I am finally getting my 07/'76 FJ40 road worthy. Last step seems to be Weber carb tuning. Yes - I've read searches here for the past few days. Yes - I have the weber carb site which basically just tells you how to set idle mixture and idle speed. Need some extra help though.
I have de-smogged 2F with Weber 38DGAS and headers. eChoke is on it and seems to be operating properly (choke closes when started then opens when warm - does this fine after warn start also). Truck has been sitting alot for past 18 months or so during rebuild. Ran great before rebuild. Note rebuild was for a new Aqualu tub and did not involve any engine work. Now get stumbling and small backfires at high revs and under load (like when you floor it or trying to accelerate at low RPM like in 2nd gear. Note it idles fine - no issues with that.
Vacuum at idle is around 17 with slight 1-2 pt fluctuation (meaning I may need to re-gap my plugs - no big deal). Dizzy looks good and no cracked cap or any bad wires. Fuel pump is giving me about 4psi so no worries there. Brand new OEM fuel filter in it - old one cut open looked good with no rust or particles in it. I bought a fuel pressure regulator to hook up as I read Webers like 3psi going in but it ran fine before sitting for 18 months with no regulator so I don't think that is issue. Checked fuel filter on the weber and that is clean also (wasn't clogged at all or sludgy).
I can't imagine timing would change since it ran well before and no real use since sitting for a while and distributor was not pulled or changed. I can check that though tonight. Same comment on valve clearances though I can re-set them if people think they could change while the truck basically sat idle (I am no expert here so let me know).
All this leads me to believe possible bad accelerator pump or clogged port there. Any ideas how to test this on a weber? I ordered the Weber HP Manual and hope that can help but its days away and winter is coming. I was about to take the carb off and soak it but thought I'd check here first for other suggestions to rule out the obvious.
Oh - I SeaFoamed it yesterday and it didn't smoke much after waiting 5 mins and restart. Also tried the choke cleaner trick where you spray it in the main body with engine running and then choke off air to create greater vaccum to try and pull free clogged jets/ports - that didn't seem to work either.
Appreciate any thoughts (besides throw the Weber away). I am convinced I can get it to work and my previous 40's stock Aisin was no joy to tune either for this carb noob so be kind.
AndrewT
I have de-smogged 2F with Weber 38DGAS and headers. eChoke is on it and seems to be operating properly (choke closes when started then opens when warm - does this fine after warn start also). Truck has been sitting alot for past 18 months or so during rebuild. Ran great before rebuild. Note rebuild was for a new Aqualu tub and did not involve any engine work. Now get stumbling and small backfires at high revs and under load (like when you floor it or trying to accelerate at low RPM like in 2nd gear. Note it idles fine - no issues with that.
Vacuum at idle is around 17 with slight 1-2 pt fluctuation (meaning I may need to re-gap my plugs - no big deal). Dizzy looks good and no cracked cap or any bad wires. Fuel pump is giving me about 4psi so no worries there. Brand new OEM fuel filter in it - old one cut open looked good with no rust or particles in it. I bought a fuel pressure regulator to hook up as I read Webers like 3psi going in but it ran fine before sitting for 18 months with no regulator so I don't think that is issue. Checked fuel filter on the weber and that is clean also (wasn't clogged at all or sludgy).
I can't imagine timing would change since it ran well before and no real use since sitting for a while and distributor was not pulled or changed. I can check that though tonight. Same comment on valve clearances though I can re-set them if people think they could change while the truck basically sat idle (I am no expert here so let me know).
All this leads me to believe possible bad accelerator pump or clogged port there. Any ideas how to test this on a weber? I ordered the Weber HP Manual and hope that can help but its days away and winter is coming. I was about to take the carb off and soak it but thought I'd check here first for other suggestions to rule out the obvious.
Oh - I SeaFoamed it yesterday and it didn't smoke much after waiting 5 mins and restart. Also tried the choke cleaner trick where you spray it in the main body with engine running and then choke off air to create greater vaccum to try and pull free clogged jets/ports - that didn't seem to work either.
Appreciate any thoughts (besides throw the Weber away). I am convinced I can get it to work and my previous 40's stock Aisin was no joy to tune either for this carb noob so be kind.
AndrewT
Last edited: