Problems keeping engine idling
![[Deleted User]](https://openforum.hetclub.org/applications/dashboard/design/images/defaulticon.png)
I am having trouble getting my car to idle. Its a 38 Terraplane, stock engine and carb (W1). I have just about checked everything and I am out of ideas. Replaced coil, replaced fuel pump(electric). The carb has been off and the low speed jet cleaned along with the passage ways. Intake manifold checked for vacuum leaks. Condensor swapped out. Compression checked and is good and constant for all 6 cylinders. Timing checked, and is dead on. Idle mixture has been tried, it seems to help short term, but doesnt solve the problem. And the screw is about 3 full turns out, compared to the 1/2 - 1 that the manual states. Pulling about 18 psi of vacuum when I can get it to idle for short periods.
I am able to get it to idle for a short period of time, then if I give it some gas and take my foot off the gas, it stalls out. Other times it will not idle at all, and I need to continuously pump the gas pedal to keep it running.
What could be wrong?
I am able to get it to idle for a short period of time, then if I give it some gas and take my foot off the gas, it stalls out. Other times it will not idle at all, and I need to continuously pump the gas pedal to keep it running.
What could be wrong?
0
Comments
-
Check for a vacuum leak-0
-
davegnh1 wrote:
Did that. Checked the intake manifold for leaks, completely disconnected the vacuum to the wipers and read vacuum from the intake manifold vacuum port. Read 18psi, which is what the tune up manual calls for.Check for a vacuum leak-0 -
I'm assuming that this occurs when the engine isn't particularly hot, so we can eliminate such things as a hot coil or vapor lock? In other words, you have the same problem whether it's hot or cold?
Could the electric pump possibly have too much pressure, and be forcing gas down your carb's throat, so to speak? Do you have an adjustable valve on the line?
You say 'timing is checked and is dead on'. I assume you've checked the timing marks with a timing light and the needle (such as it is, in the '38's) is not 'jumping around', but is fairly consistent regarding the UDC mark?
One off-the-wall idea is, that the fiber timing gear hub has broken away from the gears, and that you have a sometimes-it's-right, sometimes-it-isn't situation. I've seen this happen with the 3x5's before.
Also (I hate to ask because you've probably done this) you've played around with the distributor setting, advancing and retarding it, right? Don't go by the markings on the distributor because, as you probably realize, there is a clamp underneath the distributor that holds the advance control arm to the distributor body and if that loosens, it doesn't matter where you set the timing mark, the whole distributor will rotate.
And speaking of the distributor, be sure that the wire (where it passes through the body of the distributor) is fully insulated or you may be getting some grounding there. Probably wouldn't explain rough idling, but then...0 -
Jon B wrote:I'm assuming that this occurs when the engine isn't particularly hot, so we can eliminate such things as a hot coil or vapor lock? In other words, you have the same problem whether it's hot or cold?
Could the electric pump possibly have too much pressure, and be forcing gas down your carb's throat, so to speak? Do you have an adjustable valve on the line?
You say 'timing is checked and is dead on'. I assume you've checked the timing marks with a timing light and the needle (such as it is, in the '38's) is not 'jumping around', but is fairly consistent regarding the UDC mark?
One off-the-wall idea is, that the fiber timing gear hub has broken away from the gears, and that you have a sometimes-it's-right, sometimes-it-isn't situation. I've seen this happen with the 3x5's before.
Also (I hate to ask because you've probably done this) you've played around with the distributor setting, advancing and retarding it, right? Don't go by the markings on the distributor because, as you probably realize, there is a clamp underneath the distributor that holds the advance control arm to the distributor body and if that loosens, it doesn't matter where you set the timing mark, the whole distributor will rotate.
And speaking of the distributor, be sure that the wire (where it passes through the body of the distributor) is fully insulated or you may be getting some grounding there. Probably wouldn't explain rough idling, but then...
Not heat related, happens both warm and cold. Have had 2 different coils on with the same results. Electric fuel pump eliminated vapor locking.
The electric pump has a pressure regulator that is set at 2.5psi so there isnt extra fuel being pumped down the carb. You can hear the pump stop when the carb bowl is full.
Used a timing light and the pointer was steady on the mark on the flywheel, advancing correctly when the accelerator was pushed. So based on that I did not mess with the advance, since it seems that if the timing is right on, that changing the advanced/retard wouldnt make sense.
I will check the primary connection to the points, but I imagine that if it was grounding out, that the car would not run at all.0 -
When you pull your plugs what do they look like?0
-
51hornetA wrote:When you pull your plugs what do they look like?
