That can't be right.....

Dobalovr

Dobalovr

Being on the Cbody diet SUCKS!
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OK collective having trouble setting up a "Members" 70 318 after rebuilding the Carter BBD 2 BBL. Wasn't getting fuel to the carb from the new tank and sender so swapped out fuel pump. With a little priming car started up running but was rough and surging. RPMs fluctuating between 850-950, Vacuum gauge reading between 15-17 hg but not steady. Set idle - set mixture then went to set timing....initial was running over 25 with the advance disconnected. Backed off to 10 degrees but RPMs dropped to 500 and then stalled out. Now the car wont idle at any advance even with the idle screw all the way in. Only way to keep it running is to position cold idle cam on step 2. Timing mark is bouncing on damper and not steady. So possibilities?

Stretched or jumped timing chain?
Stuck mech advance on dizzy?
Carb float level
Low fuel pressure (fuel filter doesnt fill right up)
Burnt valve?

So surging rpms
Bouncing timing marks
Fluctuating vacuum
Wont idle
Huge initial advance reading
Feels strong at higher rpms
Nothing out of tpipe
Ran when parked
Only carb has been changed all other ignition components unchanged
New fuel tank/sender

Opinions please!
 
Sounds like there maybe multiple problems with the current engine. Got to start somewhere so you sure could try the good carb.
 
Dobalovr said:
OK collective having trouble setting up a "Members" 70 318 after rebuilding the Carter BBD 2 BBL. Wasn't getting fuel to the carb from the new tank and sender so swapped out fuel pump. With a little priming car started up running but was rough and surging. RPMs fluctuating between 850-950, Vacuum gauge reading between 15-17 hg but not steady. Set idle - set mixture then went to set timing....initial was running over 25 with the advance disconnected. Backed off to 10 degrees but RPMs dropped to 500 and then stalled out. Now the car wont idle at any advance even with the idle screw all the way in. Only way to keep it running is to position cold idle cam on step 2. Timing mark is bouncing on damper and not steady. So possibilities?

Stretched or jumped timing chain?
Stuck mech advance on dizzy?
Carb float level
Low fuel pressure (fuel filter doesnt fill right up)
Burnt valve?

So surging rpms
Bouncing timing marks
Fluctuating vacuum
Wont idle
Huge initial advance reading
Feels strong at higher rpms
Nothing out of tpipe
Ran when parked
Only carb has been changed all other ignition components unchanged
New fuel tank/sender

Opinions please!
Click to expand...
I would start by turning out both idle screws from lock to two and one half turns. If it still won't idle, that would suggest that the idle circuit for the carb is plugged. You may have to dis-assemble and blow out with compressed air. Take note to check that throttle plate gasket to carb body has all of the same holes as the original. There has been some issues with foreign made carb gaskets not being properly stamped (ie missing holes). While you have the carb off, check the float level adjustment against the gauge supplied by the carb kit manufacturer. Check the instructions as to where to measure the float level, re-set if necessary. Check the needle valve to be sure it is free from debris that keep it from seating properly.

As you replaced the tank sending unit, be sure that all connections for the hoses are tight and the none of the hoses are kinked or otherwise distressed. Same for the fuel pump. Put it all back together, if this was a carb issue, it should now run. If this vehicle will still not idle, the problem might be something other than the carb. The floating timing mark might be a clue. These cars have a mechanical advance, a rough idle that causes a change in rpms can cause the mechanical advance to fluctuate by engaging and dis-engaging, this is nothing to worry about. Since you noted 25 degrees advance at start up with out any changes, that would suggest that the timing chain might be bad. Pull off the distributor cap have a helper rotate the crankshaft back and forth to note the amount of free play before the rotor moves, if it has more than 10-12 degrees of free play, the chain is shot and needs to be replaced. This is especially likely if the vehicle has more than 80k miles on it. Did you rebuild the carb because of the rough idle? Did you check the points for proper set and resistance? Points in cars that sat idle have an annoying habit of corroding. Points that are set too close also cause a rough idle that goes away when the car is revved up.

Hope this helps
Dave
 
All good ideas Dave. The idle screws have been adjusted all the way in then backed out a couple of turns. Points are a possibility and we will check the timing chain play. Float was checked with kit gauge on reassembly. Base gasket may be but it was matched to the one in the carb. Keep the ideas coming!
 
Dobalovr said:
All good ideas Dave. The idle screws have been adjusted all the way in then backed out a couple of turns. Points are a possibility and we will check the timing chain play. Float was checked with kit gauge on reassembly. Base gasket may be but it was matched to the one in the carb. Keep the ideas coming!
Click to expand...

Another potential idea is that a leaking master cylinder will sometime trash a brake booster on a car that has been left sitting awhile. If none of the other things work, try blocking off the line to the brake booster, this would eliminate a vacuum leak there which could be causing the rough idle.

Dave
 
if the engine will run relatively steady at any rpm, the timing should remain steady as well. check the primary side with a dwell meter. low vacuum reading is a bad sign, mechanical issues, no fuel, clogged exhaust, vacuum leak as above.
 
Dobalovr said:
OK collective having trouble setting up a "Members" 70 318 after rebuilding the Carter BBD 2 BBL. Wasn't getting fuel to the carb from the new tank and sender so swapped out fuel pump. With a little priming car started up running but was rough and surging. RPMs fluctuating between 850-950, Vacuum gauge reading between 15-17 hg but not steady. Set idle - set mixture then went to set timing....initial was running over 25 with the advance disconnected. Backed off to 10 degrees but RPMs dropped to 500 and then stalled out. Now the car wont idle at any advance even with the idle screw all the way in. Only way to keep it running is to position cold idle cam on step 2. Timing mark is bouncing on damper and not steady. So possibilities?

Stretched or jumped timing chain?
Stuck mech advance on dizzy?
Carb float level
Low fuel pressure (fuel filter doesnt fill right up)
Burnt valve?

So surging rpms
Bouncing timing marks
Fluctuating vacuum
Wont idle
Huge initial advance reading
Feels strong at higher rpms
Nothing out of tpipe
Ran when parked
Only carb has been changed all other ignition components unchanged
New fuel tank/sender

Opinions please!
Click to expand...

Somebody here once said that "95% of all carburetor problems are electrical."
 
Cracks my knuckles and looks sober. Okay time to get serious here. Have you checked the thermostat?
 
check the carb base gasket....make sure it is the correct one and not backwards...I can't recall if this is important on these carbs but check it anyways...
 
mr. fix it said:
check the carb base gasket....make sure it is the correct one and not backwards...I can't recall if this is important on these carbs but check it anyways...
Click to expand...

Now that is an interesting idea. My faithful sidekick installed the carb without me being there ...
 
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