RTH Needed: Keeps blowing EFI fuse

[LiftedLexus]

Hey Guys my truck wont start. It is turning over but will not spark. I started checking fuses and the EFI fuse under the hood was blown. I have put a new 15A in twice and it has blown again both times. I know it is doing its job and blowing like it is supposed to but I need some advice on what you all think is making the fuse blow???
Fuseable link? Ground or wiring issues?
Thanks in advanced.

 

[JeepinPete]

Power to the heater in the O2 sensor is supplied by that circuit. Quite possible the O2 wires have been damaged by the front driveshaft of exhaust.

 

[richardlillard1]

When you turn the key to the on position, is the check engine light on?

 

[LiftedLexus]

When you turn the key to the on position, is the check engine light on?

The check engine light is NOT on.

 

[drowssap]

Check wires by your egr

 

[richardlillard1]

The check engine light is NOT on.

Look at your fusible links. Probably fxxxered one of them up.

 

[GeoRoss]

Years ago someone had a similar problem. It was short.

EFI Fuse Blowing -- Ideas?

Not saying yours is the same short, but that is the direction I would look.

 

[LiftedLexus]

Years ago someone had a similar problem. It was short.

EFI Fuse Blowing -- Ideas?

Not saying yours is the same short, but that is the direction I would look.

So what solved the problem was a new fuel pump?

 

[GeoRoss]

I also think there were some chaffed wires in the fuel sender that were shorting out the EFI circuit out. I may be misremembering or posted the wrong link. NorCalDoug had a couple of problems and posts about blowing the EFI circuit.

 

[LiftedLexus]

So I did some more trouble shooting and it looks like the EFI fuse blows when I turn the key to the on position. I do not have to attempt to start it for it to blow. I cant find any bad wiring anywhere. Does anyone else have any ideas?
Should I just order new fusible links and a fuel pump and replace them hoping it will take care of the problem?

 

[george_tlc]

Blowing the fuse means you have a short to ground. You need to get your meter out on resistance range and locate the short (from the 'output' of your blown EFI fuse) to ground.

Use the EWD to identify circuits on that EFI fuse signal and track down the short with the meter. With several feet of harness wiring you may be able to find your short location (or general area) by determining where the resistance is lower, i.e. on your lowest resistance range note the ohm reading as you probe between ground and the EFI wire (at different places along the wire).

Fusible links aren't shorting/blowing your fuse. You may need new fusible links, but that isn't your fuse blowing problem.

So, either spend time tracking down the short or throw money at random things... Given it appears a 100% fault condition I'd suggest spending the time to track it down while it isn't intermittent.

cheers,
george.

 

[GeoRoss]

It was a chaffed wire. I'm glad my memory isn't as bad as I thought.

EFI Fuse Blowing -- Ideas?

From this thread EFI Fuse Blowing -- Ideas?

This thread is about grounding out O2 sensor wiring Help! Stuck with a breakdown in southern Utah, 500 miles from home

Most likely you have a chaffed wire grounding out the EFI circuit as stated by George. Good luck.

 

[98 SNAKE EATER]

I had the same issue after I installed a new Bosal exhaust.

It would blow the fuse the second I turned the key.

Turns out I buggered up one if the original O2 sensors while trying to get them off the old rusty exhaust and shorted it out.

To go home that night, I just disconnected the O2 that was shorted and ordered a new one the next day.

 

[alia176]

So I did some more trouble shooting and it looks like the EFI fuse blows when I turn the key to the on position. I do not have to attempt to start it for it to blow. I cant find any bad wiring anywhere. Does anyone else have any ideas?
Should I just order new fusible links and a fuel pump and replace them hoping it will take care of the problem?

These types of threads are very educational for you as well as others. Please detail the steps you took and your results so that we can help you.

 

[lazy]

I would start by unplugging things on the EFI circuit. o2 sensors, I believe the MAF, could even check the diagnostic dongle-lower left pin, fuel pump under the rear driver's door, @ ecm, fuel pump resistor/relay, 3 port connector with 1 wire next to the behind battery box.

I don't have my ewd @ work, but can offer more when I get home....

 

[LiftedLexus]

Thank you very much for all of your responses. I have a experienced Toyota mechanic coming to my house next week to help me out. I will let him read this thread before he comes and update you with what we find. Please continue to post any good ideas or advice you have, I really appreciate all of the good info so far. Thank you!

 

[alia176]

Next week? I can't wait that long, start working on the suggestions above, chop chop!!!!

 

[Openroad98]

I had the same issue after I installed a new Bosal exhaust.

It would blow the fuse the second I turned the key.

Turns out I buggered up one if the original O2 sensors while trying to get them off the old rusty exhaust and shorted it out.

To go home that night, I just disconnected the O2 that was shorted and ordered a new one the next day.

Okay, thanks to Snake Eater for saving me a tow bill! I was on the way back from the airport with my wife, kids, & parents when my FJ80 died on the side of I-25. Did quick diag, no spark at distributor but cranks fine.

Found the 15A EFI fuse blown and swapped it with a 15A headlight fuse. Engine started and ran 5 seconds, then stalled! Felt the EFI relay was very hot, so I did a desperate shoulder-of-the-freeway search on MUD. Found this thread and suddenly remembered I had just pulled all the exhaust pipes doing my engine swap last month.

Slid underneath the vehicle and inspected all my wiring harnesses, found I had routed the driver side oxygen sensor harness over the front driveshaft and it had made contact (pretty clear from the shiny ring around the shaft), rubbed through the wire loomand the insulation on two of the wires creating a dead short to the driveshaft (hence grounding the circuit). I unplugged the O2 sensor, swapped my last headlight fuse in and drove to Napa where I picked up zip ties, electrical tape, and fuses.

Pulled up onto a tall curb and blocked the tires, then did a temporary repair until I get home tonite. Very glad to have this resource... Thanks guys!

 

[LiftedLexus]

I got it fixed! It turned out to be wiring from the supercharger that was not properly zip tied where it was supposed to be. It fell down on the manifold and melted causing the short.