EFI Fuse Issues

[NDBoost]

I need to know what would cause the EFI fuse to blow repeatedly. Ive got my ECU out and ive jiggled all the wires going to the ECU to see if that fixed it.

I looked up the TEWD online and it seems that the fuel and EGR VSV connectors T into the EFI fuse wire could this be something as well, because my connectors arent hooked up.

http://www.cygnusx1.net/supra/library/Wiring/pages/Page_047.html
15a EFI is in the grey box at the upper left hand side.

I also turned the IGNITION OFF put a new fuse in and turned it to the on position and it blew again.

thanks for the help

 

[figgie]

EFi fuse blowing means a short somewhere in that circuit. The fun stuff about troubleshooting old wiring

it can be anywhere in the harness. BUt i would do a visual inspection to see if there are any bare wires

 

[NDBoost]

alright, thanks for the help. i guess this is one of those bitchy fuses that everyone hopes doesnt short eh?

Ill go borrow a short finder from a local supra owner and get down to it!

 

[figgie]

ND

be aware that particular fuse is the one that feeds the ECU.

I would disconnect the ECU and see if it continues to blow the fuse. If it doesn't there is your culprit

 

[jmcboost]

ND

be aware that particular fuse is the one that feeds the ECU.

I would disconnect the ECU and see if it continues to blow the fuse. If it doesn't there is your culprit

I agree. Also, if any aftermarket device is connected to the ECU or harness, check that also.

 

[jetjock]

ND

be aware that particular fuse is the one that feeds the ECU.

I would disconnect the ECU and see if it continues to blow the fuse. If it doesn't there is your culprit

Yes, excellent advice in this case and a good tip in general. Disconnecting a circuit's loads is a good way to find shorts and separates the problem into either bad loads or bad wiring. Here's another little trick: take a 12 volt lamp (any lamp, an 1156 brake light will do) and place it across the fuse holder.

Get a socket or solder two wires to the lamp then put it in place of the fuse. You can solder the lamp's wires to an old fuse if needed. Since there is a short the light will be on full bright. When you find the short and clear it the light will either go out or dim quite a bit. This technique saves you from burning through a bunch of fuses and since the lamp acts to limits the current it prevents anything else from burning up.

 

[NDBoost]

Yes, excellent advice in this case and a good tip in general. Disconnecting a circuit's loads is a good way to find shorts and separates the problem into either bad loads or bad wiring. Here's another little trick: take a 12 volt lamp (any lamp, an 1156 brake light will do) and place it across the fuse holder.

Get a socket or solder two wires to the lamp then put it in place of the fuse. You can solder the lamp's wires to an old fuse if needed. Since there is a short the light will be on full bright. When you find the short and clear it the light will either go out or dim quite a bit. This technique saves you from burning through a bunch of fuses and since the lamp acts to limits the current it prevents anything else from burning up.

very good advice, but i believe the culprit was the o2 sensor wires were shorted together due to exhaust heat. The shielding was removed from it, and although my ignition switch is torn apart now i attempted to start the car and the fuse didnt blow. So i think that was my issue, ill piece it all back together tonight and see if thats what it was. For now ive gotta wash this 240sx i just bought as a DD

 

[jetjock]

Yep, a quick analysis of the schematic shows the O2 sensor heater is powered through the EFI fuse so that's your likely culprit. A short of the sensor input itself wouldn't blow the fuse but a short on the heater wiring certainly would.

 

[dbsupra90]

also check the wiring around the egr. they tend to melt w/ the heat.

 

[NDBoost]

Yep, a quick analysis of the schematic shows the O2 sensor heater is powered through the EFI fuse so that's your likely culprit. A short of the sensor input itself wouldn't blow the fuse but a short on the heater wiring certainly would.

bingo:biglaugh: :naughty: the exhaust from open DP and the 60-1 turbo i just threw on melted the insulation off the wiring shorting them out which caused the EFI fuse to blow repeatedly.

I got lazy and decided to breakout the new 240sx DD, ill piece the fuse box and interior back together later this week when i have time. For now im stuck to the beater 240sx w/ no stereo

Thanks everyone for helping with my questions.

 

[jetjock]

Good deal. You know that fiberglass silicone sheathing on the stock O2 wiring? You can but that stuff in many sizes from McMaster-Carr. Nothing works as well for protecting wiring from high heat sources and makes it pretty much last forever. For big bundles use aeroquip firesleeve. It's the same stuff used to protect hoses but works great for large harnesses too.