g741.org

Hi all,
Removed the truck from winter hibernation a couple of weeks back and I have a drivability issue. I suspect that I may be looking at a carb rebuild. Perhaps someone will recognize my symptoms and can offer a simpler solution.
In past years my truck would idle OK without choke (after warmup), but would stall at every application of throttle, without a bit of choke. Delicate “blipping” of the throttle would often get the rpms up just a bit, at which point it would take throttle without a problem.
This year the truck will not idle reliably without about ¾ to 1 inch of choke control, stalling within a minute or so of pushing off the choke. It’s pretty sensitive to this amount. A quarter inch either way from this range will allow it to die. Also, without this bit of choke, almost any touch of the accelerator at idle will cause a stall, “blipping” is no longer effective. If rpms are the least little bit above idle (I’d guess, by ear, only a hundred or two above idle), the engine takes throttle without any hesitation and runs just fine.
I’ve experimented with the idle mixture screw. It was initially set to about one and a half turns open. It is pretty insensitive to adjustment. I’ve closed it a half turn and opened it two or three turns without any effect, as measured by ear. Greater adjustment than that will kill the engine.
I’ve also experimented with hand choking the engine. I removed the air cleaner and pushed off the choke at the carb (choke cable pushes pretty easily). Before the engine died, I cupped my hands over the intake and slowly increased restriction. Nothing much happened until I’d closed off the intake enough to feel a very noticeable pull on my hands. At that point the engine rpm increased a bit (hundred or two maybe) and the idle was much smoother (very much like having an inch of choke cable out, but feeling much more vacuum on my hands than I would have expected that little bit of choke cable to have generated). Adding a bit more restriction finally killed the engine. I confirmed this idle rpm/smoothness improvement a couple of times to make sure I wasn’t imagining it, it is reproducible.
Last fall I discovered the “alignment - distributor ventilation fitting in the elbow” miracle on the Board, a pretty simple fix to stop cooking the coil. Now I’m hoping for similar good fortune with this new issue.

I can't really comment on the stalling issue other than saying check the timing.

Now, as to your idle mixture adjustment, I was told initially to close the screw completely, then open 1 1/2 to 2 full turns. Start engine, let warm up, take choke off, then turn screw clockwise until you hear a noticeable change in engine sound. Once this happens back screw off counter-clockwise until you get the same result. Then, remembering how many turns it took to go from the clockwise setting to the counter-clockwise setting, turn screw back clockwise half that amount. This should put you at an optimal setting.

Or in other words, once you have your clockwise setting say it took two turns to get to the counter clockwise setting, well, then turn screw half back, or one turn.

I have a very similar problem with needing some choke at idle and crapping out with normal accelerator pressure, requiring very gingerly pressing of the accelerator to not stall. A mechanic who helped me with some other issues said the accelerator pump inside the carb was most likely bad. I'm about to embark on a carb rebuild in a week or two, hopefully with positive results.

GregL wrote:I have a very similar problem with needing some choke at idle and crapping out with normal accelerator pressure, requiring very gingerly pressing of the accelerator to not stall. A mechanic who helped me with some other issues said the accelerator pump inside the carb was most likely bad. I'm about to embark on a carb rebuild in a week or two, hopefully with positive results.

As I suggested to the other poster, check your fuel first. The accelerator pump would have no bearing on needing choke to idle. Yet it could matter with the drive ability as you described. And being in Ca. I'm sure your stuck with E10.

dstrausb1 wrote:Hi all,
Removed the truck from winter hibernation a couple of weeks back and I have a drivability issue. I suspect that I may be looking at a carb rebuild. Perhaps someone will recognize my symptoms and can offer a simpler solution.
In past years my truck would idle OK without choke (after warmup), but would stall at every application of throttle, without a bit of choke. Delicate “blipping” of the throttle would often get the rpms up just a bit, at which point it would take throttle without a problem.
This year the truck will not idle reliably without about ¾ to 1 inch of choke control, stalling within a minute or so of pushing off the choke. It’s pretty sensitive to this amount. A quarter inch either way from this range will allow it to die. Also, without this bit of choke, almost any touch of the accelerator at idle will cause a stall, “blipping” is no longer effective. If rpms are the least little bit above idle (I’d guess, by ear, only a hundred or two above idle), the engine takes throttle without any hesitation and runs just fine.
I’ve experimented with the idle mixture screw. It was initially set to about one and a half turns open. It is pretty insensitive to adjustment. I’ve closed it a half turn and opened it two or three turns without any effect, as measured by ear. Greater adjustment than that will kill the engine.
I’ve also experimented with hand choking the engine. I removed the air cleaner and pushed off the choke at the carb (choke cable pushes pretty easily). Before the engine died, I cupped my hands over the intake and slowly increased restriction. Nothing much happened until I’d closed off the intake enough to feel a very noticeable pull on my hands. At that point the engine rpm increased a bit (hundred or two maybe) and the idle was much smoother (very much like having an inch of choke cable out, but feeling much more vacuum on my hands than I would have expected that little bit of choke cable to have generated). Adding a bit more restriction finally killed the engine. I confirmed this idle rpm/smoothness improvement a couple of times to make sure I wasn’t imagining it, it is reproducible.
Last fall I discovered the “alignment - distributor ventilation fitting in the elbow” miracle on the Board, a pretty simple fix to stop cooking the coil. Now I’m hoping for similar good fortune with this new issue.

I would strongly suggest you tear down the carb, thoroughly clean & rebuild it with a fresh rebuild kit. Sitting over the winter & stale gas corrosion is the most likely issue. Drain that tank & get fresh fuel also.