Results 1 to 19 of 19

Thread: Need help with tune up and fault identification

  1. #1
    Registered User
    Member ID
    CZCC-29165
    Join Date
    Apr 2013
    Location
    Anaheim
    Age
    31
    Posts
    5

    Default Need help with tune up and fault identification

    Hi,

    I just bought a 240z which has some engine issues. In short: The idle is very rough and initial pickup out of neutral slow. The biggest problem: The engine won't rev over 4000 under load (2nd gear and up). I did reset the point gap which made the idle a bit better (Before it would misfire and run on only 5 cylinders in idle. Then again, the gap was about half what it should be...).
    Since the valve train sounds a bit too noisy to me, and the valve clearance could be the source of the 4k problem, I measured the valves. If the measurement has been done correct ( I think it is, however it is the first time I did it) the Valve clearance is way to big. However I was not able to loosen the locking nut for the valve adjustment. And at the moment I am kinda stuck. I don't know whether there is some kind of a trick, I am doing it wrong or the nuts are just very tight...
    Would anybody with some experience in the Region LA/Anaheim be willing to help me out?
    Or can anybody recommend someone/a Garage that would be willing to help me and knows this engine?

    I am going to try it again tomorrow evening, this time with a cold engine.

    Thanks,
    Nils

  2. #2
    Registered User beermanpete's Avatar
    Member ID
    CZCC-21519
    Join Date
    Apr 2010
    Location
    Northridge, California, U.S.A.
    Age
    57
    Posts
    631

    Default

    The lock nuts for the valve adjustment can get very tight. I had to buy a longer wrench to get enough leverage to loosen mine the first time I adjusted the valves. If your wrench is not so long that it hits the strut tower when working on the #2 cylinder consider getting a longer wrench.

  3. #3
    No more body roll! SteveJ's Avatar
    Member ID
    CZCC-5413
    Join Date
    Dec 2003
    Location
    Gainesville, GA
    Age
    54
    Posts
    3,651

    Default

    Another alternative is to tap the end of the wrench with a brass hammer.
    73 240Z
    74 260Z

    Blue's collection of tech tips - A great place to look for answers
    XenonS30 -The cheap source for FSMs
    Georgia Z Club
    Fiddling with Z Cars - Z car tips & tricks and pictures of my car-loving life.
    Steve's CARtography - Just car pictures.

  4. #4
    Barn Find Daily Driver Captain_Zeros's Avatar
    Member ID
    CZCC-21373
    Join Date
    Apr 2010
    Location
    Kirkland, WA
    Age
    31
    Posts
    316

    Default

    science!
    Click image for larger version. 

Name:	wrenchlink.jpg 
Views:	110 
Size:	249.5 KB 
ID:	62424

  5. #5
    HLS30A 17574 djwarner's Avatar
    Member ID
    CZCC-27817
    Join Date
    Aug 2012
    Location
    Central FLorida
    Posts
    405

    Default

    Before touching the valves, measure them. Even clattering valve will not greatly affect performance as you describe. I would verify you don't have any vacuum leaks first. Our cars with their 40 year old rubber is great for hiding cracks in the small vacuum hoses. Another problem can be frozen distributor centrifugal advance weights.
    1971 240Z HLS30A 17574 L24-021025

  6. #6
    Registered User psdenno's Avatar
    Member ID
    CZCC-14231
    Join Date
    Apr 2007
    Location
    SoCal Desert
    Age
    73
    Posts
    1,091

    Default

    How old and in what condition are the spark plug wires?
    Dennis
    1971 240Z - Original Owner
    2010 Infiniti G37 Convertible

  7. #7
    Registered User
    Member ID
    CZCC-29165
    Join Date
    Apr 2013
    Location
    Anaheim
    Age
    31
    Posts
    5

