please help

[chevy_338]

i know i have not been on this site for some time but i do look in here and there but i am having a very big problem and i was hoping that someone could help me as i know its not a K-5 or a Chevy but i got it cheep and i could not see her go where she was going to go

so i have working on my 95 GMC Yukon so i can get it ready for winter as my Saturn is not safe in the snow. so here is my problem and im going to start from the beginning the motor that was in it had spun a bearing and had to come out so i ended up finding o a 91 motor same thing just a little different so i took every thing off the 95 one that was in it and put it all on the 91 and o yea the motor that was in it still ran i drove it 15 miles on the dad motor and pulled it out of the garage before i pulled it. so i the the motor out with no problems then got the other one ready to put in put the new one in no problems other then a locked up e-break when i was trying to push it back into the garage no big deal hit it with a hammer freed it and got it in as i was working by my self the trany took a little longer the it should of as i broke the clutch thing that goes into the master but that nothing got every thing hooked up was going to drop in the distributor so i hooked up the battery and i popped a fuse found the fuse that i popped and it was the ECM B fuse found anther one as as soon as i put it in it popped im like what the hell is going on to i unhooked the battery and started looking to see if there was a wire stuck in be tween the motor and trany nothing just like when i installed it so i just out of the blue i took off the 3 grounds on the 1 two wire 1 plug off the t-stat and the 2 two wire grounds off the intake both sets of ECM grounds and put in a new fuse in the ECM B spot and no popped fuse so just for the hell of it i took out my volt meeter and but the black lead to the battery and the positive to them grounds and bam 12 volts and i can not get rid of it been working on it for over a week now and it is still there have had many people over to look at it to see if i missed something and they can not find it


so here is some other things its doing with key off i have dash lights on cant remember what ones right now but i can find out if need be it only takes me little time to hook up the battery

other things i have tried i have unhooked every thing from the motor hooked up the battery and that same 12 volts is still there then i went a little farther unhooked every connector i could find and it is still there so then i pluged every thing back in unplugged the ECM it self gone then i key it up and its there that same 12 volts im like what the f*ck

so i thought i was back feeding though something well there is only one this still to try so i pulled every fuse all but the ecm one and its still there


PLEASE HELP

and sorry about the typing not the best speller or the best using ....
and here is some pic of her and her name is short circuit

 

[Russell]

Nice Yukon!

The ECMB fuse is used to power only two things including the PCM and the fuel pump. I've attached the wiring diagram for you to have a look at.

As you can see, the power comes from the ECMB fuse and splits off at a splice in the engine compartment. It looks like there is only one orange wire going to the PCM, but there is actually two. One goes to pin C3 and one goes to pin C1.

There is another orange wire that runs to the oil pressure switch at the back of the intake. It is used as a backup to the fuel pump relay and closes when 3 PSI of oil pressure is built in the engine. This switch and it's related wiring is a common culprit of blown ECMB fuses as the wiring can be pinched in the bellhousing (as you checked for) or can have the insulation cooked and broken off by the exhaust manifold nearby and be shorting against the block, head or valve cover.

The 4th orange wire from that splice runs to the fuel pump relay up on the firewall.

From the pressure switch and the fuel pump relay is a grey wire that splices together and runs back to your fuel pump in the tank.

All that said, having found 12V on your grounds when they are disconnected does not indicate a dead short in the circuit. Taking the ground off the block and holding it out in the air will make that ground wire appear to be positive in reference to the grounded out block and should read battery voltage if any components are activated and grounded through that connection.

Your next step should be to reconnect the grounds and disconnect the oil pressure switch at the back of the intake instead. Inspect it's wiring closely (take the loom off and look at the wires on their way up to the main harness loom) to look for failed insulation. With the pressure switch disconnected, try a new fuse and see if it blows. If it does, disconnect the fuel pump relay next and also inspect it's wiring back to the main harness. Check the fuse again.

If it still blows, then disconnect the PCM behind the fuse block and try again. If it still blows with all of the three devices disconnected, then you have a dead short between the fuse block and one of the devices. Take the loom off the main harness and carefully dig the orange wire out to find the broken insulation and to inspect the splice joint. If it does not blow after you pull out the wiring for a particular device, then the device it is connected to is suspect to have failed (unusual, but relays / switches can ground out internally)

Of course, I am assuming that the fuse blows immediately after putting a fuse in and not after turning the ignition on. If that was the case, you have a short in the grey fuel pump wire.

 

[bronc3buster842001]

Check the oil pressure switch.

 

[chevy_338]

well it says i can not view that pic you post but thank you anyways but i went out there again to night just got in and it was gone no problems what so ever so tomorrow night this truck will run if not it will be started of fire and rolled down a hill in to a lake and will sit there for ever