scotty
11-25-2001, 12:20 PM
my friend with the xj is having some trouble with his carb,so i need to enlist the advice of all the carb experts on this forum.
the engine is a 258,.040 over,mild towing cam,stock intake/exhaust with a flowmaster muffler,no convertor. the carb is a Q jet 4bbl,adapted to the stock intake with a custom plate,and mr gasket adapter.
ok last weekend we went wheelin,and he started having all kinds of trouble with it. coughing,sputtering when climbing hills. it would eventually stall,and not want to restart. closer inspection revealed no fuel squirting from the accel pump nozzels,so the first attempted fix was to put on an electric fuel pump,thinking the original had gone kaput. turned it on,bowl filled,fuel started squishing out the nozzels. back up the hill,same thing.again,no fuel.engine off,pump on,bowl filled and was fine for a few minutes.back up the hill,same thing.again no squishey. this time we take the top off the carb and fiddle with the float,and clean out some funk.was fine again for awhile.same deal. he was able to drive it home,and over the week rebuilt the carb.ran great right after,and on the way down,but started acting up again in the woods. again,running out of fuel in the bowl. we blew thru the lines,thru the sending unit,and blew out the air filter.was ok again for awhile. now we notice that it isnt acting up going up the hil backwards,so we pull the sending unit out of the tank,and the level is very low in front of the tank,high in the rear(were on a hill) so we attach a sm piece of hose to the sending unit to reach the bottom of the tank,and leave the screen off. seemed to be perfectly happy,but then started actig funky again,tho not quite as bad.
about that time it was getting dark,so we were forced to head out.on the highway home,he said he could hold his foot on the floor as long as he wanted,keeping the secondaries open,and no starvation prollems.
some other info: this is a cmputer controlled carb,but he has been running it for several months with no computer with no real adverse affects.its basically in an open loop mode,the clicky thing(mixture solenoid) keeps the metering rods in a full rich position.so we dont really think the comp controls have anything to do with it.
he has always run a return line. we did pinch it off,and this made abosolutely no difference.
the tank was just out,and is clean.
there are no visible leaks anywhere,so we dont think its suckig in air somewhere.
again,the apparent cause is fuel starvation. we dont really think the float is sticking,since you can turn the pump on and the bowl fills back up.
we dont think the pump is bad,since he can put his foot on the floor on the highway without the symptoms occuring.
we dont think its the way the carb is adapted to the intake,since mine is the smae way and still runs fine,and since he has been running this carb for several months now-prolly pretty close to a year.
sorry this post is so long,wanted to give as much info as possible. we are pretty confused at this point.
ur thots? :confused:
the engine is a 258,.040 over,mild towing cam,stock intake/exhaust with a flowmaster muffler,no convertor. the carb is a Q jet 4bbl,adapted to the stock intake with a custom plate,and mr gasket adapter.
ok last weekend we went wheelin,and he started having all kinds of trouble with it. coughing,sputtering when climbing hills. it would eventually stall,and not want to restart. closer inspection revealed no fuel squirting from the accel pump nozzels,so the first attempted fix was to put on an electric fuel pump,thinking the original had gone kaput. turned it on,bowl filled,fuel started squishing out the nozzels. back up the hill,same thing.again,no fuel.engine off,pump on,bowl filled and was fine for a few minutes.back up the hill,same thing.again no squishey. this time we take the top off the carb and fiddle with the float,and clean out some funk.was fine again for awhile.same deal. he was able to drive it home,and over the week rebuilt the carb.ran great right after,and on the way down,but started acting up again in the woods. again,running out of fuel in the bowl. we blew thru the lines,thru the sending unit,and blew out the air filter.was ok again for awhile. now we notice that it isnt acting up going up the hil backwards,so we pull the sending unit out of the tank,and the level is very low in front of the tank,high in the rear(were on a hill) so we attach a sm piece of hose to the sending unit to reach the bottom of the tank,and leave the screen off. seemed to be perfectly happy,but then started actig funky again,tho not quite as bad.
about that time it was getting dark,so we were forced to head out.on the highway home,he said he could hold his foot on the floor as long as he wanted,keeping the secondaries open,and no starvation prollems.
some other info: this is a cmputer controlled carb,but he has been running it for several months with no computer with no real adverse affects.its basically in an open loop mode,the clicky thing(mixture solenoid) keeps the metering rods in a full rich position.so we dont really think the comp controls have anything to do with it.
he has always run a return line. we did pinch it off,and this made abosolutely no difference.
the tank was just out,and is clean.
there are no visible leaks anywhere,so we dont think its suckig in air somewhere.
again,the apparent cause is fuel starvation. we dont really think the float is sticking,since you can turn the pump on and the bowl fills back up.
we dont think the pump is bad,since he can put his foot on the floor on the highway without the symptoms occuring.
we dont think its the way the carb is adapted to the intake,since mine is the smae way and still runs fine,and since he has been running this carb for several months now-prolly pretty close to a year.
sorry this post is so long,wanted to give as much info as possible. we are pretty confused at this point.
ur thots? :confused: