engine hesitates when starting off in 1st gear. I have changed the timing from 3 to 10 degrees btdc, run sea foam into carb, checked vacuum at the intake manifold- pulls around 22-23. it will drop down to around 18 if you set the timing at 0 to 2 degrees atdc but the engine will not run good. 4wd hi is useless if you are on anything other than flat smooth ground. I put the stock tires back on the truck just to see if the gearing had changed to much for 4wd hi but it still hesitates. tried all this with the snorkle on and then air cleaner back to stock with no luck. truck runs great in 4wd low. the thing that has me puzzled the most is the vacuum. from what I have read it should pull between 15-20. any higher and it is a timing issue. truck feels like you are starting off in the wrong gear. any suggestions?
thinking it may be a fuel issue. I can pull the breather off the truck, close the choke butterfly about a quarter of the way, stomp the gas and the hesitation seems to go away. with the choke butterfly opened up all the way it will stumble just a bit then rev up good. of course all of this is kind of hard to do when idling around in 4wd hi. any other way to check to see if the engine may be starving for fuel at take off? p.s. I just changed plugs and fuel filter a couple of weeks ago.
A stumble or hesitation on a carbureted engine is sometimes an indication of a accelerator pump not working well.
Get a carb. kit. Been there done that. Try not to mess with the settings to much if at all. Take the carb. apart, clean it, install new pcs. and Baaaam, It will run like new. Got to remember these trucks are 15 +- yrs old, most run great but with 50000kms + and sitting around here and there needle valve gets a little worn, accelerator pump gets weak, build up inside the orfices ect.
kind of what I was thinking. never rebuilt a carb before. not really looking forward to tackling that octopus. got any good links on how to?
check for a plugged exhaust as well...high throttle openings and rpms means no flow it it is plugged..but may run fine at low rpms
meant to say "if" it is plugged edited the previous post....just saying that a wide open throttle and high rpm need more room for gasses to escape through the exhaust..if it is restricted or partially blocked there would be adequate room for exhaust flow at low rpms...as rpms rise and more exhaust tries to make it through the restriction it backs up...like a garden hose with a kink in it..it can dribble a bit but not gush....simple check is to unhook the entire exhaust where it comes out of the exhaust manifold and just wire it out of the way..if it runs fine now then the muffler or catalytic conv. are blocked up.. you can use a vacuum gauge to test as well..idle the engine til warm and take a vacuum reading from a manifold vacuum source,not a carb vacuum line...then check the reading at around 2-3000 rpms..if the gauge reads anymore than an inch of vacuum less than the idle reading,or gradually drops then you have an exhaust restriction
Just for fun, try setting your "already warmed-up" idle to 1500+ RPM. See if that 1st and 2nd gear hesitation dosen't go away. This fixed my problems, but I think that I'm going to go with a complete carb rebuild over the winter (not just a kit), and try to lock this down to "an older carb", too rich at low idle condition. Sure seems like a condition prevalent, across the minitruck north american market.
I did idle the truck up some, (not sure what rpm) and it did seem to help some. I can close the butterfly about a quarter of the way on the carb and the hesitation seems to go away. makes me think the carb is not getting enough fuel. the truck still hesitates some when you try and putt around. how do you adjust the idle mixture screw on the carb. turned it in and out but it did not seem to do much.
vacuum leaks are 85% of carb and idling problems, use a vacuum gauge or carb cleaner, carb cleaner will send the engine to high idle if you have a vacuum leak, make sure the vacuum port in the air cleaner canister is working properly, also check that your vacuum advance hose isn’t cracked coming off the distributor to the vacuum manifold tree. The vacuum manifold tree is brass on the bottom to go in to the block and plastic on top. Plastic wears out with time and will break or leak, which causes a vacuum leak. Some manifold vacuum trees are 3 or 4 port, make sure to replace it with a new one. When I buy parts I buy 3 at a time that way I have them on hand or in case they can’t get them any more. The vacuum manifold tree is located behind the carb. If you looking at the carb from the right side of the bed, it will be to your 1 O’clock tucked down inside. Remember to use a marker or different colored tape to mark the vacuum lines so you know where everything goes back too! Good luck!’
