hey guys, had the mjlj all connected in the car and was tuning it when the serial to rj11 one of the wires broke off so i couldnt communicate with it anymore. i soldered it back up and now the mjlj is working, i can tell by the timing light, but it wont talk to the laptop for tuning! it gives the the cylinder time out reading at the bottom and it wont communicate. i checked the mjlj board and all soldered joints look good, the phone line to the serial port ive had soldered and unsoldered to make sure i have a connection.......any thoughts? please help!
Randy
mjlj wont communicate to comp.
Moderators: JeffC, rdoherty, stieg, brentp
Hello,
So, what broke, and how exactly? Which wire and where- was it the small adapter box, or the cable itself? How were you able to fix it? Can you take a picture of it what happened?
Since the controller is working but you cannot communicate anymore, it's likely coinciding with the break that occurred. I would recommend double-checking the wiring and your fix.
Remember- in the wiring diagram go by the actual pin numbers on the DB9 connector. The diagram for the RJ11 to serial adapter is showing the back-side of the DB9 connector.
So, what broke, and how exactly? Which wire and where- was it the small adapter box, or the cable itself? How were you able to fix it? Can you take a picture of it what happened?
Since the controller is working but you cannot communicate anymore, it's likely coinciding with the break that occurred. I would recommend double-checking the wiring and your fix.
Remember- in the wiring diagram go by the actual pin numbers on the DB9 connector. The diagram for the RJ11 to serial adapter is showing the back-side of the DB9 connector.
Last edited by brentp on Mon Jul 07, 2008 6:26 am, edited 2 times in total.
hi brent, just sent you an email but i guess you saw the post so you can disreguard it. the cable break was the wires from the phone cable to the serial port female plug which goes to the usb/serial adapter it was the black wire that broke i believe so i unsoldered them all, cut the ends of the wires and then stripped them again and started over, my plug looks like the one in the pic just below the diagram in the operation guide. i have it wired up the same way with the yellow wire all the way to the right on the wider part of the connector and then the red and then black in that order, as here http://www.autosportlabs.net/MJLJ_V4_Operation_Guide i cant figure out what i did wrong here.....is there a way to test my cable? i notice the wiring diagram looks like wires go to diferent connector pins in the diagram above the picture? i dont have a digital camera but in the morning i will try to take a pic with my phone and post. thanks
Randy
Randy
hi brent, i checked for voltage and ground from the wires and all is well down to the connector.....the yellow is about 4.5 volts and the red is 6.25 i am getting the 4.5 thru the rj11 connector on the megajolt but not the 6.5 thru the megajolt, but i do get it at the end of the rj11. i took the megajolt apart to check voltages once again and all works out as it should be tested in the assembly section. all joints are soldered well. the megajolt tells me cylinder run time error there doesnt seem to be a problem with the serial port cable or the hardware, i have already uninstalled and re installed. i dont know what else to look for.
Randy
Randy
Sorry I wasn't clear before. When I suggested you check the cable for continuity, I meant to put one end of the meter on one of the RJ11 pins, and the other end of the meter on the appropriate DB9 pin and see if there is continuity between the pins.... I didn't mean for you to check actual voltage levels on the serial connectors.
I've updated the graphic in the wiki to further clarify the cable pinouts:
http://www.autosportlabs.net/MJLJ_V4_Op ... rial_Cable
Use your meter in resistance / continuity mode to check each pin of your custom cable.
According to your picture- do you have conductivity between:
black wire (DB9 pin 2) and RJ11 pin #1 ?
red wire (DB9 pin 3) and RJ11 pin #2?
Yellow wire (DB9 pin 5) and RJ11 pin #3 or #4?
I've updated the graphic in the wiki to further clarify the cable pinouts:
http://www.autosportlabs.net/MJLJ_V4_Op ... rial_Cable
Use your meter in resistance / continuity mode to check each pin of your custom cable.
According to your picture- do you have conductivity between:
black wire (DB9 pin 2) and RJ11 pin #1 ?
red wire (DB9 pin 3) and RJ11 pin #2?
Yellow wire (DB9 pin 5) and RJ11 pin #3 or #4?
Hi Randy,
still odd that it was working just before the break in the wire, and after you re-soldered it, it stopped communicating. That's still a big coincidence! - unless something else happened in-between that we didn't detect.
anyway- can you test it on a different computer- say, one with a regular serial port? if necessary, power the MJLJ up on the bench with a 9V battery.
Not all USB to serial adapters are created equally, and some are less stable than others. It's been a long running topic here (search usb serial for some samples...)
still odd that it was working just before the break in the wire, and after you re-soldered it, it stopped communicating. That's still a big coincidence! - unless something else happened in-between that we didn't detect.
anyway- can you test it on a different computer- say, one with a regular serial port? if necessary, power the MJLJ up on the bench with a 9V battery.
Not all USB to serial adapters are created equally, and some are less stable than others. It's been a long running topic here (search usb serial for some samples...)
hi brent, i went to the store today and exchanged my serial adapter just in case something went wrong with it, still no dice. i only have laptop and no serial port no other computer. i may be able to borrow another laptop for a bit but i am completely stumped. the ground wire for the megajolt was apparently frayed and started to come undone so i pulled that out of the molex plug and re did the plug so thats not a problem.....if that stopped making a good ground, or an intermittant one could that have fried something? im totally lost.
Randy
Randy
Hi Randy,
Testing on a different laptop would be useful. Does it have a standard serial port?
Also, I recall you don't have an LED installed in your unit, so you need to be confident the unit is actually receiving power when you try to communicate with it. have you tried powering it on the bench as well as the car?
And, to confirm, during all this testing, the unit is otherwise alive, controlling ignition advance while your engine is running?
Thanks for hanging in there- we'll figure it out.
Testing on a different laptop would be useful. Does it have a standard serial port?
Also, I recall you don't have an LED installed in your unit, so you need to be confident the unit is actually receiving power when you try to communicate with it. have you tried powering it on the bench as well as the car?
And, to confirm, during all this testing, the unit is otherwise alive, controlling ignition advance while your engine is running?
Thanks for hanging in there- we'll figure it out.
hi brent, yes the unit is alive, i keep checking to make sure its getting power and i have checked its advancing the ignition with a timing light so im confident it works, there was nothing big that happened for me to figure out what happened, one of the wires broke off the communication cable and i resoldered and then no communication. other than that all is working and all voltage checks from the build guide work out fine.......
Randy
Randy
hi brent, i got the cable and adapter in the mail from you yesterday and tonight i hooked the computer to the megajolt and it was communicating right away no problems....im not too sure what happened, i checked my old set up for continuity and everything checked out. oh well, i guess maybe it was from me soldering the wires to the serial adapter or something along those lines. all is well with my unit now! i was also wondering.......if i decide to go with the megasquirt system, that doesnt control spark does it? if not is the megajolt compatible with it? thanks guys!
Randy
Randy