EFI fuse blows...

[crisp]

Okay, this is post #2 for crisp!

...moving right along...

'89 MKIII Turbo

I have had an issue with the EFI fuse (15A) blowing. The car will START and RUN fine... but when I begin to DRIVE it... and LOAD the motor wherein BOOST begins to "spool"... the fuse will go. I "swap it" and limp home.

I have been "swapping parts" (due to my "hunting" for the issue cause) instead of POSITIVELY identifying the ROOT CAUSE for the past couple years. (been busy with the GROWING family... 4 little kids now!) Car has mainly sat, but perhaps someone has a similar experience?

Electronics: HKS EVC, VPC, F-CON, Nology on stock coil pack.

Will BOOST SIGNAL trip the EFI circuit that way??? ...or is the TP sensor suspect? (I bought one just in case awhile back, but they must have sourced the N/A unit... so I would need to swap for the right one if that's a suspect cause...) I also suspected the ISC valve, which I "rebuilt" once when the servo was sticking... several years ago... and just replaced the "CHECK VALVE" yesterday because the rubber diaphram was "warped" and not seating positively anymore when I inspected it...

Oh, yes... I DO have the TSRM... but have not been able to isolate the issue EVEN with the book... (I'm only a shadetree mechanic, at best... help!)

PS: The O2 sensor wires are NOT melted together or shorted... and I've traced just about everything I can "think" of... but I'd do it AGAIN upon suggestion!

Let's start there...

Thank you,

-crisp

 

[Ish]

I had this problem about a year ago and was helped out by Ti from Supraforums (Great guy). What he did was follow the EFI wire starting from the fuse box. He took off the intake manifold and we noticed that the wire was touching the manifold which melted the protective plastic and was grounding itself (touching metal) causing the EFI fuse to blow. You're probably gonna have the same problem, just follow the wire starting from the fuse box.

 

[crisp]

HOLY CRAP BATMAN!


After nearly half-a-decade... my chokuroku (straight-six) is ALIVE!


Thank you, gentlemen... for you have enlightened the NEWB once again!


The HARNESS securing CLIP was not AFFIXED to the metal PROTRUSION proximate NORTH of the EGR VALVE apparatus... resulting in a SETTLING of the HARNESS upon "said EGR valve... which can become RED HOT..." hence causing (initially) DELAYED failure... (tough to pinpoint the CHANGE POINT precisely...) AND tempermental "OCCASSIONALITY" of FAILURE (appearing to be related to BOOST... but more specifically to HEAT!)

So, YEAH... I RE-CLIPPED the UN-SECURED harness clip... (once I had observed the SLIGHT MELTED CHAR on the EGR valve just below...) and FELT the ROUGH casing carcass of SLIGHTLY MELTED and WIRE-GOUNDINGLY-COMPROMISED patch on the HIDDEN FROM VIEW backside of the harness...

...and VIOLA!


HECK, I'll bet the TORQUE when I tried to hit BOOST would TILT the motor BACK causing the CONTACT to be CATALYZED by BOTH HEAT and PRESSURE... (er... or would that be tilt FORWARD???)

hmmmmm.... learned a lesson on DAY ONE here at SM...


crisp is back!

Thank you,

-crisp

 

[Ish]

Glad to hear its working now. Now that I remember I think mine had the exact same problem. There's a small hanger for the harness and mine wasn't on there so was touching the egr. And wow half a decade?

 

[crisp]

Glad to hear its working now. Now that I remember I think mine had the exact same problem. There's a small hanger for the harness and mine wasn't on there so was touching the egr. And wow half a decade?

...it takes TIME to "spawn" four young offspring...


(and they TOOK TIME away from the Supra... kinda like a "FLUX CAPACITOR"... somewhere in there... is MISSING TIME!)


Fortunately... I just caught up to this moment, and it is NOW! (I feel like DR. FRANKENSTEIN!)


WAAAAAAHHHHH ha ha ha ha ha!


...ahem.... sorry. Got a little excited.


-crisp

 

[jdub]

Yep...had the same thing happen too. I got some heat shield tubing and encased the harness in that area

 

[3p141592654]

Those two clips that attach the loom to the intake manifold turn to dust after about 15 years. You can buy new ones from Toyota for $5 each.

p/n 82711-30070

When I bought mine there were 8 left in north america.

and you can also get the brown diag box engine wire clamp (special order from Japan only)

p/n 82710-24010

 

[crisp]

Those two clips that attach the loom to the intake manifold turn to dust after about 15 years. You can buy new ones from Toyota for $5 each.

p/n 82711-30070

When I bought mine there were 8 left in north america.

and you can also get the brown diag box engine wire clamp (special order from Japan only)

p/n 82710-24010

DAMN... the solution was EASY AS "PIE"... and I suffered for years.


(Thanks for the pn particulars...)


-crisp