This is actually in a 1982 Toyota Corona sedan, but it has a 22r carbureted engine. The car has been sitting for a while, so I put a rebuilt Toy 505 carb on it last year and it ran fine. It sat over the winter and now is a hard start and bogs / cuts out to dead if you try to give it any gas. It idles ok, but a bit rough at about 800 and when you gently give it gas, it will go up to about 1100 and then start to bog and die. I replaced the fuel filter, which was full of crap and still no luck. If I put my hand over the plates, the car will run well and you can quickly gas it with no problem like it used to be. Any idea what has gone wrong?

 

Dried/varnish/ fuel residue in carb.

Modern ethanol blend fuels are death to machines that lay idle with such fuel in them.

 

Sounds like the accelerator pump not pushing the fuel in the bowl. It may be stiff or has a hole in it

 

My friend insists it's the mechanical fuel pump. He thinks the lobe on the camshaft is worn and not actuating the pump enough to fill the carb. Does that sound logical? If the lobe is worn, can one add a little metal to the pump lever arm to compensate (rather than put in an electric fuel pump)?

 

I think your friend bumped his head.

It is possible to test a fuel pump for pressure and volume produced. Fancy that.

 

Fuel filter full of crap, idles rough @ 800, starts to bog & die @ 1100, using hand as a temp choke plate it runs better & revs quicker? Clogged idle jet, idle passage, or both; engine running on main jet only.

The idle jet still passes fuel through it even above idle speeds, so it's a part of the overall fuel flow. The engine is trying to run on the main jet only at idle and you're probably a bit "lean". Placing your hand over the "plates" restricts incoming air and "richens up" the air/fuel mixture to something closer to what it should be. This compensates for the lack of fuel flow from the idle jet.

I've had this problem before with the stock carbs in vehicles that have sat a while, and I've fixed it without pulling or rebuilding the carb. This requires a can of carb cleaner with the "red extension straw", removing the two bolts at the front bottom of the fuel bowl (below the sight glass), and removing the fuel cutoff solenoid. You may have to disconnect the solenoids wire to get it out safely, so remember to re-connect it when you get it back in after cleaning. With the fuel bowl bolts out, you'll have a straight shot to both the idle & main jets. Use the "extension straw" to shoot a good amount of carb cleaner into the jets orifices (holes in the center). Also use the "straw" to shoot some carb cleaner into the port where the fuel cutoff solenoid was. That will get the cleaner into the carbs idle passages. Let it soak for 5-10 minutes and repeat. Then I'll blow a bit of compressed air into that port to help clear it out. Go easy on the compressed air; you can damage the carb if you blast it's insides with 80 PSI!

Then I take the air cleaner off and shoot some carb cleaner down the angled brass tubes at the front of the carb's throat. These are vent tubes to the fuel bowl, and with the bolts out of the bowl, this is an easy way to "wash out" any "crud" in the bottom of the bowl. It's best to place a rag below the open bolts holes to catch any carb cleaner that comes out. When done, let the whole thing air-dry for at least 15 minutes then button everything back up. When you go to start it after all this it will take a bit longer to start because the fuel bowl is dry, so don't panic. It will take some extra seconds for the fuel pump to refill the bowl.

Since your carb is a one year old rebuilt this should fix it. I would doubt any other problems with the carb, as long as it was a proper rebuild. If the cleaning doesn't fix it you've got other problems.

 

BTW, I agree with Millball. A worn fuel pump cam lobe won't do this. If there is anything wrong with a mechanical fuel pump, it's usually a ruptured diaphragm inside, and they are usually "pass/no pass" items. They either work or they don't.

 

Thank you very much for the info. I actually sprayed through the brass tube yesterday and let it set. I took the idle jet out and cleaned it. Today it ran better for a bit, but now it's rough and blowing black smoke out the exhaust. If I cover the carb, now it wants to die instead of running better. I assume that now means it's too rich. I tried leaning it out but nothing changed. I pulled the plugs and cleaned them and the cap / rotor parts. Obviously I'm not a carb expert. I'll try spraying out the carb as you said.

 

Sounds like you got it cleared than it plugged up again. It might also be time to consider being more complete and totally cleaning out the truck's fuel system, including the tank's insides. That crud in the fuel filter is coming from somewhere, and if the source (tank) isn't clean, it's going to keep happening. You could have junk in the tank, a broken or dislodged filter sock on the in-tank fuel pump.

Or it could be something else that I had to deal with. Old rubber fuel lines that were deteriorating from the inside out due to today's ethanol laced gas. The old rubber fuel line wasn't designed/formulated to handle ethanol, and over time, the ethanol breaks down the rubber. The insides of the line start throwing off small particles of rubber that can easily clog up idle passages & jets. Those things are very small so it doesn't take much for a blockage to happen. Once I replaced all the rubber fuel line sections with new ethanol rated line (plus new spring clamps, which I very much recommend), I haven't had that problem since.

Tip: The rubber fuel line on Toyota is metric and is usually 8mm. You can use 5/16 if you can't find the metric size, but I've found that Auto Zone is the only chain that regularly stocks the metric sizes. As always, take a piece of your old line with you to the store for a physical comparison to get the sizing right.