Like the title say, something odd is happening with this thing and I am scratching my head.

Setup:

5.3 LS with 24 tooth reluctor and T70 turbo
MS2 running Extra code V3.2.5
Relay Board
Home built wiring harness
Bosch 044 fuel pump (I think this is my culprit but not sure why it is doing what it is doing)


Here is what happens. I have the main switched feed running through an inline fuse holder with a 10A fuse, I originally had a 25A as that was all I had to get going, but that actually ended up melting before it blew it got so hot!

The car starts and runs fine, idles good, even smokes the tires! But for whatever reason while the engine is running the main relay gets super hot and will eventually blow the inline 10A fuse. I can turn the car on and not start it and it will sit in the driveway all day without blowing the fuse. This leads me to believe that possibly the fuel pump is causing the problem. However, the fuel pump relay never gets hot! It will get warm to the touch but never hot. The fuel pump has a 20A fuse feeding it and that has never blown.

I was under the impression that you really only needed maybe a 3 to 5 amp power source for the switched feed to the MS. Why the heck is this thing drawing so much current through the main relay when the engine is running?

I suppose I could wire up another dedicated relay for the fuel pump but that defeats the purpose of the relay board, and I am not sure that is really what is causing the problem.

Could it be an ignition issue maybe? The car runs awesome and pulls like a beast, but this fuse blowing thing is driving me nuts.

Any help is appreciated.

 

With the key on and engine off the coils aren't charging or firing, correct? There should be a huge difference in current from that state to running. I wonder if it's a coil going bad or something in that harness shorting out.

 

First thing I thought was a short in the injector or coil wiring.

Is this something that just started happening, or is this a shakedown on a fresh build?

 

Ok I am officially a dumb shit.

I went out and tore into this thing again for the 5th time.

Suddenly I found the problem. While looking at the connections from my terminal strip to the relay board I noticed that switched terminal had a piece of 16 gauge running to it and the battery side had a piece of 22 gauge running to it.

Somehow I had wired those two leads completely backwards. It was so glaring I don't know how I could have done it, or missed it after the fact.

Yes, I was running a Bosch 044 on a length of 22 gauge wire with a 10A fuse. No wonder the wiring was getting so hot and melting the fuse. I feel like an idiot. Upon rewiring, the fuel pump sounds MUCH healthier and while both the main relay and fuel pump relay still get very warm to the touch there was no fuse blowing at all while I was running it in the yard for the last hour.

The inline fuse holder and associated wiring also stay completely cool to the touch, imagine that.

I am really not sure how I managed to screw the easiest bit of wiring on the car up, but I did it!

So tomorrow I will head back out on the road and see if things are a bit better.

Long story short, always start with the basics when you troubleshoot.

 

Good to hear. Would like a good rolling burnout vid.