1994 FJ80 won't start (1 Viewer)

ratchet

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Background:
I had a low oil pressure situation that wiped out some bearings. Changing the rod bearings didn't fix the issue so I got a low mileage (about 147,000) from a 1997 FZJ80 to put in while I rebuild the original motor. Since the motor was on a stand I figured I would do the head gasket and re-seal the motor as preventative maintenance. While the head was off I had it completely rebuilt.

After pulling the original motor I swapped the accessories and manifolds on to the 1997 due to the minor changes throughout the years. I got everything installed back in the vehicle and now can't get it to start.

The issue:
I believe it is an electrical issue somewhere because I've got no spark. When the key is on the check engine light (CEL) doesn't illuminate at all (if I recall correctly it was working prior to the motor swap). Based on what I've read since the CEL doesn't illuminate that means I've got no power to the ECU (or is it ECM?) so that is the first place to start. I pulled the glove box back out and checked the connectors. I found that the four connectors plugged in to the ECU were fine but I had forgotten one of the white connectors. I plugged it in and thought for sure it would fire up but there was no change.

My fusible link appeared to be good but I changed it out anyway and have 12v at the other end of it. I've read many "No Start" threads and @Tools R Us will ask if there is power at the B+ terminal of the diagnostic connector on the firewall. I do have approximate battery voltage at that terminal. I think that means that the EFI circuit is good but am not certain.

I swapped the EFI relay with the power window one from the driver side kick panel and it didn't change anything. I can also feel the relay click when the key is turned. While it was out I tested for power at terminal 2 and have approximate battery voltage. I also put a jumper wire from terminal 2 to terminal 4 as suggested here: No Spark Update and with the jumper wire in I still have no CEL. If I am reading that right it means that my relay is good...or perhaps doesn't mean anything at all.

I also have approximate battery voltage at the brass screw in the engine fuse box.

I've also changed the 15A EFI fuse located in the under hood fuse box, 7.5A Ignition fuse located in the fuse box at the drivers knee, 15A ECU-IG located in the fuse box at the drivers knee. None appeared to be bad but changed them anyway out of an abundance of caution.

I went back through the FSM procedure for removing the engine and verified that I didn't miss any steps when putting it back in. I also pulled the main harness in to the engine bay again and checked it for damage. I found one area that must have gotten squished during the install but none of the wires were broken. I wrapped them well with electrical tape and re-installed it.

Questions:
Would trying to start the vehicle with one of the white connectors near the ECU disconnected hurt anything?
I think a good next step would be to check for power directly at the ECU but I am not sure how to do that. Can anyone point me in the right direction?
Any other suggestions as to what should I try now?

Richard.
 
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Do you have a CEL with key on, engine off?
Bilt4me, the OP stated above, quote "When the key is on the check engine light (CEL) doesn't illuminate at all (if I recall correctly it was working prior to the motor swap). Based on what I've read since the CEL doesn't illuminate that means I've got no power to the ECU (or is it ECM?) so that is the first place to start. " end quote
 

ratchet

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Tedward - I put in a new cap and rotor. As far as I know the coil is good (I drove the vehicle in to the garage about 3 weeks ago). I used the plug wires and distributor from the 97 as t hey appeared to be in good shape. I could swap in the distributor and wires from my motor but it seems that the power to the ECU issue should be sorted out first.

Bilt3me: Rifleman is correct. No CEL light at all regardless of key position or any of the troubleshooting I've done...which I think indicates no power to the ECU.
 
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Bilt4me, the OP stated above, quote "When the key is on the check engine light (CEL) doesn't illuminate at all (if I recall correctly it was working prior to the motor swap). Based on what I've read since the CEL doesn't illuminate that means I've got no power to the ECU (or is it ECM?) so that is the first place to start. " end quote
Sorry, late in the day reading comprehension is lacking.

Are you done yet?
 

ratchet

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Bilt4me: No worries. Apparently I mis-typed your name in the response anyway so typing skills are lacking on this end. Since I have no CEL light, any suggestions on where to check next? I've checked the harness and see no broken wires but an not sure what to do next because I don't know what route the power takes to gets to the ECM.
 

satchel

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If the ignition switch is turning things on, then it looks like it is related to the GAUGE fuse. Do your wipers work? If they don't, it can either be a power issue further up like the fusible links, or a ground issue further down. Check for power at either side of the gauge fuse. If you don't get anything there go up towards the fusible link.

