I need some help please

[datzenmike]

Sorry I couldn't remember everything done or read 4 pages. It's usually something simple or over looked. By repeating things you might just have an idea or think of something that was missed or overlooked...

 

How about a compression test? When they shake like that often a cylinder not firing or low compression. 

[Jwalth02]

Sorry bud I'm not trying to take it out on you just extremely frustrated with this thing.

 

I will try to get a compression test done soon, can this be accomplished on the exhaust side as the plugs are easier to get to or does it need to be done on the intake side?  Also what pressure should I be seeing?

 

Also I didn't mention when it starts sputtering the fuel pressure stays constant and the level in the bowl stays solid.

 

Lastly on the carb I know we've talked about the cut-off solenoid supplying fuel to the Idle mix screw, where does the solenoid get fuel from?  Port in the bowl?  Maybe plugged slightly?  I'm thinking about pulling the carb again and double checking it all in there as well.  Also, should the secondary be pulling air and making a high pitched hiss when idling?

 

Also the last couple of times I fired it up, the shake and lopey idle has reverted back to just sputtering when the choke opens up and shutting itself off.

[tr8er]

Does it idle smooth until the electric choke cuts out? Can you adjust the timing until it runs smooth after it warms up and idles funny? Vacuum advance diaphragms can crack after sitting a while so that could be a vacuum leak you didn't suspect. Also a timing issue.

 

I also didn't read 4 pages, but this is what I didn't see mentioned here.

[Jwalth02]

I have not been able to mess with the timing as of yet due to the fact that I cannot see the timing marks anywhere, and can't get my hands on a timing light.  I'm about to the point of marking the current spot and just turning it to see what happens.

 

Just a review:

 

Truck ran fine until I lost the stock fuel pump and then sat for about 5 years.

Installed new Facet fuel pump and pumped all the old fuel out of the tank with it.

Changed fuel filter that threads into the pump and filled tank with fresh fuel with Seafoam mixed in.

Changed all plugs with NGK replacements, Distributor cap and rotor, plug wires, and all vacuum lines.

Warmed engine up and set valve lash as per specs provided here.

Truck would not idle but runs after adjusting past idle.

Pulled the carb and cleaned all jets that I could see, the idle air slot in the side of the chamber.

Removed fuel cutoff solenoid needle.

Installed fuel pressure regulator and gauge (home made, but it is all fuel rated) and set between 4-5 psi.

Adjusted float to maintain fuel at the dot in the sight glass.

Checked plugs on both intake and exhaust side to make sure coils are firing.

Fixed vacuum leak on spacer between carb and intake manifold.

Verified wiring from dist. cap to plugs.

Truck started idling but it was with the lope and shake shown in the video.

Now it is back to the point of running till the choke opens up and it starts hissing through the secondary and finally sputters and dies.

The tach is not functioning so I can't tell what RPM it is running at but it sounds smooth and close when the choke is on.

 

Am I wasting my time with this carb?  I don't have the funds to purchase a new one or do the Weber swap.  I am to the point that it is about to go to the junkyard.

 

Hope this clears any questions up, though I am probably forgetting something.

 

And I haven't really paid any attention to the vacuum advance as Mike said earlier in this thread there is no vacuum on the advance at idle and pulling the hose and plugging it makes no change.

[datzenmike]

The idle cut is simply a shut off in the idle circuit supply down to the mixture adjustment screw. You can remove both and spray carb cleaner (can with straw) into both ends and it should come out the other to make sure it's clear. Then close the idle mix screw and spray into the idle cut to blow back into the float chamber. Actually it passes through a slow air bleed and a slow jet but if you cleaned the carb these should be clear. Carb spray stings the eyes so...

 

The carb may hiss with the air filter off, which is normal, but get a length of hose and hold one end to your ear and pass the other end all over the carb, intake and hoses. A vacuum leak can also hiss. The secondary should be quiet and closed.

 

The BCDD should be off. If not returning to off, the idle speed would be too higher. To set it to be less sensitive the adjuster can be turned counter clockwise. Keep track of the turns so it can be put back. The BCDD opens and supplies gas and air on sudden high speed (high vacuum) deceleration to reduce emissions, and then turn off above idle. It's like a tiny carb within a carb.

