FI Relay Fuse Should be 16A, but....

[KidDingo]

So I was checking out things under the dash when I discovered a rather unconventional inline fuse arrangement in the wiring for the injector relays. Not only is the fuse 30A instead of the necessary 16A, but it's not even using a correct fuse holder.





The connectors were obviously burned, so I'm assuming that someone saw fit to replace the correct set up with the only 30A fuse they had available.

Question is, why 30A?

I have replaced the bodgy arrangement with a proper fuse holder and had it loaded with a 20A fuse. The car ran. Then stopped. Then wouldn't start. Checked the 20A fuse and found it was in perfect condition, so I loaded it with a 25A fuse, and it seems fine. Starts, runs, all is good.

But why does it not run with anything less than a 25A fuse when it's supposed to take a 16A fuse? The relays are all good and appear fine - no shorts or anything.

Anyone else come across this?

[spider2081]

Did you test the 20A fuse with an ohm meter? It is not too uncommon for a fuse that looks good to test bad.

If the PO connected the fuse in that manner (shown in photo) they may also have made other mods to the car. Maybe an alarm or some additional lighting circuit has been installed and is sharing that fuse. The Aux regulator also uses that fuse. You could unplug it and see if a known good 20A fuse works.

You mentioned the contacts at the 30A looked burnt did you remove t hem when installing the new inline fuse holder??

[KidDingo]

No, I was in a bit of a rush to get it done. Will definitely try a different 20A fuse today. Will replace the connectors and test with a multimeter.

I just don't understand why it needs to draw so much current. The PO was not mechanically inclined, and the owner before him was dedicated to keeping the car original, so I'm thinking this was done by a mechanic keen to slap in a quick bandaid solution without seeking out the real issue.

Will advise results.

[aj81spider]

My two cents:

I'd be a little concerned about a 30 amp fuse. Depending on whether the wire is in a bundle, what the temperature rating of the insulation is, and whose tables you are using you are either right at or slightly over the capacity of 12 AWG wire, and well over the capacity of 14 AWG wire at 30 amps. You might find that you've melted your wiring harness or started a fire if you were pulling that kind of current. Almost certainly you'll destroy the relay.

Fiat made it 16A for a reason. I'd find out why that doesn't work and fix it... and I'd change back to a real fuse holder.

[KidDingo]

Yeah, that's why I need to work this out. It's definitely a fire hazard.

Mind you, it's been that way since I bought it over two years ago, and (knock on wood) no problems so far.

Have already installed correct fuse holder which is now housing the 25A fuse.

[76was124]

Checked the 20A fuse and found it was in perfect condition, so I loaded it with a 25A fuse, and it seems fine. Starts, runs, all is good.

But why does it not run with anything less than a 25A fuse when it's supposed to take a 16A fuse? The relays are all good and appear fine - no shorts or anything.

Just to add a little clarification, the size of a fuse won't cause a car not to run unless it is blown.

[KidDingo]

I know. But it wasn't blown. But the engine fired up as good as gold after changing to a 25A fuse.

It's baffling.

[76was124]

I know. But it wasn't blown. But the engine fired up as good as gold after changing to a 25A fuse.

It's baffling.

Either coincidence, or something intermittent with the makeshift fuse holder/wiring.