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satchel

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I would check for power at pin 4 (yellow red provides power to check engine light) of the ecu. If there is no power there, it is likely the gauge fuse or ignition. If there is power, then the ecu is not being grounded correctly and we need to search for the ground wires. If you have power to your wipers, rear heater, turn signals and what not when you put the key in the run position, then it is likely a ground issue on the ecm. Edit: that doesn't mean they work, just means you are getting power to them.

My assumption, since this is more than a check engine light issue, is that the ecm is probably getting power but not grounded. Happy to help more, this is the schematic I was looking at. https://static1.squarespace.com/sta...442806549877/1996+Toyota+Land+Cruiser+EWD.pdf
 
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If no CEL with key in ON, but not running, the first place to check is the fusible links. That indicates the ECU is in the ready state. Without that, nothing happens.
 

ratchet

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Satchel: the wipers, rear heater, and turn signals all work fine and I have power at both sides of the Gauge fuse when the key is in the run position. I'll check for power at pin 4 tomorrow morning and report back but I think your assumption about this being a ground issue is probably accurate. How would I go about diagnosing that? I apologize, I am an electrical noob and have no experience reading schematics. As I drink my morning coffee I will take a look at the link you provided and try to gain a better understanding of it.

Bilt4me: The old fusible link appeared fine but I changed it anyway and I checked for and found power at the ring terminals. I also have power to the screw in the fuse box under the hood. Wouldn't those things indicate that the fusible link is fine?

Thank you both for your help.

R.
 

satchel

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Ok, cool, you are getting it narrowed down. I would say at this point you either are not grounded at the ecu or the main ecu power is not being supplied (transistor switching power probably the b+ terminal) but we can go through the steps to determine that. If we focus on the check engine light alone (labeled as the malfunction indicator lamp), assuming that it is likely the same issue as the rest of the problems, we can narrow some more facts down. In the diagram below, where I have written GAUGE on the left, you have verified that power is coming in on the yellow wire to the top left from the gauge fuse.

From here you want to make sure you have power all the way to the ECU, which would be points 1, 2, and 3 below. I would suggest just going to number 3, which is the same pin 4 of connector D that I mentioned previously. If you are getting power there, in the run position, then you have power to 1 and 2. If not, check power at 1 and 2.

After that it gets a little hairy. What you see below pin 4 (inside the ecu) is a transistor. Think of it as a switch. When the ecu applies a signal to the left side of that transistor, what I marked as number 4, it will allow the power to flow through from my 3 (power side) to ground (assuming the ecu has a ground connected), which I marked as number 5, completing the circuit and turning the light on. So assuming you have power at pin 4 (my number 3 below), then either the ecu is not applying the signal at my number 4, or it is applying that signal and there is no ground for it to go to (my number 5 and likely some grounding wire for the ecu somewhere).

My suggestion is that you first make sure you have power to the pin 4 (my number 3 below) and then we can rule out the power side of the check engine light. While I'm sure this isn't your issue, cause other stuff doesn't have power either, let's confirm. After that, I can post up all the ground wires to the ecu I see and you can check for continuity to ground for them, and if they all have grounds then it would mean a bad ecu most likely. I'm hoping that maybe you will notice a wire coming out of one of the ecu connectors that is not connected to ground...

This stuff can get overwhelming and I suck at trying to explain it so feel free to PM me and we can walk through it on the phone or whatever if that is easier.

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satchel

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Once you have verified the above, look to see if you have power at terminal 12 of connector D. I believe this should be the power for the ecu overall, providing switching logic to transistors and such.

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The three below should have continuity to ground. Check that they do not have power first, then check continuity.

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I believe pin 6 below may be the main ground for the ecu, but it's a bit hard to tell by the diagram below. Check to make sure there is no power to it first, then see if you get continuity to ground if all else checks out.

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Sorry for all the edits, keep having problems saving the dumb pics.
 
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satchel

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One more for the night. I feel like it may be the wiring going to the ground point EC that is causing the issue, as you can see most of the points above go to this grounding spot. Maybe check this location to make sure the ground is ok before digging in too far? Could also be the IE ground in the second diagram below. I think those 2 would be your main ground points so I'm putting my money on one of those.

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ratchet

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Satchel, you ROCK! You did a fine job of explaining it...but we still haven't got it sorted out.

