S2 Still won't fire on cylinder 4

[Spacecowboyuk]

Hi all, been dipping in and out sorting various recommissioning issues on my 2.9 but 2 elude me - brake master and slave and the lack of spark on cylinder 4.

It seems to be only cylinder 4 that won't fire. The plug is wet so has fuel. I have ground a plug to the block and still no spark (sometimes I get an intermittent spark but thats rare). I have swapped leads and I think it may be a dodgy plug suppression extender but not 100%.

I've swapped the cap for a known good used one - same fault.

Outside of the suppression (where do you get those from and can I run without?), any ideas why else it might not spark on that one cylinder or what other tests I should be doing? Thanks!

[Spacecowboyuk]

Thank both I'm going to go back to basics on this.

On the brake servo and master specifically, I understand that my only real option is to go for a Racetech or Motoclan system. Ford parts are now like the Saab parts - they simply no longer exist. Have I got that right?

[Spacecowboyuk]

phillpot said:

Bin the suppressors.

Can I go direct from lead to dissy cap without them? Or do I need to change to a later cap with male connections?

[Spacecowboyuk]

Is it also possible that the dissy isn't quite in the right spot? We removed it to replace the amplifier and I'm wondering if it's slightly off, could this be a symptom?

[Spacecowboyuk]

Bit more testing done:

Sparkrights on all 6 plugs. Number 4 definitely not firing. Very occasionally a spark appears. The rest have a strong spark.

I've swapped suppressors between them all and plus 4 remains dead/barely intermittent.

6 new spark plugs

I've cleaned the cap and rotor arm again.

I've inspected the reluctor. Seems fine.

I've swapped leads about. No change.

The dissy shaft (from the top) has zero play in it.

I'm at a loss now. I noticed that on the reluctor one of the windows is bigger than the other. Can it go on in two different orientations?

Any other ideas gratefully received.

[Spacecowboyuk]

GreenV8S said:

Can you get a lead to reach from the problematic plug to one of the other posts on the dizzy?

Obviously it won't fire, but you should see the usual spark while cranking. This will prove there's nothing funny going on with the lead/plug.

Given that everything up to the rotor arm is common to all cylinders, all that's left is the rotor arm & cap. Give them a really carefull look over. For example, if the inner terminal is slightly out of spec you may have an air gap slightly bigger than it should be.

Was anything changed/worked on shortly before the problem started?

The car was laid up for 10 years. No spark, or ecu signal to fuel pump or for injectors to fire.

Engine turned over fine.

Coil changed. No spark.

Ignition amplifier changed and spark returned. Dissy was removed to do this.

Found out that, for reason still unknown, there was no earth to relays for injectors and fuel pump so wired a seperate earth to the earth going to relays and both came back to life.

The car finally started.

And that's where we are now. It runs on all except on cylinder 4 due to no spark. Very odd.

I will try getting the plug to a different dissy post and order a new arm and cap.

[Spacecowboyuk]

Do these fit out 2.9 and do without the suppressors:

https://www.ebay.co.uk/itm/355840962539?gad_source...

[Spacecowboyuk]

GreenV8S said:

Spacecowboyuk said:

Dissy was removed to do this.

I haven't run into this problem myself, but I've met people who've run into a subtle timing problem cause by getting the rotor shaft orientation wrong when you reinstall the dizzy.

As you change the orientation of the rotor shaft, you change the timing of the sparks. You can compensate by adjusting the body orientation (essentially moving the points and the posts that the rotor arm connects to) to restore the timing, The vac advance also moves the base plate holding the points. Both these adjustment mechanisms alter the alignment between the rotor arm and the contacts in the distributor cap. The rotor arm has a long contact and contacts the cap through quite a long arc, but if the shaft is oriented wrongly It's possible to get into a situation where the rotor arm is barely contacting the HT cap when the spark fires. Sometimes it will even 'double fire' and divide the spark between two cylinders.

The symptoms can be quite subtle because the orientiation changes with vac and mechanical advance, and if the spark is marginal small changes in engine load and small differences in HT circuit resistance can make the symptoms come and go. It can easily impact individual cylinders.

To see whether you have this problem, bar the engine over until it reaches the firing point for a given cylinder and see where the rotor arm is positioned relative to the terminals in the distributor cap. Also check where it's oriented when you have the amount of vac advance you expect when the problems happens. You may find it's worth disconnecting and blocking off the vac advance line to take that out of the equation while you're tracking this down. Also double check that the vac advance cannister is connected to the base plate in the distributor correctly. If the base plate is free to move you can get random timing which can easily fall outside the range that the rotor arm can handle.

I don't recall seeing a vac advance on this dissy but will look again tomorrow.

I'm also wondering if the dissy timing is slightly out. I will perform your checks but tempted to loosen the bolt and turn it each way to see if I can restore spark...

