Autosport Labs

Tested pip signal at MJ connector while plugged in and getting .1v ac, same voltage for saw with engine running. If I disconnect the MJ connector while engine running and test for voltage I get 5.9v ac on pip and .1v ac saw. Voltages are correct with engine off. This is a pre built unit version 4. I have checked the pins numerous times in the molex connector for proper connection and placement..... all is good? I have the minimum 4 wires hooked to the MJ only. What am I missing? I have followed the diagnostic charts and all checks good except for the loss of voltage when the connector is plugged in. Possible bad MJ? Help please.
Bret

I should ad that I have swapped the pip and saw wires to make sure they are not the issue. Same limp mode. Why would I loose my 5.5v pip signal when the molex is plugged in? My first impression is that the pip wire is in the wrong pin slot but I have checked again and again.

PIP is the "Position Indicator Pulse" from the EDIS to the MJ.
If you have no RPM reading on the config software (assuming it is talking to the MJ ok), then this is the wire/signal to be looking at.

SAW is the advance control (Spark Advance(or Angle) Word) from the Mj to the EDIS. If the MJ is showing RPM and tracking the engine, but the commanded advance doesnt seem to be taking effect, then you look at the SAW line.

Both are short timing pulses, so measuring their voltage with a meter is only a rough indication of whats going on. you need a scope to be certain you are seeing the right signal.. a meter gives you an average of the pulses frequency of mark/space ratio.. close enough to get an idea if its moving when you start the car and so on.

If you disconnect the MJ and measure what you think is your PIP signal from the EDIS, you should see it change from engine stopped, started, and *maybe* with varying RPM (never tried that).

SAW shouldnt change with an engine start, since its an input to the EDIS, and without the MJ connected, theres nothing to input. it *might* pickup some noise if left disconnected, so you might see something.

The PIP signal goes into the MJ CPU through the RS232 level shifting chip (Max232a). Its possible that might have been damaged which might cause the MJ to be apparently pulling the PIP signal down when connected. It shouldnt be dead, unless youve fed it something pretty nasty voltage wise though, as the input side of these chips is designed to handle pretty big + and - voltage swings, but I have read of a few people damaging them on here occasionally.

You can get these chips at any decent sized electronic components store if you want to try changing it.

Or you can just take it out of its socket and test PIP without it present as a simple test. you wont have laptop/software communications since the same chip handles that. But if you still lose the PIP signal when its connected *without* the chip in place, then you know you have the wrong pin or some sort of external short pulling it down. If its OK without the chip, but dissapears with the chip inserted, then that suggests the chip is pulling the PIP signal down and probably should be replaced.

Only do this if you are comfortable with removing and replacing chips without bending pins and so on.

Once the chip is checked, You should be able to get an RPM reading on the MJ software with *only* the PIP signal connected, which might simplify your testing..

If you do get that happening, then you can add in the SAW wire to get advance control.

Hi bartman360,

Thanks for the detailed analysis.

It seems you've covered this already- but it's worth mentioning the following:

Double check you have the PIP / SAW connected to the correct pins on the Megajolt. The diagram is facing *in* to the controller, not looking at the end of the plug- sometimes this gets confused.

Double check the PIP and SAW pin connections on the EDIS module

Try a different EDIS module- do you have a backup unit?

Double check the grounding between the Megajolt and EDIS module

Does the configuration software communicate with the Megajolt? Can it read / write ignition maps?

If all of these check out, please contact sales@autosportlabs.com and we can take it from there.

Thanks,

brentp wrote:Hi bartman360,

Thanks for the detailed analysis.

It seems you've covered this already- but it's worth mentioning the following:

Double check you have the PIP / SAW connected to the correct pins on the Megajolt. The diagram is facing *in* to the controller, not looking at the end of the plug- sometimes this gets confused.

Double check the PIP and SAW pin connections on the EDIS module

Try a different EDIS module- do you have a backup unit?

Double check the grounding between the Megajolt and EDIS module

Does the configuration software communicate with the Megajolt? Can it read / write ignition maps?

If all of these check out, please contact sales@autosportlabs.com and we can take it from there.

Thanks,

I do not have a backup edis but thinking of heading to the wrecking yard today. MJ is communicating as I am getting response from the map and I can datalog. I am almost 100% sure I have the pinout correct as I obviously have the power and ground wires correct because the MJ is firing off, and I wired the pip and saw in the same fashion as the power and ground. I will scope the signal tonight and check grounds again and get back with you.
Thanks,
Bret

Thank you, please keep us posted.

Horray, it is now working perectly. I spent the day at the local wrecking yard and scored on 4 edis modules 9.99 ea. 2 coils, 1 vr sensor. There is still about 5 more complete units and it is hard to not take all of them. Came back to the shop,swapped edis modules ans started the car......... No change!! WTF! So I started looking at the diagrams again and noticed the title of the diagram said version 3. I have version 4 and that connector has 2 more pins in the molex connector. I have no idea where I got that version 3 diagram but it is now in the garbage. I then found version 4 diagram, moved the pip pin 1 slot over and viola! All is good in sparkville.

Thanks for the help fellas.
Bret

That's great! thank you for the update!

And now you have EDIS modules for your next project (or your friend's )

Yes, I have a 78 Chevette that I stuffed a 4.3 Vortec V6 with a whipple supercharger and turbo 350 in that is going to be fired by MJ and EDIS. This just cured my firewall clearance issues. Thanks again for the support. Wonderful product and great support from the community.

Bret
DBA Madrona Autoworks Inc. Olympia, WA

Wow! Can you post pictures in the "powered by" section? Would love to see more american muscle there!

Sure, I will take some today and get them posted. Remember it is a work in progress but going to be a total sleeper (except for the hole in the hood and the holley 4 barell)!

"except"

cannot wait to see pictures of the installation!

When you get that running and make it up to the seattle area, we'd love to see it in person!