Richardsmack Posted March 22, 2023 Share Posted March 22, 2023 (edited) Hi All, It's been a while but I still have my 1998 RD688 E7 350. Yesterday I came across a strange problem with my dash electronics and starting the truck. Today again I broke my head figuring it out. Mybe you can help me in the right direction to fix it..... So yesterday I charged the batteries (one by one disconnected from the truck) as it was sitting over the winter. When I tried to start it it would run for a second and then die. I noticed the dash power to the fuel gauge, parking brake light, and heater blower stayed on while the key was in the off position. Tested the switch which was fine. Just in case I used a wire instead of the ignition switch.. same thing If I put the switch on contact the fuel gauge etc go on. When I put the switch in the off position power stays. Looked at the relays. they work fine. I took them out when the ignition was off but still had power as by pushing in the relays back in the fuse box I could hear click. Now when you actually turn the key further to start it it will fire but then dies and when the key is put in the off position the everything goes off like it should. I checked for ground issues etc but could not find anything. One thing is I'm not sure of see picture. Black box under starter relay with the little screw in the middle. Whenever I turned the truck off the gauges etc would stay on for a second or 4 and then turn off. Would it be the black box? What is it? (i found it it's a circuit breaker 105 amp) Thanks for your help 🙂 Edited March 29, 2023 by Richardsmack found black box Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted March 22, 2023 Share Posted March 22, 2023 ok, V-Mac II has a 5-7 second delay after turning the key off.. that is normal.. the black relay looking thing in the picture is a ground breaker, it looks rough. Clean the contacts. do the same for the red one next to it. also, it sounds almost like the ignition switch is bad. There is also an accessory relay below the ash tray, it can also cause these issues.. Jojo 2 Quote Link to comment Share on other sites More sharing options...
Richardsmack Posted March 22, 2023 Author Share Posted March 22, 2023 Thanks Jojo. Before when I shut it off after the delay of 5-7 seconds I heard a click.(what clicks?) Now it doesn't as the power stays on I guess. I measured trough the switch and it should be good but maybe under power it's not... But then I used a wire in the plug to bat -- ign same thing powers up and when disconnecting the wire everything stays on... I swapped the relay under the ashtray as well. Now I have to find a switch. Possible a universal one which I have to rewire to the cluster. Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted March 22, 2023 Share Posted March 22, 2023 that noise is the acc. relay.. it looks like a lawn tractor starter relay.. How about you stop spending money, (with respect) and just clean all the grounds, including the ground breaker on the firewall, there is a major ground on the block in front of the starter, and it also goes to the frame behind the left steer tire. there are also grounds behind the dash at the left corner and the right side by the fuse panel... clean all of these and the eyelets.. then retest.. are you having issues with turn signals not working right? 1 Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted March 22, 2023 Share Posted March 22, 2023 I forgot to ask you to check the condition of the fuse box on the middle of the firewall.. check all the fuse sockets for corroasion.. Is this an E-Tech (V-Mack III) or do you have an injection pump? (V-Mac II) Quote Link to comment Share on other sites More sharing options...
Richardsmack Posted March 23, 2023 Author Share Posted March 23, 2023 Thanks for the advice/hints. V-mac III. I will let you know once I cleaned the grounds etc. That lawn tractor starter relay(acc) is not to find inside the cab. Only one is on the picture which should be the starter relay... Meantime checked fuse box middle firewall. relays were corroded cleaned everything. Again thanks. Ttyl. Quote Link to comment Share on other sites More sharing options...
Richardsmack Posted March 23, 2023 Author Share Posted March 23, 2023 Cleaned the contacts on the 50A breaker and checked with multimeter(black box). Same with the starter relay. Just in case bought a new ignition switch and connected. I can't find the acc relay. All I can find see picture. The one hanging loose in front of the fuse panel is for daylight running lights (now disconnected). The other one loose see first picture is I think acc relay which I swapped. Tomorrow when the sh... rain is gone I will clean all the grounds on the frame. Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted March 23, 2023 Share Posted March 23, 2023 Yes that truck could have the cube looking relay Quote Link to comment Share on other sites More sharing options...
Richardsmack Posted March 23, 2023 Author Share Posted March 23, 2023 It must be a ground problem. Again when I put the ignition on on everything goes on. When I turn the ignition off power stays on as whenever i pull a relay and put it back it clicks plus the heather blower stays on and fuel gauge and both have nothing to do with the ecu. But then when you crank the engine it starts but shuts down right away and then everything shuts off. Sorry for repeating :-) it does not make sense to me grrrr. Will post when I make progress. Thanks for the help ! Quote Link to comment Share on other sites More sharing options...
