Guest bang847 Posted January 24, 2002 Share Posted January 24, 2002 ok... right now my Z is backfirig pretty bad. every once in a while it coughs out of the carbs...i have tried to advance the timing and also retard it but i get the same effect either ways.. just before this the car was running ok and then corosion got on the points and ignition set and i had that dremeled that off and then the car started up and ran pretty good on idle.. my friend then gunned the gass a few time and it was sounding good then the last time he gunned it backfired and then the car ran really crappy. now it barely holds idle and backfires when idling.. any idea what is wrong? what can i do? Quote Link to comment Share on other sites More sharing options...
Tim240z Posted January 24, 2002 Share Posted January 24, 2002 Bang, Sounds like it's running very lean. First, check to see if the initial backfire didn't blow off one of the vaccuum lines or plugs (if you've removed any of the lines). You prbably have a leak, letting air in leaning out the mixtures. After checking all the lines, richen up the carbs all the way to see if that helps. I have a colortune and balance tool, so stop by if you need help tuning them. Tim Quote Link to comment Share on other sites More sharing options...
Guest bang847 Posted February 11, 2002 Share Posted February 11, 2002 i have checked for unconnected vac tubes but found nothing... then i checked compression to see if a valve is dinged. then I almost gave up... then i took off the gas cap and it started up! ??? what does that mean? oh well... it is running now.. stills back fires a sometimes out the exhaust now.. again.. thanks Tim.. Quote Link to comment Share on other sites More sharing options...
Guest tom sixbey Posted February 14, 2002 Share Posted February 14, 2002 dont take it so hard bro - i still got an l24 and hitachi's (1973 garbage carbs!!!) Quote Link to comment Share on other sites More sharing options...
Guest bang847 Posted February 15, 2002 Share Posted February 15, 2002 didnt the 73's have those dreaded flat tops? ooh i heard they arent good news.. more incentive to go hybrid right? anyways. i got a 71 with the dome tops... anyone know which head is the best to get? I got a E88 head... i know there is a 8.5:1 head and a 9:1 head which one do i have? oh... any ideas on the SU's? Quote Link to comment Share on other sites More sharing options...
Mike C Posted February 16, 2002 Share Posted February 16, 2002 Check the oil first. This is the source of many woes. If you don't have one yet, get abook on syncing the carbs and get a Uni-Sync, about $25 from Summit or Jeg's. Definitely sounds like you are running lean, so check for a vacuum leak first, power booster maybe? Notorious if the car has been sitting for awhile. Quote Link to comment Share on other sites More sharing options...
jimzdat Posted February 16, 2002 Share Posted February 16, 2002 Another good source for the Uni-Syn device is your local VW shop--multi-Weber carb setups are popular for bug setups, and they sell all the tuning stuff for them. Just a thought so you don't have to wait on mail order Quote Link to comment Share on other sites More sharing options...
Tim240z Posted February 16, 2002 Share Posted February 16, 2002 Bang, Like I said, I have a sync tool and a colortune that I used when I was running SUs (webers now). Stop by if you want help tuning them. Tim Quote Link to comment Share on other sites More sharing options...
Guest bang847 Posted February 16, 2002 Share Posted February 16, 2002 Tim, at this point i dont think it will make it to your house... Thanks for the offer! but im making progress on it though... finally.. gotta get my interior in and tune it up a little.. how do i richen up the mix just to stop the backfiring? nothing precise as of yet.. wanna have a running car to work on.. to keep up the moral... Quote Link to comment Share on other sites More sharing options...
spotfitz Posted February 16, 2002 Share Posted February 16, 2002 Originally posted by bang847:Tim, at this point i dont think it will make it to your house... Thanks for the offer! but im making progress on it though... finally.. gotta get my interior in and tune it up a little.. how do i richen up the mix just to stop the backfiring? nothing precise as of yet.. wanna have a running car to work on.. to keep up the moral... Acouple of things you might want to try. On each side of each carb there are bushings for the throttle shafts. Yours are probably worn. Try putting a small glob of grease over that area on each bushing to seal it from outside air. That may be your leaning problem. Check your float levels to be sure they are spot on. The measurement from the bottom of the top to the top of the float, once it has stopped fuel flow(or air flow in this case as you blow through it to determine when it does stop) should be 1/2". While you have those floats off you might want to check the gross jet screens for crud. More then likely the grease trick will work, but if you backfire through the carb again, you'll have to reapply the grease on the throttle shaft bushings. I've thought of trying silicone in this spot, but have yet to try it. Hope it helps. Quote Link to comment Share on other sites More sharing options...
