What's wrong with my beloved 4-by?

[Red Kev]

Hi all, be nice, I'm new here Though I hope introductions were under different circumstances.

Hope you knowledgeable people might be able to supply some advice to the not-so-knowledgeable:

1992 SR5 4runner V6 (3VZE). More-or-less daily driver, though a second car.

On the way to work a couple of days ago, about 2 kilometres into trip, heard a "thunk thunk", then about 400m later, the following happened:

The accelerator stopped responding i.e. there was still pedal feel, but depressing or releasing the accelerator did nothing drive-wise;
The tachometer stopped responding -- just went to zero;
I could still rev the engine (though as I said before, this did not do anything drive-wise);
None of the gauges did anything unusual;
Coasted to a stop;
Can't recall whether the engine then stalled or if I turned it off, but thereafter it would not start.

The aforementioned "thunk thunk" felt more like intermittent fuel issue or trans issue than a piston problem, but who knows ... There were no other odd noises at any stage.

Got towed home. Found engine oil very low. Two days before I found the petrol level much lower than I would usually let it get to (kids!), but whacked ten litres in before driving so plenty of fuel. Apart from this it has been a good, reliable if thirsty ride, doesn't burn oil to my knowledge, couple of very slow leaks here and there, bit oily around the rocker covers, not unexpected of an engine this age...

Any thoughts from the symptoms described? I read on a Mazda forum (!) that the oil metering pump sensor can cause similar symptoms if tripped or fried, but couldn't find any info if the Forerunner has a similar sensor.

At first I thought it might a fuel issue (i.e.kids driven it dry and sucked some crud through) and have consequently bought a new fuel filter. Not yet installed but the more I think about it the more I don't think it fuel related.

I cannot get any spark an the engine check light will not come on at all. The engine will crank, but not run. The ECL does not come on during cranking.

I have (through some helpful posts here and elsewhere):
Checked all fuses;
Done some tests on the dizzy and coil and concluded they are good.

I suspect the igniter module or the EFI relay.

I cannot run self-diagnostics as the ECL will not come on at all.

Any thoughts appreciated. I have a part-time slashing job, and the 4by is my work truck, so I need to get it sorted.

Thanks.

 

[Red Kev]

Anyone?

 

[Red Kev]

New igniter module has not made a difference.

Seems to be voltages passing through the terminals of the diagnostics thingy. Does this signify that the EFI relay is okay?

Power is getting to the coil, though I don't know of a way to test whether or not the coil is good.

Anyone?

 

[SilentYoda3]

ok well here is what I would do. So first of all looking JUST at the spark problem you're having the circuit for that is fairly simple.
Power to from battery -> ignition switch -> coil -> plugs -> BOOM :flame:

In a very basic form of course.

Since your truck is turning over it's after the ignition switch. Since you're unsure about the coil on where it's good or not, You can unplug the coil wire that comes from the top, and set it near metal and test to see if it fires, if it does the coils good. When testing just slightly bump the start cycle, it should spark. Easier if done at night since it'll be more visible.

Is there any more information you can provide?

I could help if you posted a picture of your engine bay, I no longer have a 3.0L and some of the information I knew I've forgotten since moving to the 3.4L. A picture will help me remember what parts you do or don't have on your motor.

SINCE THIS IS ALL FROM MY MEMORY, if someone else with more mechanical experience could bare in it would be great. There are several very knowledgable people on this forum for classics that would be able to point you in a better direction. Just thought I could try and help.

Another thing is, the classics forum can be sometimes a little slow for a response, be patient though, because once responded the information is always very good and extremely helpful. Best of luck bud. :wave:

 

[Red Kev]

Thanks Yoda. Here's a pic of the engine as a memory jogger.

In this pic, the igniter and coil have been temporarily removed from the passenger side of engine bay. And the hanging spark plug is/was just a test I was doing (obviously, before I removed the coil)

Have been able to borrow a coil as a test and it has again made no difference: still no spark. Power is getting to the coil harness.

Fuel pump is good and is providing fuel to fuel rail.

Power is getting to the ECU/ECM.

Ummm, not sure what else to test. The only thing I can think of is replacing the EFI relay. Or else one of a dozen sensors has tripped and is not resetting?