Volvo 1800ES D-Jetronic MY73

As I mentioned in my introduction, I recently purchased a 1800ES. This car has a smart cosmetic aspect, but technically some points to review.
Here it is :





This car, as most of D-Jet cars, has two relays to pilot fuel pump. There was a third one, recently added according to the clean wires, that was supposed to replace one of the old ones. It was wired on ignition coil, which I think it is a mistake. With this relay the fuel pump had a strange behavior : sometimes the pump run, sometimes not. I think it was a source of problems (and I prefer original state to any modification which is not in line with original definition)

So I removed this recent relay and checked the old ones, which were in good condition. I carefully wired the two Bosch steel relays with original loom (which has not been damaged, hopefully). At position II of the contact key, now the fuel pump runs. But there are two problems :

1 - the fuel pump runs continuously at position II, before starting. It should run for 1 or 2 seconds only. Maybe something makes the ECU believe that the engine is already running ? I discovered also that fusebox (old style conical fuses) has been replaced with a chinese fusebox. But busbars included in old fuse rack are missing, so that additional wires have been added... I managed to find an original fuse box to recover original state. I will receive it in a few days.

2 - the mixture is considerably more rich now than before : the car starts not easily and spark plugs are fouled. I think that fuel pump was running with low current so that flow and pressure were low. Fuel regulator has been tuned in this condition so that now with a well running pump pressure has increased. What do you think about this assumption ? I will check fuel pressure in a few days (I'm waiting for a T 8mm-8mm-6mm to plug a manometer correctly) to check this hypothesis and go back to correct pressure value.

Around these two problems, I tried to check simple thinks according to Djet checklist :
- Trigger contacts seem in good state :



- MAP Sensor has its yellow plug intact ; resistance of primary and secondary coils are ok (84.5 and 307 Ohm)
- Coil primary and secondary resistances are OK (3.3 Ohm and 9000 Ohm)
- Throttle switch is OK and correctly installed now

So, could you help me about points 1 and 2 ? Thank you very much in advance


 

Hi Jean-Pierre,

what a nice snowhite coffin (as we call them in Germany). I start with 3 questions:

1. Does pressure sensor hold vacuum? See my test in checklist and video in compendium.
2. Has someone changed wiring so that fuel pump relay is not operated by ECU but by ignition switch? was sometimes done when ECU failed to control fuel pump.
3. Have you verified that you have correct components? You can check on Bosch website www.bosch-classic.com/de/de/produkte/fah.../?selectedFilters=10 for B20E engine for example

Thank you for your reply. For the moment the coffin stays at the garage... but it should take the road quickly with your help !

So... YES pressure sensor holds vacuum ! I did the test just now. Difficult to build a airproof test device but it holds definitely -0.35 bar for one minute, so it should hold longer.

MAP sensor is 0 280 100 015, it is OK as far as I have read.
ECU not checked yet...

Sorry, other questions will be answered later, I have to leave the place where the car parks for one day and a half.

 

So... I can answer :
1. Does pressure sensor hold vacuum? Yes
3. Bosch numbers check : All components are matching with Bosch number list, except distributor which is for B20F engine, but i think it has no direct link with my problem (Bosch Classic has kindly sent me the advance curves, which are similar)
2. Has someone changed wiring so that fuel pump relay is not operated by ECU but by ignition switch? It seems that it is not the case. I performed several electrical tests to check this point :
a. wire 19 between ECU and connector 85 of fuel pump relay is ok in terms of continuity
b. Voltage between connector 86 and -Bat is Ubat
c. Voltage between connector 85 (wire 19 from ECU) and -Bat is 130 mV always (engine running or stopped) ; my understanding is that it should be almost zero V during one or two seconds, then Ubat (to stop the pump).


 

Hi Jean-Pierre,

there is a pull-up resistor in pin 19. Only when ECU wants fuel pump active pin 19 will show 0V. If it is 130mV all the time it is either another resistor and ground connection or ECU has an issue.

So... Today is a great day, I have driven the ES on 50 km ! Carefully switching off to position 0 as soon as engine stops.
Engine runs well, although a bit with a slightly lean mixture. Spark plugs are coloured white with orange negative electrode. This is a bit surprising for me, as line pressure is set at 2 to 2.1 bar. Maybe my manometer is not accurate enough ? I ordered all the parts to build an accurate one according to Dr-Djet page.

Concerning electrical issue on fuel pump triggering, I will first put back the fuses rack and come back to a full conformity on fuses installation. Then I'll tell you if it influsences something about fuel pump activation.