[OlDatZMan]

Jwal: I've been busy but just read your thread. Posting because I just went through every frustrating thing you've gone through. Mine would start but not idle or vice versa. On an old vehicle that's been sitting troubleshooting takes time because you have to suspect and check everything thoroughly, deal with crud buildup, clean contacts and hoses, on and on, so patience is a must. On old vehicle you also can't rely on any wiring, or assume wiring or hoses have not been replaced or connected in the wrong places. I checked for intake vac leaks 3 times and only found one leak the 3rd time around; two careful checks weren't enough. All useful info I got was from Ratsun so all kudos due to the rat folks. I never got a decent handle on it til I was able to check vacuum and compression which gave me a direction to go, so I suggest those tests to know that the internals are helping and not hindering. Sitting is about the worst thing you can do to an engine/fuel system, especially if it had ethanol gas, and valve faces can corrode just enough to matter when tuning. Local chainsaw guy here kept fuel samples in glass jars of gas from his repairs. Up to 50% water in some, with some saws beyond repair less than a year old, and those are tiny tanks. He only ran av gas in his own saws. My problem was a bad valve: good cylinders at a weak (untunable) idle couldn't pull the dead cylinder, so all my ignition and fuel checks, while useful and needed, couldn't solve the valve problem. Note that Seafoam doesn't magically dissolve everything, crud is still there in some form so keep an eye on filters for a few months as gunk and debris loosen up. Two inline filters in the engine bay might not be a bad idea for a tank that has sat.

[Jwalth02]

Sorry, but BCDD?

 

I'm going to pull the carb off again and clean one more time when I get a chance.  Again on the compression does it matter which side I use intake plug or exhaust?  And would my 82 book have close enough pressures listed for it?

[OlDatZMan]

Sorry, I'm ignorant about BCDD and don't even know if you are referring to my reply. Same chamber so doesn't matter whether you use exh or intake plug holes. I pulled all my plugs to be easier on the battery, put the compression gauge in #1, where I could see the gauge face while cranking the engine, turned the engine over maybe 6 revs, and watched the gauge for the rate of pump-up to see if they rose at the same rate. Highest number on the gauge (which is saved by the gauge) I took as highest compression. I did that on cyls 1 through 4, then went back and ran 1 thru 4 again after squirting a couple healthy squirts of oil into each cylinder to see if any leak was through rings or valves, watching again for pump-up rate and final compression #. Your 82 numbers should work but you are really only interested in how close you are to the OEM compression #, how close you are to the minimum acceptable #, and the range between your numbers, 10% difference being the usual accepted maximum difference between cyls. Mine were 175, 118, 170, and 170 dry and 175, 125, 170 and 170. So my compression loss was only through one or both of #2 valves. Hopefully your #'s will be high and all close to the same and you can consider that test done and passed, the engine internally ok, and your problem(s) elsewhere.

[Jwalth02]

Thank you OlDatZMan, that sounds pretty clean cut.

 

And the BCDD was in Mike's last comment on the previous page I don't know what it stands for.

[kelowg]

Id try pulling plug wire one at a time. One that doesnt change how it runs is a dead cylinder. So then check spark plug gap/condition and if firing with it out of head. Next ck valves on that cyl.  Might try(for diag purposes) disconnecting exh coil.  Then see how runs.

[datzenmike]

California uses Boost Controlled Deceleration Device all others an Air Bypass Valve but they are similar. It reacts to high intake vacuum and bleeds air in to keep it from increasing above a specified amount. It reduces oil consumption and emissions. If the valve does not close properly the engine acts like a vacuum leak... which it is. 

 

Earlier BCDDs added air and fuel as a 'carb within a carb' and if not shutting off properly the idle would not return. 

[Doctor510]

Very often, you can be ambushed by a vacuum leak that is tough to find.   If the Vacuum advance unit diaphragm is cracked, it will cause a big vacuum leak.   Pull off the hose and plug it. (disable the vacuum adv unit) 

[datzenmike]

If connected directly to the intake a vacuum advance hose leak would have an effect. Some time in the late 60s vacuum advance was moved to a port on the carburetor. When the throttle is closed at idle the port is above the throttle plate senses ambient air pressure so no vacuum advance also unaffected by any leak. As the throttle rises off idle the port is exposed to some intake vacuum which advances the ignition but again this is not a vacuum leak even if the hose has one or is off. At wide open throttle the intake vacuum is lowest and vacuum advance at it's least.

 

This is why early 60s and older car tune ups require you to remove and cap the vacuum advance hose to set the ignition timing because it is connected directly to the intake. Newer cars with the ported advance do not require this as there is none at the proper idle.

 

Ported vacuum forces the idle to run at  static 12 degrees advance (L series) or far below what it would like to run at, basically retarded. This is to lower idle emissions. Next time you set your timing at factory specs, move the distributor slightly advance and the idle will speed up and smooth out.