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Technical SBC stalls when put in gear, can't start hot:

Discussion in 'The Hokey Ass Message Board' started by c-10 simplex, Jul 24, 2021.

  1. c-10 simplex
    Joined: Aug 24, 2009
    Posts: 1,371

    c-10 simplex
    Member

    --quadrajet

    --HEI

    --can't really get it to run under 900 rpm anymore.

    --Immediately stalls when put in gear.

    --Can't start/re-start when hot.
     
  2. Wanderlust
    Joined: Oct 27, 2019
    Posts: 787

    Wanderlust

    Check that the vacuum advance is working properly
     
  3. c-10 simplex
    Joined: Aug 24, 2009
    Posts: 1,371

    c-10 simplex
    Member

    The can moves and holds pressure. But, since i'm on ported, i don't think i'm getting any advance at "idle" (or what i call idle at 900 rpm) because the port slot is below the throttle plates at 900rpm?
     
  4. manyolcars
    Joined: Mar 30, 2001
    Posts: 9,176

    manyolcars

    look for a vacuum leak. somewhere theres a thread that says dont use ported
     
    Fuzzy Knight likes this.

  5. Fortunateson
    Joined: Apr 30, 2012
    Posts: 5,331

    Fortunateson
    Member

    I had a friend who had the very same problem. However it onl y did it when it was near a Ford. Probably intimidated...
     
  6. Aaron65
    Joined: Dec 29, 2005
    Posts: 375

    Aaron65
    Member
    from Michigan

    Try pulling the mixture screws and spraying out the idle circuits with carb cleaner and compressed air in case some trash got in.
     
    Joe Travers likes this.
  7. Vacuum leak?
    Dirty fuel , plugged lines , filter, weak pump . Electric or mechanical ?
    Tune up?
    Bad coil , bad cap, bad rotor? Maybe plugs ?
    Flat cam ?
    Plugged exhaust ?
    Car sitting for a long while or driven and issue just poped up ?

    Hook up a vacuum gauge and see what it says .

    All this can be checked in under an hour and either you find the issue or your at least pointed in the right direction.
     
    Steves46 and Wanderlust like this.
  8. c-10 simplex
    Joined: Aug 24, 2009
    Posts: 1,371

    c-10 simplex
    Member

    Did that, plus took the idle tubes out and shot compressed air thru them and ran a wire thru them. Engine seems to start easier COLD, but the other problems are still there.......
     
  9. c-10 simplex
    Joined: Aug 24, 2009
    Posts: 1,371

    c-10 simplex
    Member

    1) i am not saying absolutely NOT a vacuum leak, because i'll recheck. But i've sprayed carb cleaner around the intake and heads and carb base and nothing. Also cupped my hand over the choke horn and not only did it not speed up, it didn't slow down either. Also sprayed a little carb cleaner down the primaries and it slowed down a little for a few secs and went back to "normal" (my current "normal" that is.....)
    i understand interior vacuum leaks (like the intake gasket leaks that CAN'T be detected by spraying MAY be able to be detected by plugging the PCV and putting the vac gauge on the dipstick tube or pcv openings? (haven't tried this yet)

    2) Mostly recent(within 2 weeks) fuel, new filter, elec pump. i don't think fuel delivery is the problem.

    3) New coil/pickup coil/module. i think cap and rotor are good. Recent plugs

    4) i hope not flat cam (see #6 below)

    5) open exhaust about 20" after the "Y"

    6) Car was sitting for about 5-6 months. Drove it approx april 18th sunday night. Everything normal.
    April 19th monday night, adjusted the secondary plates, not airflaps, plates to open more, where previously they didn't open at all.

    April 20th, did some "spirited testing" (ok, i FLOORED IT, but there's no way i went past 5000rpm) and then IMMEDIATELY after this i noticed the symptoms of wanting to stall out when coming to a stop and difficult to start hot. This became more definite tuesday night when the car DID stall out at a traffic light and couldn't re-start for about 15 mins.

    So now, here we are with the following problems:
    1) Hard start cold----although that seems to be improving: Only change made was to clean out the idle tubes and i'm not convinced that solved the cold start problem because i didn't see any dirt or debris come out.

