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SIV diagnostic advice ??

Discussion in '"Stock" Alpine' started by SIVAllan, Mar 24, 2009.

  1. Jim E

    Jim E Donation Time

    Did you blow the gas line out where it conects to the cross over, the issue could be as easy as left over paint chips in the fuel line. Then again it could be a burnt exhaust valve that gets worse as the motor heats up. One other thing have you balanced the carbs? Is it better with the choke one?
  2. Andrew

    Andrew SAOCA Web/Graphics Service Donation Time

    Hi Jim,

    Has anyone ever outlined how to balance dual zenith carbs on the forum? It would be a nice thing to include as a featured article.
    I would love some information on this and what one should do, should it be done at at fast idle....etc.

  3. 63 Beamer

    63 Beamer Donation Time

    Could it be possible that the rubber fuel line is run too close to the exhaust pipe and allowing the fuel to "boil" on its way to the fuel pump?
  4. alpine_64

    alpine_64 Donation Time

    Place on a nice even shelf using a spirit level.. will stay balanced for a long time while you use your DGV/DGAV/DCOE setup
  5. puff4

    puff4 Gold Level Sponsor

    It's pretty straightforward, Andrew - just carefuly follow the workshop manual - any other instructions would simply be redundant.

    The only extra tools you may want would be a Unisyn (a manometer to measure and balance air flow), and if you're really into it, a pair of Colortune spark plugs to get the mixture exactly right. Those two, and the workshop manual, will bring your carbs in spot-on every time.

    I have been tuning S.U. and Zenith-Stromberg carb'ed cars for over 40 years now, and I find them to be really quite stable and reliable so long as the basic engine is OK. Leaky valves, uneven compression pressures, badly worn cams, faulty ignitions and other failed systems can make it *seem* like it's the carbs, but almost always it's something other than the carb. I last tuned my Zenith-Strombergs almost four years ago, and I've never had to touch them since.

    Only other note is to that there are a couple of Rootes Service Bulletins for the Zenith-Stromberg's - the float height and the damper drilling to be specific - and these should be consulted as they do make a difference in tuning.
  6. alpine_64

    alpine_64 Donation Time


    I thin kyou will find Andrew is talking about the early series carbs.. the dual DD WIP/WIA Zeniths.. they are quite diffeent to the later stromberg/zeniths. I have said this many times before.. the DD Zeniths look nice.. sound ok.. and when in tune and good fettle produce decent power... BUT.. they wear out.. are hard to get parts for and even when new had a bad rep for staying in tune.. I lived with them on my car for 8 years.. was very happy when i ditched them for DCOEs.
  7. puff4

    puff4 Gold Level Sponsor

    Allen, regarding your starvation issue, try this process to get to the root cause...

    - Make sure the engine key is OFF and there are absolutely no ignition sources anywhere near or downhill of your vehicle. Open the garage door and get plenty of ventilation.

    - Remove the output line from your fuel pump and place it into a coffee can or other unbreakable container into which you can easily see. Make sure the hose is all the way down to the the bottom of the can.

    - Manually pump the fuel pump, feeling the resistance and watching the flow of petrol into the can. As you pump it should require moderate and even finger pressure across the full stroke of the lever, and you should see pure gas flowing out of the pipe and into the can with each stroke.

    - As you continue to pump and the hose submerges, watch for bubbles... there should be a few at first and then hardly any. If you continue to see bubbles, you have an air leak *somewhere* on the intake side of your pump.

    - If the lever stroke feels uneven, especially if you can pump it but then the lever doesn't really return down properly or if it's *really* hard to pump on the up-stroke, then you likely have a blockage in the intake side of the pump and this is causing the pump to pull air in from an air-leak source.

    - Now remove the intake side of the pump and make up a short hose to go into a small can of petrol... a clean, empty Girling fluid container works well for this since it has a narrow neck and is less likely to spill.

    - Again, pump the pump manually and see what it does. If you still have air coming out, you have a leaky diaphragm - replace or rebuild the pump. If you have no air but also very little gas, your pump valves are shot - replace or rebuild the pump.

    - If the above test goes OK and you have a nice stream of largely air-free petrol going into the tin, work your way upstream - the pipe is likely blocked or pinched... visually follow every inch of it all the way from the engine compartment back to the crossover pipe and ensure the line is not crimped, impinged, bent, etc. and that there are no signs of wet spots (leaks).

    - Assuming above is OK, jam a 3 foot piece of rubber hose on the end of the fitting, open the gas cap, and blow into the tube with your mouth - don't use a pressure gun. If the line is clear you should be able to blow into the tube freely with moderate pressure and eventually will hear faint bubbling from the open tank. If you have to blow so hard you feel you're going to blow a gasket, then it's a clogged pipe.

    Hope this helps!


    (Note: if you don't have a lever on your current pump, then you'll have to crank the engine to get it to pump, but be sure to remove the power wire to the coil and only use the starter solenoid's push-button to do the cranking. Also ensure the brake is set and it's out of gear, and that everything is clear of the fan when you do the tests.)
  8. SIVAllan

    SIVAllan Donation Time

    I don't know how to reply to such an outpouring of advice and support.

    Sunbeam/SAOCA rocks!!!!!

    Let me bring you'all up to date...

    I rigged a one gallon gas can as an auxillary fuel system with new fuel line running direct to the fuel pump.

    As soon as the engine was started, gas began to spew in quantity to the ground.

    Looking beneath the car a pin hole was found almost next to the fuel pump inlet.

    That end of the replacement rubber fuel hose/fuel line consisted of about 15 inches of original fuel pipe.

    The pipe traversed in an "S" over the oil cooler pipes, then down, then horizontal, where it hooked to the replacement rubber hose.

    Over the years it had been twisted a little bit, and a pin hole developed almost next to the fuel pump inlet.

    I made a new pipe with a new ferule (?? spelling) , straight not an "S" pattern, hooked the test tank to that, let 'er run for 90 minutes while I watched and had some good beer.

    Voila! She idled fine no problem for 90 minutes.

    After a while I did see a bubble in the fuel filter every 10 seconds or so , but not in the fuel pump. That might be due to the jury rigged gas can with only press fittings no clamps.

    So that is hopeful.

    Now to hook up the gas tanks and test again...???

  9. puff4

    puff4 Gold Level Sponsor

    Yay. What do I win? ;)
  10. SIVAllan

    SIVAllan Donation Time

    Some thoughts on the suggestion regarding balanced Zeniths... ??

    Don't the zeniths allow adjustments only for idle not driving ??

    Getting them to nirvana or perfect balance for driving requires setting
    all the internal jets &&&etc to equivalency one to the other carb??

    --or equivaleancy to a specified setting, meaning variation one to the other is acceptable if within factory specified tolerances?

    Shouldn't zeniths be REAL close to balanced or in fact balanced for driving, as rebuilt or, if NOS, as bolted onto the manifold ?

    I wonder if the 'balance thing' is over rated for the zeniths ?

  11. SIVAllan

    SIVAllan Donation Time

    If this proves to be the cure, and I hope to know in a day or two by running off the car's tanks, by all means the SAOCA should provide the Distinguish Muffler Bearing award, a certificate of thanks, and 10,000 kudos :)

    And I personally will provide a ride in my Airpine once around the SUNI concours should all parties be in attendance :)

  12. RootesRacer

    RootesRacer Donation Time


    I think you are getting confused about the various meanings of "zenith" and or what balance is.

    Based on your signature, I believe you have the older WIP/WIA 1 bbl conventional carbs. There also is the "zenith stromberg 150CD" AKA stromberg, which is not conventional, its a constant depression carb, or variable venturi.
    These were used on the 1725 SV engine.

    Balance in each case is actually the synchronization of the throttle plates to one another, meaning each carb has its throttles adjusted to equalize flow at a given throttle angle. This is done by loosening the throttle link between the two carbs, adjusting each carb for flow, then locking down the linkage.

    Being mis-balance has different effects under different circumstances for each of the carb types.

    The WIA/WIP being mis-balanced will have idle and cruising issues since the progression holes are not being uncovered at the same time.

    The strombergs being mis-balanced will prevent idle or will force the main jets to be grossly mis-adjusted to provide an idle.

