3FE no start, no CEL (1 Viewer)

[Froski]

Ok,
Truck is not starting and the CEL, A/T oil temp, and charge lights are not illuminated with the key in the on position.
The truck has been daily driven for 2.5 years with only one previous problem- fixed with a new main relay.
I have downloaded and printed out the diagnostic by @jonheld
Here is what I have :
Newish fusible links - dome lights work
New main relay
12v at the brass screw in the relay box under the hood
I found 0.0-0.4 V at B+ on the diagnostic port at the firewall
What does this mean?
What is the next step?
TIA

 

[Cheap Cruiser]

Hey Froski. I chased the same issue last week. What fixed mine was an EFI relay (in engine fuse box). Got one overnighted from Amazon for $10.

I also chased down if the port installed security system was in some odd state but that checked out good.

 

[Froski]

Hey Froski. I chased the same issue last week. What fixed mine was an EFI relay (in engine fuse box). Got one overnighted from Amazon for $10.

I also chased down if the port installed security system was in some odd state but that checked out good.

Thanks for the reply, but I have a new one in there… and if my experience is any indication than you may not have fixed it, just prolonged the period until the circuit fails

 

[too tall]

Check the connections at the battery. And the fusible links. Maybe try a test light on the fusible links at the junction in the little plastic housing.

 

[too tall]

I would also check the positive post where the EFI relay mounts. I have had to re-establish that connection before when it wears or the terminal gets spread open from pulling relay in and out.

 

[jonheld]

I found 0.0-0.4 V at B+ on the diagnostic port at the firewall

If that was with the key in the ON position, it means either the EFI relay is not closed or connector EB1 is faulty.

 

[jonheld]

Also, there are 3 fusible links on an 80 Series.
Here is a cursory check of all 3 fusible links in system:
This assumes a stock configuration.

Dome lights working?
Brake lights working?
When you turn the key to ON does the CHARGE LAMP light up?

If yes to all 3, then all 3 fusible links are intact.

 

[Froski]

Thanks too tall

I would also check the positive post where the EFI relay mounts. I have had to re-establish that connection before when it wears or the terminal gets spread open from pulling relay in and out.

The supply side of the relay is getting the 12v too. Where does the logic come from for the relay? IGN? If so then I’m not getting it.

 

[jonheld]

Thanks too tall

The supply side of the relay is getting the 12v too. Where does the logic come from for the relay? IGN? If so then I’m not getting it.

EFI relay logic comes from the ECU, but if the CEL is not illuminated, then the EFI system is not in a ready state and this engine will not run.

 

[Froski]

So I jumped the supply - load contacts for the EFI relay and still did not get CEL

 

[Froski]

Fusible links- dome lights and brake lights work
Charge lamp does not light. I can’t confirm it was not burned out prior to this though.

 

[Froski]

If that was with the key in the ON position, it means either the EFI relay is not closed or connector EB1 is faulty.

I don’t think it’s closing because there is nothing coming to the logic side of the relay with the key in on position

 

[Froski]

Can you test fusible links to confirm they aren’t faulty? If so then I could eliminate the third link as the potential problem.
Any tests for figuring out what preconditions for the ECU aren’t being met?

 

[jonheld]

Can you test fusible links to confirm they aren’t faulty? If so then I could eliminate the third link as the potential problem.
Any tests for figuring out what preconditions for the ECU aren’t being met?

You can check links with a meter the same way you would check a fuse. I also gave you a quick non-invasive way to check all 3 fusible links in the post above as well as in the diagnostic.
80% of the time, a no CEL is a faulty fusible link not allowing the ECU to power up or simply the 15 amp EFI main fuse is blown.
However it can also be caused by the AFM as outlined in my diagnostic.

 

[Froski]

EFI fuse is good
I’ll check the fusible link that relates to the charge light
I’ll check the afm
Thanks

 

[Froski]

I was messing with the fuse panel in the cab with the key turned to on and I saw the lights go on- IGN fuse had a bad connection. I had tied the logic for the winch in using a flat folded contact that sandwiched the fuse contact. Pulled off the winch and sold it, pulled out the extra contact and the connection was loose.

 

[jonheld]

I was messing with the fuse panel in the cab with the key turned to on and I saw the lights go on- IGN fuse had a bad connection. I had tied the logic for the winch in using a flat folded contact that sandwiched the fuse contact. Pulled off the winch and sold it, pulled out the extra contact and the connection was loose.

That's why it says "Motor not running; key in ON position; CEL, A/T, CHARGE lamps should be on. If ALL 3 are out, check IGN fuse and fusible link AM2 or ignition switch." in bold on the first page of the diagnostic.

 

[Dusten]

Nm

 

[Froski]

I checked the condition of the fuse, just took me a bit to realize the implications of removing the tie in
Your sequence stands
Thanks

That's why it says "Motor not running; key in ON position; CEL, A/T, CHARGE lamps should be on. If ALL 3 are out, check IGN fuse and fusible link AM2 or ignition switch." in bold on the first page of the diagnostic.

Nm

 

[Marco Lau]

EFI, keep a few spares or get the late style plastic relay