please help weird running problem
Turbo Mini Forums

Hello i have been trying not to resort to asking this question as i like to work things out myself but after many hours ive failed.

Please note the follwing faults are intermittent

Car will run beautifully in all gears then

You come to pull away from a junction and it will jurke then you hear what sounds like a loud pop from the carb then it will pick up as normal. Also it will run pefect in first and second then as you get higher up the box it has really bad flat spots which get much much worse when your going uphill and you have to drop right down the box to stop it spluttering.

So far ive fitted new magnecor leads, new carb which has just been set up to 3 percent co2 as its only running in at low boost. Its got a new avonbar turbo dizzy, New pressure regulator and new bosch pump. Most things are new as the cars just had a full rebuild.

Is it right that the pressure regulator comes set up from new and thers no need to adjust it? I havent touched it as yet.

Please if anyones came across the same thing or knows a remedy let me know as im running out of ideas and am tearing my hair out with it. I cant understand how it can be fine 1 minute and unbearable the next. Cheers...............

i would have thought the regulator needs to be set up. also check what needle you have, check oil in the dash pot and that it is able to move freely

sounds like either fuel or timing, whats it like on boost?, do you have a fuel pressure gauge fitted? should be around 4-5 psi at tickover, staying around 4-5 psi above boost pressure as it rises. Is it a tailored dizzy?

133.5 bhp 123 lb torque 116mph @6640rpm 9.5psi
Shakespear RWYB 14.995 91.83mph

Hi
It does sound fuel related check fuel pressure and the above. Also check carb and manifold are bolted up correctly
Have you still got the anti run on valve fitted?
Cheers
Gavin
Cheers
Gavin

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Out of interest what size fuel lines are you using?

I'd set the fuel pressure as said above to be sure, 3.5psi at idle and get a fuel pressure gauge to see what its doing higher up the range!

Just found this graph Tom Fenton made a while back!!

Run on valve sounds like like it could be the culprit as above, temoparily block off each end and see if it improves.

133.5 bhp 123 lb torque 116mph @6640rpm 9.5psi
Shakespear RWYB 14.995 91.83mph

I'd be checking the fuel pressure anyway, whether it's the problem or not. I have the gauge if you want to borrow it ?
What plugs are you running ? & what gaps ? & have you got an intercooler fitted ? Mine quite often fouls plugs when pottering about, especially when it's cooler weather. This causes a missfire when pulling away, until the plugs clear.
I'd say your flat spots are most likely mixture related, unless the ignition's a mile out. Have you had it on the rollers yet ?

Edited by Turbo Phil on 12th Oct, 2008.

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[quote=Turbo Phil,12th Oct, 2008Mine quite often fouls plugs when pottering about, especially when it's cooler weather. This causes a missfire when pulling away, until the plugs clear.
[/quote]

You checked your compression? i had this problem, blown head gasket caused it, it was fine when it ran on boost

133.5 bhp 123 lb torque 116mph @6640rpm 9.5psi
Shakespear RWYB 14.995 91.83mph

Yeah ive checked compression and it was spot on. Im running fancy ngk plugs i got through avonbar when i bought the dizzy. Someone said about oil in the deash pot. Im gonna try this first as i filled it up yesterday and i think ive maybe put too much in. Im not running an anti run on valve in fact the new carb has no outlet for it. I wouldnt have a clue what the fuel pressure is sitting at. Thank you all for your quick comments. Much appreciated.

sounds a little bit like the fuel pressure is not going up woth the boost ,

you could take the fpr apart to see if its sticking ,

first off do stick a guage on the fuel feed to the carb and set pressure to 3.5 psi wilst its ticking over ,using the screw and locknut on the top of the fpr..

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

cheak that your fuel pump pre-filter is not too restrictive.
This caused me some head scratching after my build.
best of luck
Colin

What about the infamous part-throttle lean off pipe?

I had no end off miss-fires due to this causing the mixture to lean off.

In the 13's at last!.. Just