[Spacecowboyuk]

phillpot said:

There is no vac advance on the 2.9 efi engine. If misfire is definitely only on cylinder 4 it could be dizzy cap or a component unique to that cylinder, plug, plug lead, injector or an issue within the engine?
Having said that, injectors fire as a set of three into the manifold so would a cylinder still get some fuel mix if one injector was duff?

Spacecowboyuk said:

Do these fit out 2.9 and do without the suppressors:

https://www.ebay.co.uk/itm/355840962539?gad_source...

It will fit your distributor but more likely you will need one like this or a set of leads to fit the one in your link

Hi

1) I swapped cylinder 4 lead to another post on the dissy and spark was present. When I put the faulty post with the lead to another cylinder, the fault followed it. So it is definitely the second from the right to post number 1 that is at fault on the dissy.

2) That is the cap I have. Looks like I'm into new set of leads as well then. Are they readily available?

[Spacecowboyuk]

Adrian@ said:

Omex-ADA caps come in blue (if you are not colour averse) on Amazon £20.54 ...happy to have blue on my green 280DH with blue hoses! I changed all my injectors a while back due to a misfire. A@

Oh dear ...one of the reviews was that the buyer had ordered it because it was blue and it came in a dull grey!!! and docked the seller a review point.

Edited by Adrian@ on Friday 12th July 18:07

Found it. Cheers for the heads up

[Spacecowboyuk]

phillpot said:

Spacecowboyuk said:

That is the cap I have. Looks like I'm into new set of leads as well then. Are they readily available?

According to my "little black book" these are the leads you will need or I can sell you the cap in my photo. However they are very hard to find, it is brand new but it won't be cheap . . . . . . . £50!

https://www.ebay.co.uk/itm/404807332826

If you have a rotor arm to chuck in I'll take it

[Spacecowboyuk]

phillpot said:

Spacecowboyuk said:

If you have a rotor arm to chuck in I'll take it

I'll message you

Edited by phillpot on Friday 12th July 21:02

Cheers, responded

[Spacecowboyuk]

phillpot said:

Spacecowboyuk said:

Cheers, responded

Nothing received ?

That's odd. Says it's sent from my email? Errr I'll try it again

[Spacecowboyuk]

Spacecowboyuk said:

phillpot said:

Spacecowboyuk said:

Cheers, responded

Nothing received ?

That's odd. Says it's sent from my email? Errr I'll try it again

Also resent as a new email. Failing that, have a chat with Nick who will have my number

[Spacecowboyuk]

Spacecowboyuk said:

Spacecowboyuk said:

phillpot said:

Spacecowboyuk said:

Cheers, responded

Nothing received ?

That's odd. Says it's sent from my email? Errr I'll try it again

Also resent as a new email. Failing that, have a chat with Nick who will have my number

Got your email. In case it's playing up again, can I pop by this morning?

[Spacecowboyuk]

Thanks to @Phillpot for getting the replacement dissy cap and rotor arm out to me so fast but sadly they did not fix the issue. Still not firing (no spark plug but got fuel) on cylinder No.4.

Is it possible the dissy shaft is out of true? Visually it all looks right when I turn her over with no cap on. What a mystery.

Edited by Spacecowboyuk on Tuesday 16th July 19:57

[Spacecowboyuk]

Something looks wrong here - should the brown wire which is currently connected to positive actually be connected to the negative battery lead?



I've read elsewhere that there should be "a smallish brown wire to the -ve terminal of the battery?
If the car uses a standard ford loom that's the negative for the engine loom.
V8S uses a standard range rover loom."

That's from here:

https://www.pistonheads.com/gassing/topic.asp?h=0&...

Could that be why I'm having to introduce an earth the the relays and maybe why it's not firing on one dissy post?! When I follow it back the brown wire appears to.connect to the B+ on the alternator...

Edited by Spacecowboyuk on Wednesday 17th July 17:58

[Spacecowboyuk]

Oh and cylinder 4 spark does come back momentarily just before the engine dies as I turn the dissy counter clockwise...

[Spacecowboyuk]

GreenV8S said:

Spacecowboyuk said:

Oh and cylinder 4 spark does come back momentarily just before the engine dies as I turn the dissy counter clockwise...

Remind me - did you check for play on the dizzy shaft?

I think at this point I'd be putting foil over the terminals on the rotor cap and seeing which ones get wiped off by the rotor arm.

I have felt for play in the shaft but it feels very solid.

[Spacecowboyuk]

phillpot said:

The brown wire is correct going to the +ve


In the dizzy, under the rotor arm is a copper coloured trigger wheel thingy, could there be an issue with that, bent, corrosion, loose?

Do you mean the reluctor wheel? If so I've checked that too and it looks like new really. Not bent and runs true a far as the eye can see.