    WIA/WIP have main jets (not adjustable), but adjustable idle mixture screws.

    Strombergs have adjustable main jets, but no idle mixture screws.

    The WIA/WIP will tolerate a fair amount of throttle shaft wear, where the strombergs force you to adjust the main jet to compensate for idle air leakage, and therefore worn throttle shafts leave you with a lean idle, or very rich main/power.

  13. SIVAllan

    SIVAllan Donation Time


    I am certain that I'm confused regarding the carbs :) .

    Part of that (the least part) is that a reference to "Zeniths" means
    WIA/WIP carbys to my ears.

    And a reference to Zenith-Strombergs means our cars' Strombergs.

    Another point, that I did not make very well, is the meager adjustments available
    for the WIP carbs in partiicular.

    If one tears down the WIPs, sure some things can be done.

    But for "avg Joe Sunbeam" (like me :)) all that can be done is adjust the idle (slow running speed).

    At least that's what I've thought to date.

    Maybe the idle adjustments carry over to driving performance, I dunno, look forward to learning more :)

  14. SIVAllan

    SIVAllan Donation Time


    After installing a new pipe to the fuel pump inlet, and hooking the fuel hose to the new pipe, the car ran fine for 90 minutes using a gas can for a fuel tank.

    Today I switched to the car's fuel tanks, and the engine idled fine for 2 hours by my watch.

    I then drove up my steep drive to the street - left the sunbeam idling while I went inside to get a bottle of water - only to discover it had died again when I returned, and with the same symptoms.

    I poured a little gas in the carbs and it did ok for a moment or two.

    Turning over the engine the fuel pump and filter did not appear to fill up as rapidly as they should but I don't have the experience to know, and the fuel pressure gauge is not working.

    What else to do or try ??

    In desperation I got the car back into it's spot behind the house and drained the fuel.

    Today the center crossover pipes will be removed to inspect and hopefully find some thing that stops fuel flow.

    Is there any way to flush the tanks while they are installed and the crossover pipe is removed ??

    - or even any need to flush the tanks?

    The opening in the tanks leading to the crossover pipe is relatively large enough to let most stuff through, perhaps anything smaller than a golf ball or crab apple sized object.

    Flushing them with a water hose seems like a bad idea UNLESS water residue could evaporate or somehow be removed or neutralized:) .

    Thanks in advance!!

  15. puff4

    puff4 Gold Level Sponsor

    Allan, I'm still banking on a leak in the intake side of the pump somewhere, and possibly a clogged tube going to the tanks. I'll suggest again that you follow the process I outlined and you'll very likely find your problem. The only other possibility that this would not find is a flap of material inside the crossover pipe which is intermittently blocking the outlet to the small fuel pipe which goes up to the engine compartment.

    And unless you're going to remove the tanks, don't even think of putting water in them. Take them out, have them dipped, checked for leaks and sealed. (But didnt' you do that already??)
  16. SIVAllan

    SIVAllan Donation Time

    Thanks Kevin,

    Essentially I have completed the outlined steps, although not as methodically as I could/should have done.

    In lieu of testing the pump, it was replaced.

    The replacement pump was then hooked to an auxillary gas "tank" and allowed to run the engine.

    This revealed a pin hole in the stub of metal fuel line attached to the inlet side of the fuel pump.

    I guess the gallon gas can sitting up high plus pump pressure put more pressure on the line and it leaked, as it did not show leakage before.

    The fuel tanks were removed in spring of 2007, split open by a radiator shop, boiled out and red coated.

    The crossover pipe also was boiled and red coated.

    The recoated tanks and crossover pipe were then reinstalled with new pipe connectors from SS and a new rubbler fuel line installed from crossover pipe to pump.

    At one time between then and now the gas in the pump looked reddish and I wondered what that might signify, but the reddishness went away, so I am left to wonder if that was not relevant.

    So now to check the crossover pipe.

    I sure hope there is some sort of sludge or object kinda/sorta light enough to float given time to rise, but soggy enough to sink and clog the crossover pipe outlet to the fuel pipe, under pressure from the pump.

    The crossover pipe to fuel line opening is quite small...

