Broken Down 1992 FJ80 3FE, HELP!

Joined
Jul 28, 2012
Messages
7
I've spent some days searching and troubleshooting and need some help with ideas for what could be wrong and how to check. I'm getting a bit desperate for something else to even check.

Rig Details

  • Owned for 3 years
  • 1992 FJ80
  • 3fe
  • Engine swap 30K miles ago (previous owner ran w/ out oil)
  • ~150K miles on engine and chassis
Previous to this latest issue replaced:
  • Radiator
  • Speedometer cable
  • Starter
Current Problem (please read the background at the end to understand the context):
  • Engine will crank but won't start
  • Doesn't seem to be any spark
  • No check engine light when key turned to on
  • Just the other night I noticed that most of the circuits work just fine, but there are a few dead circuits
  • Won't come on
    • Headlights
    • Blower motor
    • AC (light doesn't come on)
    • Dash lights
  • Works fine
    • Hazard lights
    • Marker lights
What I have tried:
  • The battery that was in the truck when it initially broke down was completely dead (leading me to believe that the alternator had failed) so I have charged the battery back up and it is strong as ever but the truck just cranks.
  • Went through every single fuse I could find and test for continuity - All of the fuses that I'm aware of are the under hood fuse box and the fuse box under the steering column. There is power to both fuse boxes.
  • There are a lot of mentions of fuesable links online, but I can't seem to find any of these "fuseable links"
  • http://www.sdsysdesign.com/tlc/images/Strife/3FE EFI Diag.pdf - Found this troubleshooting guide in other ih8mud threads and followed it.
    • 1. Check for +12 VDC on brass terminal screw in under hood fuse box. This terminal is located directly to the left of the main fuse and is a Phillips screw head.
      • There is + 12 VDC on the brass terminal screw
    • 2. If no +12 VDC in fuse box, then check fusible links off positive battery terminal. While the one in the picture is not stock, the links are going to the stock locations. 2 to the black plastic junction box and one to the connector.
    • 3. If +12 VDC in fuse box and no CEL, then suspect EFI relay/fuse and associated wiring and contacts. Many have said that the wire from the EFI fuse to the EFI relay is undersized and is the root cause of all these problems. I’m not sure about this. At 2500 RPM I measured 6.25 amps across the load side of the EFI relay contacts. I believe the cause of the problem is related to the heat of the manifold combined with poor crimps on the connectors in the fuse box. Over time these connectors can become corroded and cause issues.
      • I'm not really sure what to do with this step - I would like something more concise to look into.
    • 4. Check for +12 on pin 8 (B+) on the CHECK CONNECTOR mounted on the right side of the fire wall. If +12 on pin 8 and still no CEL, then EFI circuit OK and problem is with ECU or related wiring.
      • There is no +12 on pin 8 (B+)
    • Coil/Ignitor was out of spec according to guide, tried a new one and it of course didn't solve the problem (since the check engine light isn't coming on = the computer isn't coming on)
  • Have tried a few parts as noted on other threads:
    • New EFi relay
    • New coil/ignitor
My best guess at this point is that the alternator is dead (not sure how to check with it not running, guess I could remove it and take it to a shop, but I would like to figure out the other issue first) and that there is a wiring issue (maybe these 2 things are related?). My hope is that someone can point me to a common failure or knows these symptoms well enough to point me to some trouble shooting steps.

If you want to be even more confused, read the background of this issue. It almost seems to be 2 separate (but related?) issues that happened on consecutive days.

Background
So a few weeks ago I took my entire family (3 little kids and my wife) camping. We were dragging a tent trailer way up into the mountains. 3 hours from my house and about 45 minutes of pretty serious climbing (4 wheel low dragging a tent trailer up a mountain) the entire electrical system just blinked off.

There wasn't an obvious issue (fuse, loose battery, etc) so we setup camp right there by rolling the trainer off the side of the road and having a passer by pull the truck off the road. We were really luck to break down where we did.

I spent the evening troubleshooting the truck. I happened to have a jump start battery pack with me and I was able to start the truck with the jumper pack. The second I took the jumper battery off the engine would die. My assumption at this point was that I had a bad alternator and/or battery. So the next morning I got up and threw the trailer battery into the truck, jump started the truck engine w/ my jump pack and started to drive out. I was thrilled! (we had no cell service and it would have been a lot of work to get the truck and trailer out of there).

