3rz running on 3 cyls, input required.

2444 Views 17 Replies 7 Participants Last post by Tweaka, Mar 12, 2010

anthonyr

Discussion Starter · Mar 9, 2010

Hey guys just put a turbo kit (here in aus) on my 3rz truck. Its running microtech computer, and before installing the turbo i ripped the head off to be reco'd, and reinstalled it with a cometic 1mm gasket and arp studs.

Now its all together it only runs on cyls 1-3, with 4 not working. We've tried everything to pin point the problem from new plugs, leads, changed injectors around, tested the injector wiring with a tester, swapped coils etc. Compression came up 185-200psi across the range so its def got good compression. Also pressurised each cyl to ensure the hg wasnt leaking into the coolant or oil, but this came back good.

Any input into the problem or how to fix? Ive built motors, done wiring, designed the turbo manifold, so im no slouch when it comes to cars, but this thing has me stumped. Usually compression + spark + fuel = a good cyl/engine but not this time.

Cheers

Anthony

1 - 18 of 18 Posts

Enola Gaia

· #2 · Mar 9, 2010

Just so we're clear ... When you say cylinder 4 is 'not working', do you mean:

- it's misfiring?
- it's totally 'dead' (no 'firing' at all)?

You've confirmed cylinder 4 is getting fuel, right? And you've confirmed cylinder 4 is getting spark, right? Or ... ???

I'm not familiar with MicroTech ( http://www.microtechefi.com/ ) units. Precisely which unit are you using? Did you follow any of the wiring diagrams on the MicroTech site?

anthonyr

Discussion Starter · #3 · Mar 10, 2010

Sorry. cyl 4 is totally dead. doesnt matter whether i remove the plug or remove the injector plug, it doesnt make a difference. Engine builder has no idea, nor do plenty of car orientated professionals.

Definately getting fuel and spark, and lots of compression. removed the plug and placed it on the engine cover to ensure spark and theres definately fuel getting in there.

Im using a microtech lt8, keep in mind this has been running on the car for nearly 4years without a problem.

cheers for your help

Slick Nick

· #4 · Mar 10, 2010

Damn what a problem...how did u determine its dead? More details please. Otherwise next thing to check is ur cylinder head, are the intake and exhaust valves opening and closing properly? Do they seat properly and make a tight seal? Good luck

anthonyr

Discussion Starter · #5 · Mar 10, 2010

Determined its dead because its got spark, fuel and compression but wont run lol

The head was reco'd, had a valve job and some light porting to clean up factory castings etc so the head is def perfect condition.

Comp came up 190-200psi across the range, including no4 (id expect it to be a touch on the high side as the block has been decked, the head surfaced and running the cometic gasket).

Ive pressurised each cyl and there isnt any bubbles coming into the radiator, oil, crankcase, between cyls, so combined with the other tests id say the hg is fine.

Valves are opening and closing properly, and yes they do seal but even if this was not the case (like many high mileage motors) I cant see why the cylinder would fail to run at all.

In the past with others cars, ive diagnosed similar problems by removing an injector plug or spark plug one at a time and then swapped them around to pin point the problem (i.e if 4 wasnt running id swap no 3 plug with 4 and this would then make cyl 3 the non running cyl thereby identifying the cause of the problem whatever it may be) but this is making me tear out my hair.

The microtech has a test function where it fires all outputs (coils, injectors etc) so you can test for faults, but everything works as it should.

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Enola Gaia

· #6 · Mar 10, 2010

These may be dumb questions, but ...

You've apparently confirmed the valves are working in general - i.e., they're doing *what* they're supposed to do. Have you confirmed that the Cylinder 4 valves are working exactly *when* they're supposed to be opening / sealing? If everything is present but wildly out of synch, wouldn't that render the cylinder 'dead' (as far as firing off with the others)?

Next - same questions for fuel and spark. You seem to have confirmed they work in general (i.e., 'sometime'), but have you confirmed they work exactly *when* they're supposed to work?

Is it possible you've got a transient short circuit somewhere that's killing or screwing up cylinder 4 operation when everything's assembled, but not when you remove the injector and / or spark plug?

TACOMATruckin98

· #7 · Mar 10, 2010

Good thinking enola about not working when fully assembled.
But this is a rather complex problem, I mean, with that computer there is almost no telling what it could be, I mean, it may be getting spark, but is it at the right time, is the fuel being delivered at the correct time? dunno all your engine specifics, but i mean, if something got out of wack enough your valves could be open too long and just letting the piston push the fuel mix out before firing. Theres no way you can replace this microtech unit back with a stock ECM to test it all out is there?

Speed Freek

· #8 · Mar 10, 2010

If you have Fuel, Spark, Compression, and its all timed right, it will run for sure, it must be an issue with firing out of sync somehow.

Does the plug seem totally dry? Did you hook up a noid light to see if the injector is getting a signal? Did you switch injectors around to see if the dead cylinder folows it?