Black. But they dont look much different than they did before this problem came up.0 -
Ok thats good wanted to eliminate any problems there. Are you sure that the choke on the carb is working correctly is it a manual or automatic choke? if automatic when the car heats up to operating temp is the choke opening properly? check to make sure it is not sticking.0
-
51hornetA wrote:Ok thats good wanted to eliminate any problems there. Are you sure that the choke on the carb is working correctly is it a manual or automatic choke? if automatic when the car heats up to operating temp is the choke opening properly? check to make sure it is not sticking.
Manual choke. And it is working fine. Opens fully when the choke is pushed in. Sometimes it will idle when the choke is partially on, even when the engine is warm, which led me to believe it was a fuel problem. But cleaning out the idle jet and passages did not appear to help0 -
How is the float level? also you may have to play with the advance a little to adjust for your gas type. Sometimes having the timing right on with the timing mark does not mean the car is timed correctly for your specific gas. I would adjust that just to eliminate it from your troubleshooting.0
-
Havent checked the float level, didnt want to totally dismantle the carb.
The car ran fine 2 months ago before it went up on blocks to do some work. And none of the work was carb/distributor/timing related.
Seems hard to believe that something has changed that much since the last time it ran perfectly well.0 -
You don't suppose the needle valve is stuck? From what you say, the fuel pump shuts off from time to time, indicating that the needle valve is doing its job to properly meter the gas. But of course if there was some dirt in there, holding it open, that would explain the rough running and inability to stay at idle without dying...right? Try tapping it, just for grins...0
-
I dont think its the needle valve. The fuel pump would not stop running if the valve wasnt closing. And it seems like a starvation problem, not a rich condition.0
-
You're not pulling air through the lines, perchance? I've heard of this happening, when a gas line corrodes of there is some sort of air leak. Conversely, you might be pulling too much through the line -- that is, pieces of your corroded gas tank. (Admittedly, I'm grasping at straws here.) Have you checked your various fuel filters and screens, such as the screen in the sight bowl at the pump, for crud in the line? Of course, these kinds of problems would manifest themselves not at idle, but at full throttle. And I think you indicated that your only problem was maintaining an idle...0
-
I would expect that if I were pulling air that the pump would not stop pumping.
And yes, if I step on hte accelerator, gas squirts down the carb, so the carb bowl is staying full. But just wont idle.0 -
How old is the gas in the tank? This new gas can break down fast. Have you tried adjusting the points? A little trick i have used is to rev up the engine and pull the choke on. This pulls gas trrough all the port and sometimes removes the dirt. You said if you run with the choke on part way it will idle. This seems to show its lean. Good luck chuck0
-
The gas is a couple months old. I have not touched the points more than cleaning them off. The car ran before, so I wouldn't think the points would be out of adjustment.
The lean condition is what I keep leaning towards, but I cleaned out the idle circuit, so I would think that would be enough.0 -
I don't know these old engines - just the basics but I didn't see these options mentioned..
Running well before being parked and now having a problem - kinda smells of the gas breaking down, but that would seem to make it harder to start than running at an idle... I'm curious if you tried pulling fuel from an alternate source other than the tank? (ie glass jar or other container)
Does anyone know - would the cheap gas these day breaking down cause excessive varnish to build up on fuel system parts?
Do you or someone close to you have another carb you could try out?
I know you tried a vacuum guage and noted the readings were consistent and in range...did you try putting your hand over the carb while running - or spraying some starting fluid around the base of the carb - these are some other tests to see if air is leaking past somewhere...as I remember you saying the idle screw was almost 3 full turns out it would seem the air fuel mixture is way off.
Last but not least - is there another pair of eyeballs around you trust? Sometimes someone not so close to the project (whether it be cars, programming or life) can spot something we could easily overlook.
Just trying to give you some more ideas...good luck!0 -
Anyone have any other ideas?0
-
See if you can get the engine to idle smoothly by running it on half choke or play with the choke until it does idle correctly by moving it slightly at a time in and out until you reach a good idle. If you can get it to idle on any kind of half choke or three quarter choke then you definetly have a vacuum leak some where. Try spraying carb cleaner around the base of the carb and see if it picks up speed.0
-
Well, I feel just as lost as before. Started the car this weekend to try and track down a vacuum leak by spraying carb cleaner everywhere. Had someone hold the gas to make sure the car ran, and I sprayed every seam on the intake side of the engine. Didnt find any leaks. But then the car was idling on its own without any problems. Dialed the mixture screw back into specs, and the car idled perfectly, both hot and cold.