So, we get down off the mountain to the flat dirt road and it's hot and dusty, so I look at the voltage gauge and it looks ok (it's a bit above the 12V line) so I decide we can run the AC for a minute (against my better judgement). We rolled up all the windows and I cranked up the AC.

All was well and good for 10 minutes or so, but then the engine died. There were still dash lights, so this was a different failure from the previous evening. We coasted for about a mile and came to a stop and the truck hasn't run since (~3 weeks ago). I had a couple friends show up with a flat bed and haul us away...

So now the truck is sitting in my buddy's back yard (45 min from my house) and I go out there and work on it a few times a week.

My wife thinks that the truck is mad at me because we just bought a 2001 Sequoia... :)

Thanks in advance!
 
Joined
Jul 28, 2012
Messages
7
No check engine light when key turned to on.

I have followed the 3FE EFI troubleshooting guide & replaced the EFI relay (see below or original post).

As stated above:
  • http://www.sdsysdesign.com/tlc/images/Strife/3FE EFI Diag.pdf - Found this troubleshooting guide in other ih8mud threads and followed it.
    • 1. Check for +12 VDC on brass terminal screw in under hood fuse box. This terminal is located directly to the left of the main fuse and is a Phillips screw head.
      • There is + 12 VDC on the brass terminal screw
    • 2. If no +12 VDC in fuse box, then check fusible links off positive battery terminal. While the one in the picture is not stock, the links are going to the stock locations. 2 to the black plastic junction box and one to the connector.
    • 3. If +12 VDC in fuse box and no CEL, then suspect EFI relay/fuse and associated wiring and contacts. Many have said that the wire from the EFI fuse to the EFI relay is undersized and is the root cause of all these problems. I’m not sure about this. At 2500 RPM I measured 6.25 amps across the load side of the EFI relay contacts. I believe the cause of the problem is related to the heat of the manifold combined with poor crimps on the connectors in the fuse box. Over time these connectors can become corroded and cause issues.
      • I'm not really sure what to do with this step - I would like something more concise to look into.
    • 4. Check for +12 on pin 8 (B+) on the CHECK CONNECTOR mounted on the right side of the fire wall. If +12 on pin 8 and still no CEL, then EFI circuit OK and problem is with ECU or related wiring.
      • There is no +12 on pin 8 (B+)
    • Coil/Ignitor was out of spec according to guide, tried a new one and it of course didn't solve the problem (since the check engine light isn't coming on = the computer isn't coming on)
  • Have tried a few parts as noted on other threads:
    • New EFi relay
 
Joined
Aug 6, 2016
Messages
1,448
Location
Huntsville, AL
The fusible links should be right off the battery positive terminal, inside a little black box. With no CEL light up the ECU has no power and there's no point trying to crank it.
 

jonheld

 
Joined
Dec 8, 2006
Messages
7,994
Location
New Jersey
Well, if the CEL is off when the key is in the ON position before cranking the starter then this truck will not start. Don't bother trying.
This is telling you that the EFI circuit is not armed, so there is no spark or fuel right now.

If the 3 fusible links are good (IMO they should be changed whenever you change the battery and they cost $12) then you must suspect the EFI relay and EFI fuse. Verify that pin 2 of the relay socket has +12. Then try jumping pins 2-4 in the relay socket and see if the CEL illuminates.
You should also try disconnecting the AFM connector by lifting the metal spring clip on the connector housing. DO NOT REMOVE THE 2 PHILLIPS SCREWS...EVER.
With that disconnected see if the CEL illuminates.

Relay Block Fender.jpg
 
Joined
Jul 28, 2012
Messages
7
I agree - No CEL light, no start.

There is a plastic box on the positive wires right off the batteries, but the wires are just bolted together and there is power leaving the box. There are only 3 positive wires leaving the battery:
  • Alternator - it's definitely connected, can't imagine this matters for CEL to light up
  • Under hood fuse box - it's getting power (part of the EFI trouble shooting guide)
  • Starter - it cranks just fine
 
Joined
Jul 28, 2012
Messages
7
Well, if the CEL is off when the key is in the ON position before cranking the starter then this truck will not start. Don't bother trying.
This is telling you that the EFI circuit is not armed, so there is no spark or fuel right now.

If the 3 fusible links are good (IMO they should be changed whenever you change the battery and they cost $12) then you must suspect the EFI relay and EFI fuse. Verify that pin 2 of the relay socket has +12. Then try jumping pins 2-4 in the relay socket and see if the CEL illuminates.
You should also try disconnecting the AFM connector by lifting the metal spring clip on the connector housing. DO NOT REMOVE THE 2 PHILLIPS SCREWS...EVER.
With that disconnected see if the CEL illuminates.

