Mazda B2200 engine runs very rough
 

My Mazda B2200 1991 engine started running louder & rough recently. The acceleration was very poor. I had the truck towed home. The truck will crank, but the engine runs very rough/shakes. It will barely move if I "ride" the clutch in 1st gear. I haven't checked anything yet. If I mash the accelerator hard the engine rattles inside. Does anyone have any ideas on what to check? It is an extended cab 5-speed transmission with a carburetor.

Check fuel delivery to the carburetor. Maybe the filter sock inside the gas tank or the fuel filter is clogged.

Stock carb or aftermarket Weber???

Mazda b2200 engine runs very rough
 

It is a stock carb as far as I can tell.

rough running engine
 

How can you tell if the timing belt "jumped"?

If timing belt jumps, then both the valve timing AND the ignition timing would be off. An easy way might be to check the ignition timing with a strobe timing light: if it's OK then the timing belt has not jumped.

Otherwise, most would pull off the drive belts and timing covers and rotate the engine so that the crankshaft gear is at TDC #1, but this can be done with the drive belts on, you may need a flashlight and a mirror. You can rotate the engine with a 21mm socket on the crankshaft bolt, will be easier if you pull the spark plugs first; maybe you can simply tighten the power steering belt temporarily and then use a socket on the PS pulley nut. See the woodruff key notch on the timing gear, where my red arrow points? That should point straight up at TDC #1. In my pictures, I've also painted lines at that position.

https://cimg6.ibsrv.net/gimg/www.maz...f941ee8d2e.jpg

https://cimg4.ibsrv.net/gimg/www.maz...c146111b65.jpg
With the crankshaft gear pointing straight up, you can remove the top timing cover (several 6mm x 1.0mm bolts, one is longer) and look at the camshaft gear position. The Number "1" should be pointing straight up (painted yellow in my photo) - at the V-shaped mark - if the timing belt is correct.

https://cimg2.ibsrv.net/gimg/www.maz...c2e5d337b5.jpg

https://cimg1.ibsrv.net/gimg/www.maz...1dc0293d6a.jpg

Thank you for all the information. When I get the chance I'm going to check this.

Mazda b2200 engine runs very rough
 

Thanks for the info. When I get a chance I'm going to check this.