Yet another carb/timing question

[crewzerdog]

OK, on my restoration project I've reinstalled all the vacuum lines (soft and hard lines) all the smog gear and tested all relays, etc. -- all work as spec'd in the factory emissions manual. I've also checked the fuel cut solenoid and it "clicks" as it should. Original carb and it's been rebuilt.

The truck runs good at cold start up and the choke works fine -- once the truck gets warmed up the choke breaker circuit/vac kicks in causing the truck to idle down as it should - while sitting it idles fine. Problem is once I drive it around a bit it begins to run rough and will not idle without giving it gas via the pedal. It also will flat out stall when decelerating to a stop sign or red light -- it cranks back up quickly but still will not idle on its own and runs pretty rough. I've got a vac guage and plan on checking the intake for leaks tomorrow but I've already tried spraying carb cleaner around the intake and "no reaction" - no increase in RPMs. Any suggestions?
Thanks, Tom-

 

[IDave]

First impression? Defective pump plunger. I know you rebuilt your carb, but...

 

[redrock]

I had the same problem with my 79fj40. Check your EGR valve. The valve can easily be checked by removing the vacuum line to the top of the valve. You can apply vacuum and slight positive pressure directly to the EGR valve to check it. At idle, the valve should be closed. If vacuum opens the valve, the engine will stall. To seat the valve (closed) apply positive pressure. An EGR valve should only be open above idle, or the engine will stall and quit. BTW, the 2F will run quite well with an EGR that remains closed (hint). The only issue is NOx on a smog test. New EGR valves are available if needed, but the EGR modulator is not--however, they can be re-ported.

 

[Landpimp]

whats the best way to keep the EGR closed all the time?

thanks
John


[quote author=redrock link=board=1;threadid=15306;start=msg144866#msg144866 date=1082867967]
I had the same problem with my 79fj40. Check your EGR valve. The valve can easily be checked by removing the vacuum line to the top of the valve. You can apply vacuum and slight positive pressure directly to the EGR valve to check it. At idle, the valve should be closed. If vacuum opens the valve, the engine will stall. To seat the valve (closed) apply positive pressure. An EGR valve should only be open above idle, or the engine will stall and quit. BTW, the 2F will run quite well with an EGR that remains closed (hint). The only issue is NOx on a smog test. New EGR valves are available if needed, but the EGR modulator is not--however, they can be re-ported.
[/quote]

 

[crewzerdog]

IDave, thanks for tip -- the carb atomizes fuel well when trottle lever moves - no problems there. The stalling occurs when I take my foot off the gas pedal and go to the clutch/brake on deceleration to a stop sign. If the engine RPMs are high enough (i.e. I don't push in the clutch) the truck keeps running - when the clutch gets depressed and RPMs drop I get the dreaded stall. I can adjust the idle screw to get the RPMs up but then when the engine is cranked from a cold start the idle is way too high. BTW, fuel level in the 'glass window' on the carb is as it should be - in the middle.

Redrock - the EGR area was my next stop - thanks for the suggestion. I've heard of the "get a bigger hammer" solution - literally wacking the EGR --- something about carbon buildup etc that stops the thing up. Another cruiser friend did just that and everything began to idle fine on his truck. Think I'll try the more "analytical" approach you suggest to begin with. PS - I've checked the modulator and that seems to work per the factory manual.

One last thing that may be significant, when I do adjust the idle speed screw "in" to get higher RPMs, the engine (just after a 'cold start') runs fine and the choke breaker kicks in as it should after warm up and it starts to return to "normal" idle -- same as I originally described. If the idle is set 'high' the engine will cycle up and down in RPMs every few seconds -- almost like it is looking for fuel but if I adjust the idle screw out the engine smoothes out at lower RPMs. Confused????

Thanks for the input - anyone else got any other suggestions?

 

[Dave E]

Crewzerdog,

Did you ever get this fixed(hope so)? My 73 is doing the same thing. I come to a stop sign, and it dies. It takes 5 mins to restart. I tried adjusting the idle speed, but then it idles too fast when cold. I hope you see this or someone else here can help.

Thanks
Dave

 

[spotcruiser]

Egr

John,
Just pull and plug the vacuum line that is connected to the EGR actuator.

If it is giving you problems and you want/need to keep it operational, you can clean the valve by soaking it in carb cleaner (the dip-type stuff). Dip just the valve itself, not the actuator diaphragm.



[whats the best way to keep the EGR closed all the time?

thanks
John]