This 2001 Doge Durango with a 4.7 liter V8 was sent to me from another shop. The truck had come to them with a head gasket leak, which they had already fixed. A new problem had developed though in that the ASD relay fuse in the under hood fuse box would blow sometimes and the engine did not run great. The other shop said that they had checked all of their work and could find no place where they might have shorted out any wiring. To do my job I of course had to go back through every thing that might have been checked. I started by removing the blown 30 amp ASD relay fuse.
I installed a 30 amp circuit breaker in its place and tested the amp load on the circuit by hooking the inductive amp clamp from my tester around one of the jumper wires. I turned the key on and nothing unusual. I cranked the engine and the engine fired up and ran okay but not real good. I monitored amp draw while running and everything seemed okay until the idle speed came down below 1500 rpms. The amps jumped up to about 25 amps, so I gave it a little gas to get the rpms up again and the amps started spiking to 60 + amps. They came back down after getting over 2000 rpms. This was about the strangest thing I had ever seen.
I shut the engine off and checked all of the basic wiring around the injectors and coils. All seemed okay. I checked the diagrams and found that the fuse shown below would eliminate the O2 sensor heaters so I removed it. I found an ignition capacitor on the passenger inner fender and disconnected it. I retested and the same thing happened again.
What in the world could it be? I decided to start checking the coils for amperage draw individually. Hopefully I would find a shorted coil. I removed the tape and separated the wires.
I hooked the inductive amp clamp around one of the wires. It did not matter which one.
I cranked the engine and monitored the amperage draw.
Well I’ll be, 8 amps times 8 cylinders equals 64 amps. That definitely could blow the fuse and could be the explanation of the intermittent high amp draw. Most of the cylinders could be firing at the same time, although they should not be unless the base timing is off. How could the base timing be off there is no distributor and none of the sensors are adjustable? Son of a gun, the timing chains could be off a tooth or two and that could explain the dwell overlap. Yep, engine is an overhead cam design and the chains had to be taken loose to change the head gaskets that were leaking. I have never seen a mechanical adjustment cause an electrical overload on a vehicle before. Now I have!
I called the other shop and broke the bad news to them. They picked the truck up and reset the timing chains and all it well.
This info was a life saver, thanks Sparky!
Below is my post from another forum which has details that might help others visiting this page, so I thought I’d include it.
Ok, I’ve got it sorted out so I figured I’d share my findings. First off a big thanks to Tesco2 for posting his amperage findings and results in the prior posts. Also, a big thanks to the_dmill for posting the Sparky’s article link. Findings: Secondary chains were off by one tooth each.
Summary:
I took the heads off for some work. Installed new guides but left chains, tensioners, and sprockets alone. When I got it back together the engine ran rough, tons of white smoke, misfire, and wanting to stall. Depressing the throttle (raising the rpms) to keep the engine running (under the impression that the computer may just be undergoing its “relearning stalls”) resulted in the ASD fuse blowing (and corresponding trouble code). A review of the wiring diagrams showed that the only unfused peripherals able (by themselves) to blow the 30 amp fuse, were the coils and capacitors. Tested the coils, capacitors, and harness (for shorts); everything was fine. Pulled hair out.
I read Tesco2’s post and knew that a defective sprocket couldn’t be my problem because I reused my sprockets. This knowledge in conjunction with the article at Sparky’s (https://sparkys-answers.com/2009/04/2001-dodge-durango-asd-relay-fuse-blows.html) allowed me to zero-in on the problem: my timing chains were either setup wrong, or they jumped on initial startup.
I removed the valve covers and cranked the engine to TDC. The alignment marks hadn’t changed; everything was in the same it had been during setup, with the cam marks at approximately the 12:30 position. I was aware when I set them up, that the “V8” stamps were supposed to be at the 12:00 (not 12:30) position and the fact that they weren’t caught my eye. However, I elected to trust the marks on the chains and sprockets.
It was clear that the secondary (camshaft) chains hadn’t jumped, and realistically they were the only ones that could have, given that the primary (crankshaft) chain didn’t have a tensioner that relied on oil pressure. I assumed that the primary chain timing was still set correctly, although in retrospect perhaps I shouldn’t have been quite so sure given that it was set according to its marks and here I was doubting those same marks on the secondary chains.
I used my home-brew dodge specialty wedge tool to hold the secondary chains while I rotated them both back a tooth. It is relevant to note that they were not at exactly the 12:00 position as I would have preferred, instead it was more like 11:45-11:50ish. But considering they weren’t new chains and might have been somewhat stretched, that seemed to make sense. I turned the crankshaft carefully two full times, listening/feeling for any indication of piston-to-valve contact; there was none. Put it back together and reassured myself that what I had just done wasn’t going to ruin my engine; knowing full well interference-engine timing marks were not to be trifled with.
It started right up, ran smooth, no smoke (after 15 minutes of running), no blowing fuses, no trouble codes, great power. Hope this helps someone.
It did not run well but I do not remember any coil codes.
Would this also cause the engine to stumble and stall as well as throw coil circuit codes?
Thanks for posting this info. I just encountered this same issue with a Jeep I did head gaskets on. I have done several of these Dodge 4.7 head gaskets befor and had no issue till now. This post saved me hours of work trying to figure out what was going on. Never thought timing could cause the ASD fuse to blow.
Thank,
Steven
Sparky, dig-it. Your A1 in my book. This is a great site, I will tell others. Thanks!!