91 FJ80 Engine starts then dies immediatly

[TownsvilleBloke]

Hi everyone and @jonheld !
Sorry for the sudden discontinuation of the thread,
I'm back now with it.

I unscrewed the front seat and I got the COR out (hourray!).
The initial plan was to use the engine running while AMF unplugged to get to a better working station ( I currently work on the guest parking lot of the unit complex) to move it around where my gf's corolla is, inside an actual individual garage.

And I found something new !
So the car runs around 1200rpm and then decreased while in Park (and AMF unplugged) to stabilize around 900-1000 rpm and when I switch to Drive, then engine shuts immediately.
So the car can't move at all.
I have also a similar relay here I ordered in Japan, but I didn't switch it yet.

I have a multimeter and the old COR in my hand, what should be the next steps ?

I'll follow this just to kill time but I don't have a spare battery to directly plug on the relay.

EDIT:
I've run the first test and there are the results:
with 200 ohm:

between STA and E1: 26.8 ohm
between B and FC: 144.4 ohm
between B and FP: 1 (no continuity)

I can't do the part 2 because I need to put it on the battery or something alike and I don't have the tools to do that right now.

So I guess when I start the engine in Park, while the AMF is unplugged, the Relay still works because it will have continuity between B and FP while receiving power from the battery.
But if I plug the AMF, that doesn't do it. Why ?
And then why would it stalls when I switch in Drive ?

 

[jonheld]

Again, the COR controls the fuel pump.
The COR should only activate (close) under 2 conditions.
1. when cranking the starter
2. when the flap in the AFM opens.

The fuel pump should not run with the AFM unplugged because there is no longer a ground path to fire the secondary coil of the COR.

I suspect the fuel pump circuitry has been altered to fire the pump without the engine running. Does the FP run with the key in the ON position before cranking the starter? It should NOT run.
If it does run like I suspect it will, somewhere there is a hard ground on the FC terminal of the COR.

Does the engine continue to run if you pull the COR out? It should run for a few seconds then stall.

Your idle speed should not be part of the equation, as the ECU is getting false readings all over the place because the AFM is unplugged. It doesn't know what's happening. 1986 technology.

 

[TownsvilleBloke]

Again, the COR controls the fuel pump.
The COR should only activate (close) under 2 conditions.
1. when cranking the starter
2. when the flap in the AFM opens.

The fuel pump should not run with the AFM unplugged because there is no longer a ground path to fire the secondary coil of the COR.

I suspect the fuel pump circuitry has been altered to fire the pump without the engine running. Does the FP run with the key in the ON position before cranking the starter? It should NOT run.
If it does run like I suspect it will, somewhere there is a hard ground on the FC terminal of the COR.

Does the engine continue to run if you pull the COR out? It should run for a few seconds then stall.

Your idle speed should not be part of the equation, as the ECU is getting false readings all over the place because the AFM is unplugged. It doesn't know what's happening. 1986 technology.

@jonheld
I'm a bit confused.
How do I check that the Fuel Pump run if I didn't start the engine ?
I mean so far I can tell it's running because the engine is starting, so there is fuel in there, but if it's only the key turned ON, and not the engine running, I won't be able to hear it pumping. Or perhaps it does ? Does it makes a sound ?

But okey you're right, I'll keep focus on the FC Terminal, in the car, to see if I can spot anything dodgy.
Thanks for helping with that tho. I hope we will find out what's going on and it will run again !!!

EDIT:

Nevermind, I didn't know it was actually making a sound, I'll go with that.

EDIT 2:
I found this thread, and indeed, apparently, this car was converted to LPG before (the owner didn't tell me, Toyota staff told me that).
I don't know if it has anything to do with my issue, but I thought it could be important to mention it somewhere.
After all, @OfficialGamings had a similar issue, perhaps it could lead us somewhere I don't know.

 

[jonheld]

I found this thread, and indeed, apparently, this car was converted to LPG before (the owner didn't tell me, Toyota staff told me that).
I don't know if it has anything to do with my issue, but I thought it could be important to mention it somewhere.
After all, @OfficialGamings had a similar issue, perhaps it could lead us somewhere I don't know.

I am not familiar with an LPG conversion, but I would assume you're on the correct path.

 

[OfficialGamings]

I could provide some assumptions on how an LPG kit could affect this. But once again these conversions are not all the same. And also my LPG conversion was done on a 1FZ-FE not a 3FE.

But here is some logic behind it. Essentially you can not run on two different fuel types at the same time. So In order for the LPG system to function it would need to cut power to all necessary components in part of the fuel system.

