RPM random signal

giles2005 · Post by **giles2005** » Fri Apr 10, 2015 6:36 am

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 · Post by **giles2005** » Fri Apr 10, 2015 4:39 pm

Here is a short clip of the problem.

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

Post by **brentp** » Tue Apr 14, 2015 7:19 pm

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!

giles2005 · Post by **giles2005** » Thu Apr 16, 2015 4:39 pm

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 · Post by **giles2005** » Thu Apr 16, 2015 4:44 pm

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.

Post by **brentp** » Thu Apr 16, 2015 9:31 pm

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.

giles2005 · Post by **giles2005** » Fri Apr 17, 2015 4:58 am

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 · Post by **giles2005** » Tue Apr 21, 2015 2:11 pm

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

Post by **brentp** » Tue Apr 28, 2015 10:25 pm

Have you tried perhaps a different EDIS module? this is a very odd problem, sorry!