Page 2 of 2 FirstFirst 12
Results 101 to 114 of 114

Thread: Vapor lock questions for the hotter climate guys

  1. #101
    Registered User 5thhorsemann's Avatar
    Member ID
    CZCC-22854
    Join Date
    Nov 2010
    Location
    maryland
    Age
    54
    Posts
    1,398

    Default

    Quote Originally Posted by Captain Obvious View Post
    It really doesn't matter, but I don't get your math...

    I do this:

    Assuming batch fired injectors on a four stroke engine...

    At 1000 rev/min there are 500 injections/min
    500 injections/min = 8.3 injections/sec

    Do I think a high frequency damper might be able to do something to quiet 8.3 pulses per second?

    Yes.



    On your VL issues, it sounds to me (the non-expert on such matters) that you're doing everything right except for the removal of the pusher pump.
    6 injectors firing every second rev @ 1000 rpm = 3000 injection pulses.

  2. #102
    Low Budget/High Value
    Member ID
    CZCC-20342
    Join Date
    Oct 2009
    Location
    Washington County, OR
    Posts
    3,629

    Default

    The 280Z EFI system fires once per revolution according to the FSM.

    Edit - Deleted my short story, since it was barely relevant.
    Last edited by Zed Head; 08-01-2011 at 01:10 PM.

  3. #103
    Registered User 5thhorsemann's Avatar
    Member ID
    CZCC-22854
    Join Date
    Nov 2010
    Location
    maryland
    Age
    54
    Posts
    1,398

    Default

    I guess I am speaking out of my field here, I was thinking direct port injection, which 280Z's are not. So perhaps a damper or "hammer arester" would have some stabelizing effect afterall.

  4. #104
    Marooned Fish cygnusx1's Avatar
    Member ID
    CZCC-4964
    Join Date
    Sep 2003
    Location
    Putnam Valley, New York, United States
    Age
    51
    Posts
    845

    Default

    Heat is the real enemy though.
    Dave C, Putnam, NY
    NYZCC - Membership Director

    __________________________
    1976 280Z Turbo
    1972 240Z RESTOmod
    2006 330xi 6-sp/winter/sport

    __________________________

  5. #105
    Registered User 5thhorsemann's Avatar
    Member ID
    CZCC-22854
    Join Date
    Nov 2010
    Location
    maryland
    Age
    54
    Posts
    1,398

    Default

    Ive got plenty of time to get the parts together on this fix, just got a call from my doc, had the Xrays read and determined I have 4 broken ribs and 2 bruised in my left back. I put the car in the garage yesterday and had to get help to get out of it. Looks like at least 6 weeks before I'll be able to drive it without the use of an engine lift to remove my dead a$$ from the drivers seat. Sigh.............

  6. #106
    Boat Anchor Repairman Captain Obvious's Avatar
    Member ID
    CZCC-24608
    Join Date
    Jul 2011
    Location
    Philadelphia, PA
    Posts
    1,845

    Default

    Quote Originally Posted by 5thhorsemann View Post
    Ive got plenty of time to get the parts together on this fix, just got a call from my doc, had the Xrays read and determined I have 4 broken ribs and 2 bruised in my left back.
    Dang Dude. That sounds like no fun at all. I hope you heal quickly!

    Since you've got nothing better to do right now than think about the vapor lock problems...

    There's a pdf document titled "1973 240z 1974 260z Fuel System Modification Plus" over at xenon that talks some about (Datsun's definition of) vapor lock. Probably nothing you haven't seen already, but if you haven't read that one yet, it's an interesting read.

    Also, what year is your car? I remember that you're running round tops, but I don't remember you mentioning a year.

    Speedy recovery!!

  7. #107
    Z geek at large FastWoman's Avatar
    Member ID
    CZCC-19635
    Join Date
    Jul 2009
    Location
    Hampton Roads, VA
    Posts
    2,787

    Default

    Yeah, ouch!! I guess the manual steering doesn't help the situation either.

