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Fuel delivery issues?

Old 11-01-2017, 02:34 PM
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Location: Shelton, WA
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Default Fuel delivery issues?

Hi folks,
I have some odd behaviors in my 1980 Civic Wagon that I'd like to try to figure out and maybe fix.

The one that really bothers me, is that when the accelerator pedal is pushed around half way, there is a sudden drop in power, or hesitation. Pressing it further, power comes back and everything is fine. Idling and pressing the pedal a little is also fine. This happens regardless of how fast the pedal is pressed. I wonder if the second barrel should be opening a little sooner? Anyone else have/fixed this issue?

Maybe related or not, is that when the engine is warm, if the engine stalls, it is very hard to get it started again. Thanks to the first issue above, it is very easy to stall getting going from a stop. It's been suggested that the float bowls aren't filling fast enough to restart the engine. But wouldn't that cause the engine to lose power with the pedal pressed all the way down? I don't have that problem.

Fuel pressure is at 3psi just like its supposed to be. I have a new filter on the fuel line just before the carburetor. Still perfectly clean as far as I can see. The engine and the carburetor have both recently been rebuilt. I'm hoping the carburetor just needs some fine-tuning. I'm plumb out of money for a while, LOL.

Suggestions welcome!
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Old 11-01-2017, 08:15 PM
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Default Re: Fuel delivery issues?

It sounds to me like it might be a partial blockage in the main jet circuit of the primary throttle, like some fuel deposits or a piece of trash or something, that is causing the engine to lean out at large throttle openings of JUST the primary throttle. The idle mixture is ok, and at even larger throttle openings the secondary throttle mixture is ok, but when you are running on just the primary throttle with it mostly open the overall mixture is just a bit too lean for the engine to run well. I had a Fiat that did this once and it ended up being a piece of trash stuck in the primary main jet.

Here is a test you might try. Do you have a propane torch? With the car running in Park (or neutral with the handbrake set) can you open the throttle by hand until it starts to run badly? If so then crack open the valve on the propane torch just a tiny bit, NOT MUCH, only enough that you can feel a small amount of gas blowing out against your cheek or face (because your face is very sensitive to air movement). And DON'T LIGHT IT, you want unburned propane coming out. Now while opening the throttle by hand until it runs badly, start moving the torch tip towards the primary throttle. Does it suddenly start running good again, or is there no difference? If it runs better that is because the propane richened the mixture enough to make it roughly normal again, and your problem is a lean condition caused by something blocking the primary jet circuit. If there is no difference then I have no idea what is wrong, but at least you have ruled something out. Hope that helps.
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Old 11-03-2017, 04:45 PM
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Default Re: Fuel delivery issues?

I will check that out. Thanks!
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