Help, ignition cuts out at 5k rpm

[Slick]

I've been running my car for just over a month now. Its runs really well, and i'm very happy with the peformance, but... the ignition cuts out at 5000 every time. I've got a tach wired into the power wire to the coil, and every time i reach 5k it, the tach, and the igniton cut out. Can anyone help with my problem?

Cheers,
Rod

[Todd Charles]

Do your tables go higher than 5000 rpm? Are you sure you don't have the 3.0 firware and have the rev limit set to that point? Have you tried it with the tach disconnected?

[Slick]

Tried the ignition with the tach omitted, my tables go up to 7000. And, i've set the rev limiter at 8000, but its just an output on the computer, so i dont belive that this would cause a problem. I did find that the wires to the sensor werent making very good contact, so i rectified that, but still its missing at 5000 rpm.

I am curious, though, will the MegaJolt igition work properly with a long duration cam?

Cheers,
Rod

[Scooter]

I'm running MegaSquirt with EDIS and I'm running into the same problem. Nobody on those forums know what the deal is, so I thought I'd come over here and see. Looks like I'm not the only one. Does your tach drop to near 0 rpms then back up to 5k, and so on?... Mine got worse and worse hitting a wall at 5k, then 4k, 3k, 2k then died and wouldn't start at all. Replaced the EDIS module and all was well. For a week. Then it started doing it again. So the only thing I can think is that it's a bad VR sensor sending a messed up signal to the EDIS module. I've realigned my VR sensor many times, one time it got rid of the cutting out, and all other times, it was still there. I'll be putting in a new VR sensor soon, so I'll let you know how that does.

Anyone with any ideas?

[MartinM]

Need to find out which before proceeding IMHO

If EDIS is faulty, then I would propose that the cutting out is due complete lack of sparks - should be observable via a timing light

If MegaJolt/Spark is faulty, then I would propose that the cutting out is caused by one or more of:
- EDIS (thinking that it is) not receiving any SAW signals and setting the advance to 10 degrees BTDC - which at 5000rpm probably causes a quite a big effect
- The MegaJolt/Spark getting a corrupted/noisy PIP signal making it believe that the rpm is really really high and going into rev limit mode

Detecting PIP or SAW signal problems requires at least an oscilloscope, preferably with storage capability as well. I'm trying to design some sort of external circuit at the moment that indicates whether the PIP and SAW are 'reasonable' at any particular point in time and also to indicate the amount of advance that MegaJolt is indicating to EDIS

Also, it's worth wiring up some LEDs to the programmable outputs and setting them at say 1000, 3000, 5000 and 7000 rpm - they give a good indication of what the MegaJolt/Spark thinks it's doing...
...I did this and, at one point, my (coloured) LEDs were flashing like a christmas tree - turned out to be an earthing problem, which after sorting out made the LEDs behave perfectly and increase my confidence that the box was doing what it should.


Hope this helps....

[MartinM]

Oh and of course...

Need to eliminate the VR sensor - again a 'scope is required to see the sine wave coming from it at the troublesome 5K point plus the 'discontinuiy' due to the missing tooth.

[Crock]

Some VR sensors give too high an output at high rpm and confuse the ecu. Could this be the problem? A system to reduce ecu sensitivity above a specified rpm or a change to a lower output VR sensor may help.
The zetec crank sensor is not a high output type and may be a good substitution, unless you are already using one!