have to close choke plate?? to keep car running-why??

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john27pa

john27pa

74 360/904 Duster
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I wasnt sure where to post this or how to search for this as I am being vague today lol. Anyway- I have a 360 in a 74 duster. Just put the engine in recently-from a 79 cordoba. Both engine and trans together. I cant figure out why I have to completely close the carb choke plate to get it to run. If I let it open in any way- engine shuts off like your hitting a switch. My guess is a vacuum leak. Thing is- engine ran without a problem in the cordoba. Engine did sit for about 6 months under a tarp-supposedly. Its either huge vacuum leak or maybe floats?? Im not a carb guy, so I am guessing from past experiences. The only thing that was done to engine involving vacuum leaks is that I had to change the throttle and kickdown hold downs and spring hold downs for same. I took a bolt or two out at a time and replaced as I went- didnt loosen whole side of intake at once. Either way- this shouldnt cause a vacuum leak that bad, right? The gasket never seperated. All vacuum lines on car are blocked off-all except for choke diaphragm and pcv valve. It is a 2 bbl carb. Could it be getting too much gas? not enough? vacuum? If I leave the top carb plate open, I have to keep giving the carb shots of gas to keep it running. With choke plate?? closed all the way-it runs good.
Ideas of what it may be and what to do? Things to look for and try?

Tia, John
Ps, car engine is being bypassed from ign switch. No key yet so running with coil pos through toggle switch to batt + and screwdriver to starter relay. Not sure if that changes anything- just trying to give as much info as possible. Still no juice to wiper motor, but have juice at heater blower motor. Going to redo rusty contacts on fuse block.
 
You are on the right track, and it just about has to be PROBABLY a vacuum leak or a fuel supply problem, as you say, floats or a restrcition/ problem in the fuel line/ pump/ filter/ delivery system

You mentioned "PCV is not blocked." Is it hooked up? You might TRY blocking it. The valve might be broken/ stuck/ leaking

The choke vacuum you mentioned sounds like the choke pull off. If so, this IS manifold vacuum and WILL affect idle, --but not to the extent you mention.

How about timing, where is it set?

If you can get it to idle, you can squirt a LOT of different "stuff" around the carb base, intake area to listen for the engine change. Even WD-40'll work.
 
Carb is leaking Vacuum some where, a can of WD-40 can detect this, get it running and spray the base plate and carb everywhere till you hear the engine clime in rpm's as it pulls the WD-40 in.
Or you carb is not letting gas flow, look inside with the engine OFF, pull the throttle and make sure you se a good stream of fuel on the two sides..
You can do the same to the intake, but I am guessing you carb needs to be cleaned out and the bottom bowl is full of water or gunk.
 
This happens to my small engines if I forget to drain the gasoline out of them or add Stabil.

My guess is that when the engine was sitting, there was still fuel in the carb bowl. It has gummed and is clogging the carb.

Spray a carb cleaner in the carb, especially in the bowl vent to try to fill the bowl. Also back out the idle adjustment needles a turn or so. Then start the engine and run for 15 or 30 seconds. Repeat the cleaner and start-up several times. It might work.

If not, you'll need a carb kit. Cause you may have to go into the carb and mechanically/air pressure clean it out.

Red
 
67Dart273 said:
You are on the right track, and it just about has to be PROBABLY a vacuum leak or a fuel supply problem, as you say, floats or a restrcition/ problem in the fuel line/ pump/ filter/ delivery system

You mentioned "PCV is not blocked." Is it hooked up? You might TRY blocking it. The valve might be broken/ stuck/ leaking

The choke vacuum you mentioned sounds like the choke pull off. If so, this IS manifold vacuum and WILL affect idle, --but not to the extent you mention.

How about timing, where is it set?

If you can get it to idle, you can squirt a LOT of different "stuff" around the carb base, intake area to listen for the engine change. Even WD-40'll work.
Click to expand...

X2 on what 67Dart273 said :hello2:
 
Initially I thought massive vacuum leak, I like to use a propane torch that's unlit and the oxygen mixer taped over and wave it around the motor, less messy than wd40. What's your idle speed? Maybe your normal idle is way too low and with the choke closed the idle speed increases with the fast idle cam. I like to set my choke idle at 1500 and normal idle at 1000 in neutral, 800 in gear. What's your timing set at? Manifold vacuum readings?
 
redneckmba said:
This happens to my small engines if I forget to drain the gasoline out of them or add Stabil.

My guess is that when the engine was sitting, there was still fuel in the carb bowl. It has gummed and is clogging the carb.

Spray a carb cleaner in the carb, especially in the bowl vent to try to fill the bowl. Also back out the idle adjustment needles a turn or so. Then start the engine and run for 15 or 30 seconds. Repeat the cleaner and start-up several times. It might work.

If not, you'll need a carb kit. Cause you may have to go into the carb and mechanically/air pressure clean it out.

Red
Click to expand...

This is right on but I'd just pull the carb and take it apart. In my experience trying to spray it to clean the inside from the outside just doesn't work. It's running lean but you didn't do anything to cause a massive vacuum leak. Just pull the carb and clean all passages and orifices (don't you just love that word? lol) thoroughly.
 
Thanks everyone! Im going to try the vacuum leak stuff first. Im leaning towards the jets or something having dirt or bad gas. I may pull the top off the carb and see whats going on. It did sit for about 6 months or so. I looked at it some last night and looks like the right side has some white stuff or?? on the inside. coming out of a hole there. I sprayed carb cleaner there, but it needs brushed or something.
Im going to put my 340 intake and hpTQ on after I get that(TQ) carb rebuilt. I just needed to get this running until then- which will be a little while yet, so I can move it and etc.
 
That much vacuum leak would have to be pcv or a open port on the vacuum tree screwed into the intake.
 
Guitar Jones said:
This is right on but I'd just pull the carb and take it apart. In my experience trying to spray it to clean the inside from the outside just doesn't work. It's running lean but you didn't do anything to cause a massive vacuum leak. Just pull the carb and clean all passages and orifices (don't you just love that word? lol) thoroughly.
Click to expand...

It's the carb.
Closing the choke plate would almost instantly kill and engine that was getting anywhere near the right amount of fuel through the jets.
Plus the white stuff mentioned is probably a mixture of fuel, water, and who knows what.
 
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