FJ80.... Does a short circuit in an injector stops the whole engine? (1 Viewer)

[GinoG]

Hello everyone.
I write from Italy: here I have a FJ80: in Italy there are many HDJ but there will be 2 or 3 FJ all over the country !!!
Mine is from 1991 at 260,000 miles: so far it has gone beautifully, but now it sometimes goes out due to a blockage from the ECU to the spark circuit. I changed the main relay, then a new ECU and made all the checks on the electrical part and on the fuel circuit: but for now I am still looking for the problem.
Now, however, I have a question that no one in Italy can answer: if an injector short-circuits, could it be that through the control unit this blocks the whole engine? Or, if an injector short-circuited, is it like his other problem and it just doesn't work with the car going at 5 ??
If someone can answer me, help me to do some new tests!
Greetings to all and thanks !!

 

[CJF]

Hello everyone.
I write from Italy: here I have a FJ80: in Italy there are many HDJ but there will be 2 or 3 FJ all over the country !!!
Mine is from 1991 at 260,000 miles: so far it has gone beautifully, but now it sometimes goes out due to a blockage from the ECU to the spark circuit. I changed the main relay, then a new ECU and made all the checks on the electrical part and on the fuel circuit: but for now I am still looking for the problem.
Now, however, I have a question that no one in Italy can answer: if an injector short-circuits, could it be that through the control unit this blocks the whole engine? Or, if an injector short-circuited, is it like his other problem and it just doesn't work with the car going at 5 ??
If someone can answer me, help me to do some new tests!
Greetings to all and thanks !!

Welcome. I'll page our 3FE electrical guru for you. @jonheld

 

[jonheld]

Hello everyone.
I write from Italy: here I have a FJ80: in Italy there are many HDJ but there will be 2 or 3 FJ all over the country !!!
Mine is from 1991 at 260,000 miles: so far it has gone beautifully, but now it sometimes goes out due to a blockage from the ECU to the spark circuit. I changed the main relay, then a new ECU and made all the checks on the electrical part and on the fuel circuit: but for now I am still looking for the problem.
Now, however, I have a question that no one in Italy can answer: if an injector short-circuits, could it be that through the control unit this blocks the whole engine? Or, if an injector short-circuited, is it like his other problem and it just doesn't work with the car going at 5 ??
If someone can answer me, help me to do some new tests!
Greetings to all and thanks !!

I would suggest starting from the beginning.

General Tech - 3FE EFI Diagnostics

3FE EFI Diagnostics updated for 2020

forum.ih8mud.com

 

[gummycarbs]

but now it sometimes goes out due to a blockage from the ECU to the spark circuit.

What exactly do you mean? Does it blow a fuse, or does the engine just die suddenly and can be immediately started again?

 

[GinoG]

Thanks for the 3FE Diagnostics: now I study it! even if it is difficult for me to understand such technical English… but slowly I can do it!

Gummycarbs, it is a long story and in a first phase I had found help here reading the forum.
Now I believe that multiple problems occurred at the same time.
It all started with a not-starting problems when I turned off the car when hot. At first it rarely did it only in very hot summertime, then often, then quite always.
I did a lot of checks on the various components, distributor pick up, power module, coil…. Everythings ok.
The cause was that in the hot start there was no current reaching the spark plugs. Then thanks to the forum, I changed the Main Reley and that problem disappeared.
But immediatly the car started to switch off by itself when hot and then it no longer worked until it was cold again.
And at that point I verified that it was a fuel problem. It was a long time that I had several other jobs to do, so I took advantage of it also because if not too many things could affect making it difficult to understand the real problem. Lamba probes, the exaust perforated for rust to be changed, the MAF (but the original here I could not find it and therefore I changed with Cardone 74-20070 as I had read here on the forum), cleaning of the tank and filter with fuel pump change.
The strange thing is that in all this story I never saw the yellow CEL lighting on, even by disconnecting the MAF or Lamba ... never ever, yet the light bulb works ...

The result now is that the car switches itself off when hot and restarts almost immediately. The problem is of a fuel nature, but it seems that it is the ECU that sends a block to the injectors and therefore I also tried to change the ECU because I found a good used one. This is why we thought - with my mechanic - that perhaps an injector short-circuited and this could ask ECU to stops every others. But I don't know if the FJ80 does this, or in the event of a short circuit on an injector it blocks only that one and the engine runs even if it has 5 cylinders, as some car do.

thanks to all those who want to give me their opinions!!!

 

[jonheld]

in the event of a short circuit on an injector it blocks only that one and the engine runs even if it has 5 cylinders, as some car do.

The ECU in the 3FE fires injectors in 2 banks of 3. If there was an issue with a single injector, it would likely take out the other 2 in that bank.
However, I find that VERY UNLIKELY given your description of the problem. Work through the EFI diagnostic document and remember If the CHECK ENGINE light is NOT illuminated with the key in the ON/RUN position BEFORE cranking the starter, this engine will not run.

