[buzbox]

I had a little issue with my 4age rolla last night. Basically I revved its tits off but as I was about to change gear at about 7000rpm there was a significant power loss and then started to sound like a WRX.

Basically It's running on 3 cylinders now and I've been doing some fault finding. I was hoping that the spark plug electrode shat itself so I replaced the plugs but the one's I pulled out still looked ok. While they were out I did a compression check which the pressure was even across all cylinders with an average at about 120psi.

I ran the engine for a little bit and pulled the plugs again to find which cylinder isn't firing and I found that 1 plug was still clean whereas the other's obviously has signs of them firing

So my question is, how do I test just the lead, what are the chances of just 1 lead failing and why did it fail. They are 6mm eagle leads (which may explain it) and they do appear to be fairly newish with no signs of damage.

And is there anything else I should check before reluctantly buying new leads?

[89_tintop]

do a resistance check on them using a multimetre.

is it a coil pack or dizzy engine??

if dizzy have you checked that cap

[youda]

the easiest way is to check the resistance of all the leads and see if one is way out from the rest. if they have been in there a fair while just replace them anyway.

[royce]

a plug that isnt firing will be grubby and wet

injector opening?

[buzbox]

I have replaced the cap and rotor button probably about a month or so ago so it's unlikely for that to cause any issue but it doesn't hurt to check.

As for a multimeter, well for some reason each time I use one I tend to blow them up

[youda]

another way swap the lead on that cylinder with another and see if the fault reoccurs on another cylinder or the same one.

[christover1]

If a lead has a crack in it, it can run fine till it gets hot, then break down.

[buzbox]

royce wrote:

a plug that isnt firing will be grubby and wet

injector opening?

I only ran it for less than a minute but the plug wasn't wet and I do have a spare set of injectors so I can swap them over and see.

I'll take off a lead out of the Vit and replace the suspect lead to test if the lead itself is faulty. But the leads appear to be in good condition, no cracks, white marks or deterioation.

[nascpro44]

youda wrote:

the easiest way is to check the resistance of all the leads and see if one is way out from the rest. if they have been in there a fair while just replace them anyway.

They should all be slightly different but measure them with multimeter and they should be a certin kilohms?? Per meter or sumthin like that google shal help

[Ben_Sierra]

buzbox wrote:

royce wrote:

a plug that isnt firing will be grubby and wet

injector opening?

I only ran it for less than a minute but the plug wasn't wet and I do have a spare set of injectors so I can swap them over and see.

I'll take off a lead out of the Vit and replace the suspect lead to test if the lead itself is faulty. But the leads appear to be in good condition, no cracks, white marks or deterioation.

If the plug has come out clean after a minute of running, I'd say that cylinder isn't getting fuel...

[FullyZooked]

Above is true. Clean plug is no fuel. But I would be looking twice at your compression readings.

120psi is not correct. If it is you donk is unwell. Did you allow the engine to crank continuously until top pressure was reached? Did you have the throttle body open 100%?

[buzbox]

FullyZooked wrote:

Above is true. Clean plug is no fuel. But I would be looking twice at your compression readings.

120psi is not correct. If it is you donk is unwell. Did you allow the engine to crank continuously until top pressure was reached? Did you have the throttle body open 100%?

I cranked it over for about 5 revolutions or so, I didn't have the throttle open, just cranked it over. As for it being unwell, You would be tired too if you done well over 300,000km

I thought the readings were rather low, but seemed to be consistant across all cylinders. I will re-test it, but seeing that there is compression, I thought it would be a spark issue.

I will change the sus injector and see how it go's.

[buzbox]

Well thanks guy's for the suggestions and for getting me to check the injector

I didn't need to change it but I did find that the injector plug clip had been broken and it doesn't click into place securely. I did plug it back on, put a dab of silicone and she'll be right.

Thanks for saving me precious $$$

[Scrawny]

buzbox wrote:

Well thanks guy's for the suggestions and for getting me to check the injector

I didn't need to change it but I did find that the injector plug clip had been broken and it doesn't click into place securely. I did plug it back on, put a dab of silicone and she'll be right.

Thanks for saving me precious $$$

Had that on a turbo'd Mazda, damn clip would just rattle loose and run on 3 Glad it was an easy fix for you!

[christover1]

My Baleno/Swift import engine still had manifold and injectors.
I used the Vit stuff.
Can I keep the Swift?Baleno injectors as spares?

[Scrawny]

christover1 wrote:

My Baleno/Swift import engine still had manifold and injectors.
I used the Vit stuff.
Can I keep the Swift?Baleno injectors as spares?

I'd imagine they'd be the same

[FullyZooked]

For future reference and accurate readings be sure to have the throttle open 100% and crank engine until top PSI is reached.

Glad to hear you got it fixed.

I want a 4age

[2stroker]

FullyZooked is right but be aware also that in this instance (i.e. trouble shooting a miss/ dropped cyl) the PSI reading is not as important as the fact that they are fairly even, I remember on an engine we had here we tried three different gauges my sons new Snap On gauge, my old Repco gauge and my sons original gauge which I think is a Mitivac brand, they all read different PSI and from memory there was about 10psi difference between lowest and highest. So if you are uing a cheap gauge it could read anything, just like the variation you get with tyre air pressure gauges.

[FullyZooked]

Yup, seen it many times 2 gauges reading within +-10 of each other, one cheapy as low as 30psi difference on all cylinders. As you say, as long as the pressures are within 5-10 psi of each other this will rule out valves, compression as an issue.