Let Ignition Problem

[G1C]

Hi,
I am completly stuck with an ignitoin fault of some kind on my let engine and was pointed in the direction of your club as I don't suppose there is anyone better to ask.

The engine was an xe engine but have fitted the low compression pistons, steel head gasket, modified top hat and xe throttle body, uprated bolts and all the other let essentials but using a custom made manifold and t3 turbo with let loom and ecu.

After getting it in and all sorted it would only fire occasionally on the first cylinder, so first thing to check was the timing which was spot on I even changed the verniers to the standard pulleys to make sure.
With a bit more messing and laying all the plugs on top of the engine it only sparks on cylinder 1 spark plug everytime. I have fitted a new dizzy, coil, ignition module and crankshaft sensor but still only sparks on cyl 1 spark plug so I am now looking towards the ecu but any ideas and help will be greatfully appreciated.

Cheers
Graham

[T.F.S.]

sounds like ecu fault mate

for your tech info try <a href="http://www.migweb.co.uk" target="_blank">www.migweb.co.uk</a> a lot more knowlege on there

[ice]

defo sounds like the ecu or chipset

[Stupink]

presume the coil output is only sparking once then? if it was timing out for whatever reason you'd still have all 4 sparks there just out of time on the dizzy to make it to the plug [img]/smile.gif[/img]

[G1C]

The timing was just the first thought due to it only firing ocasionally and having the verniers on but after a few more checks found it only to have the 1 spark on cylinder 1
After messing a bit more today I am thinking the crankshaft sensor more than the ecu now due to it sparked the 1 and only time ever on plug 2, Which if I am right in thinking the ecu only sends out 1 pulse at a time so that side of it must be working.
I tested the new crankshaft sensor today which gives a much higer signal so am thinking pages may have sent the wrong 1 so have ordered a genuine gm sensor from vauxhall and will give that a try as it is the crankshaft sensor that determines when it is time to fire by the notches on the exciter ring on the crankshaft each being 3 degrees I think so has to be worth a try.

[Stupink]

yeah definately if you're getting a different reading, it was my first thought untill i re-read that you'd already replaced it. but new doesnt allways mean right or working [img]/smile.gif[/img] keep us updated [img]/smile.gif[/img]

[G1C]

Update,

I changed the crankshaft sensor for a new genuine gm sensor and the problem is still the same, So the only things that are not new are the ecu and wiring loom which out of the two I would think has to be the ecu.
I will try and borrow one before buying to make sure though as they aint cheap these days.
Cheers for the help and will let you know more.

Graham

[Stupink]

have you checked the frequency of the coil output to make sure it is only outputting that one spark that is making it to no.1 yet? worth doing before shelling out anything. I would guess it probably is just doing that one, as its unlikely one would be in time if the other 3 wernt, but it has to be worth investigation for the small time it would take [img]/smile.gif[/img]

[G1C]

Just another thought, are the let and xe distributors different from each other as I think the one I am using is an xe distributor.

[Stupink]

I'm fairly sure they are the same. so it shouldnt be that.
What other differences are there in the setup from a std let? Do you know the LET engine well to know that you have all the sensors etc as they should be?

[G1C]

I checked the coil for sparking today and it is firing spot on and loads of sparks so they are somehow not getting through the distributor, I have now tried another ecu and still the same so defo not the ecu.
I read the hall sensor is inside the dizzy which gives the cylinder recognition hence my last question, I know this has to be somthing so stupid and proberley ovious but am running out of ideas I work in a garage and none of the lads there can come up with anything (but we are hgv mechanics so diesel is our game lol)

[dj_smurph]

ar eyou getting the engine management light on if so have you done the paper clip test

[Stupink]

Excellent news, hoped that would be the case, should be easier to hunt down.
so basically all 4 sparks are there, but either A the route from the input lead to the spark plug is broken on 3 of the 4, OR the timing is so far out that the rotor arm is not near enough the contact point for the sparks to jump.
You've checked with a multimeter between the contact points inside the distributer and the electrode on the spark plugs?

As you're getting one spark consistently it can't really be the middle conductor or rotor arm resistance etc.

The distributer cannot be rotated, Have you checked that the rotor arm is being driven though? turn the engine over slowly by hand on the crank with the plugs out, and make sure the rotor arm spins correctly, and that with mild force (hold it with your hand) it will still spin as it should and isnt slipping. the lug might not be aligned correctly with the cam drive, or the allen key on it might be loose and allowing it to spin etc etc. it might just be sitting there in position1 constantly.

[G1C]

I have had the diagnostic bloke down today and he says the coil is still only putting out the 1 spark it just looks more rapid, after a bit of bit of head scratching and testing here and there he says it is defo the ecu or the sensor ring on the crank.
So I am sending my ecu's down to a mate to try on his car and if they are both ok it looks like it's going to be an engine out job and bottom end strip down, I can't see what can go wrong on the sensor ring but it is the only thing that is not new and is part of the ignition setup so will have to give it ago.

I will keep you posted.

[Stupink]

have you tried to start it with any of the sensors disconnected to see if any of them make it better/worse?