76 Duster hesitation problem

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rpcopp

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Hello FABO members, I’ve been lurking in the shadows of this site for a few months now and haven’t posted till now. Let me start by apologizing for not saying hi earlier and waiting till I have a problem for my first post. My son and I have been working on a 1976 Duster for a while now and took it on the road for the first time today. If I were to describe how it ran in one word, it would be terrible. When in gear and accelerating, the car would bog down to the point of stalling and only releasing the throttle would allow it to recover. It has a 318 with no mods to speak of and has California emissions. Idle RPM is set at 750 with the timing at 0* (timing setting is due to California smog testing requirements). I have a feeling its something simple that I am overlooking but can’t seam to figure it out. Any assistance will be greatly appreciated. Thanks in advance, randy...
 
Gumed up carb? Been awhile since it has been on the road?
 
a plugged fuel filter will cause that. idle fine but wont allow enough fuel through at higher rpm's. the sock on the pickup in the tank may be plugged also.
do you have to have it smog tested? if not reset your timing. btw, WELCOME!!!!
 
How long has the fuel been in the tank? I've had gas go bad on me in 6 months.
 
accelerator pump circuit bad? i thought that 76 was smog exempt? wasn't it the last year??
 
Try this: On your car there is a vacuum valve on the air cleaner - as you look from the front, it's on the right side of the air cleaner - called the OSAC NOx valve. There are 2 vacuum lines attached to it. One goes to a vacuum port on the carb, and the other goes to the vacuum advance on the distributor. The purpose of the valve is to delay vacuum going to the distributor when the engine is cold. They are notorious for going bad. Take both vacuum hoses off the OSAC valve and use one to go directly from the same carb port to the vacuum advance. This should greatly improve perfermorance at all speeds. Let us know how you make out!
 
Thanks for the welcome Betty! Here are a few more details that I failed to mention in my first post.
The carb is a freshly rebuilt Carter purchaced online from the carburetor exchange so I think a gummed up carb or a faulty accelerator pump circuit is unlikely.
The engine accelerates just fine with no load (in park) its just in gear (drive or reverse) where it dies on us.
Scamp, I noticed that the OSAC NOx valve was not working prior to the drive yesterday and had already bypassed it.

Could there be a vacuume leak that only has symptoms when there is a load applied to the engine?

BTW, thanks everyone for the replys!!
 
I would advance the timing 8 degrees BTC if it was me. Certainly couldn't hurt to try, it might even take more than that before it pings. Just set back to 0 so it runs crappy when the e-test come up again-LOL.
 
Well the problem is somewhat resolved. Scamp80602 mantioned the OSAC NOx valve and that got me thinking ablut vacuum line plumbing. Im not sure which port on the carb the distributor advance comes off of but when I moved it from one of the lowest (base of carb) to one higher up the car ran much better. I had to re-adjust the timing and idle speeds but now it accelerates much better. It still feels a bit sluggish to me though, there is a small exhaust leak just aft of the pitman arm and the muffler is shot, does anyone think this could cause acceleration problems due to back pressure problems?
 
Two other things that come to mind: Are you hitting your shift points?? If the kickdown linkage is stuck or otherwise not functioning correctly, this will affect shift points - they'll happen too quickly, and you won't stay in 1st and 2nd for very long. 3rd will come at about 18-20MPH. I mention this because you said that the carb was recently replaced. Also, your car should have an 8.25 with 2.45 gears - not the quickest off the line, but great for emissions and highway mileage.
 
Johnny dart - The plugs, wires, cap, rotor and coil are all new
Scamp - Thanks for the link, The car actually has it still attached but I dont think that the carb is the exact replacement, doesnt have the same number of ports. The kickdown linkage appears to be operating properly as far as I can tell, no binding and it moves the arm on the transmission. BTW, on the vacuum diagram it shows a TIC valve, what the heck is that?
I still have to do a good vacuum leak check, all the hoses have been replaced but I havent checked them or the intake manifold with carb cleaner.

Thanks for everyones help so far..... randy...
 
Randy it sounds like it is running lean. Even though you mentioned it is a rebuilt carb. I can tell you that don't mean it is good. Alot of rebuilders have people working there that don't know squat about how the thing their rebuilding actually works. They just get paid to disassemble and reassemble something. I have taken apart numerous carbs. that were rebuilt by big rebuilders that had the float settings way off, jets either mis-matched or completely wrong for the application. Even seen wrong gaskets used. Sorry but I never trust rebuilt carbs. from parts houses. You also mentioned it doesn't have the same number of ports. If that's the case how did you hook up the emmissions devices? If their not hooked up correctly that can cause major issues. California cars were set to run lean to begin with so if you got the wrong carb. you may have recieved one that has even smaller jets in it. First thing to do is check with who you got it from and tell them that it don't match up with the vacuum lines so it's not the right application and try to get the correct one. Hopefully they can get you the right one and it will be rebuilt right.

66Dartman had a good idea to advance the timing up a few degrees. That will certainly help the accelleration. And fuel mileage. Just listen for pinging (spark knock) when you accelerate. If it pings back it off a couple of degrees until it stops pinging.

You mentioned after you moved the vacuum line going to the distributor that you had to readjust the timing. Does that mean you are adjusting the timing with the vacuum line connected to the dist. If so that's not correct. You should be adjusting the timing with the line unhooked from the dist. and plugged. Then after the timing is set hook the line back up.
 
I think that you should do as mentioned above. Adjust your timing after your E-check. Give yourself a little more advance and you will feel like you are driving a new car.
 
Same number of ports? Is there extra holes on the carb not hooked up to anything? If so you've got a vacuum leak, and there's you're problem, most likely.
 
Problem(s) resolved.. First of all I would like to thank everyone for their input, very helpfull. Secondly I would like to apoligize for the delay in getting back to everyone. I am a Goverment Contractor and have been out of the area for a while... Anyway, the problem was due to two conditions. The vacuum line to the power brake booster was split on the bottom causing a significant leak and I also discovered that the pickup in the distributor was loose and it was striking the reluctor. Replaced the line and rebuilt the distributor. Smog check here I come...
 
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