Hi all, I have a question about very bad bogging that I have on a 1970 skylark Custom with a SP code 350. To see my previous thread about this car and how I got to this point go here: http://www.v8buick.com/showthread.php?300489-350-Going-Boom-Won-t-Start Anyways, the car will bog and often die if I give it anything over very light throttle. It idles and revs fine in park but under any load the problem is present. Sometimes just putting the car in gear is enough to make it stall. When the problem happens the engine wheezes and makes a sound like it's dieseling. My first though was that this was a fuel problem, but now I am leaning towards ignition. I have done the following to the fuel system: -Removed and cleaned fuel tank -Installed new fuel level sender and pickup sock -Replaced 10 year old rubber fuel lines at tank and pump -Replaced fuel pump -Got Q-Jet rebuilt by Ken and Everyday Performance. After all this I am still having the same problem. Today I installed an inline Aeromotive fuel pressure gauge so I can finally get to the bottom of what was going on. Probably should have done this before!! ou: My observation first is that needle bounces around 8 psi, with a variance of 0.5 to 1 psi, and bounces faster with engine speed. Is this normal for a mechanical fuel pump? I read ~8 psi at idle, cruising, and when I give it more gas to incur the problem. The fuel pressure doesn't seem to be related to my problem, but I wanted to see what you all thought before I start spending money on the ignition. The other thing that has me thinking ignition it that the car was previously not running and sitting for 10 years when I got it, and started running again when I replaced the points and condenser. This looked so ridiculous I had to take a few pictures: Don't worry, the holes in the grille were already there! And yes that is an old sock providing vibration dampening and paint protection. :laugh:
Had the Q-jet converted to electric choke by Ken, it does open, but the high idle doesn't seem to want to work. I will mess with that after I figure out what this issue is. Timing is set at 12 BTDC. Have not power timed or set dwell yet. I actually have no idle how to set dwell (first points car). Would it just be the timing? If this turns out to to be the ignition I am debating between getting my distributor converted to a small body HEI by Dave, or getting a Mallory Comp S/S (they are on sale right now). Would be replacing the coil, wires, and plugs as well. Wires are new but they are crappy and I have had to repair end terminals which have become un-crimped already.
Your fuel pressure is definitely good. at 12 degrees it should run ok. will it rev ok in park or neutral or does it want to stall then too?
It revs fine in park and neutral but has the problem under load. The car originally went out "with a bang" 10 years ago. I had thought it was the timing chain but the car fired up after I replaced the points, condenser, cap and rotor. Also did the plugs at that time. The car would make a super loud backfire when cranking and the owner said it was the same sound it made when it died 10 years before. Seems it was an ignition related issue. Now it runs but bogs bad.
I had a car run similar to that and it turned out the power piston in the q-jet was stuck wide open. Do you have a vacuum gauge you can put on it?
I've commented on your previous thread and I wanna add something here. I had very similar situation that I already told you about (fuel line on pump)... Something else came to mind. Did you change the fuel filter at the carb? I know you think this is ignition issue but I wanted to check since mine was similar but a fuel issue.
Look at the cam that lifts the secondary jets. If it is broken, it will give these symptoms, since the air valve opens up but the fuel isn't delivered.
The carb came back from the rebuild with a new filter, but I swapped a new one in today when I installed the gauge just in case. I made sure to not install the carb until I cleaned the gas tank to avoid running 10 year old fuel through it. Since the carb is rebuilt, I am sort of ruling carb issues out on this one, though I will give the pump arm a look as well as the secondary hangers. Are these both things I can check with the carb on the car? I fell like I've done everything possible to the fuel system at this point, short of changing the hard lines, but that doesn't seem necessary with my 8 psi of fuel pressure. I only have a cheap vacuum gauge that I'm not sure is accurate, but I will try and get my hands on a better one to rule that out. Am I wrong to suspect the ignition at this point? If it were a vacuum issue would I get these symptoms? The issue is worse on some days and better on others, to me that sounds like electrical?
I assume you set timing with vacuum advance plugged? Check if mechanical advance is advancing. Check if vacuum advance is on manifold vacuum or ported vacuum( none at idle,needs open throttle for vacuum).
8 psi of fuel seems pretty high for a qjet. They normally like low psi hi volume 5 psi to 6 is where i think it should be
8 psi and a new rebuilt carb. It is the point system causing the bog problem. Replace condenser and check points for pitting. The coil could be the problem of not getting enough spark to the plugs. This always happens under load since the coil needs more juice at this time to fire the plug. Check dwell first then check the timing. The one piece point and condenser systems were junk at best. The points with a separate points and condenser always worked better. I always used the high performance set if I could get them. 8 psi is high for any carb. put in a fuel pressure regulator as close as you can to the carb. you could have cracks in the distributor cap so look for that inside. clean the ends where the rotor comes in close contact to with a small file or wire brush and clean it out with air. Take a look at nite to see if sparks are flying everywhere from the wires this will cause a bog problem too. Check the vac canister by sucking on the hose and see if the timing moves with light. you can use a suction pump if you have one. if the timing does not move this can cause a bog. Change out the coil and see if that cures the problem.
If your choke doesn't fully open or high idle isn't working right then the secondaries can remain locked out and not open. Is it possible that it IS running off the high idle? What is your timing at above idle, like up to 3000rpm or so? I second suspecting timing was checked with vacuum advance adding to it, that would cause the backfiring. It will never run decent with the dwell incorrect. Google setting without a meter...is it turn IN until misfire and then back out a bit, or the other way around?
Ill bet the wire going to the coil from the starter is no good run a wire from the battery straight to the coil and see if it still bogs..
...Or measure the voltage at the coil (or resistance of the yellow wire). Those definitely go bad. Be careful running more than 8 volts at the coil for long, you can burn it out. A new wire and a Chrysler ballast resistor works well.
Started with the easiest thing first and replaced the coil today, no change. Over this week I will: -Mess with timing -Connect vacuum gague -Check resistance of wire going from starter to coil -Try and verify proper choke operation Wish me luck and thanks again everyone! I will post with updates.
Have you confirmed that the electric choke unit is opening the choke flap? Regardless of the fast idle, that flap must open as the engine warms up.
Dwell affects timing. adjust the dwell FIRST before looking at the timing. Disconnect and plug the vacuum advance before setting timing.
