CANT Figure this out...Fuel Injector Fuse keeps blowing when ignition is turned

[DarkGreenQ45]

My car is a 1997 Q45 with the 4.1L and was running fine, until yesterday i cranked it up and all it did was turn over, and over and over. The engine will not fire up, so I checked all the fuses and the 15amp fuel injector fuse was blown, so I replaced it and cranked it up again and the exact same thing happens, the same fuse is blown again. Can anyone help me diagnose this? Any help would be appreciated.

[Infinitiguy19]

Well I don't know if you are suffering from bad injectors such as us with our 1990-1996 Q45.

But if there is a way to OHM or test the injectors please do so and report back the results.

How did the car run before this happened?

Have you done anything to the fuel system?

What about the rest of the car what kind of maintace have you done?

Go here to see the service manual for you Q45: http://Nicoclub.com/FSM

If all else fails then take it to the proffesionals such as T3 or the dealer (If you seek the Dealer route see to it that only the Senior Infiniti Tech only works on your car).

Good Luck and Happy New Year

[qsiguy]

There should be an injector harness you can unplug to determine if it's in the injectors or the harness. If it doesn't blow with the injector harness unplugged, you'll then need to ohm the injectors and figure out which one is shorted. If it's in the car it could be much more time consuming to track down.

Any recent work been done to the vehicle? Alterations? Oil change, etc?

[Drake57]

Most if not all fuel injectors in gasoline powered automotive applications have one side of the injectors tied to a constant 12 volt supply when the ignition is turned on, and the ECU momentarily grounds the other side when a fuel pulse is needed, so if the fuse blows each time key is turned on, you have a hard short to ground either in the harness or a fuel injector itself.

It should be pretty easy to find with an ohm meter - just check the resistance between the harness and ground, or between injector and ground. That the harness will disconnect should make it easy to isolate components to find your short. I don't know about the 97s but the earlier series (90 - 94?), the injector coils are "high impedance" - about 12 ohms pin to pin. You should read infinite resistance to ground (no conductance) when disconnected from harness.

A schematic and wiring diagram would be helpful, no surprise there.

If you are not up on basic electronics, google resistance, and ohm meter.

I don't mean to be too painfully detailed, but I do not know your background/experience level.

Have fun with it, Drake.

[DarkGreenQ45]

Well I believe I'm going to take it to the Infiniti dealer or import shop. Since I can get the car to duplicate the blown fuse everytime, does that mean the technician can track down the problem relatively easy?

[maxnix]

Or you should with a DVM.

[elwesso]

Well I believe I'm going to take it to the Infiniti dealer or import shop. Since I can get the car to duplicate the blown fuse everytime, does that mean the technician can track down the problem relatively easy?

Try and do what the above poster said and unplug the injector harness and see what it does. Then it will be easy to determine what the problem is.

Take your pick, but this problem if you take it to the dealer is going to be expensive to fix. Theyre gonna charge you a bunch to find it and then probably replace a bunch of crap that doesnt need replacing. Dealerships like to replace parts, not find problems! Im confident if you're willing to spend some time with it we can fix it for basically no money, or at least track the problem down. Its a much better idea to have a pretty good idea on whta needs to get done before you take it to a shop; thats when they start raping you (when you say FIX MY CAR).

[elwesso]

Briefly looking at the FSM you're looking to unplug engine subharness 1

Look at page EL 434... You're looking for connector F22 and F26

This is kinda convenient, on early Q all injectors are on the same connector, on your car F22/F101 controls the odd cylinders (1,3,5,7) , and F26/F106 controls the even cylinders (2,4,6,8) and the engine coolant temp sensor.

unplug those one at a time and see which one causes the fuse to blow. My guess if the fuse is blown what you could do is unplug the battery and check continuity/resistance on that fuse and see which one causes the resistance to drop down to nothing.

[DarkGreenQ45]

Where exactly are these two harness connectors that I need to unplug (F22 and F26). They don't have labels on the connectors so I'm not too sure of what I'm looking at. Any pics would be helpful as well, thanks.

[maxnix]

Another way to discover if it is the coilpack or beyond (it might be in the connector wiring) is to disconnect the coilpacks then reconnect them on at a time until the fuse blows, replace the fuse and continue until they are all connected.

Anynoe not qualified or not careful work on the car lately.

[elwesso]

Where exactly are these two harness connectors that I need to unplug (F22 and F26). They don't have labels on the connectors so I'm not too sure of what I'm looking at. Any pics would be helpful as well, thanks.

I told you exactly where to find a diagram. Page EL-434 in the FSM. you have a FSM, right??????????????

[maxnix]

I told you exactly where to find a diagram. Page EL-434 in the FSM. you have a FSM, right??????????????

Ohm testing should reveal a shorted injector, right?

[DarkGreenQ45]

Ok, I disconnected both the F22 and the F26 connectors and turned the ignition and the 15amp fuel injector fuse still blew. What else could be routed into that fuse that would cause this to happen?

[maxnix]

Maybe you should check what is routed to that fuse (outside of OEM harness) then trace if nothing else.