mackncheese Posted March 22, 2012 Share Posted March 22, 2012 I have a new to me 1999 RD690S with an E7 etech vmac lll. the other day it spun over a bunch and would not start. It had been running an hour earlier. I was ready to call my wife for a ride and tried it one more time and it started and has run fine for a day now. any idea what to check? I don't want it to bite me one day. Is there a fuel pump solenoid? If so where is it? Any other ideas. thanks for your help. Quote Link to comment https://www.bigmacktrucks.com/topic/24023-99-rd690s-intermittent-starting-problem/ Share on other sites More sharing options...
39 Baby Mack Posted March 22, 2012 Share Posted March 22, 2012 I don't know about a V-MAC IIIHad that problem a couple times with our MH's with V-MAC I, turned out to be the power relay which is constantly energized when the key is in the run position.Ron Quote Link to comment https://www.bigmacktrucks.com/topic/24023-99-rd690s-intermittent-starting-problem/#findComment-109292 Share on other sites More sharing options...
Frmconcrete09 Posted March 22, 2012 Share Posted March 22, 2012 There is a little black plastic type fuel return line running from the front of the head to the pump, ...does it do this after setting every time ? If it does that is probably the problem,. anytime we have our rd s start cranking and cranking that line usually has a small hole in it . If it is the line it's an easy fix . Quote Link to comment https://www.bigmacktrucks.com/topic/24023-99-rd690s-intermittent-starting-problem/#findComment-109296 Share on other sites More sharing options...
hatcity Posted March 22, 2012 Share Posted March 22, 2012 It happens once in a while on mine E-7. Was told engine position sensor. There are two on the engine. Only happens if I have run the truck then shut down and try to restart shortly. Not too worried as the truck normally runs all day, shut down at the end. Quote Success is only a stones throw away.................................................................for a Palestinian Link to comment https://www.bigmacktrucks.com/topic/24023-99-rd690s-intermittent-starting-problem/#findComment-109297 Share on other sites More sharing options...
Mackpro Posted March 22, 2012 Share Posted March 22, 2012 Pull down the metal kick panel in front of the passenger seat below the fuse panel. Behind this panel you will find the ABS ECM and the VECU ECM. The ABS ECM will say WABCO or Bendix or some other ABS system maker . What you want to look for is the Mack VECU ECM. Its a thin black plastic rectangular ECM . It has 3 push in wire connectors but places for four. First thing to check is see if the VECU ECM is faceing up where the connectors come in from the top. If so thats a bad sign, water seems to so how get into the ECM when facing up. Regardless unplug all 3 connectors and check for green or damaged pins. If all OK and the ECM is faceing up , unbolt it and turn it faceing down and reconnect all plugins. Next is to try to catch it "not starting" and check to make sure all 4 power relays (next to fuse panel) are powering up. I think #3 power relay fires up the engine ECM. If this relay fails all will seem to work but crank no start and this failure will not set a code. Quote Link to comment https://www.bigmacktrucks.com/topic/24023-99-rd690s-intermittent-starting-problem/#findComment-109305 Share on other sites More sharing options...
Frmconcrete09 Posted March 22, 2012 Share Posted March 22, 2012 Pull down the metal kick panel in front of the passenger seat below the fuse panel. Behind this panel you will find the ABS ECM and the VECU ECM. The ABS ECM will say WABCO or Bendix or some other ABS system maker . What you want to look for is the Mack VECU ECM. Its a thin black plastic rectangular ECM . It has 3 push in wire connectors but places for four. First thing to check is see if the VECU ECM is faceing up where the connectors come in from the top. If so thats a bad sign, water seems to so how get into the ECM when facing up. Regardless unplug all 3 connectors and check for green or damaged pins. If all OK and the ECM is faceing up , unbolt it and turn it faceing down and reconnect all plugins. Next is to try to catch it "not starting" and check to make sure all 4 power relays (next to fuse panel) are powering up. I think #3 power relay fires up the engine ECM. If this relay fails all will seem to work but crank no start and this failure will not set a code.Nice to know thanks for the input Quote Link to comment https://www.bigmacktrucks.com/topic/24023-99-rd690s-intermittent-starting-problem/#findComment-109307 Share on other sites More sharing options...
mackncheese Posted March 22, 2012 Author Share Posted March 22, 2012 (edited) Thank you all for the info. I will dig into it over the weekend unless the problem shows up before then. I will let the forum know what I find. If I find the VECU proper with no corrosion should I buy a power relay and keep it on the truck? Edited March 22, 2012 by mackncheese Quote Link to comment https://www.bigmacktrucks.com/topic/24023-99-rd690s-intermittent-starting-problem/#findComment-109316 Share on other sites More sharing options...
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