Let me know, I am pretty good at figuring this stuff out. Or just PM me if I dont reply to this thread.

anthonyr

Discussion Starter · #9 · Mar 11, 2010

The plug definately has fuel on it, and 100% has spark. Hooked up a noid light and its getting signal (confirmed also when i put no 4 wiring onto no 3 injector). Switched everything a few times, no4 remains the dead cyl.

I doubt its a short as when i swap the wiring around on the spark plug or injector no4 still is the bad cyl.

Ill check the shim clearances with a feeler gauge to rule out the valve clearances (i just didnt bother as the clearances were done before i put the head back on by the engine builder). FIngers crossed its just this!

Cheers guys for your replies. If you think of anything else keep the suggestions coming.

TACOMATruckin98

· #10 · Mar 11, 2010

im not sure if its been adressed but i couldnt find it if it has, has the engine after being built ever run, or has it had cylinder 4 dead from the first start? and could you tell us how the engine is all set up? this might help rule things to be questioned or unquestionable

Speed Freek

· #11 · Mar 11, 2010

anthonyr said:
The plug definately has fuel on it, and 100% has spark. Hooked up a noid light and its getting signal (confirmed also when i put no 4 wiring onto no 3 injector). Switched everything a few times, no4 remains the dead cyl.

I doubt its a short as when i swap the wiring around on the spark plug or injector no4 still is the bad cyl.

Ill check the shim clearances with a feeler gauge to rule out the valve clearances (i just didnt bother as the clearances were done before i put the head back on by the engine builder). FIngers crossed its just this!

Cheers guys for your replies. If you think of anything else keep the suggestions coming.

If you have equal compression in all cylinders your valves arent open (tight), it doesnt mean they dont need adj, but they shouldnt not be at "no clearance" and your still getting good comp numbers.

Fuel+spark+compression=combustion as you know, one of these is missing or out of sync, it has to be, otherwise it would do something..

Tweaka

· #12 · Mar 12, 2010

Have you got it started. eg does it attempt to run all be it very ****ty?
Check both intake and exhaust lifters may be either damaged or has a air lock (poor rebuild).
Also you say the injector #4 fire's............. but does it fire at the correct time?
Before you attempted to start it after the head was put on did you make sure there was oil pressure to the top of the head, did you fully sink the lifters in oil before putting them in

Can ya wind it over by hand?

anthonyr

Discussion Starter · #13 · Mar 12, 2010

Engine was running, just 4 wasnt.

Anyway we got it fixed today, and ended in the biggest laughing fit ever once we found the problem. Its one of those big mistakes you do in your life and never repeat it. Glad nothing was damaged as a result as a lot of cash has been thrown into it (new motor, new turbo setup, steam pipe manifold with merge collector etc etc)

A new rule to the known equation of fuel+spark+compression=combustion is AIR. Who can guess why no4 cylinder wouldnt be getting air?

On a side note, being untuned, heaps and heaps of timing pulled out and running very rich, it pulls like a steam train. The turbo is a masterpower 700hp jobbie with a real small rear housing. Should make close to 400rwhp (this is aus hp too) and is high compression. Saw positive pressure at 2000rpm and then its on in an instant

smiles all round

Slick Nick

· #14 · Mar 12, 2010

So what was the problem? your settings in your computer or intake?

03TacoPre

· #15 · Mar 12, 2010

anthonyr said:
Engine was running, just 4 wasnt.

Anyway we got it fixed today, and ended in the biggest laughing fit ever once we found the problem. Its one of those big mistakes you do in your life and never repeat it. Glad nothing was damaged as a result as a lot of cash has been thrown into it (new motor, new turbo setup, steam pipe manifold with merge collector etc etc)

A new rule to the known equation of fuel+spark+compression=combustion is AIR. Who can guess why no4 cylinder wouldnt be getting air?

On a side note, being untuned, heaps and heaps of timing pulled out and running very rich, it pulls like a steam train. The turbo is a masterpower 700hp jobbie with a real small rear housing. Should make close to 400rwhp (this is aus hp too) and is high compression. Saw positive pressure at 2000rpm and then its on in an instant smiles all round

Forgot about a rag in the plumbing?

No clue otherwise.

anthonyr

Discussion Starter · #16 · Mar 12, 2010

HAHA my singlet in the plenum that was pushed down into runner 4.

Only reason I thought to check was i was looking for my singlet and remembered i stuffed it down the intake when i pulled the throttle body off to put a new gasket on, and i didnt want anything falling down there. Just forgot to take it out! Biggest brain fart ever!

Lucky it was a singlet and not a small rag else the rag would have been sucked into the engine. It was seriously wedged in there hard and took a bit of pulling to set it free!

Thanks heaps for the suggestions guys

Slick Nick

· #17 · Mar 12, 2010

OMG thats pretty funny...well at least thats all there is to it

Tweaka

· #18 · Mar 12, 2010

if all you can make is 400hp on a forged bottom end 3rz then you better see another tuner.

ON a stock engine i got 320hp on 17psi

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