    I will examine the new rubber fuel line but given the time pressure, perhaps it would be beneficial to replace it as that is a low cost item... ??

  17. SIVAllan

    SIVAllan Donation Time

    A note on a newly found aspect of the problem...

    When removing the crossover pipe, I noticed that the join on the right side was not perfect and had been leaking fuel into the corner of the boot.

    There was sufficient leakage to buckle and blister the paint in that corner of the boot, and the leak was active as I found dampness in the boot.

    So there is (soon to be "was") ANOTHER leak in the fuel system that could or would have contributed to the fuel pump sucking wind.

    I sure hope this is the winning ticket.

    But while I can see how this would contribute to fuel pump sucking air, it is not clear how this would only shut down the engine after it warmed up and time passed.

    I saw no problems with the crossover pipe except most of the red liner had vanished.

  18. SIVAllan

    SIVAllan Donation Time

    I'm still reading replies and searching for a cure :) but wanted to add a couple points...

    1--regarding a tuneup workshop for Zeniths (all kinds) - that is an excellent idea.

    I hope I have not sounded negative on the idea, and hopefully I've not said anything more rookyish than usual.

    At one time I had a copy of the zenith WIP WIA factory tech bulletin and I'll search if anyone is interested in a fax or a scan.

    2--I bought the biggest screw driver I could find that will fit a fuel line clamp and put a big hurt on each and every clamp between the fuel pump and the gas inlet on the fuel tank, including all crossover tube joins.

    3--I drained the tanks and installed fresh fuel along with 4 oz of Marvel Mystery Oil in the tanks to clean out anything that may need cleaning out from tanks to carbs.

    4--I removed and inspected the central crossover tube, found no sign of a blockage and reinstalled it. I reamed out the outlet to fuel line "piplet" with a wire brush just to be sure.

    I DID notice that much of the red liner has vanished from the crossover tubes making me wonder if it vanished from the fuel tanks as well........

    5--I don't see any more fuel pump bubbles but do see excitement in the fuel filter - maybe that is due to its elongated shape as the pump pulses it looks bubbly but really isn't ??

    6--the piece of crap inline fuel pressure gauge is not working and will be returned.

    There must be one that works on the market somewhere.

    7--I inspected each inch of the fuel line for wet spots or holes but could find neither from carbs to crossover pipe.

    8--the engine now idles but won't run unattended for too long so the carbs may need a tweek to mate to this engine...

    If I add a little choke it helps.


    I'd like to add a note on how the two fuel leaks discovered recently came to be...

    A while back, I had a problem (that was of my doing) with the seal around the fuel tank sender device.

    If I filled up with fuel, it would run out the top of that tank.

    I got tired of not being able to fix that leak and left the car with a nearby shop to fix.

    They pulled that tank and somehow got the seal to work right and reinstalled that tank.

    While they were at it, they did not get the crossover pipe "joins" right and the one on that side leaked so I returned and had them fix that.

    Unknown to me, when they slid the crossover pipe to the right to free up the left gas tank, they got the crossover pipe join poorly aligned on the right side..

    It was way over to one side, barely fitting at all, but not noticeable to the eye - until I yanked the crossover pipe last night and found the leak.

    Also the shop said the stub of metal fuel line to the fuel pump inlet was twisted a little bit (as I knew and ignored) and that they had 'straightened it some."

    Where they twisted that pipe a pinhole leak developed.

  19. Bill Blue

    Bill Blue Platinum Level Sponsor

    Allan, I hate to sound pig headed (well, not really), but have you checked the quality of the spark? A rich mixture is easier to ignite than a lean one. So your comment about the choke makes me to wonder if you are looking in the wrong place now that you seem to have enough gas to the carbs.

    No comment about the red stuff other than several board members contend it is the ONLY tank liner worth messing with. Of course, I used the silver stuff. Maybe all red stuff is not created equal.

  20. SIVAllan

    SIVAllan Donation Time


    No I have not - will check the spark quality tomorrow.

    Besides making each plug wire arc to metal, and observing, maybe there is a more objective method ??

    I can also swap the plugs easily to see if that is a variable in this problem.



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