[Diy_efi] info request

Tue Aug 22 13:40:57 UTC 2006

The method of full-load enrichment is very different among the various 
D-jetronic implementations out there.

The oldest one is using a vacuum switch which shorts pin 2 or 9 to pin 
14 of the ECU at full load, this will change a bias voltage to the 
monostable that is controlled by the pressure sensor. In this case, 
decreasing the resistors R207/R208 or R208/R209 (parallel connected) in 
the ECU will give more full-load enrichment.

The next method is using a non-linearity in the pressure sensor, by 
fitting an extra membrane in addition to the usual "barometer" bellow. 
In this case, there is a sealed adjustment screw in the pressure sensor 
which sets the limit of travel for the membrane and hence the full load 
enrichment.

And the newest method is using a WOT switch, like more modern Bosch 
systems. It is connected in approximately the same way as the old vacuum 
switch, and there are the same reference numbers of the resistors to be 
altered.

However, please note that the pinouts of the D-jetronic ECUs are not all 
the same. There is a lot of small differences and it is always safest to 
refer to a wiring diagram for the actual car you are working on and then 
double check that the car's wiring harness seems to be wired like the 
schematic. The full load enrichment resistors in the ECU have always one 
end connected to the pin for the vacuum/WOT switch. A good thing is that 
in most cases, all wires in the harnesses are marked with the 
corresponding pin numbers of the ECU, so it is relatively easy to 
reverse engineer a D-jetronic harness and make an own wiring diagram.