    Default

    Quote Originally Posted by djwarner View Post
    Before touching the valves, measure them. Even clattering valve will not greatly affect performance as you describe. I would verify you don't have any vacuum leaks first. Our cars with their 40 year old rubber is great for hiding cracks in the small vacuum hoses. Another problem can be frozen distributor centrifugal advance weights.
    Hi,
    Thanks for all the help. I actually managed to get the valves adjusted yesterday (Cold and with some tapping on the wrench it worked out). The valves were pretty out of specs. Some by factor 2!
    It already runs a lot better than before and revs up to 5000 under load. There it starts to misfire. But I haven't had a change to set the timing right yet. I will set that today, and if I can get around to it also the carbs (The back 3 plugs are pretty black...). I will try balancing with a tube, since I could not get hold of a Unyson flow meter (Does anybody know, which auto parts/tools store sells them?).
    I'll let you know if I am succesfull. If the tune up does not deliver the results, I will start chasing vakum leaks.

    Best,
    Nils

    Edit: Distributor was the first thing i checked. It is fully rebuilt and works like a charm. I just had to set the point gap right. Spark plugs and wires are all new.
    Last edited by wenzlern; 04-09-2013 at 04:22 PM.

  8. #8
    No more body roll! SteveJ's Avatar
    Member ID
    CZCC-5413
    Join Date
    Dec 2003
    Location
    Gainesville, GA
    Age
    54
    Posts
    3,651
    73 240Z
    74 260Z

    Blue's collection of tech tips - A great place to look for answers
    XenonS30 -The cheap source for FSMs
    Georgia Z Club
    Fiddling with Z Cars - Z car tips & tricks and pictures of my car-loving life.
    Steve's CARtography - Just car pictures.

  9. #9
    Registered User LeonV's Avatar
    Member ID
    CZCC-19146
    Join Date
    Apr 2009
    Location
    Bay Area, CA
    Posts
    1,961

    Default

    Save yourself the trouble and get a STE-SK syncrometer instead of a Unisyn. Same price and magnitudes better. I gave my last Unisyn away for free...
    2/74 260Z

  10. #10
    No more body roll! SteveJ's Avatar
    Member ID
    CZCC-5413
    Join Date
    Dec 2003
    Location
    Gainesville, GA
    Age
    54
    Posts
    3,651

    Default

    Thanks, Leon. I couldn't remember the name of the other one. I have that hiding in my garage somewhere, though I'm sure it's not sitting next to the Unisyn.
    73 240Z
    74 260Z

    Blue's collection of tech tips - A great place to look for answers
    XenonS30 -The cheap source for FSMs
    Georgia Z Club
    Fiddling with Z Cars - Z car tips & tricks and pictures of my car-loving life.
    Steve's CARtography - Just car pictures.

  11. #11
    Registered User LeonV's Avatar
    Member ID
    CZCC-19146
    Join Date
    Apr 2009
    Location
    Bay Area, CA
    Posts
    1,961

    Default

    Quote Originally Posted by SteveJ View Post
    Thanks, Leon. I couldn't remember the name of the other one. I have that hiding in my garage somewhere, though I'm sure it's not sitting next to the Unisyn.
    Sure thing.
    2/74 260Z

  12. #12
    Registered User Gary in NJ's Avatar
    Member ID
    CZCC-21253
    Join Date
    Mar 2010
    Location
    Amongst the twisty roads
    Posts
    1,057
    Last edited by Gary in NJ; 04-10-2013 at 07:53 AM.
    Gary
    Guardian of HLS30-91415
    Previous Owner of a 10/70 240Z ('83-'85)

  13. #13
    No more body roll! SteveJ's Avatar
    Member ID
    CZCC-5413
    Join Date
    Dec 2003
    Location
    Gainesville, GA
    Age
    54
    Posts
    3,651

    Default

    That's the one I bought. I found mine on eBay.
    73 240Z
    74 260Z

    Blue's collection of tech tips - A great place to look for answers
    XenonS30 -The cheap source for FSMs
    Georgia Z Club
    Fiddling with Z Cars - Z car tips & tricks and pictures of my car-loving life.
    Steve's CARtography - Just car pictures.

