raidinmd

hey everyone 1990 pickup v6 manual trans, gotta small problem, I took my truck to the hills for the first time yesterday and when I engaged 4 wheel drive my truck died on the spot, thankfully I was close to the camp and got a lift form a nice stranger. came back with my friend and we looked at it and I was getting no spark, I replaced the coil pack and still no go. finally checked the fuses and turned out the EFI fuse (15A) was blown, replaced it and it fired right up, I also should note that 4 wheel was disengaged before putting in the new fuse, drove to camp and then we went out, tried to use 4 wheel again and it went to H4 and was going (thought I don't know if the 4 wheel light came on) and then went to 4 low and bam there went the fuse again. we kept replacing the fuse but it would blow when you cranked the engine, got it back to camp and disengaged 4 wheel and again, replaced fuse and she fires up. drove it all the way home in H2 no problem. also a small note the lights for the air controls had shut off since almost after i bought the truck (feb 2014) but came back on for a while and then off and back on for the ride home. i'm not experienced with wiring at all so any help would be appreciated.

wyoming9

iTrader: (1)

Your 100% sure it was the EFI fuse and not the Engine Fuse??

I don`t have the EWD for 90 so I can look ahead or back .

But if the switch is shorted that turns on the dash light(4x4) it will take out the Engine Fuse on the older style/

On the 92 it will take out the 10amp gauge fuse.

Being the age of the truck who knows what might be hooked to what.

rattlewagon

Check your o2 sensor wires. They hang right by the tranny/transfer and if they short out it could blow the efi fuse.

raidinmd

defiantly was the EFI fuse, I double checked.

i looked and I think this is the wire you are talking about, this part here looked a little burnt but it was zip tied back it looked like. it's just weird that it would short only when moving the shiftier to 4x4 mode. i'll inspect further when the ground isn't melting my skin, I have to run to the junk yard this week and pick up a new taillight anyway, might be able to pull some wires.

RAD4Runner

Quite possibly that wire. Check your schematic for color code or physically traces. On the 22RE, when back-up light switch or wiring to it shorts to ground, it takes out Engine fuse.
Might be different on your year-model.

The fuse names on out trucks do not really make sense, and Toyota wiring sucks in that it combines non-essential items (that even when defective will still allow truck to run, like back-up light and turn signals) with essential items (that when broken will prevent truck from running (i.e., ECU, alternator, etc) into one fuse Like the Engine fuse.

Another example is the "Charge" fuse. It does not enable charging, rather, it powers the "charge" error light. The "Engine" fuse enables (excitation) charging.
Like I had always said, back thenmToyota had much better mechanical engineers than electrical engineers.

RAD4Runner

If it's "slightly" burned, it is slightly bad. Replace it. But also trace it so you'll find the answer to your question why blow the fuse only in 4WD mode.

osv

what actuates the 4wd light? isn't it a wire plugged into the trans/transfer case?

maybe try unplugging it there, then see if the fuse blows.

RAD4Runner

Concur. And inspect the rest of the wiring while you're down there.
Related but not exactly same (this is on 22RE) is poor wire management to transmission or transfer case switch...

raidinmd

so I pulled that plug and won't ya know it doesn't blow the fuse anymore and will run in H4 and L4. I also found this open wire (black w/ white stripe) near the fuse box by the battery. I can't really figure from the wiring diagram what it is.

RAD4Runner

Cool! Then must be internal short in the 4WD switch. Try taking it out and inspecting to see if it's repairable (i.e., dirt/foreign matter that causes it to short).
If can't figure from wiring diagram, next best thing is to peel off harness cover and trace it physically.

raidinmd

so i took the truck to the shop for an issue unrelated to this but I also told the mech there about it too and he's gonna check it out as well as the oil leak that is going on. i'll have an update when i get more info.

raidinmd

got my truck back and he could not find anything that would cause the truck to blow the fuse, he ran it in 4x4 off and on on the lift for an hour and nothing blew and checks the siring all over, crazy, on a side note that black wire was for my A/C and now it is hooked up and blowing cold air which is nice here in my town since it's hot out here in central California. i drove it in H4 and L4 down my street again after getting it back and it went fine. no clue as to why its ok now.

raidinmd

wow so it did it again, tried running it in H4 and it went, then stopped and shifted into L4 and bam there went the fuse. I but a dollar that something is shorting at the shifter, i'm gonna take off the cover and inspect it this weekend

wyoming9

iTrader: (1)

Pretty easy to tell if the switch is shorted with your Meter.

Unless you have something else piggy backed onto the same circuit.

Or the fuse opening is unrelated and pure chance seems doubtful though.

Does this truck have any electrically controlled lockers that might be wired into this circuit as well .

Wired to engage when ever shifting into 4High or Low ??

raidinmd

they are automatic lockers and are controlled by the selector by the stick. i could not really answer how it works as I have no experience with this truck or wiring in general this is my first yota and I on'y bought it this feburary. I don't have a meter and I don't even know what one looks like or how to use one.

raidinmd

could badly wired speakers cause a problem? i unhooked a non working sub in the back seat before all this started. i'm still at a loss here. the mechanic couldn't find anything wrong with the wiring

wyoming9

iTrader: (1)

The only way the speakers could effect this is if the stereo is connected to the same circuit as the 4x4 switch.

If one of those lockers is on the way out and draws to much current it will open the fuse ??

Being a intermittent problem if it did not happen while at the shop pretty hard to find.

If you were close I would be glad to help.

raidinmd

I would welcome the help if you were near. but the lockers are not electric from what my mech told me, they run off a vacuum, its really weird it sometimes it blows the fuse and sometimes it does not.

raidinmd

update: still haven't found whats causing my problem, i had my truck at a different shop and they didn't know whats up either, they peeled back the o2 wires and found nothing wrong. idk whats going on or how to properly trace wires, i don't if it's related but i am having minor issues with other things like my oil pressure gauge would only work part of the time and my brand new starter wasn't working either all the time, i would need to tap it to get it to work, took it back and autozone tested it and it passed twice, put it back on and it is working now but idk if it will stay that way, feels like this truck is cursed and so am I for winding up with bad vehicles

wyoming9

iTrader: (1)

The fact your not able or don`t have a place to work on your truck make it difficult at best.

Sometimes it does take longer then others to get all the bugs worked out.