Hi I’m new to this form, I recently purchased a 1991 Mazda b2200 carb. Model it had been sitting for 6 years. At first start up (to make sure truck ran) engine was running very smoothly so then I did a full tune up spark plugs, spark plug wires, distributor cap and rotor, fresh oil change, ignition control module, drop and clean gas tank, and new fuel filter.
Now the truck idles high about 1200rpm when giving it gas parked or driving it revs down then instantly shots up, it’s eating gas like crazy, truck shakes/skips if gas pedal is not pushed in all the way while driving like if it’s fuel starvation. Also up hills it looses some power starts loosing some speed and rpm’s also won’t go up, like if you gotta catch speed to not loose power and speed at a hill. And sometimes truck starts sputtering while drive at 3000 rpm. I hope yall can understand I appreciate it!

 

Sounds like misadjusted float or float needle sticking/leaking. That would explain why revving the engine helps it run better.

 

Welcome to the forum

Before you start looking at or changing any carburetor setting or parts.....
If as you said it was running fine before you changed those parts you mentioned I would first suspect that a hose (vacuum) was accidently broken or disconnected?

 

Welcome to the forums!

When you first started it up, was the gas tank cleaned already? Or did you just add some fuel to the uncleaned gas tank and start it?

If the truck sat 6 years, and there was fuel in the tank when it was parked, that fuel would have dried up and left deposits in the bottom of the tank. Adding new fuel to that dirty tank would cause the new fuel to mix with the old fuel deposits, and that mixture would get pulled into the carb via the fuel pump, and then clog up the fuel passages in the factory carb. If that is the case, the carb will need to be taken apart and cleaned.

Is your truck a manual trans truck? Or an auto trans truck? The auto trans truck will have an "in tank" fuel pump if its an all stock setup......manual trans will have a fuel pump mounted to the rear passenger side of the cylinder head. In either truck, the fuel sock on the bottom of the fuel pickup/fuel sender could be clogged up if the fuel tank had some old fuel deposits in it.

Did you remove the fuel sender to allow better cleaning of the fuel tank?

Let us know, and we'll have a better idea of what may be going on with your truck. Thanks.

 

He did say its eating gas like crazy...

 

Thank you for the responses, it is a 5 speed single cab everything is original besides the new parts I mentioned. I did drive the truck for a little before I cleaned the fuel tank, to check what or if there was something else I needed to change. I won’t lie the tank was very very bad, I believe that was my first mistake. I did change the fuel filter again after the tank was cleaned and now the fuel coming out of the filter is very clean the first filter was very milky/mud looking. I sprayed carb cleaner around the vacuum hoses to see if I had a vacuum leak but everything checked out good. The old spark plugs the truck had were Bosch platinum +4 the new ones I installed are ngk copper BPR5ES.
I drove it around today and same symptoms I have to give it full throttle when drive if I only give it half or anything besides full throttle it starts bucking. And still revving high, engine shaking, press gas pedal revs down like it wants to die then spikes up. I did get the ac to start working tho so that’s a plus. Also I did remove the sending unit to clean tank and I do know where the fuel pump is.

 

Forgot to mention the new spark plugs are really black pretty bad lots of carbon.

 

My “guess” at this point is may be time to pull the carb and rebuild it. Sounds like that is about the only thing you have not done and seems reasonable considering?

MeB2000 works on these way more then I do or have in years so he may have other ideas?

 

What would be the best option rebuild the carburetor or buy a new after market?

 

Definitely to buy a Weber carb from Redline. The stock carb is very hard to rebuild, mainly because it has a solenoid inside of it that can give you troubles if it gets dirty inside of it......you can definitely try to clean it first, since it won't cost you anything.....that is what I would do. You might get lucky......once you pull the top of the carb off, you will see how nasty the bowl is......just clean it all the best that you can, blow out any passages that you can see with compressed air (about 20-25 lbs is all you need), and see if you can get it working good again. If not, go the Weber route if there is no emission testing in your area.

It has always amazed me how much trash (mainly rust particles I'm assuming) can get by the paper fuel filter! Here are some pics of a stock B2200 carb that I worked on.......the gas tank was definitely rusty!