  14. #14
    Registered User Willoughby Z's Avatar
    Member ID
    CZCC-23509
    Join Date
    Jan 2011
    Location
    Norfolk VA
    Age
    67
    Posts
    400

    Default

    Quote Originally Posted by wenzlern View Post
    Hi,
    ...I'll let you know if I am succesfull. If the tune up does not deliver the results, I will start chasing vakum leaks.
    A proper tune-up starts with components and parts in good condition. First, you have to insure that there are no vacuum leaks. Second, that all electrical connections are clean and tight. You're wasting your time to try and perform a tune-up before you have created a stable electro-mechanical baseline.

    HLS30 371-239 (1/77)
    Every time he touched her, she told him that places where she wanted to be more beautiful!
    Mr.Tamura said it is like an old craftsman of Buddha statue,he did not creat it, Buddha itself...
    Kats

    FSM: http://www.xenons30.com/reference.html
    EFI "bible" : http://www.4moores.com/280z/files/280zfuelinjectionbook.pdf

  15. #15
    Nova Scotia,Canada,Earth Blue's Avatar
    Member ID
    CZCC-7641
    Join Date
    Jan 2005
    Location
    NS
    Posts
    4,085

    Default

    Careful with the synchronometer choice. The STE has two versions. Get the BK (Silver) one as it can read higher flow.

    The STE meters seem to be designed for lower flow from a single cylinder per carb throat. A Z with SU's has 3 cylinders drawing through one carb throat. The Unisyn is better for higher RPM balancing @ 3,000rpm.
    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
    The person who buys on price alone is this man's lawful prey.


    John Ruskin (1819 - 1900)



    ZCars in Eastern Canada seaport ready for shipment to Europe

    http://ZSportCanada.com


  16. #16
    Registered User LeonV's Avatar
    Member ID
    CZCC-19146
    Join Date
    Apr 2009
    Location
    Bay Area, CA
    Posts
    1,961

    Default

    Quote Originally Posted by Blue View Post
    Careful with the synchronometer choice. The STE has two versions. Get the BK (Silver) one as it can read higher flow.

    The STE meters seem to be designed for lower flow from a single cylinder per carb throat. A Z with SU's has 3 cylinders drawing through one carb throat. The Unisyn is better for higher RPM balancing @ 3,000rpm.
    Are you sure about that, Phil?

    http://www.classiczcars.com/forums/c...-arghhhhh.html
    2/74 260Z

  17. #17
    Registered User
    Member ID
    CZCC-29165
    Join Date
    Apr 2013
    Location
    Anaheim
    Age
    31
    Posts
    5

    Default

    Hi,

    I found out that zcarparts.com is just near my work, so I could get a STE directly from them.
    I know that the general tune has to be proper to do a proper tuning of the carbs. However most hoses seem to be in good condition and I have already gone through the rest of the ignition and the valves. Having said that... There is of course a vacuum leak .
    With the help of the gauge I could get a good idle tune, but at 1500 the front carb can not be tuned to the back one completly, even with the balancing screw all the way loose. With other words, something on the front carb is leaking. I will get a bottle of carb cleaner tomorrow and start chasing that leak...
    It was still no wast of time, since it is a lot better than with what I started (I have 6 perfect looking spark plugs, instead of 3 good and 3 black ones), a low and stable idle and a good initial pickup.

    Thanks for the tip's, especially about the STE gauge, it works really well!

