15amp EFI Fuse keeps blowing (1 Viewer)

[reykool]

Have read several threads of similar symptoms, but none where efi fuse keeps blowing.

Background... My rig is a 97 LX450. Was driving home from camping trip and died without warning. Was running good up til it quit running. Did what I could at 11pm with whatever car knowledge I had. Thinking back to that night I remember lifting the MAF connector wire and water spilling out of the protective sheathing (which worried me a bit that night). Called AAA and got home safe and sound by 2am that night.

Anyway... The engine cranks but no start, no CEL and here's what I have tried to date...

Put in new fusible link (original was butchered by PO. wonder how it ran to begin with?)
Put in aftermarket EFI Main Relay (ordered oem just in case & should have in cpl days)
Wipers, headlights, radio, etc. work. (read threads that said to check these items)
Checked 50A AM1 fuse for continuity and was okay.
Checked 30A FL Power fuse at dash for continuity and was okay.

Still cranks and no start no CEL.
Notice clicking when turning on key. Think clicking is coming from EFI Relay.

15 amp EFI fuse blows every time I turn the key (have not seen any other threads that mention this symptom).

Almost forgot, there is a 30A fuse that is blown under the dash. There are 3-30A fuses on three separate wires under the dash. The blown fuse is on a red wire (power I assume?) I trust no work that's been done by PO and don't know what's original and what's not, so not sure what these three wires and fuses are.

Your suggestions are greatly appreciated! Need to get running asap because I am moving in 5 weeks.

 

[greentruck]

That MAF wiring is fragile. Not sure you're supposed to be able to do that. Could that be it? The water being inside could just be condensation, but could be an issue aside from the wiring.

 

[Rifleman]

In the factory service manual, there will be a point, by point, trouble shooting test you can use to eliminate the MAF as your problem. I'd start there, seeing as you said that water came pouring out of the MAF connector. If that's not your cause, then it's time to start looking at the electrical manual to find out what other equipment is on the circuit that keeps popping. Then you can eliminate each piece of equipment to see what item on that circuit causes the fuse to pop, then trouble shoot that item. Since you said in your post that the 15 amp fuse pops just as soon as you turn the key, that sounds like a dead short to ground to me.

 

[TrickyT]

Lots of stuff gets power when you turn the ignition switch to "on". As a first step in isolating where the problem is, try removing the EFI Main Relay (it's in relay block #2, in the engine compartment) and then seeing if the EFI fuse still blows. I strongly suspect it won't, which means there's only a few circuits you need to check. First look under the vehicle at the wiring that goes to the oxygen sensors. The heaters for the O2 sensor are powered through the EFI main relay and several people have had that wiring fray and short out to chassis. And as other have mentions, power to the MAF comes through the EFI main relay, so you should inspect the wiring going to the MAF and if that looks good you could unplug the MAF connector and, after putting the EFI relay back in, see if the fuse still blows with the MAF disconnected. This type of "fault isolation" will help you focus in on the bad component or wiring.

If the EFI fuse still blows with the EFI relay removed then you'll need to look at different stuff than those things I pointed you at above. Post up what you find and we'll give you more ideas on what to check.

Edit: Sorry, forgot to include the fuel pump as another circuit powered through the EFI main relay. This is another area others have problems, especially with a short circuit inside the fuel tank. If the O2 sensor wiring and MAF wiring is okay, then you could put the EFI main relay back and instead disconnect the fuel pump relay (it's in the engine compartment, bolted to the DS fender). Then if the fuse doesn't blow you know the short is in the fuel pump circuit.

 

[reykool]

Will try the suggestions above in the next few days and get back with what I find.

 

[Hinterland]

Have read several threads of similar symptoms, but none where efi fuse keeps blowing.

Background... My rig is a 97 LX450. Was driving home from camping trip and died without warning. Was running good up til it quit running. Did what I could at 11pm with whatever car knowledge I had. Thinking back to that night I remember lifting the MAF connector wire and water spilling out of the protective sheathing (which worried me a bit that night). Called AAA and got home safe and sound by 2am that night.

Anyway... The engine cranks but no start, no CEL and here's what I have tried to date...

Put in new fusible link (original was butchered by PO. wonder how it ran to begin with?)
Put in aftermarket EFI Main Relay (ordered oem just in case & should have in cpl days)
Wipers, headlights, radio, etc. work. (read threads that said to check these items)
Checked 50A AM1 fuse for continuity and was okay.
Checked 30A FL Power fuse at dash for continuity and was okay.