    Here's hoping you heal quickly and well. In the meantime, you can drive your Z vicariously through all of us!
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

  8. #108
    Registered User 5thhorsemann's Avatar
    Member ID
    CZCC-22854
    Join Date
    Nov 2010
    Location
    maryland
    Age
    54
    Posts
    1,398

    Default

    It's a 73 with all the 72 intake stuff. I have the 73 recall manual for the VL mods, but aside from the pusher pump I've done all the recommended mod's. I won't have to worry about VL as it will be nice and cool by the time I can drive it again, thanks for the well wishes.

  9. #109
    Boat Anchor Repairman Captain Obvious's Avatar
    Member ID
    CZCC-24608
    Join Date
    Jul 2011
    Location
    Philadelphia, PA
    Posts
    1,845

    Default

    Quote Originally Posted by 5thhorsemann View Post
    It's a 73 with all the 72 intake stuff. I have the 73 recall manual for the VL mods, but aside from the pusher pump I've done all the recommended mod's. I won't have to worry about VL as it will be nice and cool by the time I can drive it again, thanks for the well wishes.
    So from the factory, you originally had the earlier version of the flat tops, right? I've got a mostly stock 260 with the later version of the flat-tops. Haven't had it long enough to know if I've got a vapor lock issue or not.

    So why is it that the 73's and 74's are so notorious for VL? It might just be a mistaken impression on my part, but it seems to me you might hear mention about 70-72 occasionally. However, it's not the resounding cry of "known issue" that you get when you mention 73 or 74.

    The first, most obvious answer that everyone jumps all over is the flat-tops. Well, you've taken that out of the equation already. Next is that the 74 got an electric pusher pump from the factory. But the 70-72 got along OK without one, right?

    So is there something else about the 73 and 74 that makes them more prone to VL than the previous years? Fuel rail design maybe?

    Quote Originally Posted by 5thhorsemann View Post
    Back to the VL. he fuel filter is before the pump, and mounted at about the same height, thats how I came to the VL conclusion so quickly. I could see that the filter was empty, and when it did begin to fill the fuel was boiling within the filter itself.
    You're saying that you parked the car hot and the fuel filter was full when you shut if off, but after sitting for 15 minutes in the sun, the filter was empty? Is that before or after it runs for half a block?

    I won't have to worry about VL as it will be nice and cool by the time I can drive it again, thanks for the well wishes.
    That's just sad...

  10. #110
    Registered User 5thhorsemann's Avatar
    Member ID
    CZCC-22854
    Join Date
    Nov 2010
    Location
    maryland
    Age
    54
    Posts
    1,398

    Default

    I think it may have something to do with the coolent flow through the flat top carbs, thats just a hunch. The hood vents on the 74 will ease the kind of issue I'm experiencing.

    The fuel boils off when the car is parked and it won't start without cooling the lines with water. Once I get it in motion the engine bay cools off and the car runs okay.

  11. #111
    Boat Anchor Repairman Captain Obvious's Avatar
    Member ID
    CZCC-24608
    Join Date
    Jul 2011
    Location
    Philadelphia, PA
    Posts
    1,845

    Default

    Quote Originally Posted by 5thhorsemann View Post
    I think it may have something to do with the coolent flow through the flat top carbs, thats just a hunch. The hood vents on the 74 will ease the kind of issue I'm experiencing.

    The fuel boils off when the car is parked and it won't start without cooling the lines with water. Once I get it in motion the engine bay cools off and the car runs okay.
    But the 72 round tops have coolant flowing through them as well though. And you don't even have flat tops anymore.

    I don't know... I'm just trying to figure out why you (with a 73) are seemingly having more problems than the 70, 71, and 72 owners out there. Even the ones in hot climates. Not that MD is "cold", but there are lots hotter. I'm wondering if there's some other 73 remnant that's complicating matters.

    About the fuel boiling in the filter... I doubt that's where the fuel is boiling. The filter is cool compared to anything that actually touches the engine. Maybe it's boiling in the intake side of the fuel pump and the resultant vapor is backflushing the fuel out of the filter and back into the tank? They don't run any check valves in that line to prevent that, do they? My 74 has an electric pusher pump that probably acts as a check valve, but you don't (currently) have a pump.

    You could park it hot and then use locking pliers to clamp off the hose on the intake side of the fuel filter and see what happens then. If you don't let it go back into the tank, the pressure will go up, and raise the boiling point?

