V6 refusing to fire - help please

[colin1]

Dave
you mentioned somewhere in the thread about buying a replacement off eBay

I would bite the bullet and buy OE

eBay knock-offs promote nought but much wailing and gnashing of teeth

[Robsey]

Amazing the price on these...
Between £84 and £140 for a new genuine bosch unit.

I would definitely give everything a good clean including the connector pins.

Being sat on the wing, these things can easily suffer from damp... that coolant powder on top indicates another potential source of moisture / damp attack.

[colin1]

Amazing the price on these...
Between £84 and £140 for a new genuine bosch unit.

I would definitely give everything a good clean including the connector pins.

Being sat on the wing, these things can easily suffer from damp... that coolant powder on top indicates another potential source of moisture / damp attack.

Second-hand OE then..

Yes, hopefully it just

a. isn't 'sat' properly, and
b. a good clean will sort it out, along with prevention measures applied to whatever it's hiding under so that we're not revisiting this one again in six months time

[Lowrider Dave]

Thanks - and as you've both mention above, I plan to clean it up and retry. I wouldn't buy a cheap one off ebay- just some secondhand OE ones were available and that would be cheaper than the £100+ for a new one. I shall post progress when I do it.

[Lowrider Dave]

Secondhand LT module from Ireland arrived today, battled the crap designed engine bay to get it fixed in position, connected everything up and...s0d all. Continues just to turn over and over with no hint of firing. Now considering how much to sell it for as an ongoing concern as I cannot be bothered with it now. I don't have the time, money or inclination.

[colin1]

Dave
sorry to hear that, I feel a level of responsibility for your wasted purchase as it was largely me who pointed you in that direction.

Did you manage to spark anything against the block to see if you actually have one?

[Lowrider Dave]

Don't feel responsible at all Colin, it could have well been the fault and I wouldn't have thought of it! Haven't tried to get a spark as I need a second pair of hands due to the lack of space in the garage.

[James McGrath]

Would be a shame to sell after all the work you've put into it Dave.

I don't mind helping you out with it after the southern meeting on the 17th April.

[Cavalier342]

Sorry to hear you've not solved it yet.. Definitely something spark/sensor related... I hope you get to the bottom of it, after all the work that's gone into it!

[Lowrider Dave]

Would be a shame to sell after all the work you've put into it Dave.

I don't mind helping you out with it after the southern meeting on the 17th April.

Thanks James, I was hoping to have sold it by then! I have no idea where to start now on it, it has many sensors, most in almost inaccessible places and too expensive to use the 'buy and try' method of eliminating problems. I've put so much time and money into it I'm not really interested in spending anymore unless it was a garage with full diagnostic. But as I can't even get it out of my garage, just getting it to a recovery vehicle is almost impossible!

[James McGrath]

Maybe someone with a Tech 1 unit could help.

[planetc]

Tc31 will clear if you crank it before checking, it's only there until it's cranked each time you turn the ignition on. If it remains after cranking then look at the crank sensor. I've seen plenty of people dismiss it as 'always there' but it's not if you crank it.
Are you sure it's not flooded Dave? Very common to find modern fuel injected cars flooded, particularly this time of year with warm days and sudden temperature drops. Also extremely common to find them flooded when they have been started b the not run for long enough to clear the initial 'chuck shitloads of fuel in mode' following startup.

[Lowrider Dave]

Cheers cake eater. I undid the fuel pipes and a load of fuel came out, so I know it was getting fuel but whether it's being over fueled I don't know - it didn't 'sound' like it.
Someone from Migweb is going to try and come round one afternoon this week to help me determine spark and cast a fresh set of eyes over it.
So, if I am understanding you right, I should check to see if the Tc31 is there BEFORE I crank, and then check again AFTER I crank and if it is STILL showing up then it's a crank sensor fault?

[Lowrider Dave]

Paperclip test result:
BEFORE I crank = 31
AFTER I crank = nothing (apart from 12)

[planetc]

Crank sensor is good then, if you have spark then I'd be suspecting it's flooded. Pull the fuel pump fuse and crank it over for a bit, see if it starts to splutter. The trick with the flooded ones is to give them just enough fuel for the clear cylinders to fire but not so much that the flooded ones remain flooded. You can do it by squeezing the feed pipe with a pair of pliers too

[Lowrider Dave]

Cheers. Hopefully I get to check the spark this week when I can get an extra set of hands to help.

[Lowrider Dave]

Dan from Migweb came round two days on the trot to help me with this problem. We tested loads of items and everything seemed to be working in theory. Manually stimulating the crank sensor fooled the car into thinking it was running so that seemed to be the key, but testing the pins it read okay...curious. We had Dan's oscilloscope to check bits and pieces but still nothing made sense, after putting back the crank sensor I tried to start the V6 again and she fired up!
We have no idea what exactly was the problem or how it has been cured but I'm claiming a victory and have since taken it for a good blast along the motorway to clear the cobwebs out. I have ordered a new sensor to be on the safe side.

[Robsey]

I dread to think what you did to manually stimulate it - ha ha.

But good to hear that it is sorted at least for now.

[James McGrath]

Glad you've made progress with this. Hopefully that will be the end of the problem for you.

[colin1]

...after putting back the crank sensor I tried to start the V6 again and she fired up!
...

Hmm I didn't think of that
Did you perchance give the sensor a quick wipe before you put it back?
This sometimes does work but you were right to order a replacement, it usually means the sensor is on it's way out

Good to hear you've solved though

[planetc]

I've seen a few v6 crank sensors that would be intermittent with heating and cooling expansion and contraction. I followed one off the bottom of the m1 once spraying it with carb cleaner every quarter of a mile to cool it down so it would run again

[planetc]

I still think it was flooded myself though

[Lowrider Dave]

I dread to think what you did to manually stimulate it

To prove the Hall was working, Dan rubbed a socket bar over the sensor end vigorously - coining the 'phrase of the week': "To w@nk off a sensor"... much mirth ensued. But it proved it was doing it's job...it's odd after we had removed it twice and put it back, the car suddenly started and has done so every time since.

Fuel pressure was tested too and plugs checked and no fuel was found on them, it seems the injectors don't release fuel unless the firing circuit is active - as it wasn't, they didn't which lead to a back log of fuel to shoot out when we tested the valve!

[colin1]

...Fuel pressure was tested too and plugs checked and no fuel was found on them, it seems the injectors don't release fuel unless the firing circuit is active - as it wasn't, they didn't which lead to a back log of fuel to shoot out when we tested the valve!

Not sure how V6s work but if the crank is fouling, fuel is normally cut off at the pump, not the injectors

[planetc]

^ what he said....... Immobiliser however cuts injector pulse, as does the injector circuit relay if it is one of the later ones with a separate relay.
I still think it was flooded and that you cleared it inadvertently playing with the crank sensor, but unless it does it again we'll never know