Just installed a plug-n-play VEMS ecu : engine wont start
 

Everything seems working fine, TPS calibrated, MAP is reading fine, fuel pump is priming, but it seems I can't get the engine to run for some reason, the only issue is that I can't get the WB sensor to work for some reason, it heats up fine but it reads nothing, I tried inserting another known to work sensor with the same results.

Any VEMS user could share his/her knowlege please?

I am not familiar with VEMs specifically, but most of the ECUs require a nice, strong Tach input or they will not provide sparkage anf fuel (beyond the initial prime).......The Crank/dizzy/cam input, timed properly (one or more of these) is usually required for the ECU to understand TDC/timing to provide fuel and spark at the right time. Are you getting a tach signal?
regards,
al


PS: I'm sure that there is a VEMS Users Forum. You'll likely get better info/help there.

How strong is your battery? Sometimes modern electronics wig out if battery is on the weak side.

I just had a similar issue with an electronic CDI from P a r t s K l a s s i k. My battery was old and on its last legs. A new battery later it fired right up.

I know nothing about VEMS, but the WB sensor isn't normally used to start the motor, because they don't get hot enough to generate anything the ECU can use for 2-3 minutes after the engine starts/sensor heater gets power. And you'd probably be well advised to start the motor initially in open-loop, dial in the maps and go closed-loop later (if at all).

On a Motec, if the O2 sensor errors/reads nothing, chances are good that the calibration number is too far off and the ECU is ignoring the values - because it considers it bogus (Motec diagnostics will show an error in this case - what does your ECU software show?).

The calibration figure you enter in a Motec is the resistance of the laser-trimmed resistor in the sensor, multiplied by 10. You can prod this out with an ohm meter - this is be the same number as the free-air calibration routine returns. The values change as the sensor ages, too - especially if it gets contaminated...

As ALL sensors have different, individual values, you should calibrate or change this value after swapping sensors. If they're close enough, another sensor may work - but that'd be just dumb luck...

Most ECUs want to "see" a number of complete cycles from the position sensors, in order to be convinced that the motor is turning and it has sync, before it will fire the injectors or the plugs. On a Motec, this number is 2 - the motor will not fire the plugs or pulse the injectors before the ECU has seen two complete revolutions.

So are your injectors pulsing and the ignition firing?

If not, assuming that all your wiring is good/connected correctly and you're using mag sensors, try increasing the "floor" on the input signal(s); the voltage is low and the signal noisy when cranking, and it could be getting confused. I get ~1.2V out of my Bosch position sensor when cranking; ignoring anything less than 0.5V below 600 RPM get me a fast, reliable sync.

If the injectors are pulsing and coils/plugs are sparking and the motor doesn't run, then you may have the offset (angle) set incorrectly for the ECU to figure out where TDC is relative to the sensor signal (which is pretty much what Al was saying) But without more information about your crank/ref sensors and what's configured in the VEMS setup, can't really say.

I already replied to your email, first thing in the monday morning.
Your first option should be waiting for my reply, with any standalone it is useless to post help-topic without logs etc, it would be just a guesswork.

P.S. There is nothing wrong with any sensor, ECU etc, just there are steps that need to be taken before attempting to start.

Seems that the problem is solved, crank sensor gap needed some adjustment: https://www.youtube.com/watch?v=bUcWeeSRTmA&feature=youtu.be

Was easy enough to diagnose with triggerlog recording ;)

Peeps,
Have you or one of your customers thought about doing a build thread of an EFI conversion like Al does quite well?

I think there would be many interested in seeing a VEMS conversion and the end results., particularly the plug n' play ones that you seem to have covered better than anyone else.

I'm in this process right now and have a ton of pictures and videos, I'll be glad to post them all but my main issue is that English is not my mother tongue so I'm worried that I wont be able to describe what I'm doing correctly.

kamaro,
You should be proud of your English skills. I would not have picked it wasn't your primary language.

Please chronical your build.