Its still the same gas in the tank. And nothing was changed from last weekend to this weekend. I am at a complete loss. The car appears to be running fine now, but I am not sure I trust it.0 -
Can you every really trust something that old ~ I barely trust myself sometimes
Must have been a little gunk somewhere holding something up - possibly the carb cleaner helped clear it out?
I know you said you have an electric fuel pump on the car - I wonder...maybe pump out a quart or so into a clear container and let it sit to see if it has any contaminants/seperation or debris.0 -
Well, just like I thought. The car is having problems idling again. Nothing was done to it. Started up on a Saturday and ran perfectly, two days later it was started and has the idle problem again. Nothing was done to the car at all in those 2 days. The gas was only a couple weeks old, with fuel stabilizer in it. What on earth could it be?0
-
Do you have access to another carburetor that is proven to be ok? Perhaps another Hudson person in your area has one.
If the car ran perfectly on a Saturday, then the problem came back, and it runs only with the mixture screw out twice as far as normal, then it is very likely in the carb, seeing as you have likely eliminated a vacuum leak.
(If you want to check the vacuum again, this time use a hand-held propane torch that is UNLIT. It is much safer than spraying carb cleaner on a running engine, and is more precise. You simply hold the torch with the propane valve on and point it near obvious leak areas, such as base of carb.
Also, make sure you have a fuel filter after the last fuel pump in line, and have it be a modern in-line type. If you have such a filter on the car, and it is fresh, I would then put on a proven carb, or have your carb rebuilt by someone who does it professionally, rather than changing more parts and driving yourself crazy.0 -
You mentioned that you checked the intake gaskets a couple of times. Have you tried some propane around the carb base? I don't know what sort of gasket/spacer arrangement that your's has but cracked spacers (from being overtightened once) are not unusual. You said in your initial post that after idling for a while (when it was able to idle) you would give it gas, release the accelerator, and it would die. Did it (does it) ever backfire a little through the carb? That type of backfire is frequently caled a "lean misfire" and is a result of too little gas. On the other hand, vaccuum leaks (intake manifold gasket or otherwise) cause too lean a mixture in the combustion chamber. So lean that the fuel only partially burns and the result is the smell of excess fuel in the exhaust. When this happens, quite ironically, the tailpipe exhaust will smell like the car is running rich. So, any lean misfires (small pops, or backfires) through the carb? Rich exhaust? How about the carb base gaskets, have they been used too many times? I want to mention that at some point you might want to make absolutely sure that the carburetor itself is completely tight. Make sure that the base hasn't loosened from the throttle body. If you ever get it idling well again, try leaning a little on the carb in different directions. Also, press down on it. Maybe by manipulating it, or one of the vaccuum lines, as well, you might be able to get it to act up for you. There's one last thing that I'd like to mention and that's something that I've run into with much newer carbs than your's, but it might apply. People sometimes mistakenly rely on the fast idle screw (the one on the cam that's operated by pulling the choke cable) to maintain idle even after the cable has been pressed all of the way in. That screw should completely fall off of the fast idle cam when the cable is pushed in. The idle is then controlled by a second screw usually quite near the butterfly in the base of the carb. If you, or anyone else reading this, ever has an occasion to adjust your choke cable, I suggest that you leave the cable positioned in such a way that when the choke cable is pushed in fully (and, of course, the choke butterfly is completely open) the knob inside the car be not quite touching the dash. A little clearance here (perhaps a sixteenth of an inch) will always ensure that even with a little binding in the cable or linkage, the choke will always be open fully.0
-
I just thought of one more thing. When carburetors have seen a lot of use the throttle shaft hole (in the base) will wear to the point that substantial amounts of air are sucked into the carb around the shaft. This plays havoc with engine idling. While this type of wear happens slowly over time, when it finally causes trouble it can be somewhat intermitent intially. The only solution is to replace the carb or take it off and have the base drilled out and rebushed. Make sure to "play" a little propane around this area of the carb also.0
This discussion has been closed.
Categories
- 37K All Categories
- 106 Hudson 1916 - 1929
- 19 Upcoming Events
- 91 Essex Super 6
- 28.6K HUDSON
- 562 "How To" - Skills, mechanical and other wise
- 995 Street Rods
- 150 American Motors
- 175 The Flathead Forum
- 49 Manuals, etc,.
- 78 Hudson 8
- 44 FORUM - Instructions and Tips on using the forum
- 2.8K CLASSIFIEDS
- 602 Vehicles
- 2.1K Parts & Pieces
- 77 Literature & Memorabilia
- Hudson 1916 - 1929 Yahoo Groups Archived Photos