More ECU/MPS/CHT..., From the other side of the pond Options

[chmillman]

I didn’t want to hijack the thread below this one started by Jose, so I am starting a new one (sorry if this is not a good idea).

I am also having some work done on my 2.0 D-Jet and some similar issues. My car is officially a ’74 – built on 1 November 1973 - but it has a ’73 (Euro) engine number (GB007311) as well as a ’73 ECU and MPS (both 037). I have been unable to get any info from Porsche as to whether the motor is original or not - as the car was built in late '73, it might be original, but the car was restored in France in 2011, no idea if they changed the motor or not.

Back to the FI- in addition to cleaning and testing the injectors, changing the hoses, etc. my FI guy has found and fixed a bunch of stuff – frayed and dicey connections etc. He is however unable to get the ECU tuned so that both the CO and HC values are within their suggested ranges at the same time. The car has some light hesitation at low speeds and loads - like when driving at a steady state in a 50kmh city zone.

The MPS checks out OK both for vacuum and static resistance tests. It was rebuilt by Fuel Injection Corp. in CA in the summer of 2014 - culdn't get any more info than that from them.The 270 ohm ballast resistor is there and OK. My FI guy thinks it might be one of those fairly rare cases where some components in the ECU are cooked. Pulling it out of the car and sticking your nose inside the connector hole, it smells a lot like old overheated electronics – in comparison to a couple of others he has in storage which hardly smell at all – or maybe a bit of a musty smell.

I have another ECU in good condition to test – but it’s an 0 280 000 040, not an 037. It does have the same VW part number - 022 906 021 E. According to the info I found this is also supposed to work with an 037 MPS…





Maybe doesn’t need the 270 ohm ballast resistor on the CHT sensor. Anyone have any experience with this? This is Euro stuff I know, so some of the USA model info will not apply.

Speaking of the CHT sensor, that is also wrong. It’s not an 017 (unobtanium), but it’s not an 012 either. IIRC it’s an 003 – which I have seen various info about, some of it conflicting. Richer at cold start or remedy for excessive fuel consumption... In any case I think we will replace that with an 012, as an 017 seems to be out of the question.

More coming as we progress on this hopefully this week.

[Superhawk996]

Maybe doesn’t need the 270 ohm ballast resistor on the CHT sensor. Anyone have any experience with this? This is Euro stuff I know, so some of the USA model info will not apply.

Speaking of the CHT sensor, that is also wrong. It’s not an 017 (unobtanium), but it’s not an 012 either. IIRC it’s an 003 – which I have seen various info about, some of it conflicting. Richer at cold start or remedy for excessive fuel consumption... In any case I think we will replace that with an 012, as an 017 seems to be out of the question.

More coming as we progress on this hopefully this week.

Regarding the ballast resistor - it is most likely needed.

The 73’ 2.0L was basically running a 1.7L ECU with trickery applied to get the 1.7l ECU delivering proper fuel for the displacement and volumetric efficiency increase.

This was done primarily with the CHT, ballast resistor, and the MPS.

The ballast resistor adds 270 ohm across the entire operating range. As a percentage of total resistance, the 270 ohms is small when cold, but it very large when at operating temperature. This resistance addition enriches the mixture across the entire operating range.

The ballast resistor is very easy to add & remove so it’s an easy experiment to see what it does or doesn’t do for your car.

You should post a WTB for the 017 CHT sensor - they’re still out there but they do command a price premium. Be aware that some of the aftermarket CHT’s have a dicey reliability. Better to pay a premium for NOS Bosch if you can find one.

[Superhawk996]

WRT the ECU - you shouldn’t be guessing if it’s good or bad. Plenty of folks out there with the proper ECU tester.

Not sure what the situation is in Europe but JeffBowlsby has one here as do several of the ECU repair houses.

One other item to consider is that there are reports that the MPS’s rebuilt by some companies were not using the proper copper-beryllium diaphragm. My understanding is that even Tangerine Racing’s correct diaphragm is now out of stock and he’s trying to find a supplier that will do a copper-beryllium diaphragm. So it’s hard to say if your rebuilt MPS was tuned exactly as it should be. That is then compounded by the fact that modern gasoline isn’t blended the same as it used to be 50 years ago so some “tuning” is to be expected.

At some point, it’s going to make more sense to convert to modern EFI than to keep struggling to find parts but I don’t think we are at that point just yet.

[emerygt350]

I thought the euro engines had carbs?

If I were you, I would get the tangerine racing upgraded tunable outer stop and just be prepared to tune it yourself. AFR gauge needed to do that right. CHT gauge is important too but not necessary.

Not having the right cht is just going to make stuff harder. I would pull it and make your own curve to see how it lines up with the 017. If it isn't close I would start searching.

[wonkipop]

I thought the euro engines had carbs?

If I were you, I would get the tangerine racing upgraded tunable outer stop and just be prepared to tune it yourself. AFR gauge needed to do that right. CHT gauge is important too but not necessary.