Best regards

Torbj?rn Forsman

Phil wrote:
> your post implies some in-depth knowledge of D jet.
> Do you have any info about tuning the full load (analog) "tables". We 
> can change the pressure for a linear/across the rpm range change (like 
> changing a main jet). How can one change the curve of the "table" (like 
> changing an air correction jet). I assume it involves changing some 
> resistance and/or capacitance values in the box. Phil Hunt. Phil's 
> Foreign Car Service (former Volvo's From Hell driver-now very interested 
> non participant)
> ----- Original Message ----- From: "Torbj?rn Forsman" 
> <torbjorn.forsman at gengas.nu>
> To: <diy_efi at diy-efi.org>
> Sent: Wednesday, August 16, 2006 5:04 PM
> Subject: Re: [Diy_efi] info request
> 
> 
>> A Volvo P1800E (like all other fuel injected Volvos of that era with 
>> B20E, B20F, B30E or B30F engines) has Bosch D-jetronic injection from 
>> about 1969 to 1973. From 1974 on, all 4-cylinder models used the 
>> mechanical K-jetronic system instead.
>> The 6-cylinder Volvo 164E however still used D-jetronic until 1975, 
>> when that model was superseded by the 264, with a completely different 
>> engine and K-jetronic.
>>
>> The D-jetronic was the world's first mass produced EFI system. It was 
>> initially developed by Bendix, but Bendix saw no future for it and 
>> sold the whole concept to Bosch in the mid-60's. Bosch then in a few 
>> years developed it to a field useable system, it was first used on the 
>> VW 1600E '68, and by 1969 it was implemented by a lot of european car 
>> manufacturers.
>>
>> Of course, that early system has some weaknesses.
>>
>> The temperature sensors (for coolant and air temperature) often get 
>> open-circuit.
>>
>> Early throttle position switches are not well sealed and must often be 
>> cleaned to work well.
>>
>> The pressure sensor (a very vital component) contains a metal membrane 
>> that may crack. Also, it is sensitive to dirt coming by the vacuum line.
>> It is a odd design, a transformer where a part of the core is moved 
>> according to the intake manifold vacuum. That transformer is connected 
>> in the feedback path of a monostable flip-flop in the ECU, which 
>> determines the injector opening time.
>>
>> ECUs made before 1972 has big problems with all feedthroughs between 
>> the sides of the double-side PCBs, they are implemented as component 
>> pins soldered on both sides (no plated-through holes). Due to thermal 
>> fatigue, the soldering will soon crack on either side of all such 
>> feedthroughs. From 1972 on, those were replaced by "C-jumpers", i.e. a 
>> short jumper where one leg is soldered on the primary side and the 
>> other on the secondary side.
>>
>> The injector drive transistors (germanium parts, ASZ18 or similar) are 
>> said to fail often in hot climates, although I never have seen a such 
>> fault here in Sweden. Probably, this is a bigger problem on ECUs for 
>> 6- or 8-cylinder engines where the transistors are more heavily loaded 
>> and more heat from the injector ballast resistors is generated within 
>> the ECU.
>>
>> A non-electrical problem is that the short pieces of fuel hose crimped 
>> to each injector is of low quality and soon gets leaky. This has 
>> caused many fires. On injectors manufactured before about 1973, the  
>> crimp can be filed away, the hose replaced and secured by a normal 
>> hose clamp. On newer injectors, a special hose replacement set was 
>> once upon a time available from Bosch.
>>
>> Best regards
>>
>> Torbj?rn Forsman
>>
>> Dmitri Pronin wrote:
>>
>>> Don't they have Bosch "mechincal" FI?
>>> ----- Original Message ----- From: "Rick McLeod" 
>>> <dunvegan at sbcglobal.net>
>>> To: <diy_efi at diy-efi.org>
>>> Sent: Tuesday, August 15, 2006 7:29 PM
>>> Subject: Re: [Diy_efi] info request
>>>
>>>
>>>> Also, the references I find show the 1800E to be EFI as of approx 
>>>> 1969 or so, maybe 1970, so suspect this one (1971) to be EFI
>>>>
>>>>
>>>>
>>>> ----- Original Message ----
>>>> From: Rick McLeod <dunvegan at sbcglobal.net>
>>>> To: diy_efi at diy-efi.org
>>>> Sent: Tuesday, August 15, 2006 10:00:23 AM
>>>> Subject: Re: [Diy_efi] info request
>>>>
>>>>
>>>> So, if not, I still need to know some info, as I'd like to convert 
>>>> to EFI if it is not the greatest system, if it's a good mechanical 
>>>> then I won't bother, but I don't know what it is at all and the car 
>>>> is some 1000 miles from me, I can't just go pop the bonnet!
>>>>
>>>>
>>>> ----- Original Message ----
>>>> From: Dmitri Pronin <dmitri_pronin at mail.ru>
>>>> To: Rick McLeod <dunvegan at sbcglobal.net>; diy_efi at diy-efi.org
>>>> Sent: Tuesday, August 15, 2006 9:01:22 AM
>>>> Subject: Re: [Diy_efi] info request
>>>>
>>>>
>>>> Wow!!!
>>>>
>>>> That one is one nice car! However, its injection system is not in 
>>>> fact an
>>>> EFI.
>>>>
>>>> Dmitri.
>>>>
>>>> ----- Original Message ----- From: "Rick McLeod" 
>>>> <dunvegan at sbcglobal.net>
>>>> To: "diyefi" <diy_efi at diy-efi.org>
>>>> Sent: Tuesday, August 15, 2006 4:55 PM
>>>> Subject: [Diy_efi] info request
>>>>
>>>>
>>>>> Does anyone know anything about a Volvo 1971 1800E w/ 2.0Litre 
>>>>> FuelInj,
>>>>> like what system is used for control?
>>>>>
>>>>> I am looking at one but currently don't know much about it other 
>>>>> than I
>>>>> know the owner very well and own 3 recent 90's 850's currently.
>>>>>
>>>>> Any info appreciated, links to tech, etc.
>>>>> _______________________________________________
>>>>> Diy_efi mailing list
>>>>> Diy_efi at diy-efi.org
>>>>> Subscribe: http://lists.diy-efi.org/mailman/listinfo/diy_efi
>>>>> Main WWW page:  http://www.diy-efi.org/diy_efi
>>>>>
>>>>>
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>>>
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>>
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