MAP sensor "locks" up!!!

[23tbucket]

I did a short datalog today. I got the MAP to "lock-up" everytime the engine was started. When the engine was shut off with the stop button rather than with the key the MAP would read normal? The voltage at the MAP sensor stayed at 4.967 v. at all times.
Maybe something can be noticed in this datalog?

jan17,2013.msl

Thanks; Clifford

[grippo]

I am not sure what is going on here. If the engine is running but the MAP sensor is locked up, and you put a voltmeter on the MAP input pin that goes to Ampseal pin 24, and you rev the engine, does the voltage stay locked on the meter ? That test would tell us whether there is a hardware or software problem.

You have a dual tach input configuration with no toothed wheel. The 2.9x code is really more appropriate for this mode, but the present code should work also. I have found some bugs in it when no trigger wheel is used, but it has taken time because most people using it have wheels. I haven't released the latest fix, which may be applicable to your problem, but I am attaching a 3.780c code which has this latest fix and may resolve your problem. You can use the same ini and msq files.

[23tbucket]

Grippo; The MAP voltage stays at 4.967 v. when reving the engine. Even while cranking the voltage is at 4.967.

I'd like to try that new code. Sorry for asking, but I don't know....Do I need to do the bootloader thing to install the new code?

[grippo]

If the MAP voltage between Ampseal pin 24 and sensor ground matches the TS Gauge in the sense that the voltage reads 5 V and the gauge reads max kPa for the sensor then you have an electrical problem that a code change is not going to fix. The code should always read a kPa value that matches the voltmeter, and if the latter locks up at a value so should the Gauge. But if you are measuring the VRef voltage, then that should stay at or near 5V at all times.

To load the code you need the Downloader programmer and you need to ground the bootload wire before powering on the processor. This tells the microsquirt that it should prepare to download code and wait for the PC Downloader program to start sending it.

[23tbucket]

Grippo; Yes, it was the Vref I had the voltmeter on ("C" pin in the MAP pigtail or microsquirt pin #28).

Today I hooked up the voltmeter to sensor ground (MAP pigtail "A" or microsquirt pin #20) and sensor output (MAP pigtail "B" or microsquirt pin #24).

Key on MAP showed 4.467 v. and 95.4 kpa on the tunerstudio gauge....engine not running.

Start engine ...voltmeter at 3.3 v. and tunerstudio gauge at about 79.7. Revved engine a few times...both voltmeter and gauge move up and down as load changed...as expected. The voltmeter was hard to follow, but I think the output was anywhere from 2.3 v. to 3.5 depending on the load. The MAP gauge followed the load as well.

All was working good until I shut the engine down with the on-off button. Re-started and MAP gauge stuck at 71 kpa. Revved engine a few times... the voltmeter showed similar readings as before ....but the MAP gauge did not move.

Shut down and re-started using the key switch...the gauge was reading correctly again and the volts moved as the load changed as it should.

I should note: It seems to me I can get the gauge to lock up every time I shut the engine down with the handlebar on-off switch and restart....yet if I turn the ignition on with the key switch things seem to work okay for a bit. It has been just the last couple of days I have been using the handlebar switch. Before, when I used the key switch, the MAP gauge would randomly lock up...sometimes it would run for a half hour before the lock-up issue.

I'm an old guy...I still have most of my hair....but I may start pulling some out soon..lol

Thanks for your patience; Clifford

I'll wait until you reply before I go ahead and download the new code

[grippo]

Ok if the gauge was stuck, but the voltmeter was changing, then it is very likely the code, so I would try the download. I'm not sure why the key on-off vs button on-off makes a difference, but hopefully the problem will go away in both cases with the code change.

[23tbucket]

Grippo; I downloaded that new code today........I could not get the MAP gauge to lock-up on tunerstudio at all...on off with the button or key...the gauge would read properly each time the engine was re-started....everything worked just great.... I think we have solved the issue and I can keep my hair!!!

A big thank you to Matt and Grippo....you fellows rock...or as us old guys would say...groovy man.

;Clifford

Note; I still intend to upgrade the ignition regardless.

[dontz125]

I'm not sure why the key on-off vs button on-off makes a difference

Depending on how he has it wired, hitting the kill switch would leave the uS powered on, while turning the key would shut it off; upon turning the key back on, the uS completely resets. So - sounds to me like losing the tach signal is what's 'sticking' the MAP reading.

23tbucket - if you'd be willing, perhaps try an experiment -

• reload the old code
  stall the engine - while stopped in gear, let the clutch out
  without touching the key or kill switch, restart the engine (clutch in, obviously )

Is the MAP stuck?

[23tbucket]

Dontz; Na...I don't want to mess with downloading the old code. Everything is working perfectly now with the new code installed. Why the MAP would lock up was certainly a head scratcher. Even if it was an tach signal blip that caused the initial lock-up of the MAP...you would think it (the MAP) would start working again while the engine kept running? No ignition blips ever seen in the data logs either?

Update: I installed the new optic sensed ignition system today. I hooked up the tach signal wires exactly how they were before....and..no tach signal again!!
Messed around with diodes and resistors and finally got the elusive tach signal back again. Crazy!!

The engine does seem to run a bit smoother with the new ignition......all the signals (including the MAP) are giving good readings. I think I am ready for some highway tuning.....as soon as this snow goes....

[Towelie]

The code you're running does use MAP crank angle sampling, but I'm not sure how the sampling behaves if there's an RPM input hiccup. It is possible the sampling may freeze up.

So if you have no crank angle sensors hooked up and the fuse removed from the fuel pump relay.(so there is no rpm input) should you still get a working map reading(mine is just frozen at 18kpa and fluctuates ever so slightly, but doesn't respond to changes in MAP)?

Sorry to hijack!