I recently attached a pre-emissions carb off of a 510 pickup on to my 620 pickup. It will run for a short while, but it only idles. It won't accept and gas. Instead it dies. We don't know if we have the solenoid hooked up right, or if the timing is off. The truck hasn't been running regularly for four months now. Is it time to change out the gas or is the problem something else?

I want to get this truck running. Other that putting a manual choke kit on and fixing the idle it will be ready to go.

Check the accelerator pump operation.
Make sure that with the engine off looking into the carby that when you give it full throttle that a jet off fuel is getting sprayed in to the carb.
If not - and its been sitting around for some time, the accel pump plunger may have perforated or split.
Also if you ever suspect the shutoff solenoid - it just has to have 12volts to it when the ignition is on. If you ever think its a problem take it off and remove the guts and reinstall it - just to make sure it hasn't become stuck.
Hope some of this helps.

If the solenoid is faulty / not hooked up, it would not idle. This is the "idle cut off" solenoid.
It sounds to me like there is no fuel flow through the other circuits, so it would probably pay to partly dismantle it on the bench & confirm that these circuits are clear with compressed air.
If the accelerator pump was not working, you would still be able to bring the revs up by either partly obstructing the air horn with your hand, or by slowly opening the throttle. The accelerator pump is really of benefit only when the throttle is opened quickly.

Even if the fuel is stale, it should still run OK, just not as good, & it will probably stink a bit.

All of the above assumes that your fuel pump is fully servicable.

It's got gas, it's got air, it's got spark. But it doesn't run right. It just wants to flood. It has a new accelerator pump on it. What about the air idle screws? For some reason when you give is some gas it sprays a fine mist out into the air and the engine just floods out. Like it can't burn it or something.??

It may take some careful examination to find the real problem. Be patient, and check everything out. Check out the updated Hitachi troubleshooting article.

Thanks for the info, we put silicon gasket maker on all the contacting parts and bolted it on real tight. We also adjusted the timing. It's running now, but it idles very high. We don't have any way of adjusting it. I recomended that we shorten the arm that leads to the accelerator pump. How can we lower the idle? The air screw doesn't seem to help much.

Quote:Bad idea. This is designed to work correctly at the original length.

Quote:Do you mean the idle speed screw? Look at the linkage and make sure that the throttle is closing all the way once the engine is fully warm*:
- If it's not closing, figure out why
- If it is closed, but still won't idle down, you have an air leak (vacuum leak)
- It idles down but dies (and will only keep running at high idle), the anti-dieseling valve (fuel cut-off valve) might broken or not installed correctly.

When cold, the choke is supposed to keep the idle higher.

hey migweldeddatsun, where are you located?

Quote:Where do you see this mist? Above the carburetor when the air filter is off? Or out the tailpipe?

When you give it some gas, it's supposed to spray fuel into the carb, just below the choke butterfly. If it is spraying up from the carb (mist appears above the carb), I would guess that the carb is not put together correctly.

Quote:It might not be flooding. If it 'coughs' as it dies, it's probably lean (too much air getting in somewhere).

If you have assembled the carb with silicon, then you may well have created your own problem as the silicon spreads out when the parts are re-assembled & it oozes into passages where it aint s'posed to go, blocking fuel & air passages.

Silicon is for fixing drains. I won't have it in my workshop as it seems to cause far more problems than it cures. I use "Cat red"

If you HAVE used silicon in the carb instead of gaskets, then a new gasket kit will go a long way to fixing it.

I am fighting my Hitachi at the moment.
I was having mysterious and intermittent running problems (would only idle with full choke, and then roughly, very poor mid-range torque, but okay top end. Turns out the top half of my carb was warped from over-tightening the screws (it's VERY important to avoid this). The warp was allowing air through the carb body around the float bowl.