1974 412LS ECU circuit diagram?

nick sparrow · Post by **nick sparrow** » Tue Oct 30, 2001 6:50 pm

Does anyone know where I could find a circuit diagram for the control unit (ECU) for a 1974 D-Jetronic system? Any help most appreciated, I was thinking of building an updated one using modern components and may be adding a few extras……. such as an oxygen sensor and maybe if poss a knock sensor……..

But anyway I just wanted to know if these diagrams were out there somewhere. Although I have just been informed that there are aftermarket control units available for this set up of D-Jet……has anyone done this before or have you used an aftermarket one ….what were the results?

ray greenwood · Post by **ray greenwood** » Wed Oct 31, 2001 9:22 am

There should be no D-jet in 411/412 after august of 73, but I may be mistaken. It should all be L-jet at that point. The only way to add an 02 sensor to the D-jet, is to use one similar to what the sabb 900 uses. This is a single wire non-heated (or you could use a heated) lambda system that is outboard to the injection system. It has circuits to enrich by means of using an electrically activated vacume bleed switch (this would cause the pressure sensor in D-jet to enrich) and for even greater full load enrichment, it has a circuit to allow the use of the cold start injector for extra enrichment (turbo model). The main baseline fuel mixture adjustment is with the frequency valve (line pressure metering injector). The frequency valve would have to replace the stock fuel pressure regulator on your D-jet. Thats a whoooole lot of calibration work. Why do you want an 02 sensor on your D-jet? It actually has quite effective adjustments avialable already. Yes the frequency valve would be a better addition...and could give better overall economy and emissions, but there are a ton of improvments/tweaks to be done before you reach the point where you should think about installing an 02 sensor. There is actually no way to integrate the 02 sensor into the D-type system. It will be an outboard system whose purpose is to cause a desired reaction within the closed D-jet loop. Ray

nick sparrow · Post by **nick sparrow** » Wed Oct 31, 2001 3:52 pm

Hi thanks for that I thought it might be a bit tricky but you have to ask these things. I am pretty sure its a D-jet set up I will check this tonight. The car in question may of been altered prior to me owning it. Also I cannot remember who but there was talk of being able to do some modifications to the D-jet to get a bit more power?......if so do you know what they might be....I am a novice at this injection stuff but would like to give it a try. My last car ran some old carbs and it ran....well not all that well.

nick

ray greenwood · Post by **ray greenwood** » Thu Nov 01, 2001 11:00 pm

I've dropped a lot of posts into this over the last couple of months, but give me a fewa nd I will try to get a concise list of where to start by end of day. Ray

m504specs · Post by **m504specs** » Fri Nov 02, 2001 10:45 am

I have just obtained copies of wiring and EFI diagrams that seem to be very accurate for the 1972, 1973, and 1974 type 4's. If someone wants to e-mail me off the list with an explanation of how to upload them, I will be happy to do that. m504specs@hotmail.com