Wont run properly

[comotion]

1972 z 6cyl twin carbs. Hard to start. then idles fine.. But stalls if you give more gas. If you try to rev up it backfires. Made sure I had good gas.connected electrical fuel pump and no change. Is it a ignition problem of fuel system problem? Where to start?

Thanks

Raff

[zKars]

Possible timing issue, then maybe fuel pressure/delivery issue. Factory service manual downloades are here : xenons30.com

[Jetaway]

1972 z 6cyl twin carbs. Hard to start. then idles fine.. But stalls if you give more gas. If you try to rev up it backfires. Made sure I had good gas.connected electrical fuel pump and no change. Is it a ignition problem of fuel system problem? Where to start?

Thanks

Raff

New to you car?

Chris

[comotion]

Yes. The car was completely restored. Sat in garage for several years and started about every two months. Just idled for 15 to 30 min. Never driven. I thought maybe the floats in carb were stuck resulting in flooding. But i am not sure how the top of the carbs comes off. When you remove the screws on top you cannot pull the top off the carb. Hangs up on something internally. Someone suggested that the points and condenser may be bad..???Vaccuum not advancing

[olzed]

This sounds to me llike lack of fuel, but you say you have plenty of fuel. How have you checked that?

If the car has sat for a while the tank could be full of crud.

[madkaw]

Sitting around like that and then only idling the car is not good.

You said you have "good gas"-so you started with fresh fuel? That fuel will be no good in your tank.

take your air cleaner off and push the pistons up into the domes of the carbs and let them free fall. I'll bet they stick. If they do, you need to take the domes off and clean the inside of the so its nice and smooth.

You have to rotate the float lids to get them off-counter clockwise I think.

Check this stuff out first, then get back with us.

Oh, and pull your plugs-all that idling-probably with the choke on has probably carboned them up

[Bruce Palmer]

Popping back through the carbs sounds lean.....

[kenz240z]

You mentioned hooking up the electrical pump. Is it an aftermarket electrical pump, or original factory electric pump? If it is the factory pump, there is a fuel filter inside it that is likely clogged up with crud from the tank (ask me how I know...).

[Jetaway]

Yup, fuel or electrical all right;)

Though my guess is fuel, I'd do a basic electrical check first, if only because I'd rather stand than crawl under the car.

Steve suggested pulling the plugs and having a look-see. Good place to start. Replace the points and condenser, its cheap and you can't easily test the condenser anyway. Verify the points setting. Inspect cap and rotor for corrosion, burns, anything unusual. Replace if necessary. Make sure you have a good connection on the distributor and plug end.

Drive car, if possible, otherwise let it warm up a bit at idle.

Mark the timing marks with chalk or something else bright. Hook up a timing light. Disconnect and plug vacuum advance hose. Start car, get the idle as close to 650 as possible by adjusting screw on the long throttle lever or, if that does nothing, by adjusting idle setting screw on each carb 1/8th of a turn at a time. Check timing. Adjust to spec, if necessary. Hook up vacuum advance hose. Idle speed should increase and timing advance 5 - 7 degrees more or less (check manual -- my advance is dead, so I haven't bother to look it up in awhile). If idle speed doesn't increase and timing doesn't advance, you have a dead vacuum advance. Do something with the vacuum hose -- leave it on the advance if you don't hear a hissing or plug it otherwise. Go back and advance the timing 7 - 10 degrees. See what happens when you bring it off idle. Still running bad? Fuel side, others have a lot more experience with that than me (so far, cross fingers) so I turn it over to them.

Chris

[comotion]

Still wont run properly

I checked the points and timing. OK

Connected electric fuel pump to engine and to fresh gas in can.

Starts and idles OK

When you accelerate engine it backfires and sputers.

Carburetor pistons are free and drop when raised.

But some times gas leaks from carb and that makes me think it is flooding

Tried to take top off carb, tried to turn it clockwise, counterclockwise but hangs up on float and cant get top off.

Is there a trick to doing this ????

[madkaw]

The trick is patience:) You have to turn and tilt and hold your mouth just right and then you will get it- seriously it is a bit tricky, but they should come off.

You might find that the old gas has varnished up your needle and seat and causing the floats to do crazy stuff.

Don't forget to check for vacuum leaks, could be an old hose has gotten hard over the years and cracked.

Edited October 4, 2011 by madkaw

[Jetaway]

Still wont run properly

I checked the points and timing. OK

Connected electric fuel pump to engine and to fresh gas in can.

Starts and idles OK

When you accelerate engine it backfires and sputers.

Carburetor pistons are free and drop when raised.

But some times gas leaks from carb and that makes me think it is flooding

Tried to take top off carb, tried to turn it clockwise, counterclockwise but hangs up on float and cant get top off.

Is there a trick to doing this ????

You did check the vacuum advance, right?

Taking off the top of the float chamber is, uh, frustrating. Lift, turn (I don't remember which way), tilt a bit, take a deep breath and keep trying. Eventually it will seem to just come out in your hand. Putting it back on is much the same, if that's any consolation.

Probably not.

Search for "float level" in the Carburetor Systems forum. You'll find a handy gauge to make and plenty of tips on how to measure the fuel level.

Chris