Quagmire Posted May 29, 2008 Share Posted May 29, 2008 Quick question- And before anyone says anything i know this should be under military but hey the largest number of v8's has got to be the RaRo forum surely? Anyway... Dads 101 runs really sweet.... until you take the oil filler cap off whilst its running, then it starts to run really rough. :1-picture6: Further investigation showed that there is a vacuum being created, trying to suck air down into rocker cover- see pic of sandwich bag being drawn into filler neck below: With filler blocked by cap/hand/sandwich bag it runs fine. Is this a bad thing? Any ideas on causes? Cheers Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 29, 2008 Share Posted May 29, 2008 I don't think anything is wrong tbh, sucking through the oil filler is normaly for many engine that vent the crankcase back into the inlet. By removing the cap, you are allowing a LOT more air into the crankcase, and therefore sucked in through the crankcase breather and stuffed into the carbs/inlet. Basically you are probably weakening the mixture by taking it off, which will make it run rough. The crankcase on a V8 is pretty much sealed except for the filter on the rear left rocker cover (assuming you have one, not 100% on the older V8s), by opening it you are letting it breathe very freeling, and upsetting the designed balance. That's my take on it anyhow Quote Link to comment Share on other sites More sharing options...
paintman Posted May 29, 2008 Share Posted May 29, 2008 Land Rovers have enough problems without looking for more If it's running sweet like you say when assembled as was intended leave it alone! Quote Link to comment Share on other sites More sharing options...
Bull Bar Cowboy Posted May 29, 2008 Share Posted May 29, 2008 No its not a bad thing, it is perfectly correct with a closed loop breathing system..............when you remove the cap you are increasing the airflow into the fuelling thus making it run lean.................. Ian Quote Link to comment Share on other sites More sharing options...
Rustyrangie Posted June 2, 2008 Share Posted June 2, 2008 I'll go along with this. I had a similar problem with my wife's Merc 230, started to run rough and sometimes stall at idle. The fault was eventually traced to a split O ring on the dipstick! The crankcase needs to be sealed or excess air will be drawn in to the induction system upsetting the mixture. Bob Quote Link to comment Share on other sites More sharing options...
Quagmire Posted June 3, 2008 Author Share Posted June 3, 2008 Thanks for the replies guys- dont know why i hadnt thought of that seeing as you can clearly (well almost) see the hoses from the rocker covers into the carbs.... Quote Link to comment Share on other sites More sharing options...
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