View attachment 1317187
I think the fuseable links were just omitted (previous owner) - getting power to all 3 positive wires coming from the battery.
Tried a new EFI relay - haven't tried jumping, that's something to try.
We even disconnected the AFM (MAF?) and had no luck with that either.
 
Joined
Jul 28, 2012
Messages
7
I finally took the diagram that jonheld provided out to my truck (it's 30 minutes from my house) and it isn't identical to the picture and tests a little different - so I held off on jumpering 2-4 to see if the CEL (check engine light) would turn on.

The bump on the relay socket is oriented differently than pictured in jonheld's post:



Testing it I got the following readings:





I'm having trouble finding a diagram that accurately shows me which of the blades are 1-2-3-4
 
Joined
Apr 17, 2016
Messages
29
Location
arkansas
i'm certainly no master mechanic, but i have owned a 91 for about 10yrs.
years ago while mine was at the mechanic for something else it had no start issue, my mechanic tried to jump it off some way and burned up the ecu, had to buy another. the fusable link direct to the ecu to power it was burned out and they didn't know this beast complexities. long story short, get it to an expert to change ecu, and he replaced the fuseable link with a regular 20amp fuse. some time ago, i changed the fuse out to one of those jumbo fuses just to get more current. i believe one of those links is direct link to power ecu. without that no cel, without cel no start because the ecu not powered.
 
Joined
Apr 26, 2015
Messages
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Location
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Here's a couple pics fwiw, on them fusible links. I had to change mine last winter, I knew mine was in poor shape, and it let go when I was wheeling with many accessories on, including headlights, light bar, heater/defroster and stereo. Mine is a 96, so I'm not sure if they're identical, or vary, but right off the positive post you should see one of these ...
IMG_20160920_194310.jpg

And the lil black box mentioned looks like this guy
IMG_20160920_194251.jpg

I read you said you had power, what's the ohms like? Mine worked, but was frayed all to hell.
 
Joined
Sep 11, 2014
Messages
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Location
San Lorenzo Ca
Take a look at your relay on how it plugs into the socket. Two of the terminals should be the load side of the relay, when you jump those see if the CEL comes on.
 
Joined
Jul 28, 2012
Messages
7
Thanks jonheld - I'll take a look at the relay the next time I'm out there and see if I can decipher the pin out diagram, that would really help.

Phildoh - those photos of the fuseable links are very helpful, I'll put them on my list of items to replace, but I am getting good voltage from the battery to most of the places I've checked (all 3 fuseable links are ok).

My next steps will be to take more readings on the EFI plug and to look at the relay to see if it's got a pin-out diagram. Probably won't get out there for a month :-(

In the meantime here are some diagrams to show my confusion about the difference between the diagram and my EFI plug:




Appreciate the help.
 

jonheld

 
Joined
Dec 8, 2006
Messages
7,994
Location
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In the meantime here are some diagrams to show my confusion about the difference between the diagram and my EFI plug:
Appreciate the help.
OK, stay with me here. There are 4 pins arranged in a square. All you have to do is verify 1 and you immediately know what the rest are. This is because, and I'm just going out on limb here, the terminals on the bottom of the relay haven't changed places.

You KNOW that pin 2 is +12. You HAVE a pin that reads +12. Therefore we will now assume that +12 is on pin 2.
Now follow that pin clockwise around the socket. The next one you get to will be pin 4, followed by 3, followed by 1.

You will also notice that my diagram is color coded for each pin. That corresponds to the color of the wire that Toyota used for each pin in the socket according to the schematic. Ground is brown (pin 1), +12 is red with a yellow stripe (pin 2), the logic signal from the ECU is red (pin 3), and the load side of the relay that feeds the EFI system is yellow with a red stripe (pin 4).
 

jonheld

 
Joined
Dec 8, 2006
Messages
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i changed the fuse out to one of those jumbo fuses just to get more current.
That's not the way fuses work. They can't increase or decrease current flow. Increasing the size/capacity of a fuse doesn't change the associated circuits draw or capacity. It just increases the chance of something else burning up before the fuse pops.
 
Joined
Nov 29, 2014
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Utah
Does anyone have a diagram for the fuse box in the dash? my diagrams says its the f 13 fuse box i dont know why my book is missing it.
 
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