    BTW - My 74 doesn't have hood vents. I don't think that started until the 280.

  12. #112
    Registered User ConchZ's Avatar
    Member ID
    CZCC-17507
    Join Date
    Aug 2008
    Location
    Kansas City, MO
    Age
    50
    Posts
    342

    Default Possible solution?

    Here's an idea that I just got from an old Datsun mechanic who used to work at a Datsun dealer in Phoenix during the early 80s. I haven't tried it, as I've been warned by another guy, Bonzi Lon, not to do it. On a carbed Z, he says the fuel return outlet of the fuel rail has a restriction in it that helps maintain pressure. He says they drilled it open just a bit, which allowed more fuel flow out, thereby increasing circulation, and cooling the fuel rail, resulting in zero vapor lock in Phoenix Zs. Bonzi Lon warned me that the restriction is necessary in order to maintain fuel pressure in the rail. Has anyone tried this? I have an extra fuel rail that I'm tempted to try it on, as this summer heat is causing vapor lock for me. I did get some improvement from richening up the mixture. Another source of my vapor lock is probably a weak cooling fan clutch and the fact that I have no fan shroud. I just ordered an electric fan and shroud kit from MSA that I'm going to try out, in hopes that it helps not only my vapor lock, but mostly that it helps improve my AC's cooling capacity. That is a nice looking piece of kit. If it helps my AC, eliminates the drag from the stock fan, makes the engine run cooler, PLUS helps the vapor lock, it'll be worth the money. If it doesn't fix the vapor lock, maybe I'll opening up the return outlet on my fuel rail just a little bit.

  13. #113
    Registered User 5thhorsemann's Avatar
    Member ID
    CZCC-22854
    Join Date
    Nov 2010
    Location
    maryland
    Age
    54
    Posts
    1,398

    Default

    That seems reasonable, but I would think you should go slow with the drillling, no more than one or two wire sizes at a time. Just keep going till the problem eases, too fast and you might end up with too low a pressure which will agrivate the VL.

  14. #114
    Boat Anchor Repairman Captain Obvious's Avatar
    Member ID
    CZCC-24608
    Join Date
    Jul 2011
    Location
    Philadelphia, PA
    Posts
    1,845

    Default

    Quote Originally Posted by ConchZ View Post
    On a carbed Z, he says the fuel return outlet of the fuel rail has a restriction in it that helps maintain pressure. He says they drilled it open just a bit, which allowed more fuel flow out, thereby increasing circulation, and cooling the fuel rail, resulting in zero vapor lock
    That orifice is a rudimentary fuel pressure regulator.

    If you enlarge that restriction, it will lower the fuel rail pressure and if you drill it out too much, it will cause a problem. There needs to be enough pressure under all load conditions to force fuel through the fuel lines (which is uphill in spots), filter screens, and push open the float valves.

    How far can you go (if at all) before it becomes a problem? I have no idea.

    I slept through that part of class, but I don't think the extra flow will do much for a temperature change in the rail. I can see my return flow because I've currentlly got my return line flowing into a catch can. At idle (light load) there's a surprisingly large amount of fuel being returned to the tank already.

    Can you take a couple thousandths off without causing a problem? Probably.

    Would it do anything good for you? Probably not.

    I'm no expert, but I consider it risky.

    Haha! Now you've heard two divergent opinions... Good luck with whatever you do, and I hope you kick your VL problems.

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Vapor Lock??
    By xcyter in forum Open S30 Z Discussions
    Replies: 5
    Last Post: 03-28-2008, 10:40 PM
  2. vapor lock?
    By 76Datsun280z in forum Help Me !!
    Replies: 17
    Last Post: 01-02-2008, 11:55 AM
  3. Vapor Lock
    By 280z in forum Engine and Drivetrain (S30)
    Replies: 10
    Last Post: 03-10-2004, 06:10 PM
  4. What to do about vapor lock
    By ROOPZ in forum Fuel Injection (S30)
    Replies: 6
    Last Post: 11-03-2003, 11:46 AM
  5. Vapor Lock
    By mandtw in forum Carburetors (S30)
    Replies: 3
    Last Post: 07-18-2003, 08:13 AM

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
  •