Richardsmack Posted March 24, 2023 Author Share Posted March 24, 2023 Today I cleaned all the grounds. Cleaned battery terminals and connection cables. Disconnected ecu and tried the ignition no difference. Cleaned the fuses and checked them. Disconnected the alternator and tried. The power stays on if the ignition is off. When starting it turns the starter when let go of the key everything shuts off proper. I noticed that when turning the key in the on position I don't see the orange engine fault lighting up anymore. checked and changed that bulb. Anyways I'm out of options. When I take every relay out everything is out/off except for the parking brake light. When I put the relays in everything has power still with ignition off..... Time for a beer. So it keeps the power on but I cannot find another relay which might be sticking............................. I'm out of ideas. Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted March 24, 2023 Share Posted March 24, 2023 Was the starter replaced recently? Quote Link to comment Share on other sites More sharing options...
Richardsmack Posted March 24, 2023 Author Share Posted March 24, 2023 Maybe I fried the ecu..... Quote Link to comment Share on other sites More sharing options...
Richardsmack Posted March 25, 2023 Author Share Posted March 25, 2023 Day #4..... Was reading the truck manual and it pointed to a circuit electrical box behind a panel under dash passenger side. Opened the panel up and discovered the box and disconnected it. Water came out...... Drying and cleaning it now. Hopefully it still works. If not I have to look for another box. Let's hope for the best. While drying I have to see where water comes into the cab. I'm getting somewhere :-) Will let you know. Thanks ! Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted March 25, 2023 Share Posted March 25, 2023 Good find.... That is the V.E.C.U. looks like the wind shield is letting rain come in.. I think you can spray it clean with electrical contact cleaner that is 'sensor safe'.. Quote Link to comment Share on other sites More sharing options...
mechohaulic Posted March 25, 2023 Share Posted March 25, 2023 sharp looking unit; shouldn't have been any doubt in your mind in terms of making the trip ;; a Mack was doing the moving .. 1 Quote Link to comment Share on other sites More sharing options...
Richardsmack Posted March 25, 2023 Author Share Posted March 25, 2023 Well as kinda expected the unit is fried. It works a bit better though. So now I have to find the module for a reasonable price. Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted March 25, 2023 Share Posted March 25, 2023 Sorry Bud... however,,, it is really good that you found this issue.. i say Good Job.. Quote Link to comment Share on other sites More sharing options...
Popular Post Richardsmack Posted March 26, 2023 Author Popular Post Share Posted March 26, 2023 Thanks :-) At least all the wiring is looked over and everything is clean now. Once I find the new/used V.E.C.U I'm going fabricate a plastic cover so that it can't happen anymore. It has been a good learning curve as well. Will let you know when the box is in and if it works. Thanks! 2 1 Quote Link to comment Share on other sites More sharing options...
Richardsmack Posted March 28, 2023 Author Share Posted March 28, 2023 Put in the new/used vecu from a CH with the same part#: It started right up Yeee Haaaa. Thanks everyone for your help. Quote Link to comment Share on other sites More sharing options...
Richardsmack Posted March 29, 2023 Author Share Posted March 29, 2023 Made a MacGyver plastic cover :-) Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted March 29, 2023 Share Posted March 29, 2023 😅👍 Quote Link to comment Share on other sites More sharing options...
Richardsmack Posted March 29, 2023 Author Share Posted March 29, 2023 Pffff. Had it idling for a while then it shut itself off. Started it the after 10 min it did shut off again. Engine code bulb did not work. Now it does. Fault code 6-4 which is J-1939 link which is communication between de VECU en computer aside of the engine. So now I have to check connections again.... Man I hate electronics. 1 Quote Link to comment Share on other sites More sharing options...
Richardsmack Posted March 30, 2023 Author Share Posted March 30, 2023 Checked connections and they're ok. So I think the software versions are different between the old and the new VECU. However I keeps on running when driving. Have to do some other work before the inspection and then it needs to be hooked up to a computer to verify the programming.... Quote Link to comment Share on other sites More sharing options...
Richardsmack Posted June 21, 2023 Author Share Posted June 21, 2023 Still having the 6-4 code. Trucks is in limp mode. I went to the dealer 2.5 hr drive one way. After they installed the software on the laptop and with help from mack support (3 hours later) they were able to read the ecu and the vecu. In the ecu was a different vin# and it read e7-460.... I think they updated the vecu with this vin#. Not sure as I was not there all the time. The problem stayed the same. Even though I measured all the connections and wires they decide to do that again. No luck. 7 hours later. The mechanic was afraid to program the ecu with my own vin# because he was afraid the truck would not run anymore after the update. So now I'm really stuck.... Would it be a 460? or just the ecu from a 460? I'm almost sure it's a 350 as the truck came with that engine and it shows on the valve cover. I'm out of options. If a mack dealer can't fix stuff... It would be nice if I could send the ecu and the vecu to someone who knows what he's doing. If you have any ideas please let me know. Thanks for your help. Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted June 21, 2023 Share Posted June 21, 2023 on the fire wall, by the steering column, is a gray wire with 2 or more wires. it has a triangular weatherpack plug on it... are the contacts and wires in good condition? that is the 1939 line under the hood.. it is part of the engine harness.. here is an example from the engine I currently have in my shop. 1 Quote Link to comment Share on other sites More sharing options...
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