Still cranks and no start no CEL.
Notice clicking when turning on key. Think clicking is coming from EFI Relay.

15 amp EFI fuse blows every time I turn the key (have not seen any other threads that mention this symptom).

Almost forgot, there is a 30A fuse that is blown under the dash. There are 3-30A fuses on three separate wires under the dash. The blown fuse is on a red wire (power I assume?) I trust no work that's been done by PO and don't know what's original and what's not, so not sure what these three wires and fuses are.

Your suggestions are greatly appreciated! Need to get running asap because I am moving in 5 weeks.

One of our friends had this start happening while out on the rubicon. He went through a ton of fuses. Turns out it was a problem with the harness right behind the motor where it comes close to the head. He was able to fix by adding protective insulation. Might start there.

 

[Hornd]

2 quick things to check to rule out (independant of this issue) is

• ECU Harness behind Glove Box

• Is Harness Wrapped where it passes EGR Pipe on RH back of Motor? Unwrap and check and replace with new wrapping cost is $20 (just bought new wrap)

I keep blowing EFI fuses

 

[98 SNAKE EATER]

After I installed a new Bosal exhaust, I had the same issue.

Turns out I fudged one if the the O2 sensors while removing it from the rusty factory exhaust and shorted it out

After unplugging the O2, she started right up without blowing the fuse, so I put in an order for a replacement the next day.

Might be worth a shot to just try unplugging the to rule them out.

 

[reykool]

Hey guys it was the O2 Sensor shorting out on the exhaust. I knew that's what it was once I scooted under, grabbed the sensor line and felt it lightly stuck to the exhaust. Unplugged sensor, put new 15A EFI Fuse, turned the key and had the CEL. Turned over and almost started, then battery died . Charging it now.

So couple questions...
I've read other posts that suggest changing oil because the possibility of fuel draining down in oil pan from turning over repeatedly. Is this a legit concern? If so do I change oil and filter?

Also, the wires didn't look bad on the O2 sensor. Looks like one wire is barely bare, very hard to see the bare wire at all. Do you all suggest new sensor or try and repair? If new one, is the sensor closest to the engine the "upstream" sensor?

Thanks guys for your input!!!

 

[ppc]

If the wire itself is intact and just the insulation is damaged then wrap it carefullly with good quality electrical tape, cover the complete harness in split loom and secure the harness with some zip ties so it doesn't happen again. I wouldn't be concerned about changing the oil unless it is due anyway.

 

[TrickyT]

Glad you found the problem. Do what @ppc says and you should be good to go.

 

[reykool]

Awesome to have a place like this to come for help. And in this case, that only cost me around $50 to fix with extra parts to spare.

Thanks again guys!

 

[alia176]

Good job dude! These types of threads only add to the knowledgebase on this board.

 

[reykool]

Hey guys just thought I'd type an update.

There was only one wire on the O2 sensor that had the insulation damaged. It was one of the black ground(?) wires. The physical wire was fully in tact, so I put electrical tape and new split loom just like @ppc suggested, plugged sensor back in, connected the fully charged battery and started right up. She actually seems to be running better than before, no joke!

I would have never guessed it would be something "seemingly" so minor.

Also as a preventative measure, I bought some spark plug wire insulation (the cloth kind) from NAPA and 1-1/4" piece of split loom and covered the part of the wiring harness at the back of the engine. I figured spending the $12 now would save me a lot of time and stress in the future.

Thanks a million!

 

[blkprj80]

Black with a red stripe is ignition. Goes lotsa places.
Glad you nailed it!

 

[ZackR]

Just had mine die without warning while driving on a local forest service road (bumpy but nothing crazy). Checked the EFI fuse and it was blown, replaced it and it blew again when attempting to restart the engine. Checked the forum on my phone and found this thread, proceeded to disconnect the O2 sensor from the harness, replaced the fuse again and it fired right up (CEL is now on for obvious reasons).

Things that came to mind:

1. I should probably start carrying a multimeter in my toolkit
2. I should figure out a plan of who to call if I'm actually broken down on the trails in my area.

Next step is to troubleshoot the wiring and O2 sensor. As it sits the O2 sensors are 13 years and 140k miles old so its probably due anyways.