wierd problem
Turbo Mini Forums

hi everone,
went out for a drive last night, i have been tweaking the base map to try and get in the ball park ready for a rolling road session, i had been experiencing some backfiring and bogging down at high rpm in 3rd and 4th gear, and some tweaking was improving matters, however on my way home it started to back fire again badly, i could hear it backfiring through the carb pretty badly, so i pulled over and it cut out.
now i cant start it up again! i have put new plugs in (the old ones were fine, perhaps a little bit black but nothing major)
new plugs made no difference, i have checked and i am getting sparks.
all i get when i turn it over now is lots and lots of backfiring through the carb and nothing else. i tried swapping the leads over just in case they somehow got swapped (getting desperate here lol) but its just the same.
i am not sure if this is a megajolt/edis issue, an issue with timing or wether the carb is dead.
i cant believe my car has been back on the road for 5 days and its dead already
any ideas anyone?
Dan
p.s the spec is
a series engine, 1380 cc
kent 286 cam
weber 45 dcoe on long manifold
mjlj with tps option

just to add, when i got it home and checked under the bonnet, there was fuel coming from around a bolt on the carb (number 1 on the picture)

i have tightened it back up, but it wasn't doing that before, and i am not sure what could cause it to loosen.

have you done a compression test?

no, not yet, but someone on another forum suggested this as well, so i am off to get a compression tester and see what i can find.
cheers
Dan :)

out of interest, would you mind posting a pic of your webers tps setup?

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

Compression wouldn't course a backfire from the carb.... got to be firing at the wrong time. Is the crack sensor been hit but somthing or the sensor wire no longer earthed? try disconetting the HT leads and cranking it over and see how it turns over.

if an inlet isnt closed it might pop

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

If the problem is carb related as maybe indicated by the leak at the brass fitting it might be worth checking the following.
1) under the brass fitting is a filter, this may be blocked.
2) The needle valve may be stuck in it's housing or the float may be stuck on it's splindle. A bit unlikely but it's easy to check by removing the top cover on the carb.
It sounds as though the mixture has become progressivley weaker, hence the above possibilities.
Have you a pressure regulator fitted? These carbs really do need one set at around 3-4 psi.
The above is supposing it is the carb but remember 90% of all misfires are ignition related.
It's worth having a look at the above it will only take 30 mins or so.
Let us know how you get on
Regards
Dave

hi guys, thanks for all the replies, much apreciated.
got a compression tester, cylinders 1-3 were at 14bar and cylinder 4 was 13.5bar. that doesn't seem like a huge difference.
i will get on and check those things on the carb, cheers for the tip danboy. i am running a filter king regulator, i will try and get hold of a pressure guage and test it.
webers are very daunting to me! they seem so complicated compared to the su carbs lol
i checked my vr sensor and all is good there.
i will report back any findings.
cheers
Dan :)
p.s
pic of my tps, its a weber alpha one.

Hi,
I'd take a good look at the crank sensor, it usually does that when the end of it has been ground away....
Cheers,
Gavin :)

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i took the crank sensor off and checked it earlier, it looked fine.

Hi,
It does sound like timing from the backfiring from carb and exhaust.
Have you tried it with just the edis, could the trigger wheel / pulley have moved?
I say this because mine is nearly the same spec as yours, did exacalty the same on Sunday, but my trigger wheel had sheered a bolt off and ground the sensor away.
Cheers,
Gavin :)

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i will double check the sensor location and make sure that it hasent moved, i am using the kad trigger wheel so there may be a chance that the trigger wheel has rotated.
thanks for the tip:)

cheers for the pics, and good luck sorting it!

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

Fixed it!
the crank trigger wheel had rotated, so i had to pull the bloody radiator out and reset it all. i did it up suer tight this time so hopefully it wont happen again, i turned it over and it roared back to life instantly!
cheers for all the help guys, and cheers to you bat for directing me in to that area!
thanks
Dan :)
next stop rolling road!

Hi,
I've learnt from experience myself on this one over the weekend! :(
Glad you've got it sorted now :)
Cheers,
Gavin :)

VEMs Authorised Installer / Re-seller. K head kits now available!

WB/EGT gauges. Click here for customers write-up

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My Mini build diary

Right so a really good VR sensor bracket is the key.

sounds like the actual problem was the bolt on trigger wheel was the problem, not the VR sensor bracket.