MS 2 ECU relay cable connection problem

[hoffmanuno76]

I finally got my Megasquirt up and running on my Jeep CJ7's 258 last night. I had to reflash my firmware, but I got it to start. I can't run it for more than a minute or two since I don't have the coolant system hooked up, but that's enough for now. I seem to have some sort of connection problem between the MS ecu and relay board connection. The end of the cable that plugs into the ECU seems to sometimes not have a proper connection and the fuel pump and injectors won't fire or cold start led come on when you try to start the engine. If, with the ignition switch in the on position, you wiggle around the connection a lot it fixes the connection, as you can then hear the fuel pump turn on and off. I then can tighten the screws holding it to the ECU and it will then start up and idle steadily. But if I move around the box with the cable still tightly screwed to the ECU it will then usually show the same above symptoms and I have to start the cable wiggling process all over again. My jim stim appeared to work ok in the ECU while I was powering it up, loading on firmware, and testing out the O2, tach, and tps functions. I bought the relay board to ECU cable from DIY, so I'd assume it should be ok. I put the ECU together myself, but I'd think I did an ok job with it if it's at least starting now. The only options that come to mind are a bad/loose wire connection inside the cable connector, a bad solder connection on the ECU connector board, or a bad/loose pin connection internally on the ECU connector on the board. Any thoughts before I go back through them?

Another weird thing is that the only LED of the 3 on my ECU to light is the middle one for cold start. The injectors are clearly working, since it is starting and idling, but shouldn't the LED light come on the ECU as well? All of my connections are soldered and heat shrinked and/or taped up. I even solderd all the wired directly to the relay board to ensure a good connection that wouldn't pop loose for any reason.

[hoffmanuno76]

I did some more testing on that cable connection. My megasquirt ECU connection side is on the board and case solidly with no movement and my continuity tester says its connected to the board just fine. The female plug on the cable for the ECU side seemed ok. I took the cable end off and tugged a little on the wires and they didn't move. I then connected it back to the MS ECU and turned on the connection. The fuel pump came on when I bent the wires all the way up and back over the box every time. But when it is in the normal position the pump would occasionally click on and off. I then started moving the wires around one by one on the female plug with the ignition on and listened to see if there was an interruption that caused the pump to click on and off. Sure enough it did it only on the red 12v power wire. That wire was solidly in the plug but sometimes just wouldn't connect to the pin. If I pushed it in a little with the tip of an awl it would usually connect and turn the pump on. Since this connection in the plug is bad I'm going to cut the entire plug end off and use a spare female plug I had sitting around from the MS relay build, cut the cable in half to get it to the proper length for my console set up, and then solder each wire on the plug and heat shrink tube over each connection after I'm done. I really don't want myself or someone else stranded because of a crappy plug connection. I'd send it back to DIY Autotune where I bought it, but I bought it months ago and I don't think they'd take it back, even if it took this long before I could properly test it out. I really wasn't happy with the quality of the cable connection. I thought the ends would be soldered on solidly and not pulling so tightly out of the plug. The rest of their stuff has been pretty high quality though.

[trakkies]

When soldering the DB37 to harness, cut a bit of thin cardboard - cigarette packet etc - and fit between the two rows. Will prevent any possibility of solder running between them. You only need to sleeve every other cable. I use rubber Hellerman sleeving which won't be damaged by touching with the iron. It's only the high current cables which are tricky - main grounds and injector drives.

[hoffmanuno76]

Thanks for the advice Trakkies. I hadn't even thought that I'd only need to shrink wrap every other one. I was a little worried about soldereing the wires, so I thought I would wait until all the wires were soldered on until I would slide the shrink wrap down and then heat them up all at once. I definitely will do the thin piece of cardboard trick too.

[hoffmanuno76]

The problem was definitely a bad cable connection on the cable that DIY Autotune sold me. Probably was just that one power wire not connecting in the female end for some reason. Cutting the cable in half made the cable fit better in my jeep's locking center console anyway. I had a little difficulty with 3 of the wires not wanting to stay solder on the pins on the spare female connector I had, but I eventually got them soldered on solidly. I shrink tubed all the connections but the exposed shielding ground for the tach so it should never have a shorting problem again. I almost thought about covering them in clear epoxy before screwing the cover down on the connector, but if something every went wrong it'd be a pain to try and fix it. The new cable end works well and now it won't randomly cut out when I move the ecu or touch the ECU cable end. I velcro mounted the ECU and relay box in my center console, so now it is solidly held in place and can also be quickly removed if there is a problem. Now I just need to connect my laptop up and start programming the ECU to get it to start and run better. First I have to get my radiator and cooling hoses connected back up. Hopefully in a couple of weeks I might be ready for a test drive.

[trakkies]

IMHO, it's important to support the cables some way off from the actual pins to avoid any strain on them - hence the cord grip found in most DB connector hoods. If this is done the cable to pin joints - either solder or crimped - should have a long life.

[T3Bunny]

I finally got my Megasquirt up and running on my Jeep CJ7's 258 last night....

Would you be willing to share details of your ignition interface and setup? I am new to Jeeps (Sparkin a buddies) and for the life of me I can't find ANY solid information out there on the ignition system in this CJ7. It is an '84.

My scope is down at the moment of course... I am seeing what appears to be a VR sensor in the dzzy, yet with three wires.

[T3Bunny]

I Posted a thread on my questions here: viewtopic.php?f=89&t=41391