I keep blowing EFI fuses (1 Viewer)

[jesterb]

My wifes 94 FZJ80 died while she was running errands. I went to save the day and found that it had a blown EFI fuse. I replacewd the fuse and started the truck but it promptly died. I was able to start it again but it would only run if I was keeping the idle up a bit. I drove it about half way home when it died again. This time I thought it was best to pull it with my 62. It was running fine till today. I havent checked codes because I wasnt sure if it were the same codes as those of my 62. Any ideas?

 

[jesterb]

By the way, I'm Jes Harrington from Jackson,MS. Ive posted a few times on the 60/62 board but this is my first time with the 80 folks. I've met a few of yall at the LSLC ride in Katemcy. Glad to be here

 

[landtoy80]

Is the check engine light on?

 

[jesterb]

No CE light

 

[Junk]

Jes, I'll pm you with contact info for my buddy JH that had this issue with his 91. He ended up rebuilding some of the box and the connectors going into it. But yeah, for awhile he had a whole baggie of relays with him in case it happened again.

 

[Safado]

Probably a short somewhere...Hopefully this JH Junk is referring to will save you some time with the troubleshooting.

 

[ppc]

Others had had similar problems and the cause was the O2 sensors being grounded near the bellhousing of the transmission. Another culprit might be the main engine wiring harness shorting out as it either goes around the EGR valve or where the harness attaches to the ECU behind the glovebox.

 

[jesterb]

I'll check the O2 sensor. My exhaust did start rattling a few days ago. I also had the wiring harness replaced about a month ago. Thanks for all the help, I'll keep you posted.

 

[Beowulf]

I think Phil is on to it. The O2 sensor wire routing on the 94's has been known to be a problem.

-B-

 

[NorCalDoug]

My '94 had the same problem. Started right after I had my O2 sensors replaced. Blew out 3 EFI fuses before figuring out what the problem was...towed 3 times to the shop was not fun...now I carry extra fuses.

Here's a link to some info sent to me by Morgan Fletcher when I was going through the same problem -- seems that he had the same issues as well.
http://www.birfield.com/archives/html/80scool/2001-12/msg01034.html
http://www.birfield.com/~morgan/tech/2nd_O2_wires.html

HTH.

 

[jesterb]

It's fixed! I checked all O2 sensors and wiring. It was good. I checked wiring all around the EGR and ECU. Good there too. Then I started thinking (sometimes that is deadly), if it were a short, why would it be running so rough between blown fuses. I reached back to my younger days when everything had a carb on it. My EFI truck was running like a cold manual carb that needed to be choked. I decided that the EFI main relay was staying open. I installed a new relay and let the engine idle for about 15 minutes to let the ECU adjust. No more blown fuses,engine now idleing at 650 RPM.

 

[Beowulf]

>> My EFI truck was running like a cold manual carb that needed to be choked. I decided that the EFI main relay was staying open. <<

I'm not sure why A led you to B, but it was a great detective job and appears to have fixed the problem. Have you tested the EFI main relay you removed and confirmed it is bad?

-B-

 

[jesterb]

Yeah, it was bad. There was alot more detective work involved than just going from "manually carbed that needs to be choked to bad efi relay" but thats what got the wheels turning.

 

[GXO]

Jes, I'll pm you with contact info for my buddy JH that had this issue with his 91. He ended up rebuilding some of the box and the connectors going into it. But yeah, for awhile he had a whole baggie of relays with him in case it happened again.

Different issue Junk. I have a 91 and that animal is a defective design by Toyota. The wires in the EFI relay circuit (fuse to relay, relay to EB1 connector) in a 91 are too small a gauge and overheat the relay...POP!

Later models should not be seeing this issue.

 

[jesterb]

Another thing it fixed is my high idle. Before i changed the EFI relay, the truck was idleing at about 1500 to 1700 when cold. It would drop about 100 rpm for every 15 seconds or so of idle time. When I started the truck this morning it idled at 1050 cold with a/c on then dropped to 650 within 30 seconds. Everyone told me that FZJ's idle high. Maybe everone I talked to needed to change their main EFI relay.

 

[Beowulf]

>> Maybe everone I talked to needed to change their main EFI relay. <<

This is definitely worth doing a test the next time someone reports this issue to the forum.

-B-