1986 Mazda B2000


I have a 1986 Mazda B2000, purchased new, and now with 89,000 miles. The engine has electronic ignition and a carburetor.

The problem is that the engine starts and runs, but after a few minutes it will die and not restart for several minutes. It does crank over.

In trying to solve the problem, I have replaced the fuel filter, coil, the distributor cap, the rotor, spark plug wires, coil wire, and the pick-up coil in the distributor. The fuel pump was replace in 2011 at 85,000 miles. The spark plugs were replaced at 86,000 miles in 2011.

The carburetor is getting fuel.

I suspect that there is something electrical that was getting hot and failing.
Now, the truck will not start at all so whatever was failing, has failed.

Any suggestions would be appreciated.


When attempting to restart the engine do you pump the accelerator? If the engine will restart by pumping the accelerator and remain running if revved to1500 rpm there may be a problem with the EGR valve or theEGR ports. Or possibly the carburetor base is leaking. When starting cold the choke can richen the mixture and increase the idle speed to get the engine to run until the choke drops off and then it can die from the lean mixture.

Does it only do this on a cold engine or does it do it on a warmed up engine also?

it was always starting when cold, but will not start at all now. I think I flooded it earlier today by pumping the accelerator too much.
when it did start, keeping the RPM high did allow it to keep running. When I sensed it was dying, I could pump the gas and usually keep it running.
I will investigate the EGR valve and ports. I don’t see any signs of the carburetor leaking.

It sounds from the symptoms like it is running too rich. One thing that can cause this is if the float in the carb is sticking or has developed a leak and not floating any more. That will cause the fuel level in the carb to be too high, and rich operation is the result. Assuming all the vacuum lines and connections checked out ok, and no vacuum operated accessories had a leaky diaphragm, and there wasn’t anything obviously wrong via visual inspection (like no-spark), I’d probably start with the carb float if this happened on my 70’s Ford truck.

Edit: To get it to start if it is really flooded you may need to remove the spark plugs and let it sit overnight so the gas can evaporate from the cyclinders.

Offhand, this could be a carburetor problem. Maybe one or more of the following; choke, choke pull-off diaphragm, or a fault with the anti-diesel solenoid or circuit that controls it.
The solenoid is a device on the carb that shuts off the idle circuit when the key is turned off.

I’m not sure how deep your knowledge of carburetion is but all of those items are easy to check.

When you have a no-start situation after it dies will it attempt to start if you hold the accelerator pedal all the way to the floor?

This is the same truck as a Ford Ranger of the same year. The control module for the electronic ignition is a common problem in Ford’s of this era. They just fail, and heat is a factor. I killed one on an '85 v6 by leaving the ignition key in run position after the car stalled on a boat launch ramp. After 30 minutes of fiddling with the boat the car would not start. A new control module was the answer.

Wow, @UncleTurbo, a no-start on a boat ramp with the trailer attached? That’s a bad day!

One questions I’ve alwalys wondered, how does the vacuum operated choke pull down on a carb work? On my Ford truck it has a MotoCraft 2150 carb, and I think that carb has a choke pull down, a rod about 1/4 inch in diameter that pokes up through the top of the carb. I’ve fiddled with it, just to make sure it is not binding up, but I’ve never known how to test it.

The specifications for adjusting the choke pull down give a drill bit diameter to gauge the space between the choke plate and the venturi. The pull down rod is bent or sometimes an adjustment screw is turned to set the gap that will be made when manifold vacuum pulls the rod.

I do remember using a drill to measure the space between the choke plate and the housing when I rebuilt my truck’s carb some years ago. I must have just been pushing on that rod to get it to operate. Should I have used a vacuum pump instead?

I guess my lack of understanding of the purpose of this device is of a more fundamental nature. What is the purpose of that rod in the first place? Is it to set the choke on, when the engine is cold, or to dechoke (turn the choke to off, when the engine is warmed up)? And why is vacuum involved?

I owned a 1987 b2000 and a friend had a 1986 b2000, a bad ignition control module would cause the same symptoms your describing in both vehicles. HTH

It’s easy to eliminate the ignition system. Simply attach a timing light and see if you have spark when you’re trying to start it. If you do, go directly to the carburetor. My guess is that you will.

George made an interesting comment about the inner workings of a carburetor. The float bowl is there to provide a very specific very low pressure supply of gas. The float operates a needle valve that allows gas into the bowl when the level begins to drop, and shuts the supply off when the bowl is full. It is not uncommon on old carburetors for the floats to become saturated (foam types) or leak (metal can type). When that happens, the float sinks and the system allows the full pressure of the fuel pump to push gas through the system and into the venturi, flooding the engine. Metering is effectively lost.

Carburetors also have a feature called an “accelerator pump” that sprays fuel into the venturi when you push the pedal for acceleration. It also has a mechanically or vacuum-operated system that opens the choke when you do this to allow more air.

Carburetors also have a temperature-controlled “high idle system” that keeps the throttle plate partially open when the engine is cold (keeps the idle high until the engine warms up) and is tied in with the choke control.

The last item is controlled by a temperature. I’m not sure whether your vehicle uses a bimetallic spring to control those features of the temperature of the coolant (both have been used by manufacturers in the past) but it’ll be one or the other.

And, lastly, you should check that you have adequate fuel supply at the proper pressure.

It might make sense to buy a repair manual.