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Ignition Fuse Blowing on Dyno

2K views 10 replies 6 participants last post by  Rizzydee 
#1 ·
Hey Guys,

Question for the masses: Finally took my car to get Dyno'ed. The tuner said when it "torques back real hard" the car dies and it's always the 10A ignition Fuse that's popped. You can drive the car fine on the streets, but anytime the car is under a high load the it pops the fuse. If it were a grounding issue I would think it would happen all the time, but since it's only under high torque does anyone else know what it might be? Thanks in advance for suggestions.
 
#3 ·
I don't have any idea. I'll throw this out though, the amount of energy needed for a spark to jump a gap goes up when the pressure goes up meaning the coil has to put out a higher voltage to the plugs. Perhaps when on the dyno the cylinder pressures got high to the point that the coils are drawing too much current and causing the fuse to blow. In over 40 years of wrenching on cars I've never seen this happen, but it is possible I guess. Personally, I'd do a good resistance check on all the coils to see if they are in spec and near uniform with each other. Check the wiring in the system for good connections, especially the grounds (95% of strange wiring problems are caused by bad grounds).
It's possible you're seeing this only on a dyno because the cylinder pressures are getting higher there, or it might be because with no movement through the air the engine bay is getting more heat soaked than when you're driving down the road. Keep us updated on what you find.
Rob
 
#4 ·
Gents, thanks for the suggestions. I'm currently using the factory engine ground location for a few different components: surge tank fuel pump, A2W IC fan, a circuit panel I added for my cabin gauges. Is it possible to overload a grounding point?
 
#10 · (Edited)
Fixed the ground issue. Ended up that the cable bunch going into my engine bay fuse box had come loose over the years and as the engine moved shifting through the gears on the dyno they were pulling slightly on the pins and grounding the ignition Fuse out. We re-pinned and extended the harness and there have been no more issues. Ended up with 272hp and torque was 186 on the Dyno.

Thanks to everyone for the input and advice. There are some big minds on this forum!
 
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