MonkeyBoy Posted June 29, 2004 Share Posted June 29, 2004 Hi all, Had a problem this weekend, driving along from Oxford to Essex and felt a dull thud from the foot well, then the car really struggled over 3000rpm, it's like it's firing on 3 cylinders or something, or just can't get enough fuel. It's a similar effect of hitting a rev limiter, just sounds horrible. This only happens under load, when reving at standstill it is absolutely fine. The car is a 1700 XF, pretty much all standard, electronic ignition. I've tried... Carbs: Check they're balanced, it's idling pretty well. Checked plugs, were a bit sooty but it's been running a little rich now for a while. Had the tops off and looked in the bowl, floats seemed ok and moved freely. Looked down trumpets and butterflies seem to move ok. Electrics: Changed plugs, changed coil. Checked dizzy cap, looks fine, checked HT leads, look fine. Ran it in the dark and no signs of tracing. Checked connections to battery, alternator. Other: Had a very quick peek under the rocker cover and all seems ok. So, what do i do now 🤔 Check timing ? (how?) Check fuel pump ? Dismantle carbs ? Dismantle dizzy ? With all of these options i'm not sure what i'm looking for but can give it a go I've read a few other posts with similar problems but most seem to have been fixed by doing what i've already done, except someone who changed their alternator, not sure i want to do it unless i know it's going to fix the problem, also when i put the lights on it doesn't affect anything. Any ideas chaps ? Thanks Alistair Link to comment Share on other sites More sharing options...
Graham Sewell Posted June 29, 2004 Share Posted June 29, 2004 I had this happen to me a few years ago - and it was diagnosed as absolutely no advance on the dizzy. Locked solid at 14' and hence ran like a dog under load. Low tech luddite - xflow and proud! Link to comment Share on other sites More sharing options...
MonkeyBoy Posted June 29, 2004 Author Share Posted June 29, 2004 Cheers Graham. Being someone who is slighty numptyish, how do i fix this ? Strip and rebuild dizzy ? check and adjust timing with a strobe ? Link to comment Share on other sites More sharing options...
Graham Sewell Posted June 29, 2004 Share Posted June 29, 2004 Check if this is the case using a strobe lamp and see if the advance kicks in - should be some advance by 3000rpm and major advance (ahead of 14' BTDC) by 4000rpm. If this does not happen then the dizzy will need to be stripped or replaced. Depending on whether my plans work out, I may have a complete Aldon dizzy with ignitor for sale soon. Low tech luddite - xflow and proud! Link to comment Share on other sites More sharing options...
AlanB Posted June 29, 2004 Share Posted June 29, 2004 Worth checking that the vacuum advance pipe to the distributor is OK. HTH. Link to comment Share on other sites More sharing options...
Graham Perry Posted June 29, 2004 Share Posted June 29, 2004 Ther is no vaccum pipe with 40/45Carbs on a seven. Link to comment Share on other sites More sharing options...
Alex Gurr Posted June 29, 2004 Share Posted June 29, 2004 Not again mate 😳. Sorry to hear that it's not running too well, but on the bright side you really are learning a lot as you go along. I will be back at the weekend if you want a hand with anything Link to comment Share on other sites More sharing options...
MonkeyBoy Posted June 29, 2004 Author Share Posted June 29, 2004 Cheers Alex, i'm around this weekend so may need a hand if it's not fixed, if it is then we could go blatting if you're free. Went out and bought a funky strobe lamp this lunchtime so that's tonights job Cheers for the help Graham, will let you know how i get on. One great thing about the car is that i've learnt loads about it, all part of the fun of owning a Seven Edited by - MonkeyBoy on 29 Jun 2004 15:44:04 Link to comment Share on other sites More sharing options...
Ferrino Posted June 29, 2004 Share Posted June 29, 2004 If the problem does turn out to be a non-advancing dizzy, it might be an ideal opportunity for you to go 3D with Mr Shurvinton and the DIY ECUs he's putting together, although I understand he's still away at the moment. An affordable mappable 3D ignition system. You could either lock any mechanical advance and retain the dizzy to purely distribute the spark or you could go the full monty and do EDIS. I'm hoping to go for the 'keep-the-dizzy' option later this Summer (albeit not on a X-Flow) so that we can sort out the progression and hopefully smooth out the delivery and lighten BP's pockets a smidgen. Link to comment Share on other sites More sharing options...
Roger King Posted June 29, 2004 Share Posted June 29, 2004 Check that one of the Auxilliary Venturis in the carbs hasn't come loose. When this happens, everything is as normal on light throttle or low revs, but you lose a cylinder at higher revs / throttle openings because it is starved of fuel. This normally happens if the external locnut and screw drop out. To check, take the air filters off and look down the carbs. The Aux Vent is the first thing you see after the ram pipe. Check them all against each other to see if one has rotated. They are handed, so you will have two one way round and two the other. Link to comment Share on other sites More sharing options...
MonkeyBoy Posted June 29, 2004 Author Share Posted June 29, 2004 Thanks Ferrino, i'm very interested in Bill's project and am certainly up for 3D mapping, i think it would be a great project for a X-Flow on webbers. I think i favour the 'keep-the-dizzy' option as well Just hope i can fix this problem so i can get some use out of the car until then Alistair Link to comment Share on other sites More sharing options...
Manxseven Posted June 29, 2004 Share Posted June 29, 2004 As you heard a dull thud, do check your engine mountings. Would be ok when revving it but soon as you put load on it (drive it) engine maybe moving 😳 Simon Emmens Caterham and Pussy Photos here 😬 Link to comment Share on other sites More sharing options...
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