Hi all, have a unit at my shop which got new injectors two been dripping and one coil was out-of-spec after replacing truck started just fine was running smoothly, no issues, no smoking, etc. The next morning final test and after turning the key I do hear the injectors buzz when the ignitions switch is on - so far good, normal, but the buzz is all the time not stopping just slowing down the frequency, any advice? So, checked all the conectors and the wiring, no signs of corrosion, no broken cables, no visible rubbing spots. I put new relays, went through the cable resistance and voltage tests-> all shows OK Batteries charged overnight with solid 12.5V / ECM shows 12.3V on tester The truck is very clean, as it was a depot vehicle previously with low mileage. The regular buzz takes 13s and the slow goes for another 1 minute and 47s for a total 2 minutes. I tried to start the engine after the "wait to start" light switch off and the slow buzz was still present and the engine very quick reved-up, so I switched it off even quicker : ) I didn't tried after the 2 minutes, as I'm uncertain what the error is - I also tried a different FICM/IDM with similar result The engine is practically a bigger 6.0 Powerstroke with the same ECM/IDM or FICM just not with Ford SW inside. Did someone had such a error already got or some hints where to look? Thanks for any advise.
The length of the buzz test is programmed into the ECM so swapping out the ECM eliminates it as the problem. There is a power supply harness that connects to the batteries and to the main harness near the firewall. Navistar calls it the clean power harness. There can be several connectors between the batteries and the firewall harness depending where the battery box is located. There may be one or two 40 amp ATO fuses in the battery box feeding the clean power harness. The connectors loose their grip in the mating connector and the 40 amp fuses sometimes the plastic connector housings may start to melt inside near the connectors. The wires are 8 gauge and the ground is white and the positive are usually red and purple. I would pull the harness out and inspect it. I've seen rubbed spots on the insulation on the clean power harness where the copper conductor was green and turned to powder and the truck was driven to the shop. If you can get the male half of the connector you could use it to test the grip on the female connectors. If any are questionable I would splice them. This should be the manual for your truck check the build date on the door frame to make sure. Truck wiring manual: 3000 4000 7000 electrical Another handy diagram: 04-06 DT466
Thanks mekanik! I replaced already the battery pigtail with the fuse holders together with the relays as I saw some signs of heat development around the IDM fuse holder. Unfortunately, I don't have different ECM handy, so need to look for one first. To what cable exactly to pull are you referring? All connectors I could only find, has been checked, opened - nothing I could see or mesure. Now I'm starting to believe that the ECM is somewhat defect. But, I'm curious if there are more trucks out there with the same symptoms.
Can you post the last eight of the VIN or PM it to me?
Thanks, PM send
The ECM's don't give a lot of trouble however the IDM's do occasionally fail. The clean power harness has three wires in it there should be a two wire plug at the battery box with two positive wires and a single wire plug with the ground wire. The harness follows the battery cables to the starter where it then connects to the harness at the firewall. You should be able to unplug both ends and take it out for inspection. The clean power harness supplies the current to run the engine. I have seen a lot of bizarre engine problems caused by this harness.
Thanks for all, after the exercise with the ECM, tomorrow I will pull the harness out. I don't want to overlook something now.
I run all the cables and conectors again everything good finally I decided to heat-up the ECM with a heat gun because as I changed the injectors the truck was inside. You won't believe the buzz went to normal - so I pulled the ECM and put it into the freezer for couple hours, now guess what - the slow buzz is back, heat on it and you can switch that on and off - WOW Now is time for new ECM and hopefully I'll be good. That was the first time I saw something like this.