Coffeyrd Posted December 18, 2013 Share Posted December 18, 2013 Truck always started right away. Starter was bad so we changed it. While doing that, I hit the ecm with the wrench contacting the hot lead off the starter and got a nice spark off the ecm housing. It was cold and getting dark so I had another guy connecting the batteries while I connected the starter. Anyway, now the truck cranks but won't fire. We had it plugged in and a torpedo heater going and got everything nice and warm but nothing. Checked all the fuses and they are ok. Fires off of ether but that is it. Cracked the lines on the head and had fuel from all 6 lines but still nothing. Not even a puff of smoke. Could it be something got shorted in the ecm so the eup's aren't getting a signal to fire? What does it cost to have these things repaired or do you just find a used one. Thanks in advance! Quote Link to comment Share on other sites More sharing options...
bts-4120 Posted December 18, 2013 Share Posted December 18, 2013 you check the ground breaker on the fire wall? Quote Link to comment Share on other sites More sharing options...
Coffeyrd Posted December 18, 2013 Author Share Posted December 18, 2013 No I didn't know it existed. Where is it and how do I test it? This is an RD688. Thanks for the reply! Quote Link to comment Share on other sites More sharing options...
turckster Posted December 19, 2013 Share Posted December 19, 2013 Jump the terminals together on the ground relay, if the engine starts right off then there you go. Most of the time they are located on the firewall. Quote Link to comment Share on other sites More sharing options...
boyd Posted December 19, 2013 Share Posted December 19, 2013 if you have another unit, that is close in specs. you can just plug that ecm in to your wiring harness to see if it fires then. then you will know if your shorted your ecm out. i wouldnt run with the temp ecm, because it could cause damage if the parameters are not set rite. but you can at least see if that is the issue. or your local mack dealer may have one you can borrow just to see if this is the case.. Quote Link to comment Share on other sites More sharing options...
Coffeyrd Posted December 19, 2013 Author Share Posted December 19, 2013 Jumped the ground breaker and still nothing. Had a guy come out with an Eaton portable scanner and it would not pickup anything and when he tried to reboot it with it plugged in, the screen would go black. Because of that he figured the ecm on the side of the engine was fried. Question: Would a new ecm from Mack be ready to go or do they need the actual truck in their possession to program it? Quote Link to comment Share on other sites More sharing options...
staxx Posted December 20, 2013 Share Posted December 20, 2013 New modules come with no info , you will need your truck there to program the new module. If the software is close you should be able to install and run the truck temporaly to get it to the shop for programing. Quote Link to comment Share on other sites More sharing options...
boyd Posted December 20, 2013 Share Posted December 20, 2013 as long as you have a ecm that you know is good. you can hook up and if trtuck runs, you will be able to confirm this is what you need to replace. Quote Link to comment Share on other sites More sharing options...
staxx Posted December 20, 2013 Share Posted December 20, 2013 Make sure you hooked the engine harness positive wire back up after changing the starter , it hangs on the main engine harness rite below the intake manifold and very easy to miss. Also make sure all the block grounds are hooked up and tight . Also inside the cab to the left of your fuse panel make sure your power relays 1,2,3 have power coming in and out. Quote Link to comment Share on other sites More sharing options...
Coffeyrd Posted December 20, 2013 Author Share Posted December 20, 2013 Thanks, I'll check those relays. I have no other ecm to try and all the wires are hooked up. I found a place I can get my ecm rebuilt and won't have to bring it to Mack for a re-flash. Thanks for all the ideas, I'll let you all know what happens. Quote Link to comment Share on other sites More sharing options...
R.E.D Posted December 21, 2013 Share Posted December 21, 2013 Had the same issue with my truck a month back...same symptons...I was without work for a month ...ended up being the ecm...pickup up a used one for 800 bucks after I plugged it in and fired right up...lik3 the guys said...source out an ecm from a buddy and try it..even if it dont have the same power ratin it should start ...then you can go off from there....also make sure you unplug batteries when dealin with the ecm... Quote Link to comment Share on other sites More sharing options...
Coffeyrd Posted January 16, 2014 Author Share Posted January 16, 2014 Fixed! Had a guy come out and hook up a scanner. He couldn't get anything. When he tried to reboot the scanner with it plugged in the screen would go black. Sent it to a place in Texas and they said it was fine. Told them the scanner story and they rechecked the ecm and said that indeed it was fried. It cost 8 or 900 bucks to have repaired. Stuck it in the truck and she fired right up and runs great! Quote Link to comment Share on other sites More sharing options...
boyd Posted January 23, 2014 Share Posted January 23, 2014 Good deal Quote Link to comment Share on other sites More sharing options...
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