 

[GinoG]

The ECU in the 3FE fires injectors in 2 banks of 3. If there was an issue with a single injector, it would likely take out the other 2 in that bank.
However, I find that VERY UNLIKELY given your description of the problem. Work through the EFI diagnostic document and remember If the CHECK ENGINE light is NOT illuminated with the key in the ON/RUN position BEFORE cranking the starter, this engine will not run.

Thanks, that was clear to me.
I explained myself wrong: the yellow light is on with the key in in the run position before cranking the engine and then it goes off. But I am amazed that it never turned on with the engine running even when I removed the connector to the MAF or the Lamba sensor or other temperature sensors on the engine.
Situations in some of which maybe the engine ran badly but ran anyway and I would have expected the warning light on (with the engine running).

 

[jonheld]

Thanks, that was clear to me.
I explained myself wrong: the yellow light is on with the key in in the run position before cranking the engine and then it goes off. But I am amazed that it never turned on with the engine running even when I removed the connector to the MAF or the Lamba sensor or other temperature sensors on the engine.
Situations in some of which maybe the engine ran badly but ran anyway and I would have expected the warning light on (with the engine running).

Please remember that the ECU in your truck was designed in 1986. This is first generation fuel injection. Removing the connector on the AFM (not a MAF on this engine) won't throw a code. Not sure what you mean by a "Lamba" sensor.
Buongiorno.

 

[gummycarbs]

Not sure what you mean by a "Lamba" sensor.

Probably Lambda, i.e. oxygen sensor.

 

[GinoG]

Yes, thank you. The sensors in the exhaust for the oxigen.
I had one with the cable cutted, but in that case the yellow light shouldn't have come on with the engine running to signal an anomaly?
Or even here I am expecting too much from my old diagnostic system!
I have read the file for the 3FE diagnostic procedure.
However this mainly refers to engine not running problems at startup. However, I did some of the instrumental checks indicated to check parts of the electrical system (coils, distributor pick-up ...), but other indications will be useful for other checks and o'll do these too.
My problem now is not with starting, but that the engine suddenly stops while driving because there is no fuel supply even if the single parts (pump, pressure regulator, injectors) seem to work well
Thanks anyway to everyone

 

[blinkerfluid]

Hello everyone.
I write from Italy: here I have a FJ80: in Italy there are many HDJ but there will be 2 or 3 FJ all over the country !!!
Mine is from 1991 at 260,000 miles: so far it has gone beautifully, but now it sometimes goes out due to a blockage from the ECU to the spark circuit. I changed the main relay, then a new ECU and made all the checks on the electrical part and on the fuel circuit: but for now I am still looking for the problem.
Now, however, I have a question that no one in Italy can answer: if an injector short-circuits, could it be that through the control unit this blocks the whole engine? Or, if an injector short-circuited, is it like his other problem and it just doesn't work with the car going at 5 ??
If someone can answer me, help me to do some new tests!
Greetings to all and thanks !!

a short in the +12v of the injector will cause the efi fuse to blow

 

[jonheld]

a short in the +12v of the injector will cause the efi fuse to blow

Not on a 3FE. The +12 for the injectors is off the AM2 fusible link through the ignition switch.

 

[UsedLuxury]

Could the EFI relay be dropping out when it gets hot?

 

[proteolytic]

Could the EFI relay be dropping out when it gets hot?

seems pretty consistent with EFI relay. It was mentioned that he replaced the main relay - not sure if that meant EFI or not. He may want to consider changing relay to camry relay. Other possibilities could be fuel pump is giving out (either because of age or strain). Have fuel filter and fuel pump "sock" filter been changed?

 

[Trollhole]

If the fuel pump would cut out the vehicle wouldn’t die suddenly. It would lose pressure and run poorly for at least a few seconds if not more before dying.

I’d be looking at the coil, igniter, or as stated the main relay.

Hard for an injector to short out. It’s not hard for the wiring to the injectors to.

 

[jonheld]

OP stated that the CEL was illuminated, which rules out the EFI relay.

 

[proteolytic]

seems pretty consistent with EFI relay. It was mentioned that he replaced the main relay - not sure if that meant EFI or not. He may want to consider changing relay to camry relay. Other possibilities could be fuel pump is giving out (either because of age or strain). Have fuel filter and fuel pump "sock" filter been changed?

sorry, also saw that he changed fuel pump and filter. Interesting that this only happens when the truck is warmed up. Would electrical (wires/plugs) be sensitive to warm engine bay like this?

 

[GinoG]

sorry, also saw that he changed fuel pump and filter. Interesting that this only happens when the truck is warmed up. Would electrical (wires/plugs) be sensitive to warm engine bay like this?

Hi, thanks to those who answer !!
Yes, I changed the Mani Releay: this 90987-02004. I call it like this, that because this is the name as a spare, but I believe it is the Efi Relay. Not with the Camry I had read about, but with an original Toyota because the only one available immediately.
And also fuel pump and filter. Coil has been well verified and is ok.
This is because I thought about the possible electrical problem with an injector that blocks everything: but right taht maybe it only does it on its bank.
Right that could be the wiring and not the injectors. Good idea.
I saw that it is also difficult to find the injectors if not Chinese stuff that I really don't trust .... I was thinking of buying a couple and testing them by changing them randomly ...