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.