Miles Posted February 17, 2002 Share Posted February 17, 2002 I had the same problems as you are (lean sag/backfiring). To richen the mixture turn the mixture adjusting wheel at the bottom of the each carb clockwise looking from bottom up or counter clockwise looking top down. Start with screwing the mixture in all the way until it stops on each carb and then back it out in full turn increments. Make each carb has the same number of turns. Mine runs best at three turns out (in lean direction). It no longer back fires, but I still have a slight lean sag on partial throttle. I suspect a hose is leaking and I know that the throttle shafts are warn on my 240Z. Mine no longer back fires and starts easy. I am going to live with with a lean sag at partial throttle until I do the V8 swap this summer. Also, there are some good carb tuning tips I received from other members in the L6 section of the forum. Look for my posts on backfiring. Miles Quote Link to comment Share on other sites More sharing options...
Guest bang847 Posted February 18, 2002 Share Posted February 18, 2002 hey guys,, thanks for alll the help!!! it turned out that my points were too worn.... replaced it and now it runns like a Z... anyways i lost that little pill of points grease that came with my points... any substitutes?? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 26, 2002 Share Posted March 26, 2002 When you turn the knurled adjusting knob all the way in on the bottom of the SU's,wouldn't it lean it out? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 26, 2002 Share Posted March 26, 2002 Has anybody ever tried using the colortune test spark plug in the Victoria British catalog? For dialing in the carbs? is it worth the $40? Quote Link to comment Share on other sites More sharing options...
Tim240z Posted March 26, 2002 Share Posted March 26, 2002 Has anybody ever tried using the colortune test spark plug in the Victoria British catalog?For dialing in the carbs? is it worth the $40? I bought one.It works as advertised. Well worth it. anyways i lost that little pill of points grease that came with my points... any substitutes?? Just pop over to the parts store and pick up a tube, otherwise in a pinch, vaseline will work.Tim Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted March 27, 2002 Share Posted March 27, 2002 Got on the boards late, but looks like you have it all figured out. Just wanted to say that if you are backfiring the first place to look is the ignition. This is often caused by cross firing between cylinders. The fix is a new distribtor cap, rotor and points. The inside of the cap should be clean. Any dust or brown soot is usually evidence of more than one plug firing at time. Replace the cap (and not with a trak auto cheapy). I have a 70 Z that had SU's. Another way to check for vacuum leaks is with starter fluid. Spray some around the throttle shaft bushings and if you see a change in the idle RPM, they are leaking. My Z use to need premium gas and octane booster because of leaky bushings. New carbs made it run fine on regular. Quote Link to comment Share on other sites More sharing options...
Guest bang847 Posted March 28, 2002 Share Posted March 28, 2002 Yeah, it was the ignition... after i filed off the points and greased them the car ran better.. still backfired when i let go of the gas at high speeds though.. stupid auto trans... solved that problem by removing the smog pump belt... Replace the cap (and not with a trak auto cheapy). if not a cheapy trak auto (now CSK auto)cap then where to get them? I bought a bakelite cap on ebay but those are gettin rare... I was gonna see if anyone at MSA wanted it for a restoration job... I can use it but it looks so nice out of the car.. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted March 28, 2002 Share Posted March 28, 2002 I usually go to a mom and pop style autostore. The brand names I use to get were Standard Ignition. I say avoid the chain store ones because I have had bad experiences in the past and it is a bitch to figure out when brand new parts are bad. But, it has been several years since I bought ignition parts for my Z. If MSA doesn't carry them then I am sure Nissan does. Quote Link to comment Share on other sites More sharing options...
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