V6 breakdown symptoms

[Mrs Feynmans Bongos]

Yesterday gave my V6 her weekly run to work (20 miles) and back.. almost. She broke down 1.5 miles from home. Would appreciate expert thoughts on what may have happened, advice what to do next.

She has been running really well, sailed through MOT August (just needed an ABS sensor);

Leaked oil around head until a couple of years ago (MOT comments). "Blue Devil Oil Stop Leak" applied 2023 (when oil filter last replaced) seemed to have eliminated this;

With only ~3 litres of fuel left at work, I added 5 litres of E5 Super from my can (warning went OFF until halfway home). Filled up with E5 as planned 2 miles from home;

Left garage ok, 300m later held on roundabout by traffic lights. On exiting roundabout, engine cut out with ?usual Oil, Ignition warning lights, no strange noises or smells at all, was able to coast aside safely despite power steering loss;

Tried to restart a few times: she cranks and splutters but does not catch. Electrics otherwise seem ok (lights, dash, aircon, radio). No oil evident underneath or on road nearly, nothing looks wrong under bonnet, but I couldn't face raising seat cowls in the dark so walked home.

THOUGHTS PLEASE.

Oil starvation?
Misfuel? (Garage's fault, pump said £145.9 ppl E5!)
Fuse or relay blown? (which, as engine-type not cabin)
HT leads failed? (Had vermin trouble some years ago)
Spark plug failed? (replaced 10 years, 40k miles ago)
Fuel blockage? (unwise to run tank so low)
:

HELP APPRECIATED

[g8dhe]

Not really a lot to go on given that it just stopped, my first line would be distributor and HT coil areas. If it was an HT lead or a spark plug only one cylinder would be affected, for all cylinders to go would tend to point to HT generation and distribution, the fact that it had been running would suggest that there wasn't any moisture causing problems, so either the coil its connection to the distributor, king lead or the distributor itself.

[Mrs Feynmans Bongos]

Thanks Geoff.

Garage recalled the receipt for me: it shows SUPER UNLEADED, they have no recent misfuel reports from that pump.

COIL, DISTRIBUTOR, KING LEAD: any way an amateur like me without garage equipment (only a multimeter!) can rule those in or out, or is it just a case of replacing them in-turn? (maybe at side of road, if I can order them for Monday, given recovery will be a £200 trailer job!)

[g8dhe]

Well have you first tried looking at them that can sometimes offer a clue ?
Try cleaning the them up to remove all the road muck that gets sprayed up on them ?
Taking the distributor cap off and inspecting inside make sure you keep its exact position noted, the contacts inside and the rotor do have an odd looking rough surface to them which is correct - this sometimes confuses people if there not aware!
Diagrams of the various parts listed here under Ignition and Distributor https://www.lushprojects.com/bongoparts ... Btr.html#4

[Doone]

Theres no common problem why a V6 suddenly cuts out, they do it so rarely unless the cambelt breaks.
As it happened after you'd run low on fuel, you could check the fuel filter.
Dirt can block the filter enough to cause fuel starvation.
Especially if it hasn't been replaced recently.

[Mrs Feynmans Bongos]

I tried a few things today, given she's less than 2 miles from home. Mild and sunny so could have been worse..

Found NOTHING on the dipstick, worryingly (even if stranded on a slight slope) After adding 3.5 litres of 5W30 she now shows FULL on the stick when cold:: but is this too much? Clearly I need to check oil more often..

That made me wonder whether oil starvation is detected, whereupon oil warning lights-up which cuts ignition? (the opposite of my assumption about Friday breakdown: namely ignition/engine stopped, causing an incidental warning light as oil pressure fell).

So then I replaced HT leads: removing ones I fitted 10 years ago, which are showing recent vermin damage to rubber boots and cable insulation (also some nuts on the cylinder head!). Reconnected to in situ DISTRIBUTOR assuming:
- dizzy sockets are correctly shown on:
https://bongospares.co.uk/shop/p/distributor-cap-v6-new
- those sockets should go to plugs/cylinders as numbered in
viewtopic.php?t=68624#p648223, presumably numbered from FRONT of Bongo?

Whereupon she cranks and sounds like she wants to start even more than on Friday and Saturday! On locking up, I also left my solar charger plugged in on the dashboard.

So it looks like the DIZZY next, then maybe SPARK PLUGS,
both fitted by me 10 years, 40k miles ago. Could they be end of life? What about the COIL: still original one, 100k miles.

Thanks for replying Allan (great to see you still on here even while retired: we can't spare you you know!) Not sure if I can check/replace FUEL FILTER from cabin via the cowls though? I am trying NOT to need to get it recovered!

