Severe bog

[Recian]

So every older guy I've talked to thinks my problem is my accelerator pump but I'm not so sure. I'll explain.

When I go to pull out in traffic and floor it the truck falls on its face. My road is a heavy traffic road and I've gota turn left and it's next to a turn so I can't see more than 1/8 mile from the road so getting home is a bit hard. It did this bogging before rebuilding the dualjet (I know 2bbl but I've got a quad just waiting to get the little misc parts for it) but it's way worse now. I may as well ease into the gas. It accelerates harder that way. It does act like the accelerator pump isn't squirting that bit of gas when needed but the thing is usually after flooring it to 45mph which usually takes at least 30 secs the truck will be 1/8-1/4 tank lower than it was like it's running way too rich but there's no smoke or smell. I replaced the plugs with delco's, OE style wires and cap/button. I can pull the plug out of the front of the cat and drive it and it doesn't help so I know the converter isn't clogged. I'm wondering if it's the vac. advance. I know it's hooked to a thermo cut off valve and I live about 2 miles from work so it rarely warms up completely.

If it is a carb problem I'd like to know before rebuilding my q-jet so I know what to look for. I've got it apart and the pieces soaking in carb cleaner. The 2 carbs are identical on the inside just with the added 2 bbls.

[byeoficr]

just my two cents. you can check for vacuum leak with a can of carb cleaner. just spray around fittings if the truck idles up there is a vacuum leak. personally i would check for an electrical issue. a plug wire loose, fouled plug, or cap arcing. they tend to mimic fuel issues.

[Unca]

also pop the cap off and look at the weights in the distributor. If they aren't working properly, the timing cant advance as it should.

[Recian]

I checked all that when I did the ignition system. I've replaced all the vacuum lines too. Haven't checked to see if the thermo valves are supplying vacuum to their respective components when warm.
Posted via Mobile Device

[geezer#99]

When it bogs is it totally warmed up?
What motor?
Do you have headers?
What air cleaner?
Got a pic of your motor?

[Recian]

It does it hot or cold. 305 2bbl with EVAP, Thermo air, EGR, No smog pump, stock everything and its all there and hooked up
Posted via Mobile Device

[geezer#99]

If you think it's the vac advance just run a new hose from a manifold vac source.
What's your timing set at?

[motornut]

check if the advance weights are worn out,oblonged holes,plastic bits worn out
i had a sticky advance can
gunk stuck between the pump and filter,remove line and drain
tie off your choke,to be sure its off,run it like that for a couple of days
remove the back flow valve from the fram gas filter
float sticking?

[Recian]

My advance components are all metal. I checked them when I did the cap and they move freely and springs return like they should. Idk on the timing. No plate on the cover and I don't have a good light
Posted via Mobile Device

[Recian]

I replaced the float with needle/seat during rebuild. Backflow valve?
Posted via Mobile Device

[motornut]

there are usally plastic bits around the spring shafts(bushings)
but they crack and come apart
gas filter just happened this spring
http://67-72chevytrucks.com/vboard/s...d.php?t=579621

[geezer#99]

Originally Posted by Recian

My advance components are all metal. I checked them when I did the cap and they move freely and springs return like they should. Idk on the timing. No plate on the cover and I don't have a good light
Posted via Mobile Device

TRy advancing the timing without a light or the plate. Measure from somewhere on the firewall (a bolt head or screw or make a mark)to the vacuum pot nipple on the distributor. Write that number down. Now advance your timing about 1/2 inch. See what that does. You can always put it back to original with a quick measurement.

[Recian]

That's how I time my older nissans with distributor. That's what I was planning. This morning I took the vacuum off the egr and straight shot the advance to the carb and it seems to be much peppier. This afternoon ill put gas in it and drive it more under different circumstances. I think those thermo vacuum switches need to go
Posted via Mobile Device

[Recian]

Also I didn't have the feeler gauges to check my points while I was doing the cap. The previous owner put 60k on the truck and did nothing to it but have walmart change the oil occasionally
Posted via Mobile Device

[INSIDIOUS '86]

Originally Posted by Recian

Also I didn't have the feeler gauges to check my points while I was doing the cap. The previous owner put 60k on the truck and did nothing to it but have walmart change the oil occasionally
Posted via Mobile Device

Are you running points in this truck?
Posted via Mobile Device

[Recian]

It looks just like the picture posted above. They look like points with a reluctor wheel

[Recian]

I've noticed something else about the truck that it's had since I got it. Should have posted this up front but it always has a long crank time and when it fires I have to give it gas to keep it alive almost like a fuel pressure leakdown such as a bad pressure regulator on a fuel injected vehicle. If it sits for 30 mins or so it'll fire up no issues. I'm wondering if the pump can't keep up

[Recian]

I was going through the shed earlier and found a vacuum gauge in the bottom of my tool box. Turns out I'm running 8-9" at idle and 13" off idle. The truck smooths out off idle also. I should be running over 10" at idle

[geezer#99]

Choke working?
Mis-adjusted choke can cause long cranking as can leaky fuel wells in the carb. Takes a bit to fill the fuel bowl again.
Did you try bumping the timing?

[Recian]

Choke was an issue. Now that I rebuilt the carb and replaced the choke thermostat It works great. However it doesn't do the one pump set deal like it should. It sets with one pump but the truck still needs gas when starting. I'm thinking fuel leakdown in the carb when it sits since it diesels when I shut it off. I figure rebuilding the carb would fix it. My next step was to mark and turn the distributor

[68longhorn]

What year is it?

[Recian]

1981
Posted via Mobile Device

[68longhorn]

ok to old for the esc distributor.

[Recian]

I tinkered with it today. I made a few carb adjustments and got it way better. I played with timing some before doing that but it made the truck spark knock so I had to set it back where it was. Setting it lower than where it's at and it'll die out. I wish I had a timing plate so I could put a light on it and set it perfectly in spec. I think the carb mixture screw was my issue. It idles a little rough, I think the engine is just tired. It runs smoothly just has no real balls. Now I see how weak the 305 really is when it's running right with the 2bbl. Got a quadrajet and edelbrock performer intake to put on. Hope that helps

[bilfman]

Did you check the fuel filter? Could be plugged. Under light load it lets enough through, but in a WOT situation it could not be letting enough through. Just a thought since you seem to have checked most other stuff.

Some peeps have inlines and forget about the one in the carb.