Lost RPM + on Megatune only getting 4.82v

[Will]

Hi My car was running fine until a few weeks ago and now cranking wont show any rpm's at all.
Also in the megatune software its showing I'm only getting a battery voltage of 4.82v.

I have read about the P259 chip causing no cranking, but I still have working fuel pump relay etc.
I am using a V3 prebuilt harness and all voltages going into the ECU it's self read at 12.6v.
I have tested the cranking wires, plugs etc and all have continuity, also when I connect the VR sensor to a multimeter the ohm's reading slighty change when you touch the sensor with a piece of steel.

No other sensor seems to be faulty and seems to work in Megatune.

Car is an AE86 with a 4AGE.
Using Hi ohm injectors, toyota water, air temp and tps sensors and a ford VR sensor on a 36-1 crank wheel.
Also running Alpha-N.

Could someone please point me in a direction of what to sart testing on the ECU.

Thanks Will

[Sprocket]

Check the Voltage calibration number is the same as it was previously, in either basic or constants menu. Megatune should throw up an error when you try and burn to the ECU with a volt reading of less than 10 volts I think. If the calibration number is the same as you have before, there may be a problem elsewhere that I cannot help with. The RPM and P259 chip failure wont pull the 12v down.

Only other thing I can suggest is that you check all the ground wires are connected clean and strong!!!

[Will]

Ok thanks, will have a look for some old tune files I first got with the ECU and check what is in them.

Could with the ECU thinking I only have 4.8v make it shut down the crank trigger side of things? Or is it possible that the p259 is bad? I guess I might be using another chip to turn the fuel pump on and off?

[Will]

Right I have sorted the voltage out, looked at an old map file.
Still got no RPM though, cut pin 21 on the P259 chip and still no RPM.

Didn't think the chip was faulty as my fuel pump worked ok before I cut the pin.
After every few trys of cranking sometimes MS give a trigger error working, could it be the VR chip is faulty or the actual sensor?

I have checked the wiring from one end of the loom to the other and all ok, think its like about 0.1 / 0.2 OHM each wire.
Is there an acurate way to test the VR sensor out? I got a digital multimeter.

Thanks for anyone who can help.

Will

[Sprocket]

If the Battery calibration value was indeed different, the question I ask is why?

Have you upgraded firmare at all?

it might be worth your while to check all setings with known settings.

What is the Constant for RPM calc value?

[Will]

I think the config probs have come from the serial cable, always had probs with it. Pulled it apart and it basicly the solder joints fell apart, never seen something so shockingly soldered. The 2 comunication pins look like the have/could touch each other.

So need to fix that.

I have tested the sensor on AC mode on multimeter and is giving a signal between 0.250 and 0.570v.

Once I have fixed the serial cable and check all settings are correct with an old MAP I will do the sound card cable check to see if the ECU will get and RPM so I know if the ECU is at fault or not.

[Will]

I have fixed the serial cable.

Done some more testing, read on this page 6th Post down about turning trigger type to coil instead of multi tooth to see if you get an RPM.
I got an RPM signal but it varied from about 350RPM to 4000ish. Does that mean the sensor is on its broke?
I have tried a multimeter set to AC and got about 0.250 to 0.570v while cranking though.
http://195.159.109.134/vemsuk/forum/index.php/topic,816.0.html

The sensor im using is like this...


O the Constant for cranking is 3000

[rob@vems.co.uk]

It does seem like the sensor is fine - but there shouldn't be that much of a variation when cranking.
If you take out the plugs and spin the engine over you should get a higher steadier reading on both the ACV and RPM signal.

Your crank trigger wheel is still centrally mounted isnt it? (theres no rust or movement on it is there?)

Did you do the Soundcard test?

If the sensor is good and the VEMS is okay then it suggests that theres a problem with cable or configuration.

[Will]

The thing that is confusing me is if I set the trigger type to coil then I get an rpm signal, if rather eratic.
But when it's set on the proper multi tooth setting I don't get an RPM, just a red bar on Trigger Errors on the main screen.

I guess it might be worth running a new cable to the VR sensor to see if that fixes it, as I'm not to impressed with the solder joints in this prebuilt V3 loom although crimped parts are fine.
Will also do a sound card test when I get chance.

Trigger wheel is all fine brand new crank pully and wheel only been on there for about 3 months?

I can't see it beeing a config issue as was working fine and tried to put older configs on and makes no difference, unless the firmware needs reloading?

[Sprocket]

Have you tried reversing the polarity of the wires at the sensor?

Sounds daft but i know some one who managed to get the engine running, then upgraded to 1.0.73 firmware and lost the rpm signal. we spent 2 hours chasing the problem the we said bollox to it, lets reverse the polarity on the sensor. It worked straight off! Bizar!

[Will]

Will give it ago just incase I managed to swap the wires over when checking them all out. Worth a try anyway!

[Will]

I have swaped the VR sensor wires over, still don't get an RPM in normal multitooth mode, but in coil trigger mode I seem to get a more stable signal.

Here is msq file of my map incase anyone can see any errors? It's firmware 1.0.73 btw
http://www.box.net/shared/li2luf6tk3

When ever I load a map up I always get 2 errors in the log file, one beeing about antilag and it switches it on.
http://www.box.net/shared/gk4v56m7zp

Here is the log with multitooth trigger
http://www.box.net/shared/lx24ikstd5

Here is the log with coil type trigger
http://www.box.net/shared/so3bi3jzvf

Still need to get round to replacing the wire to the VR sensor and doing a soundcard check, but I don't have much time to test or even get to a shop to buy cable to test with.

It might be quicker for me to post the ECU to some one if anyone is willing to have a look at it?
Atleast I would know if the ECU was faulty or not, then I could just replace the sensor and wiring if the ECU is fine.

[Sprocket]

What type of trigger wheel is on this engine? 36-1? as the primary trigger settings look wrong for a 36-1

[Will]

Yea its a 36-1 wheel.

I'm begining to wonder if the settings are saving onto the ECU ok?
When I loaded other maps onto the ECU the settings seemed the same.

Might try loading the maps onto another PC with MT in ofline mode so I can just read the files and see what the settings are and compare them between older MAP's etc.

Might see about loading the MAP onto the ECU with another PC instead of the laptop, incase its sending errors over?

[Sprocket]

Yea its a 36-1 wheel.

ok

you need to change the 'angular width of tooth' to 3