    2) Stalls when put in gear

    3) Can't start/ re-start hot.

    7) Vac gauge reads 15-ish fairly steady, but this concerns me as i have a stock cam----179/195 @.050".
     


  10. My guess is dirt in the fuel system.


    Did you do all the parts replacing chasing this issue or before ?

    if you smother the carb with your hand or a rag will it stay running or stall out ?
     
  11. Crank that bitch up to about 3000 rpm and choke it out with a rag. Is the filter stopped up in the carb?
     
  12. Aaron65
    Joined: Dec 29, 2005
    Posts: 375

    Aaron65
    Member
    from Michigan

    You said you adjusted your secondary plates...is it possible they're not closing all the way now? Have you checked the vacuum pulloffs for the choke and secondaries?
     
  13. pirate
    Joined: Jun 29, 2006
    Posts: 1,024

    pirate
    Member
    from Alabama

    Is the fuel system venting?
     
  14. c-10 simplex
    Joined: Aug 24, 2009
    Posts: 1,371

    c-10 simplex
    Member

    Filters replaced as part of routine maintenance. Coil/pickup coil/module replaced as a result of chasing (this) tail... Engine will stay running if cupping the choke tower.

    Pre-pump and inline (in the fuel inlet of q-jet) new.

    The secondaries are closing all the way, but i tried another carb, a 2G and it's doing the same thing....

    You mean thru the bowl vents?

    Vac advance disconnected, but initial set 8-10 btdc----don't want to get too greedy for now for fear of detonation.....
     
    Elcohaulic likes this.
  15. poncho catalina
    Joined: Sep 22, 2008
    Posts: 87

    poncho catalina
    Member
    from summit il

    check pcv valve/line and if it has a vacuum brake booster for leaks.
    G.M. paper gas filters if put in backwards will shut off the fuel
     
    Elcohaulic likes this.
  16. c-10 simplex
    Joined: Aug 24, 2009
    Posts: 1,371

    c-10 simplex
    Member

    pcv new and checked good. Brake booster was blocked off to eliminate it. Inline fuel filter put in correct position.
     
  17. What Type of Dizzy. do you have.????

    just my 3.5 cents

    Live Learn & Die a Fool
     
  18. MAD MIKE
    Joined: Aug 1, 2009
    Posts: 772

    MAD MIKE
    Member
    from 94577

    Since the car was sitting for a while, how old is the gas that's in the tank?
    New ethanol laced fuel can be a problem if it sits.
    Put some fuel drier and fresh 91/92 in the tank.
     
  19. pirate
    Joined: Jun 29, 2006
    Posts: 1,024

    pirate
    Member
    from Alabama

    I actually meant the fuel tank. A friend actually went through something similar. Starved for gas at higher speeds, hard to start after just shutting down hot. Gas cap had a vent but gasket covered hole. After driving for a bit would not idle well.
     
    Joe Travers likes this.
  20. Wrench97
    Joined: Jan 29, 2020
    Posts: 679

    Wrench97

    Give the pick up wires in the Dizzy a little tug to make sure they didn't break.
     
    Elcohaulic likes this.
  21. What your Saying sound's like the Timing is To Far Advance,! which
    would make too Hard to Start when Hot.
    so you would have to wait till it gets Cold & if it is the Timming
    That would be Why it wont Rev. to High.!
    Just my 3.5 cents

    Live Learn & Die a Fool
     
  22. BamaMav
    Joined: Jun 19, 2011
    Posts: 6,709

    BamaMav
    Member
    from Berry, AL

    Went through that with my IH farm tractor after putting on a new gas cap. Would start and run fine until it got hot. Turned out the vented cap wasn't vented after all. Drilled a 1/16" in it, no more problems....
     
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  23. c-10 simplex
    Joined: Aug 24, 2009
    Posts: 1,371

    c-10 simplex
    Member

    UPDATE:

    Ok, i think i may have solved it, but i need your help and input to make it work.

