3FE Head Gasket (1 Viewer)

[Rush]

Sure sounds like you're not getting fuel.

Exactly. (Not enough fuel, at very least.)
I was worried the old fuel had gummed up my freshly cleaned up injectors...
I'll confirm injector voltage/operation, then pull out a plug to see if it's wet.

 

[Rush]

@jonheld 12 volts at each injector plug, with one pin at zero -once all three per bank are disconnected. No change in grounding/continuity to ground of the zero volt pin when cranking. 12 pin shows volts while cranking at 11.something.

What should I see on that other pin when the injectors fire, and is a ground against the head correct to detect it?

 

[jonheld]

@jonheld 12 volts at each injector plug, with one pin at zero -once all three per bank are disconnected. No change in grounding/continuity to ground of the zero volt pin when cranking. 12 pin shows volts while cranking at 11.something.

What should I see on that other pin when the injectors fire, and is a ground against the head correct to detect it?

That's a very confusing couple of statements.

Each injector gets a constant +12 with the key in the ON position on pin 2 (black wire/green stripe).
The ECU sends logic low PULSES to pin 1 of each to fire the injectors. If there was a constant ground, then the injectors would be dumping fuel into the intake.

You probably won't be able to read the pulses on a standard DMM, but I wouldn't expect to see a hard ground on pin 1. Again, that would keep the injector coil energized and fuel would be pouring out.

 

[jonheld]

Also, keep in mind that when measuring voltage on the injector connectors with the injectors in circuit, I would expect to see +12 on both pins as you're measuring across a coil. The ECU will ground 1 side (pin 1) for a brief moment to fire each bank. Again, the ECU pulses (logic low) the banks of injectors to fire them.

 

[Rush]

Also, keep in mind that when measuring voltage on the injector connectors with the injectors in circuit, I would expect to see +12 on both pins as you're measuring across a coil. The ECU will ground 1 side (pin 1) for a brief moment to fire each bank. Again, the ECU pulses (logic low) the banks of injectors to fire them.

Sorry for the confusion and my wording, I'll clarify.
I did see 12v on both pins of each injector until the third injector was disconnected.

When cranking it drops to 11ish, which sounds like it should be fine.

So I misunderstood you, then: It's not a true grounding, but a logic low.
The question remains of how to detect this. I'll Google it, and inspect accordingly.

I'll also confirm the harness has provided continuity on these yellow/white+blue wires back to the ECU.

 

[jonheld]

So I misunderstood you, then: It's not a true grounding, but a logic low.
The question remains of how to detect this. I'll Google it, and inspect accordingly.

I would use an oscilloscope in order to see the pulses. A DMM will not react quickly enough.
That's easy for me because I have one

You should be able to hear an injector if you place a hose to your ear and the other end on the injector or fuel rail while cranking. I have never tried this, but it sounds reasonable to me.

 

[Rush]

I would use an oscilloscope in order to see the pulses. A DMM will not react quickly enough.
That's easy for me because I have one

You should be able to hear an injector if you place a hose to your ear and the other end on the injector or fuel rail while cranking. I have never tried this, but it sounds reasonable to me.

Thanks, that's what I'm finding.

I have a few ideas of what I can try to detect physical operation:
1. Mechanic stethoscope
2. Feel with finger per the FSM

And for injector signal:
3. Test light/noid light at connector
4. Plug in known-good injector and feel for operation
5. Test light at connection to ECU

 

[Rush]

Test light fires on each injector connector while cranking.

So it's one of the injectors, then?

I'll pulse each injector with my tester, to confirm they all at least operate.

 

[Rush]

So... Most of the injectors I cleaned in an ultrasonic for half an hour and then backflushed/flushed with carb cleaner (while pulsing), now do not fire strong.
I hooked up my injector tester to each of them, and the first 4 injectors all required my mechanic's stethoscope pressed against them to hear any clicking. Even then, it was faint.

Injector #6, however, can be heard pulsing from across the engine bay.

I'll remove the intake and fuel rail tonight after work.

I really hope it's just varnish from the old gas, and I don't have borked injectors. They ohmed out fine, so I'm a bit puzzled at what could be causing the vast difference in sound from injector to injector now that they're installed -if not something impeding their mechanical function.

 

[Rush]

It's confirmed, they are only actuating faintly.
I've got them in the ultrasonic again, maybe they'll loosen up with the heat and detergent.

New pintle caps and basket filters are a week out, so I've got time to see if they'll perform again.

 

[jonheld]

It's confirmed, they are only actuating faintly.
I've got them in the ultrasonic again, maybe they'll loosen up with the heat and detergent.

New pintle caps and basket filters are a week out, so I've got time to see if they'll perform again.

I think these are the guys that come recommended by the forum. Not very expensive and quick turn around.

Fuel Injector Cleaning - Page -1

 

[Rush]

I think these are the guys that come recommended by the forum. Not very expensive and quick turn around.

Fuel Injector Cleaning - Page -1

Thanks again for all the diagnostic help, Jon. I'll call them and a few others right now.

Not to forget @BILT4ME's help either!

Glad to have a supportive community to lean on when needed.
I just hope I can give back in a meaningful way.

 

[Rush]

 

[jonheld]

Well that certainly looks promising.

 

[Rush]

Well that certainly looks promising.

Haha, it runs! There's a little mechanic shop in SLC that does injectors.
He was doing brake lines on a recently-purchased-for~$50K FJ40, and had me come look at it when I picked up the injectors.

I got home, put it back together. Set the timing, did the cam break-in, and changed the oil.

Did I mention that it RUNS!?!

 

[Roastchestnuts]

Haha, it runs! There's a little mechanic shop in SLC that does injectors.
He was doing brake lines on a recently-purchased-for~$50K FJ40, and had me come look at it when I picked up the injectors.

I got home, put it back together. Set the timing, did the cam break-in, and changed the oil.

Did I mention that it RUNS!?!

Reading this 3 year old thread makes me really miss my old 3fe fj80. One day Ill get another. so happens a fj80 with a blown head gasket is for sale really close to me... tempting.