3FE No Start Issue

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Lka1988

Lka1988

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EDIT: It runs! Click here for update.


This is not for me, but for a buddy of mine. 1992 FJ80 w/3FE, 187,000 miles, totally unmolested.

He recently replaced his starter due to the classic sticky contacts. Now it cranks great, but it won't fire. We replaced the fusible links as they were pretty wasted, but that didn't fix anything.

3FE guys, here's a clue: The CEL is NOT lit up like it should be. EFI relay is good, and so is the fuse. What else should we be looking for? And yes, he does have the FSM.


TIA
-Lane
 
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If the CEL is not lighting up then the ECU computer under the glove box needs to be checked. Also, is the truck in park? If it's not then nothing will crank, but you would've seen a CEL.

Check ECU per FSM.
 
The starter will crank, but the motor won't fire up. You can hear the fuel pump pretty loudly, is that normal?

I'll let him know about the ECU.
 
Lane,

Look up Jon Held's website.

He has a complete diagnostics write-up for the 3FE EFI system. Goes something like, "No CEL? Check for 12v here. If not, part x is bad. Else, check for 12v here. If not..."

Curtis
 
If it's cranking then the ECU is fine. Sorry, I missed that in your first post. Now you need to check fuel and spark. If you can hear the fuel pump then fuel is usually ok. Lets look at spark: You already checked the EFI relay, fuses, ECU should be ok. That leaves, ignitor, coil, and distributor, or bad grounds / wiring.

Checking the distributor, ignitor and coil is easy. Get a test light and connect the ground to battery. Disconnect the wire going from the coil ignitor to the distributor. If you get light then those two are ok. Move on to disconnecting the wire from dizzy to injectors and cehck again. This will check those systems and narrow down your search. Most problems are caused by things we have touched.

Check to make sure he grounded the starter properly. Check all wires running near the starter. Also check battery ground since he disconnected that to access the starter.

Summary:
Check grounds at battery and starter
Check spark at 3 components using test light.

Can you tell I had this issue not 2 months ago. :)

-Randy
 
Thanks Curtis. I was at work for the last 8 hours and couldn't look anything up...
 
Printed the diagnostics PDF, we'll work on it soon.
 
Ok, we THINK we figured it out. We did some testing (switched stuff between our trucks) earlier and ruled out the ECU, coil/igniter, fusible links, EFI relay, and EFI fuse.

Here's where we think the problem is; it's the Black w/Green wire that goes into the coil. According to the FSM, when the key is in the "ON" position, that wire gets 12 volts. There's a nice little break in the insulation, you can see broken copper strands.

Here are two pics of the problem area:
damage1.webp
damage2.webp
 
We measured voltage at the terminal with the key ON. The voltage reading was pretty erratic, ranging from 0V to 12V and everything in between, due to the broken wire.

We know that this is A problem, but we really need to know if it is THE problem...
 
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No start No CEL

This is exactly what happened to me a few weeks ago. Thanks to this great forum, I solved it in a few minutes using Jon Held's writeup

In my case, I followed the writeup and I got to the B+ connector at the diagnostics port to check 12V. Nada. NO CEL either.

The problem was the grey EB1 connected with the yellow/red wire coming from the relay. Check that connector. The wire could be loose or brittle due to age.

BTW can anyone please tell me how to properly open up that grey connector. What's the trick. Where are the tabs?

TIA
 
Those pictures look like mouse chews.

DougM
 
The black wire with the green stripe on pin 1 of the coil is +12 (B+) coming from the ignition switch. That should be constant +12 unless your ignition switch is faulty.

I'm pretty sure this would NOT yield the situation of the CE light not being lit. In fact I'm certain that with the coil and igniter removed from the truck the CE light would still light. No I haven't tried that but there is nothing in the schemo to make me believe otherwise.

You swapped parts between trucks to eliminate possibilities, which is good, but you did not eliminate wiring problems associated with the EFI circuit.

I would try jumping the load side of the EFI relay (pins 2-4) and see if the CE light illuminates. If it does then try to crank and see if she fires. If she runs then you can eliminate a host of possibilities. If the CE light doesn't light then stay your course and continue on.

Remember, without the CE light tally, you will have nothing, nil, nada, bubkyis.
 
Ok, nothing happened. Fuel pump stayed on as long as the terminals were jumped, but not much more. No CEL.
 
Jon- You were right about the coil not causing a no-CEL condition.
 
So let's recap here- James' Cruiser has passed all of Jon's little tests:

+12v at brass terminal screw under hood
Fusible links are BRAND NEW, like less than a week.
EFI Relay/fuse are both good
+12v at B+ terminal in firewall diagnostic box

Still no CEL.
 
Also- I've checked just about every 12v source going to the ECU, at the ECU; all are good. ECU is getting power...
 
Did I mention that we're not getting spark?
 
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