If there is no longer an LPG system in the vehicle I would recommend trying to jump a two pins in the diagnosis box that provides the fuel pump with full power. (Assuming that these pins are available, Im not too familiar with this year and model).
NOTE: these pins do not provide a perm solution!

It could also be the case that the wiring was left in behind the dash from the LPG system.

Try and chase back the aftermarket wiring. It might lead you to somewhere. From my own rig I had a aftermarket relay that stopped working so it could turn from LPG to Petrol.

 

[TownsvilleBloke]

I could provide some assumptions on how an LPG kit could affect this. But once again these conversions are not all the same. And also my LPG conversion was done on a 1FZ-FE not a 3FE.

But here is some logic behind it. Essentially you can not run on two different fuel types at the same time. So In order for the LPG system to function it would need to cut power to all necessary components in part of the fuel system.

If there is no longer an LPG system in the vehicle I would recommend trying to jump a two pins in the diagnosis box that provides the fuel pump with full power. (Assuming that these pins are available, Im not too familiar with this year and model).
NOTE: these pins do not provide a perm solution!

It could also be the case that the wiring was left in behind the dash from the LPG system.

Try and chase back the aftermarket wiring. It might lead you to somewhere. From my own rig I had a aftermarket relay that stopped working so it could turn from LPG to Petrol.

Do you think it could be actually behind the dash then ??

Today it was raining like crazy so I didn't work on the rig (stuck in open air in the parking lot),
but as soon as it's possible, I'll go first with the step @jonheld recommended (check if the fuel pump is running while key on ON, trying to run without the relay, or remove it while engine is running.)
And then, I'm hesitating:
@jonheld mentioned a hard ground after the FC terminal and the AFM (I guess, looking at the schema), so I should I guess follow the wires from there until it ends on the AFM. Which could also involve my AFM could be faulty, despite the fact it's brand new refurbished.
That still doesn't explain why the engine is running in Park, it shouldn't with the AFM unplugged.
So there should be still a shortcut somewhere.
On the other hand. if it was, a long time ago, a LPG rig, I guess all the "customs" are in the fuel pump area, so under the rear seats.

But let's buck up ! It must be right under my eyes, I just can't see it now.
Anyway, thanks guys for your answers , I'll update you soon with the next steps.

EDIT: Wait I'm wrong actually, it can't be the AFM except if there is a short in it between 12v and ground, if it's faulty it means "circuit opened", and "circuit opened" doesn't equal "hard ground", like @jonheld mentioned.

 

[TownsvilleBloke]

_

 

[jonheld]

my AFM could be faulty, despite the fact it's brand new refurbished.

Can't be the AFM if it runs with the AFM unplugged.
Fuel pump logic has been changed.

 

[TownsvilleBloke]

Hi !
@jonheld
Ok I got some bad/interesting news:
The fuel pump is not pumping while key is ON, or I'm deaf:


Also, I have ONE try with the AFM plugged on (it starts and dies after half a second), and then this is what is happening on second try:

The battery dies, and I have to use jumper kit to start it again in "AFM unplugged" mode.

Also, after 10-15 sec in "AFM unplugged mode", it starts to smell fuel very bad.

I've tried to run it without the COR earlier, and the engine doesn't start at all.
I tried to unplug it while it runs, but it's too tricky. It takes me at least one minute to get it off fiddling with my fingers as long as my nails are long enough to grab the clips out, otherwise it's just hopeless. As the fuel smell start to be concerning, I just cut the engine off if it takes too long in my attempt to remove it while running.

 

[TownsvilleBloke]

I FIXED THE CAR ******* it !!!
The AFM was out. I checked with the multimeter and there was infinite resistance between E2 and VS terminals.
I opened the top silicon part, found the gap and I foldered it.
It's a shame because it was actually litteraly refurbished by a store on Aliexpress, so it was a "new" part.
It runs again now!!
Thanks @jonheld for helping me to understand the car and driving me through the diagnosis.
Thanks @TheBussman for guessing what it was before everyone else .

Cheers guys !

 

[TheBussman]

I FIXED THE CAR ******* it !!!
The AFM was out. I checked with the multimeter and there was infinite resistance between E2 and VS terminals.
I opened the top silicon part, found the gap and I foldered it.
It's a shame because it was actually litteraly refurbished by a store on Aliexpress, so it was a "new" part.
It runs again now!!
Thanks @jonheld for helping me to understand the car and driving me through the diagnosis.
Thanks @TheBussman for guessing what it was before everyone else .

Cheers guys !

good to hear!