First of all, I want to confirm I am reading the schematics right. Pin 4 has a D by it which means it is on connector E7D of the ECU connectors. When I look at page 68 of the link you provided it shows that E7D is the second largest of the connectors attaching to the ECU.

Assuming that is correct, when I look at connector E7D unfortunately the colors aren't the same as what is shown in the schematic. The same is true of the wire colors on connector E4A (the one the you circled the ground wires). Perhaps this is because my vehicle is a 1994 and the schematics are for a 1996? I would have thought that they are the same but apparently not.

Regardless, I did some testing (which I am not sure means anything since the wires don't line up with the schematics) and found the following:
E7D Pin 4 has power and is Yellow with a White stripe
E7D Pin 12 has power and is Yellow with a Red strip
Diagnostic port B+ has power

Ground point EC was loose. Apparently I attached it but forgot to tighten the bolt. I tightened the bolt and thought for sure that would fix the problems but everything is still the same. I checked the ground quality here by touching one lead to the bolt, the wire and then the air intake chamber with the other lead touching the battery negative terminal while my mulitmeter was set to audible continuity setting. I got a beep at each component. This means the ground is good right?

Ground point IE was tight and had not been disturbed. I checked this by touching one lead to the bolt then to each wire connector and got a beep for each one. Again, this means the ground is good right?

E4A 13 has continuity to ground at both EC and IE and is Brown (I checked this by touching one lead to the pin at the connector and the other to ground point IE and got a beep. That is the correct way to do it right?)
E4A 16 has no continuity to ground at either IE or EC and is a black wire with a white stripe
E4A 26 has continuity to ground at both EC and IE and is Brown (tested the same way as E4A 13 described above)
E7D 6 (the one you believe may be the main ground for the ECU) has no wire in it

I've acquired schematics for a 1994 and attached them. Hopefully this, in addition to the information above will shed some light on the issue.
 

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satchel

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Yeah that is quite a difference in the schematic between those years, so I'll need to look this one over. Glad you caught that.
 

satchel

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Alrighty then. Now that I am looking at the correct schematic for your truck, try checking for continuity to ground for the circled pins below.

You have already verified continuity for connector pins E10A26 and E10A13 below (may want to check them all the way back to the negative of the batt), but you will need to do the same for E10A24 now. If those all have ground, check for ground continuity at the data link connetor circled below, pin E1 (in this schematic I think the universal source of your problems is related to that connector). Make sure you have a good connection at that data link connector. If those all pass the test, check for voltage at the batt+ (diff than the +b) which is pin E7D2. In all these checks, you are just checking the pin in the connector itself, not the pin in the ecu.

As for checking for continuity:
Make sure to check for voltage on the wire before checking continuity to make sure you don't have a live circuit.
Simplest way to check for ground continuity is to always have one of the leads touching the negative of the battery, so a long wire if necessary. I'm now assuming there is likely something going on at your connection for the data link connector so check those connections really well. Might as well check for power at pin 2 of that data link connector as well.

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ratchet

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I double checked E10A26 and E10A13 for current (there was none) and then continuity to ground with one lead on the negative terminal of the battery (there was continuity). I also did the same for E10A24 and got the same results (no current and had continuity to ground).

I also checked the data link connector pin E1 for continuity to ground (with one lead on the negative battery terminal) and found continuity.

I checked the Batt+ (E7D2) and found approximate battery voltage.

I wasn't sure which one was Pin 2 at the data link connector so I checked all of them (with the key at the on position, the ECU plugged in, and the negative lead on the negative battery terminal; I've attached a picture of the data link cap which has all these abbreviations) and found the following:
Fp: no voltage
W: approximate battery voltage
E1: no voltage
Ox1: no voltage
AB: has no connector
OP1: has no connector
TEM: has no connector
IG-: approximate battery voltage
CCo: has no connector
TE1: approximate battery voltage
TE2: approximate battery voltage
CC2: has no connector
Tc: approximate battery voltage
OP2: has no connector
+B: approximate battery voltage
VF1: approximately 144 mV
VF2: approximately 144 mV
Ox2: no voltage
Ts: approximate battery voltage
Tt: voltage fluctuated around approximately 500 mV
OP3: has no connector

When I say approximate battery voltage I mean approximately 10-12 volts. I can get exact values if necessary.

This is so frustrating. Thanks for sticking with me on it.

Any other ideas?

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