MAF issue

[Alex Crow]

OK, so now we need to trace why no 12v at pin 1...

 

[Alex Crow]

So, pin 1 gets power through fuse F24/8 circuit 15 auxiliary fuse, which I believe is mounted on its own near the engine ECU - you may have seen it.

 

[bhonok]

So, pin 1 gets power through fuse F24/8 circuit 15 auxiliary fuse, which I believe is mounted on its own near the engine ECU - you may have seen it.

Alex you are Genius. This fuse so hidden I would've never found it, if you didn't send me looking. I replaced it and now I have 12 volts on pin 1 plug 1 and guess what... now I have 12 V supply on pin 11 at plug 4 to go all the way to pin 2 on MAF. I yet do not know the improvement it might make, but you have one happy guy here, that see things starting to fall into right places. Thanks a million

 

[Alex Crow]

OK, something blew the fuse, could be the vent line heater in the breather at the turbo intake.
Guess we'll see if it blows again.

 

[bhonok]

" vent line heater in the breather at the turbo intake."... At the moment it is all Greek to me. I need a pointers or maybe GPS...

 

[Alex Crow]

I wouldn't worry - it may be fine now, no need to do any more unless the fuse goes again.

 

[bhonok]

MAF ECU issue

Hi again. With your and forum help I continue sorting thing out. Now that my MAF and ECU powered I had a chance to test MAF. It sends all the right signals to ECU. 5v from pin 4 and variable voltage from pin 5. About 1.9v at idling and rasing to 3.1v at 2.500 rpm. Yet, if I disconnect MAF motor revs the same...It looks like ECU doesn't care or could it be "nobody home"

 

[Alex Crow]

What specific fault do you now have, and what fault codes are currently being flagged?

 

[bhonok]

sorry... shooting in the dark. I can't access scanner for a few days...

 

[oigle]

Hi again. With your and forum help I continue sorting thing out. Now that my MAF and ECU powered I had a chance to test MAF. It sends all the right signals to ECU. 5v from pin 4 and variable voltage from pin 5. About 1.9v at idling and rasing to 3.1v at 2.500 rpm. Yet, if I disconnect MAF motor revs the same...It looks like ECU doesn't care or could it be "nobody home"

Are you talking just free revving in neutral of are you saying it drives the same with or without the maf?

 

[bhonok]

I am going for a little trip. Will report in a few hours what happens on freeway with or without Mr. MAF

 

[bhonok]

Exactly. It drives the same with or without MAF. I went 30 km half with and half without MAF. I didn't have any testing gadgets connected, but it felt similar. My car was never a great performer and since I bought it 6 month ago it was in a limp mode , going decent on straight stretch and laboring heavily up hill. Since I shunted servomotor jammed flaps and deleted EGR it runs much easier and even climbing hills doing 60-70 km. There is still black smoke on acceleration and no clear kick-down, but I can push it to 3,000 rpm. Diesel consumption of cause sucks...

 

[oigle]

That would seem to indicate that the maf isn't doing its job, but I'll leave it to experts like Alex to comment further.

 

[bhonok]

Sure, I will appreciate Alex's comments, but as I reported in post 47th Maf seems to be sending all the right signals/voltages to ECU. Hard to blame MAF...
Thanks

 

[Alex Crow]

Move forwards with fault codes now please.

 

[bhonok]

Hi Alex. Unfortunately diagnostic is being delayed.. system is out of order...
Quick question about M55 delete..
You said : wire in a resistor between the signal (PWM) wire and the 12v wire to the M55 motor.. Will it be the same just to stick 5 Kohm resistor pins into a motor connector ? Thanks

 

[Alex Crow]

... just to stick 5 Kohm resistor pins into a motor connector ? Thanks

Yes, that is the idea and works quite well, although you might want to make sure it is well protected.

 

[bhonok]

Yes, that is the idea and works quite well, although you might want to make sure it is well protected.

Oh, I made sure of this. Thanks.
If I may ask some more advice...
My car is 2001 ML270 CDI and probably doesn't require sophistication of SDS. Maybe you can recommend some basic tool that can read DTC and communicate with ECU .
This car came to me without thermostat . It is always very warm here in Panama so I am not in a harry to install one, also recirculating motor for coolant is shut. Local mechanics advised me to delete it and reconnect hoses, since heating is never needed here...I did it. Is it a good idea to shunt a connector for the motor, so it will not send a unwanted signals to ECU? And if you agree could you recommend the resistor size .

 

[Alex Crow]

Some people find 'Carsoft' a reasonable DIY tool for Mercedes diagnostics.

No need to do anything about the coolant circulation pump.

 

[oigle]

Oh, I made sure of this. Thanks.
If I may ask some more advice...
My car is 2001 ML270 CDI and probably doesn't require sophistication of SDS. Maybe you can recommend some basic tool that can read DTC and communicate with ECU .
This car came to me without thermostat . It is always very warm here in Panama so I am not in a harry to install one, also recirculating motor for coolant is shut. Local mechanics advised me to delete it and reconnect hoses, since heating is never needed here...I did it. Is it a good idea to shunt a connector for the motor, so it will not send a unwanted signals to ECU? And if you agree could you recommend the resistor size .

Just a small comment re the thermostat. I understand the climate issue as we are not a lot different here in Oz.
However, the thermostat's use is multi-purpose. Firstly, it warms the motor to proper operating temp quickly - don't have to warm the entire cooling system. This is important as the motor tolerances are engineered to run at a set temp (about 82°C). Secondly, the worst thing one can do with a motor is have temps fluctuate over a large range - continuous expansion and contraction of the block and head isn't good. Without a thermo, you will get hotter going up hills and cool down rapidly down the other side - not good. Thirdly, the thermo controls the rate of flow of the coolant. Too high a flow can actually be detrimental to maximum cooling ability of the radiator. Cavitation can also occur in the cooling channels in the head with excess flow rate.
All in all, you SHOULD have a thermostat fitted.

Cheers

Ian.