RPM random signal

EDIS and Megajolt installation related topics. Be sure to review the <a href="http://www.autosportlabs.net/MJLJ_V4_vehicle_installation_guide">Vehicle installation guide</a>

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giles2005
Posts: 6
Joined: Fri Apr 10, 2015 6:19 am

RPM random signal

Post by giles2005 »

Hi there,

I'm currently putting the finishing touches to my old megajolt v2 install I have a few small problems with rpm signal.
On the test bench I was getting perfect rpm signal and the same after installing to the car but was still using old ignition system to run the car so I could test everything was working.
Its only when I fully switched over to the megajolt that I get random rpm signal problems at idle and when trying to apply revs.
It will read idle 900rpm but jump up to 2000rpm every second yet the engine itself is staying at a constant 900rpm.
Iv replaced the vr sensor and the problems stays the same.
As soon as reverted back to the distributer but still have the megajolt powered and running under the software the rpm problem goes away.
This has left me a little confused!

giles2005
Posts: 6
Joined: Fri Apr 10, 2015 6:19 am

Post by giles2005 »

Here is a short clip of the problem.

https://www.youtube.com/watch?v=Gn-nAUMiUgc

brentp
Site Admin
Posts: 6274
Joined: Wed Jan 24, 2007 6:36 am

Post by brentp »

Hi,

So Megajolt gets it's RPM signal from the EDIS module. Are you saying the EDIS module was still reading the crank signal from the sensor, but running 'head less', while the engine was still running on the distributor?

I would check wire shielding, grounding (use a star grounding technique) and also check the high tension ignition cables for cracks or wear, and make sure you're running resistor plugs.

let us know what you find out!
Brent Picasso
CEO and Founder, Autosport Labs
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giles2005
Posts: 6
Joined: Fri Apr 10, 2015 6:19 am

Post by giles2005 »

Hi there,

Thanks for the response to answer a few questions.

Im getting a perfect signal from the edis module when im running with the distributor, (ford coil pack still connected and new leads just not hooked up to the spark plugs as the distributor is running the engine)

The leads are brand new ACCUSPARK 8mm silicone carbon core and the caps are NGK LB05F (5k ohm resistor)

Iv also used brand new 2 core shielded cable for the pip and saw and the same for the Crank Sensor and both are grounded using the star technique.

Any suggestions would be great.

giles2005
Posts: 6
Joined: Fri Apr 10, 2015 6:19 am

Post by giles2005 »

Forgot to mention the ht leads are the same setup virtually as im running with the distributor other than the different connection type for the ford coil pack as apposed to the distributor.

brentp
Site Admin
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Joined: Wed Jan 24, 2007 6:36 am

Post by brentp »

So thinking about what is different between the scenarios (connected and not connected). Are you observing a mis-fire when running on EDIS, coinciding with the jump in RPM? The Megajolt reads the RPM using the PIP signal; it's possible that noise on this connection might be causing this glitch.

Are you grounding the shield for PIP/SAW at one location, as well as the Megajolt? If you can put a scope on the PIP wire, that would be ideal.
Brent Picasso
CEO and Founder, Autosport Labs
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giles2005
Posts: 6
Joined: Fri Apr 10, 2015 6:19 am

Post by giles2005 »

Hi there,

Nope no misfire at idle when running on edis/megajolt only when you apply revs.

The pip and saw cable has the same shielding as its a two core shielded cable and everything is grounded at the same location.
I don't have access to scope or now how to use one.

Could it be a faulty edis module?

giles2005
Posts: 6
Joined: Fri Apr 10, 2015 6:19 am

Post by giles2005 »

Right iv just tried a new coil pack just incase it was a problem with that but sadly still the same problem.

brentp
Site Admin
Posts: 6274
Joined: Wed Jan 24, 2007 6:36 am

Post by brentp »

Have you tried perhaps a different EDIS module? this is a very odd problem, sorry!
Brent Picasso
CEO and Founder, Autosport Labs
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