ORANGEZ Posted April 21, 2008 Share Posted April 21, 2008 72 Datsun with a rebuilt swapped motor. Problem: Idles high when car is on and when ignition is turned off the car sputters for 2 mins then turns off. Cranks but doesnt start when turned on. Takes a few times of cranking then turns on. I was told by owner when purchased car first carb nearest to radiator needs rebuild. Has anyone else had this problem? Ive driven car around drives fine other than 2 problems stated above. Quote Link to comment Share on other sites More sharing options...
TrumpetRhapsody Posted April 21, 2008 Share Posted April 21, 2008 Just a guess here but... A tune up of the carbs would probably help your high idle. The sputtering once turned off is probably an improperly done alternator swap back feeding the ignition circuit. I don't have the link handy, but do a search for alternator upgrade and look for something about a diode IIRC. Quote Link to comment Share on other sites More sharing options...
jasper Posted April 21, 2008 Share Posted April 21, 2008 High idle is usaually caused by a vacuum leak, or carb(s) throttle not closed. "dieseling" can result from both. AKA run on. Both can also cause hard cold start . Solve one problem and you'll probably solve the others. Quote Link to comment Share on other sites More sharing options...
ORANGEZ Posted April 23, 2008 Author Share Posted April 23, 2008 Ok I started at it idled high for 3 minutes. When i turned it off this time it sputtered for 30 seconds thensome black smoke came out of the carb closes to the radiator then it shut off. Bad carb? What do you think? Quote Link to comment Share on other sites More sharing options...
ORANGEZ Posted May 18, 2008 Author Share Posted May 18, 2008 Ok switched out carbs with a good working set that ran totally fine on my bros 240z. Ok car runs sweet with perfect idle. Problem: Engine still sputters for 10-15 seconds when I turn it off. Then finally shuts off. Where should i start to troubleshoot next? Quote Link to comment Share on other sites More sharing options...
ORANGEZ Posted June 7, 2008 Author Share Posted June 7, 2008 Would a loose intake manifold or exhaust manifold cause dieseling? I can hear an exhaust leak and wondered if this adds to the dieseling problem ive been having. Quote Link to comment Share on other sites More sharing options...
SHO-Z Posted June 7, 2008 Share Posted June 7, 2008 Most likely you have excessive carbon build up in your engine. Hot spots in the carbon cause the dieseling. There are some comerical products that you spray into the engine when running that can help. One of the old school way is to to get the engine up to temp, rev the engine and dump water into the carb, sort of hard on a side draft. I have done this on V8 in the past an it did work. Personally I think you should go with one of the comercial products, Quote Link to comment Share on other sites More sharing options...
ORANGEZ Posted June 9, 2008 Author Share Posted June 9, 2008 Has anyone tried sea foam on their datsuns? non FI models? Does this stuff really work? Ive been reading good reviews about it. Quote Link to comment Share on other sites More sharing options...
johnc Posted June 9, 2008 Share Posted June 9, 2008 You need to do a complete tune-up on the car and fix all vacuum leaks. After-run is caused by many things and is indicative of a poorly tuned car. Sea Foam won't fix your problem, it may mask it for a short time, but there's something basically wrong with the tune of your engine. Quote Link to comment Share on other sites More sharing options...
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