Jet running too lean- help please

Unknown
Unknown
edited November -1 in HUDSON
I have a '54 Hudson Jetliner with the single carb engine. I just replaced the manifolds to solve an intake manifold air leak. i no longer have the air leak, but the engine won't keep running without the choke being nearly closed, even when at full operating temperature. I have plugged all vacuum lines, tried 2 different carbs, one just rebuilt, replacde the fuel filter, checked carb base and manifolds for air leaks, but no luck. It starts with priming and will run with the choke closed. As the choke opens I have to keep adding extra fuel or closing the choke to keep the engine running. The choke heater tube is missing, so I had to fit a Studebaker one to get the choke to open at all, but it still isn't opening any where near as fast or as much as it should. Even fully warmed up I have to prime the carb to get it to start. Both carburetors behave the same. The fuel pump appears to be pumping well.
I've run out of ideas and would appreciate any expert Hudson advice.
Thanks,
Bruce Kerslake

Comments

  • Geoff
    Geoff Senior Contributor
    The key here is that you have replaced the manifold. It is likely that you still have a leak somewhere. It could be between the exhaust and the intake. Have you checked for vacuum? Either use a vacuum gauge, or remove the coil lead, hold the choke open, and get someone to crank the engine over with the accelerator pedal held right down, and put your hand over the carby throat. it should be sucked down real hard as the engine cranks over. If not, you still have a leak somewhere. Good luck,
    Geoff
  • Park_W
    Park_W Senior Contributor
    As Geoff has suggested, the replacement manifolds may be rusted/corroded through in the heat riser area to create a leak between exhaust and intake passages.
  • [Deleted User]
    [Deleted User]
    With the engine running put some laquer thinner in a squirt can. Squirt on suspected leak spots /gaskets and if you find an open vacume leak the engine speed will increase .
    Roger
  • [Deleted User]
    [Deleted User]
    Don't use laquer thinner as the fumes can explode. Start engine and spray brake- clean on one spot at a time, and if a vacuum leak, it will stall the engine. Is your carb a single barrel or the 2 barrel WGD? Check the timing for you could have a bad timing chain. Walt.
  • Unknown
    Unknown
    I have used spray carburetor cleaner on suspected leak spots. The only place I get a response is down the carburetor throat- a substantial speed up. I will be checking the vacuum next- as soon as the rain stops. My carport is not very weather tight, so kind of risky to be dragging the trouble light cord through the wet to work under the hood. The manifolds appeared to be in excellent shape, but I suppose there could be a hidden crack in the intake manifold preheat area. I hope not as it wasn't easy to find the manifolds.

    Bruce Kerslake
  • Unknown
    Unknown
    Jason at Vintage Coach may have a pair of Jet manifolds, it is the single carb version. Call him if you need them. Tues. to Sat. 8am to 5pm @ 909-823-9168
  • Unknown
    Unknown
    I ran tests with the vacuum gauge today. It ran 15 to 18 inches of vacuum at what I guess was about 1500 rpm with the choke barely cracked open. The reading was steady. If I opened the choke butterfly the reading dropped to about 12 inches and was less steady. Of course it won't stay running more than a minute with the choke open, even though the throttle is still on the fast idle cam. The readings rose slightly as the engine warmed up, at least until the choke opened too far. As I mentioned before, the choke opening is slower than normal as I do not have the proper choke heat tube.
    I am not a professional mechanic and am not familiar with using a vacuum gauge for diagnosis, so I hope someone can enlighten me. I know the engine has some wear as it does put out blue smoke when running, however it sounds pretty good.
    I certainly hope it doesn't end up being a defective manifold as I just paid $185 to have a very nicely looking set shipped out from Pennsylvania.
    Thanks,
    Bruce
  • Unknown
    Unknown
    I just checked the Mechanical Procedure manual and it suggests my readings may be caused by incorrect ignition timing. This is a possibility as I can't get it to idle down sufficiently to set the timing with a light. When I first got the car, the timing was so far advanced it would barely crank at all, so I retarded the timing by ear I suppose I could set the timing by backing out the fast idle screw, disconnecting the choke tube to keep the choke closed long enough to set the timing.
    Bruce
  • Geoff
    Geoff Senior Contributor
    You have to go back to basics and statically check the ignition timing. Then start the engine, and preferably use a timing light to have the spark set at t.d.c. at idle. Where are you taking your vacuum reading from? It should be from the wiper take-off point, not the distributor connection. If the car ran okay before you changed the manifold then I still suspect a leak somewhere, but it could be a blocked main jet. However, if this was the case it should idle okay. You really have to check every aspect, fuel delivery, spark intensity, and timing. It's really difficult to give you a diagnosis by remote control. Good luck.
  • Unknown
    Unknown
    I'm taking the vacuum reading from the intake manifold connection for the wipers. I will statically time the engine tomorrow as the timing light still shows at least a couple of inches advanced from the mark. I still can't get the engine to idle down below 1000 rpm.
    The engine did not run well before I changed manifolds as there was a significant air leak where the manifolds bolted to the block. I removed the manifolds to replace the gasket and found the intake manifold broken where it mounted to the exhaust manifold. That was the reason for replacing the manifolds.
    Thanks
  • Unknown
    Unknown
    I now set the timing statically. This brought the idle speed down some. I also shortened the makeshift choke tube to improve the choke opening. I found the rebuilt carb was not that clean inside, so I cleaned it out, re-oiled the accelerator pump plunger and adjusted the choke level higher. After all this it now starts cold and will run and drive until it warms up completely. At this point it will no longer idle and won't restart without priming. The carb does not respond to idle mixture screw adjustments.
    I've never experienced a car that wouldn't respond to tune-up and normal maintenance fixes like this one. I'm afraid I have too many other collector cars waiting for work on them that will respond to TLC, so I may have to sell this one and cut my losses.
    Thanks for all your help.
    Bruce
  • Geoff
    Geoff Senior Contributor
    I still suspect an air leak somewhere.
  • Unknown
    Unknown
    O.K. time to grab a few straws. When you changed manifolds, did you check the block side, the ports, with a straight edge, or did you just bolt them on? Also did you loosen the bolts holding the intake and exhaust together and retighten them after you bolted them to the block? either way you could have a vacuum leak and probably do. Everything you've posted seems to indicate a leak. You could have a leak at the bottom of the port which is very hard to detect. I'll have to go along with Geoff on this one. Good luck.
  • Unknown
    Unknown
    I checked the port flanges with a straight edge. Also, I don't get any change in the engine speed spraying carb cleaner along where the manifold bolts to the block as I did before replacing the gasket and manifolds.
    I did not loosen the nuts on the studs between the intake manifold and the exhaust manifold. However, wouldn't a leak here just be an exhaust leak? This connection just allows exhaust heat to preheat the intake manifold, doesn't it? Maybe my whole understanding of this system is wrong. I hesitate to mess with this connection too much as the ears on this flange appear to be prone to breaking off. That's what was broken on my original intake manifold. It is hard to test this connection for leaks as it is hidden under the heat shield. Please let me know if an intake leak is possible at that connection.
    Are the vacuum readings I got (15 to 17 inches really low enough for an air leak? I assumes for a worn engine those readings weren't too bad.
    Thanks again,
    Bruce
  • [Deleted User]
    [Deleted User]
    I still say you have late timing, a bad timing chain or tight valves. Try setting your valves cold at intake 0.014 and exhaust 0.017. You also can have the wrong jets in your carburetor or metering rods. Walt.
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