Not having the right cht is just going to make stuff harder. I would pull it and make your own curve to see how it lines up with the 017. If it isn't close I would start searching.

only euro market 74/75 1.8 had twin carbs.
same goes for the car the same engine was in. 74 412. twin carbs for europe.
at around that time VW was in the business of dumping and discontinueing with D jet.
persisted in the 914 2.0 but they were migrating across to L Jet or de-specing to carbs depending on market and regulation. cheaper and simpler.

i could be wrong but i think the only significant difference between euro 2.0s and USA 2.0s is the compression ratio? USA cars had to be able to run on unleaded.
think the rest of its the same. but i'm not up on 2.0 cars. (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/beerchug.gif)

[chmillman]

WRT the ECU - you shouldn’t be guessing if it’s good or bad. Plenty of folks out there with the proper ECU tester.

Not sure what the situation is in Europe but JeffBowlsby has one here as do several of the ECU repair houses.

One other item to consider is that there are reports that the MPS’s rebuilt by some companies were not using the proper copper-beryllium diaphragm. My understanding is that even Tangerine Racing’s correct diaphragm is now out of stock and he’s trying to find a supplier that will do a copper-beryllium diaphragm. So it’s hard to say if your rebuilt MPS was tuned exactly as it should be. That is then compounded by the fact that modern gasoline isn’t blended the same as it used to be 50 years ago so some “tuning” is to be expected.

At some point, it’s going to make more sense to convert to modern EFI than to keep struggling to find parts but I don’t think we are at that point just yet.

Well, in this tiny country I don't think anyone has one - otherwise my FI guy - who specializes in D-Jets on all kinds of cars - Mercedes, Citroen, Porsche etc. - would have one or know where one is. Not the case.

Hmm, the idea that the MPS might not be properly rebuilt is a bit distressing, it has however worked for awhile now (given that the rebuild is over 10 years ago). Unfortunately I couldn't get any info from the rebuilder as to what was done on the unit and what components were used.

The alternative here is to send the ECU and the MPS directly to Bosch in Germany. They can repair both. 1K Euros for the ECU, extra (unspecified) for the MPS if necessary...

https://www.bosch-repair-service.com/en/eng...-0280000037001/

As far as converting to modern FI, I don't think so - I would just go with carbs. At least here, one could find people to tune them. With some aftermarket FI, nobody would want to touch it, and the car would probably have a dimisnished resale value.

[emerygt350]

I don't think you need to go there yet. The wrong cht can cause terrible issues. Just pull it and compare first.

Lots of known working ECUs out there. I have an extra 037 I picked up for 60 dollars on eBay. They seem to be very robust.

The only difference in the mps would be the diaphragm material being weaker. Nothing else you can sanely replace in that thing. "Tuning" the mps was probably setting it to some predetermined point. You should tune it to your engine and modern fuel. Particularly with a euro version engine.

[chmillman]

I don't think you need to go there yet. The wrong cht can cause terrible issues. Just pull it and compare first.

What I understood is that when the engine is warm, the CHT should have nearly no resistance, and that the ECU will basically ignore anything less than 300 ohms - i.e. if the engine is warmed up, connecting the CHT input from the ECU to ground (bridging the CHT) the engine should still run normally. Maybe I got that wrong. So the difference would be how the engine actually behaves during the warmup phase - assuming of course that the CHT actually works as designed and is not open circuit, shorted out or intermittent.

[quote name='emerygt350' date='Jul 28 2025, 12:51 PM' post='3216989']
Lots of known working ECUs out there. I have an extra 037 I picked up for 60 dollars on eBay. They seem to be very robust.
{/quote]

Wow - didn't find anything here anything near that price... The 040 I have here cost a lot more than that. Will keep looking. I assume the US model 037's are however different than the Euro models? GA/GC motors vs. GB?

[Franz_x]

Hello from Germany,

Have you tried here yet --> https://jetronic.org/de/d-jetronic

Franz

[chmillman]

Hello from Germany,

Have you tried here yet --> https://jetronic.org/de/d-jetronic

Franz

Hi From Switzerland (French part),

Yes, I have read a lot of the information on the Dr-DJet site, thanks. Also on Brad Anders' site, still going through some of it, lots to read and digest.

I am not doing the work on this - I am simply not equipped with the proper tools or experience - the car at a classic car electronics shop who specializes in Bosch injection systems maintenance and repair.

[emerygt350]

The 037 ECU, as far as I can tell reading the histories, is the same as the 1.7 of 1973/72(?). All they did was put a little cheater spacer in the 037 mps and tuned the mps for the 2.0, and of course added the resistor in the cht wire.

My car has a 2.0 (GA) bumped up to 2056 and a 8.8ish to 1 compression ratio.. I have an afr and notice the ECU bumping the mixture around even after the car is more than warmed up. Between temp sensor 1 and temp sensor 2 I suspect the Germans were really looking at micromanaging the mixture for whatever reason. Perhaps because they could. I have put Bluetooth controlled variable resistance in that cht line so I could richen it up on the fly. I didn't notice a 300 ohm rule. I could go below that and further lean the mixture.

Anyway, wish I could send you my extra 037 for testing but shipping would be silly expensive.

[chmillman]

I didn't notice a 300 ohm rule. I could go below that and further lean the mixture.

I believe I found that in a post here, but can't find it right now.

Anyway, wish I could send you my extra 037 for testing but shipping would be silly expensive.

Yep... In both directions. (IMG:style_emoticons/default/sad.gif)