    Please view this 4 min video:


    Thinking the intake gaskets on the underside might be leaking, because i was really baffled as to what else it could be, i basically did the same as the above test---plugged both the fresh air inlet and pcv outlet in both valve covers and plugged the pcv port on the carb. Then measured vacuum in the crankcase----none, which is good.

    But the engine started very easy---within one crank revolution and no more stalling---can idle in gear all day.

    1) So why would plugging both holes in the valve covers stop stalling? i still need a pcv system, or at least a CV system. So, i can't leave it like this.

    2) What about the pcv system would cause stalling? Note that i replaced the pcv valve about 3 weeks ago thinking it may have been the problem.
    a) i have to add in, now that i think about it, the hose going to the carb from the pcv valve MIGHT not have fit the carb's port properly---letting air leak?
     
    pprather likes this.
  24. jimmy six
    Joined: Mar 21, 2006
    Posts: 14,799

    jimmy six
    ALLIANCE MEMBER

    Plug in the PVC valve in to the rocker cover leaving the plug on the opposite side rocker cover and you should have 1-3.5 inches of vacuum. It a test for engine to see if is sealed properly. Then work from there with testing other areas. I like starter fluid spray with a plastic stinger nozzle to pinpoint the exact spot.

    What you did should show pressure. It’s blow-by and all engine have it.
     
  25. c-10 simplex
    Joined: Aug 24, 2009
    Posts: 1,371

    c-10 simplex
    Member

    When you say testing other areas---you mean for vacuum leaks?

    My vacuum gauge, (it's actually one attached to a pump and i should probably get a real vacuum gauge,) only shows vacuum not pressure. But at least, there was no crankcase vacuum which i ASSume is a good thing?
     
  26. spanners
    Joined: Feb 24, 2009
    Posts: 2,073

    spanners
    Member

    Sounds like one of those vacuum lines is sucking air.
     
    Joe Travers likes this.
  27. c-10 simplex
    Joined: Aug 24, 2009
    Posts: 1,371

    c-10 simplex
    Member

    P.S.
    Post # 26 is complete Bull's hit:
    What happened is i noticed that the choke flap was kinda flapping/not tight against the choke tower when choke coil/engine cold. So, i adjusted it richer.

    But, this made it so i couldn't get off low step (the choke linkage itself is out of proper adjustment....) after the choke coil heated up completely. So, i pushed the tab down to get it to curb idle. But, when i put it in gear, just out of recent habit---since i can only keep the engine running in gear if i use both feet, i kinda tapped the gas----well this put everything back on low-step, or possibly mid-step idle---since there's still tension on the choke.

    THAT'S why it wouldn't stall out in gear yesterday----because it was at like 2000rpm in idle.....! So, all that horseplop about plugging the valve covers, plugging pcv and all that jazz likely had nothing to do with anything. i have no idea why it's now starting easy when cold---maybe because the choke was tighter.....

    So, problem NOT solved. And, i question my ability to function as an "adult." Seriously.
     
    Last edited: Jul 26, 2021
    Budget36 and David Gersic like this.
  28. Joe Travers
    Joined: Mar 21, 2021
    Posts: 708

    Joe Travers
    Member
    from Louisiana

    Definitely a vacuum leak. Vacuum @ idle for stock cam should be 3+ inches higher on a fresh engine if idle circuit is functioning properly.

    Joe
     
  29. jimmy six
    Joined: Mar 21, 2006
    Posts: 14,799

    jimmy six
    ALLIANCE MEMBER

    The gauge you have is fine. What I’m saying is a properly performing PCV system should show 1-3.5 inches of vacuum when installed with the outside air vent closed which you did with a plug on a valve cover. The best place to test IS the dip stick tube. I have a professional test kit and it has vacuum and pressure on a single gauge.

    And yes. Testing for vacuum leaks for me as I said is a can of starter fluid and a plastic extension to pin point the leaks.
     
    Joe Travers likes this.
  30. xlr8
    Joined: Jun 26, 2006
    Posts: 700

    xlr8
    Member
    from Idaho

    Have you checked out transmission issues? Vacuum modulator leak or possibly a bad convertor locking up and killing the engine?
     
    jimmy six likes this.

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