1989 3FE Cranks but doesn’t Start

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Jan 12, 2017
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79
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Cleveland, TN
Need some help from all the 3FE experts. Last weekend I swapped in a new to me 3FE from a 1988 FJ62 into my 1989. Swapped over the wiring harness. Everything went well until time to start the engine. It’s cranks over very well but will not start. It was not getting any fuel or spark.

So far I have checked all grounds and fuses. Fusible links seems to checkout good. EFI relay didn’t seem to checkout so I jumped it and now I have 12v to the B+ on the diagnostic port. I also now have fuel but no spark. The other thing is that the check engine light does not illuminate when I turn the key.

Any idea what this could be or what else to check?

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Joined
Jan 12, 2017
Messages
79
Location
Cleveland, TN
If a 3FE doesnt have spark you don't have something plugged in or you have a bad connection. It's as simple as that
Everything is plugged in and the connections looks good but i will double check that. I’m thinking it is something to do with the CEL not lighting up.
is the distributor rotating when the engine turns over?
was the engine known good before the swap?
I’ll have to take the cap off and check that and yes the engine was known good and it was only pulled as the PO was doing an LS swap.
 
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I know you said the fusible link "seems good" but this is exactly what happened to my 89 after I replaced all of the battery cables and grounds. I must have broken some of the already frayed wires on the fusible link and it was no longer making a connection to the igniter and injection. Double check all of the green wires.
 
Joined
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Messages
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Location
Cleveland, TN
I know you said the fusible link "seems good" but this is exactly what happened to my 89 after I replaced all of the battery cables and grounds. I must have broken some of the already frayed wires on the fusible link and it was no longer making a connection to the igniter and injection. Double check all of the green wires.
Yes I will double check them but per FSM they checked out good with a multimeter but I guess not a 100% since I’ve never tested any before.
 
Joined
Jul 21, 2012
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Rhode Island USA
What do you mean when you say you "swapped the wiring harness"? If you're swapping 3FE like-for-like, you shouldn't swap the harness. Leave the harness on the engine, unplug the ~3 plugs under the dash behind the glovebox and pull plugs through the firewall. It's way easier that way, you disturb the wiring far less, and you are much less likely to forget a ground.

If the CEL worked before the swap, but doesn't now, your computer is not powering up. Either from not getting power, or not be grounded.

The computer in these trucks has several power connections - B+, Batt, IGSW and Grounds. B+ comes from the EFI main relay, "Batt" is constant 12v whenever the battery is connected, and IGSW is switched 12v from the ignition switch.

Toyota does things differently than most manufacturers. In most American cars, the main EFI/PCM relay is controlled directly by the ignition switch. You turn the key on, everything has power. With Toyotas, the PCM controls the Main EFI relay. So you turn the ignition switch on, IGSW gets power, which wakes the computer up. The computer then turns on the Main EFI relay, which energizes the rest of the system.

Since you have no CEL and no Main EFI relay kicking in, it indicates that the computer isn't waking up/getting power. You will need to check all grounds very carefully. You will need to make sure that the "Batt" connection has constant 12v power (this is the Main EFI fuse under the dash), and that the IGSW wire gets power when you turn the ignition switch on. IGSW gets power from the ignition fuse.

Here's a diagram: https://www.ih8mud.com/tech/88lc-wire/88lc-wd2.gif
 
Joined
Jan 12, 2017
Messages
79
Location
Cleveland, TN
What do you mean when you say you "swapped the wiring harness"? If you're swapping 3FE like-for-like, you shouldn't swap the harness. Leave the harness on the engine, unplug the ~3 plugs under the dash behind the glovebox and pull plugs through the firewall. It's way easier that way, you disturb the wiring far less, and you are much less likely to forget a ground.

If the CEL worked before the swap, but doesn't now, your computer is not powering up. Either from not getting power, or not be grounded.

The computer in these trucks has several power connections - B+, Batt, IGSW and Grounds. B+ comes from the EFI main relay, "Batt" is constant 12v whenever the battery is connected, and IGSW is switched 12v from the ignition switch.

Toyota does things differently than most manufacturers. In most American cars, the main EFI/PCM relay is controlled directly by the ignition switch. You turn the key on, everything has power. With Toyotas, the PCM controls the Main EFI relay. So you turn the ignition switch on, IGSW gets power, which wakes the computer up. The computer then turns on the Main EFI relay, which energizes the rest of the system.

Since you have no CEL and no Main EFI relay kicking in, it indicates that the computer isn't waking up/getting power. You will need to check all grounds very carefully. You will need to make sure that the "Batt" connection has constant 12v power (this is the Main EFI fuse under the dash), and that the IGSW wire gets power when you turn the ignition switch on. IGSW gets power from the ignition fuse.

Here's a diagram: https://www.ih8mud.com/tech/88lc-wire/88lc-wd2.gif
The plan was to not touch the harness but the 88 and 89 have a few different plugs and different computers so I had to swap everything to match my 89 body harness and computer. If I recall right I checked B+ and Batt at the computer and they had power but I will go back and check IGSW although I know the EFI fuse is good. Where are the grounds needed for the ecu fo receive power no sure how to read the wiring diagram for that? All the major grounds that I know off are connected and good?
 
Joined
Jul 21, 2012
Messages
328
Location
Rhode Island USA
Main EFI ground is bolted to the block or head from what I recall. It's simple enough to check at the computer if your ground is good. The ground wires are brown and brown-black. Turn the key on, and use a multi-meter to check the voltage between a brown wire at the ECU and chassis/body ground. It should read 0 volts. They also bring a ground wire (E1) up to the diagnostic connector, and you can check there.

FWIW: 88-90 FJ62 Federal emissions computers are all functionally the same. Even though the plugs are different colors, they still work. The only difference is between California and Non-California trucks. You'll get an EGR temp code if you plug a California ECU into a non-california engine. FJ80 computers are completely different however.
 

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