found a leak in my gas analyzer. When the leak was solved, I found a much more acceptable value : 1.77 % CO, 1.84 % O2, 12.5 % CO2 ; lambda = 1.03, HC = 95 ppm.

This is a very good result. I did not do many things except spraying on MPS, coolant and air temp sensors connectors a very effective product for electrical connections : Deoxit D5.

So, I have to thank you all for helping me investigating on D-Jetronic which is more familiar to me now.

I also am working on a '73 Volvo 1800ES. And I have read Dr. Djet's description of the Throttle Valve Switch (TVS). There appear to have been two different 4-pin TVSs used on the Volvo 1800s, and if I understand correctly, the pin positions differ between the two. The early one had the cover held on by screws, the later by clips on the cover. 

My questions are

• how might one know which was original on the car, and
• when did the transition from early to late take place?

I have never seen the early style so I don't know if it would be possible to plug the ECU connector that went to the early style into the new style and have the wrong terminals connected to the ECU. 

(Sorry, I also don't see how to start a new post on the forum.)