carb (I think) problems

[Curtice]

I have searched through some threads and have some ideas, but wanted some thoughts on my specific situation.

I recently started up my 40 for the first time in 10 years. Had some work done on the engine and carb rebuilt and seemed to be running ok, but would sputter and cut. Realized I had a waaaaaay rusty gas tank (too late I realized some of the rusty sediment junk was getting past my fuel filter.), so I had it cleaned and sealed. Put the tank back in and replace fuel lines. The first time I started it up, it purred beautifully and I let it run for a few minutes, but that was the only time.

Now I can hardly get it to start. The carb is getting fuel, as I can see fuel squirting in when I pump the gas. The couple of times I have got it started, it won't idle - I can keep it running by holding down the gas pedal, but even then its rough. It also backfires a bit in the carb when turning over.

Is this just a idle adjustment or mixture problem (too lean)? Or could the carb be gunked up in unseen places from the bad gas and I need to take out and clean? It doesn't look that bad eyeballing it. Or something else? Would just like some troubleshooting ideas.

It's a 1980 with a 2F. Carb is Aisin (I think stock to this truck?, but recently rebuilt).

Thanks.

 

[FJforty]

You said it.

(too late I realized some of the rusty sediment junk was getting past my fuel filter.)

Lots of small passages in a carb. Someone needs to rebuild it. Use small wire and air to open up the passageways.

 

[Pin_Head]

Hard to say based on the description. What happens when you put the choke on?

 

[Curtice]

Hard to say based on the description. What happens when you put the choke on?

actually starts better without the choke on.

Got it to idle today after holding the gas down for a long time, but when I hold a bit of gas, the engine revs up and down on its own.

 

[Pin_Head]

It sounds like it needs some choke to run when cold. Most do. How does it run on the road once it warms up?

 

[Curtice]

It sounds like it needs some choke to run when cold. Most do. How does it run on the road once it warms up?

Doesn't run too well when driving. Starts cutting out a bit at about 30 mph. Also, once I drive it for a bit, it eventually dies and hard to start back up again.

 

[Pin_Head]

I would suggest taking the air horn (top cover) off of the carb and looking in the fuel bowl and needle valve for grit. If you find some, take the carb off and clean it out ant try again. "Doesn't run too well" is a bit vague, but "cutting out" could be not getting enough fuel. Could be a lot of other things, which is why more detail about the frequency and circumstances helps.

 

[kurtnkegger]

I recently started up my 40 for the first time in 10 years. Had some work done on the engine and carb rebuilt and seemed to be running ok, but would sputter and cut.

This may have something to do with your ignition...You haven't really said what work was done on your motor. Sputter and cut could mean you have bad wires, or coil, and not getting a good enough spark to ignite the fuel making it in to the chamber...

You have a tough job diagnosing problems based on a few minutes of run time after 10 years of a dormant motor...

 

[mdonivan]

Going thru this myself with mine and a buddy is going thru this with his bronco. We both ran gas from a rusty tank and it bypassed the filter and got into the carb. I have done everything short of a rebuild, but the kit is coming this week. Without pulling the carb apart to get into the small jets and ports, the rust just won't come out. It will load up, backfire thru the carb and then load up again. Good luck, but I agree with FJforty.

 

[Curtice]

Thanks for the thoughts everyone. Sounds like I need to provide more details - I was trying to present my problem without going into a long explanation. Also, I am just learning, so I apologize if my descriptions are a bit vague, I am not completely sure of the correct terminology. I can take it in somewhere to have it looked at, and I might do that, but I do want to learn about this, so I can maintain on my own without having to take it to the shop every time I run into a problem.

Like I said, it wasn't started for years. When I wanted to get it up and running I took it to a mechanic, who replaced the head gasket, we put a new head on as well, added an electric fuel pump, and rebuilt the carb. After the work, it seemed to run well, but that lasted only a day or two. It started having problems starting - just wouldn't start like it was getting no fuel. It would start occasionally, but would sputter and cut, sometimes just dying completely. While troubleshooting, I realized the gas tank had a hole in it (which had probably been there since before I purchased it 10 years ago) - looked like someone drilled a hole from the cab down into the tank. Anyway, looked in the tank and found a ton of rust. Realized the rust and sediment was getting past the filter and pumped into the carb. I figured this was the source of my problems, so I cleaned and sealed the tank, replaced fuel lines, but now still having the same problems. I wonder if the rusty gas screwed things up.

Symptoms:

• Will only start up sometimes, after quite a bit of turnover.
• Starts better without choke
• Have to keep the gas pedal down for about 5 minutes in order to finally idle
• Idle is a bit rough - engine shakes - sounds like not getting enough gas
• When I hold the gas pedal down to rev it, if I hold the pedal steady, the engine revs up and down on its own (as if I am pushing the gas pedal in and out)
• If driving, begins to sputter at around 25 - 30 mph and will completely die after about 15 minutes of driving around.

Thanks for the ideas. For now, I think I will take the suggestion to remove the carb and clean it out. I was hoping to not have to rebuild it again, since just did that, but if mdonivan sounds like a similar problem, I might have to go down that road. But any other ideas that a newbie mechanic can handle are appreciated.

 

[landcrusher909]

Check the idle solenoid and make sure its working, with the motor off disconnect the wire turn the key on then make contact, i its working correctly you will hear it click, do this several times to make sure its not sticking if it is pull it of the carb and clean it with carb cleaner. Check for vacumme leaks start with the brake booster pull the hose off and seal it up then try starting it, go thru all the vacume lines Good Luck