backfiring out of carb, then shuting off when put in gear

[moose73]

truck was running great then started spitnsput backfiring out of the carb. messed with timing replaced a plugwire and runs good in park then put in gear in will die? any suggestions

 

[dyeager535]

WAG, vacuum leak along with incorrect timing. Higher engine speed covers up the bad vacuum leak, under load, engine RPM drops too low, and stalls from the vacuum leak.

Also could be mech. advance mechanism in the distributor. Along with 80 million other things unfortunately.

If idle speed is correct, then I'd doubt plugs/wires, as it would lope a bit at idle. Can always disconnect one plug wire at a time while its running to make sure the cylinder is firing, cheaper than buying new plugs and wires all the time.

 

[mudhog]

Re: backfiring out of carb, then shutting off when put in gear

start it up with the air cleaner off then cup your hands over the top of the carb if the idle goes up you have a vacuum leak if it kills it you have another problem /forums/images/graemlins/eek.gif

 

[bee32]

When did it start? I would say vacume advance on the distributer. Check the line coming off the carb to it first to make sure it is getting a tight seal. If it is then look at replacing the distributer. Don't overlook Timing. Get a light and put it on there. An ear is good, but nothing is better than a light.

 

[dyeager535]

[ QUOTE ]
If it is then look at replacing the distributer

[/ QUOTE ]

You can rebuild these things cheaply and easily, not sure why you'd throw a distributor away. /forums/images/graemlins/confused.gif

 

[bee32]

True!

 

[moose73]

i replace the pickup coil and mechancal advance it tested bad at low rpms at the parts store vacuum advance was okay havent put the light to it yet or checked the plug/wire. someone said a float could be hung up but in idles and revs great in park?

 

[milspecjimmy]

plugged fuel filter making it super lean, or a bad valve, stuck valve. thats my guess