[g8dhe]

The dashboard light is merely an Oil Pressure light to indicate that there is a problem, it controls nothing else other than the light;

However its worrying that you could fit 3.5l of oil in that would tend to indicate that you had lost a lot as the total is 4.5l in the specifications!

[Mrs Feynmans Bongos]

Ah thanks Geoff. Sounds much more likely the Oil warning is just the effect of the engine cut-out then, not the cause.

As Allan suggested, I am actually thinking now a FUEL BLOCKAGE best fits the facts as investigated. It died immediately after fuelling from very low, HT leads ruled out, unlikely Dizzy +Rotor (although I have ordered new ones) given it "wants to start" anyway these are only "40k miles" and it has been running well.

Can I replace Fuel filter from above/cabin via engine cowls? Is this designed to "block" rather than fuel pipes? Or more advisable to bite the bullet and recover it to a garage now, as fuel blockage is quite an expert job?

[Doone]

The numbers on that link are correct.
The cap will only fit one way.

The fuel filter is under the van, at the front of the fuel tank. It's a black canister on the chassis. Its held on with a bolt through the bracket & 2x 10ml nuts. When you disconnect the pipe, fuel might spray out.

Trouble is, we're just guessing and the fuel thing may not be the problem as your electrics sound pretty old and may be worn out. They're pretty crucial on the V6. And it sounds like its improved a bit by changing the plug leads.

I'd check the coil lead. It runs from the coil to the distributor cap. You can check the ohms with a multimeter. The correct readings will be on the forum somewhere I expect.

And check the rotor arm, its inside the distributor cap. If its covered in scorch marks or is corroded, change it.

As you've lost so much oil, it suggests you've had a leak possibly from camseals?
The oil could be on the TDC sensor, giving a bad signal. This would also cause starting problems.

[Mrs Feynmans Bongos]

UPDATE

So my V6 was recovered to a local garage, who didn't just replace the fuel filter, first tested for a spark: NONE

He thinks it needs a new COIL PACK. I'm paranoid I messed up swapping HT leads back to the originals (rodent damage on newer ones in situ on breakdown), so mentioned the ?King Lead, had I connected it correctly? then the Distributor, could it be that?

But he stuck with the Coil Pack so obvs I'll get him a replacement. He has helped me before (replacing bitten fuel pipes twice, before I fitted braided). Just checking if failure of original Mazda COIL PACK after 100k miles sounds plausible to experts here, ie fits the symptoms?

[Doone]

Its plausible.
He probably tested the coil lead.
But double check that he has. Because if that fails, there'd also be no spark.

[Mrs Feynmans Bongos]

New COIL arrived today, was replaced but still no spark.

Local garage is nice enough, but is now suspecting Camshaft cannot be turning, thus CAMBELT or related PULLEY failure. Is this plausible, does it fit the symptoms, i.e. (shortly after fill-up) cut-out but with no strange noises, since when it seems to "want to" start but cannot.

He's a bit nonplussed that I'm consulting forums, but I will insist that he next checks COIL LEAD (is that the so-called "king" HT lead, or another? Not least because having swapped all HT leads I'm a bit nervous I messed up) before removing e.g ROCKER COVER. And if there's no spark via a good coil lead, presumably I can return the new Dizzy, Rotor Arm I have bought, given they're downstream?

If he's right, I know this could be expensive/fatal. With COIL LEAD ruled out, is it better to next remove ROCKER or CAMBELT cover? Cambelt + pulley were changed 40k miles ago. After a cambelt failure, does one know there's damage just via "rough running"? I think it would have been in 1st when I pulled away from roundabout traffic lights and it cut-out, leaving me to coast to a halt.

Any more thoughts, suggestions, tips from Supreme Beings appreciated, that I can gently convey to my garage

[g8dhe]

I can't think that they would have missed a broken camshaft belt, its a long belt running under the plastic cover at the front of the engine, it normally drops out if it snaps! I had mine go just before last Xmas!

If they have checked for HT from the coil and there is none then several possibilities but this should be bread and butter work for a garage to diagnose!

[Mrs Feynmans Bongos]

Thanks Geoff.

What happened when your CAMBELT failed? Did engine just cut-out like mine, when pulling away or at speed? Any "collateral damage" or just a new belt & your V6 was fine?

I need hope!

[g8dhe]

I was climbing up a small rise, heard a small thump thought perhaps I had driven over a bird or something, and then felt the van just gliding to a halt! Couldn't quite make a layby either! Tried to start and obviously from the speed of the starter motor (quite fast) the entire engine wasn't connected together! Called AA and after a quick perusal we found the cambelt coiled up under the cover, so a tow back to my garage that wasn't too far away, otherwise it would have needed a flatbed which on the small back road would have been interesting! Yes engine cut-out of course but no damage the V6 is a clearance engine so no problems.