    Regards,
    Nils

  18. #18
    Ultimate Restorations e-tek's Avatar
    Member ID
    CZCC-18557
    Join Date
    Jan 2009
    Location
    Saskatoon, Saskatchewan, Canada
    Posts
    245

    Default

    Sounds like you are well on your way to figuring it out! The issue of stumbling at a higher rev point or load, is almost always due to either (vacuum or centrifugal) advance not allowing the distributor to advance, OR, a fuel restriction. While you want to be sure both carbs are sucking, you can do that very quickly by putting your hand over the intake area of each carb. So long as they both suck the palm of your hand in, you are good to look elsewhere first. Once you iron-out the basic SPARK-FUEL issues, you can then balance the carbs.
    I did a 100-point restoration (meaning EVERY ITEM WAS NEW OR REBUILT) on a vehicle last year and was chasing a very similar issue. I had gone through EVERYTHING imaginable, including removing the fuel line and pushing air through it, as well as measuring the volume of fuel coming to the carb when cranking - which was normal. After another few hours of chasing my tail (3 fuel pumps, rebuilding carb 3x, rebuilding distributor 2x and more!), I found it to be a 3" long flexible elbow in the fuel line that was collapsing when the engine was loaded (revved up)! ARRRGH!

    It's a learning game for me - repeated daily!
    E-tek Racing and Restorations

    Visit me at : www.E-tekRestorations.com

    or check my Blog: www.E-tekRestorations.blogspot.com

  19. #19
    Registered User
    Member ID
    CZCC-29165
    Join Date
    Apr 2013
    Location
    Anaheim
    Age
    31
    Posts
    5

    Default

    Quote Originally Posted by e-tek View Post
    Sounds like you are well on your way to figuring it out! The issue of stumbling at a higher rev point or load, is almost always due to either (vacuum or centrifugal) advance not allowing the distributor to advance, OR, a fuel restriction. While you want to be sure both carbs are sucking, you can do that very quickly by putting your hand over the intake area of each carb. So long as they both suck the palm of your hand in, you are good to look elsewhere first. Once you iron-out the basic SPARK-FUEL issues, you can then balance the carbs.
    I did a 100-point restoration (meaning EVERY ITEM WAS NEW OR REBUILT) on a vehicle last year and was chasing a very similar issue. I had gone through EVERYTHING imaginable, including removing the fuel line and pushing air through it, as well as measuring the volume of fuel coming to the carb when cranking - which was normal. After another few hours of chasing my tail (3 fuel pumps, rebuilding carb 3x, rebuilding distributor 2x and more!), I found it to be a 3" long flexible elbow in the fuel line that was collapsing when the engine was loaded (revved up)! ARRRGH!

    It's a learning game for me - repeated daily!
    Hi,
    God, I hope (and will assume for the moment) that my problem is not that sneaky .
    The plan is to first figure out where it sucks wrong air. If I have to take of the manifold to fix it, I am going to be tempted to just get rid of the whole emission stuff at the same time. I also still have to check the float level at the carbs. This could also be the reason for the behavior at 5k (fuel starvation). Hopefully I will get a chance to put it on a lift this weekend to determine the state of exhaust, exhaust manifold and bushings. This will then determine what to do next. As soon as the mechanical is in a good condition I'll have to start with the interior (Reno car, no rust but all plastic parts are shot) and put the doors and the trunk lid in straighter than they are now.

    Regards,
    Nils

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. FI still finding the fault ... ??
    By gator in forum Electrical (S30)
    Replies: 4
    Last Post: 02-21-2006, 09:37 PM
  2. how to track minor fault??
    By gator in forum Electrical (S30)
    Replies: 1
    Last Post: 01-04-2006, 12:30 AM
  3. fault still not fixed ??!!
    By gator in forum Electrical (S30)
    Replies: 1
    Last Post: 10-29-2005, 09:36 AM
  4. Possibly fixed fault ??
    By gator in forum Electrical (S30)
    Replies: 0
    Last Post: 10-26-2005, 07:49 PM
  5. finding the fault .. help
    By gator in forum Electrical (S30)
    Replies: 4
    Last Post: 10-24-2005, 11:55 PM

Bookmarks

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •