Intermittent Weirdness

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Zuffen

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After 6,000k's of reliable running the 1UZ has decided to do my head in, again!

There have been no changes made to the wiring or work in the engine bay in the last 6 months.

Over the last 2 weeks the car will fire up and run well for a few minutes then just stop.

Fortunately each time it has stopped it was still on my driveway so I can get it back under cover, as it doesn't have a roof.

It still has fuel pressure (it has a gauge on the fuel rail) but it also has 12v power to both pins of the injector clips.

Now I know there should be power on only 1 pin of the injector clip and the earth is activated by the ECU to make the injector function, but why is there power to both pins?

Obviously there isn't power to both pins when the engine is cold or it wouldn't start.

There's 12v power at the igniters as it should be.

I've checked all connections in the engine bay and haven't found anything loose or astray.

The spark plugs look good and no sign of running rich, as I thought it may be flooding for some reason before I found the power at the injector clip weirdness.

The last time I drove the car I gave it a pretty good flogging and it was running really well.

I can borrow another ECU to test it isn't ECU driven but my ECU was serviced and checked by a very competent workshop. I don't expect a change of ECU to solve the problem.

I'm open to suggestions.
 
Rod, I would put the DVM on an injector clip, and on the terminal that you're fairly sure should be the ECU side that normally gets pulled to earth to fire the injector.

I would then go one by one and disconnect all the other injector clips from their injectors. If you lose the +12 when you disconnect one of the injectors, you may have found either a shorted injector, or a bad lead to the injector.

Failing that, I'd disconnect the main ECU connector and then check the injector clips for continuity, and give them a wiggle test while you're checking them.
 
Power at both sides of the injector is normal. Basic electrical 101. Until the component is switched (injector earthed by ecu) there will be 12 volts all the way to the switch. When the switch it activated the component works and there is earth tested after the component.

1uz issues - Check coils- Normally fire and stop. Check for spark. Try some engine start. Check Ignitors are well earthed (Shouldnt have changed but still check. )

Cheers
 
Thanks Gents.

I have code 14 & 15 so trying a different set of igniters.

The injector pigtail has power both sides when disconnected, should have specified that. To me there shouldn't be any power on one side as it's waiting for the ECU to pull it down to earth.

On strange code is code 78? doesn't seem to exist.

I think it will be either coils or igniters as it runs for a few minutes (very well in fact) then stops.

I pulled a spark plug yesterday and turned it over to see if it had spark and the engine started first flick of the key as it had cooled down whilst I removed the plug covers and got a plug out. To me the igniters or coils are overheating and shutting down. Can't think why both sets would be overheating.

More fun today.
 
code 78 is fuel pump computer where applicable, or 1st/2nd fuel pump relay, for cars with fuel pump resistor instead of computer

you mentioned igniters, so it's nonvvt
Would be nice to see when / in what order the codes reappear after clearing them
 
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The engine is from an SC400/Soarer but it runs with a tachometric relay to get around the fuel computer.

I had a play today but still have power on both pins of the disconnected injector plug.

My spare igniters don't fit as they are the second sort that Toyota use.

I'm pretty sure I can borrow a set from another member.

Perhaps tomorrow I'll have a look at the ECU plug and see if anything has gone wrong there.
 
Good morning.

As it's a group fired injector setup you need to unplug both injectors from each set to drop the 12 volts on both sides of the injector plug. I suspect you are seeing the 12 volt feed through the second injector on the pair.

I did a code 14 the other day. It would stall at times , sometimes start straight away, sometimes not. Sometimes it didn't start cold but if it did it ran fine. I checked it over and told the customer it was a coil problem. He didn't believe me but I suggested we try it and see. Sure enough it was the issue. Runs fine now. Most of the time code 14 or 15 is a coil issue. Often when one fails the engine will stop as the ECU turns off the injectors to save the converter. It can be tricky as they often start and run OK on engine start.

Having both code 14 and 15 is a little strange. Have you cleared them and then tried again? I would be fitting two new coils first. They aren't expensive and are normally due anyway.

Good luck
 
Kelvin,

Thanks for the information.

I have a couple of old coils so I'll throw them on and see what happens.

If it solves the problem I'll get 2 new ones.

As you say they are nearly 20 years old so they've done well.

I'll let you know how it goes.
 
I haven't bothered replacing the coils with an old set I have.

I've ordered two new ones and I'll fit them when they turn up.

They're cheap enough to be less than the price of half a set of Spark Plugs!
 
Well it's up and running again.

My new coils turned up this morning so I fitted and them and no difference.

The next step was to check the igniters were powering up. To do this means I need to remove the airbox and generally fight with it. Whilst doing this I had left the ignition on and the fuel pump would intermittently run.

My fuel pump runs through a tachometric relay meaning it gets power for a few seconds when the ignition is turned on then is becomes active when it senses the engine is running. There are two ways to get a signal to the relay, 1 via an injector or 2 an igniter. I had chosen the latter.

I figured out the igniter was turning on and off to cause the fuel pump to run and a little probing found a bad earth on the igniters.

The car has a fibreglass body and the earth is via a designated wire attached to the igniter's cradle and under a bolt on a subframe. The bolt had come loose and a small bump was all it took to take the earth off the igniters.

So the car has new coils (not a bad idea) and a new earth connection to ensure it keeps running.

I'm just lucky it decided to give trouble on my own driveway as there's no way this thing will fit on a car trailer as it's about 2150 wide!

Now to get out and drive it is topless car weather.
 
good job, enjoy the nice weather

you said earlier that coils were cheap

how much are they down under? toyota stuff or refurbished or 2nd hand or after market or?
 


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