Beyond Frustrated - Wont start/stay running
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As the title suggests, I am at my wits end...
So some background on the car: I "finished" (they are never really finished) the restoration on this vehicle back in 2008. Its a 68 Dodge Dart Convertible with a 225 slant six and the 904 TF. At which point the engine was rebuilt back to stock specs- cam, pistons, boring, timing chain, bearings, carb rebuilt etc. The distributor gear was replaced 2-4 years ago. Fast forward to this spring: I did a tune up with new points, condenser, plugs, cap rotor and a couple other parts that wont have a bearing on this issue (like a steering gear, pitman arm and idler arm).
This past Sunday I was driving back from a church outing heading down the interstate here in Pittsburgh. I noticed a little "bucking" while driving. Basically the car wasnt moving as smooth as it normally does. Took my foot off the gas and felt the bucking stop, which tells me it was engine related. It started to get increasingly worse, to the point my passenger noticed it. At this time I was at an interchange and was going from one interstate road to the next via a 270 degree turn so I had to decrease speed. When the turn was ending onto the entrance ramp I needed to pick up speed. Well pressed the accelerator and the bucking continued and would not accelerate. Tried putting it in neutral to rev the engine to get it up to speed, that didnt work, further clarification that it was an engine problem. So I pulled off to the side of the road and there we sat.
Once on the side of the road I started checking a few things. The car would not start, just crank. depression of the throttle linkage gave me gas from the accelerator pump, so I know I was getting fuel through the line, past the filter and into the carb (the gas that was in the car was maybe a week old, if that. Got the latest tank from Speedway). So that leads me to ignition. So call the old man and he suggests it is either Coil or condenser. Well I had a spare condenser so I figured Id try and change it out while we wait for the tow truck. Well I didnt have the metric wrench to get the nut off the points so I had to remove the points to get a socket on that nut. Well in the process of this, I dropped those screws numerous of times, and one time it fell in the distributor... So I removed the distributor to basically fish that screw out. After turning it upside down and shaking it a little it came out. Well i got the distributor back in and everything back together for the tow truck guy to come. Needless to say it wouldnt start...
So that puts us where I have been pulling my hair out these past three nights not getting enough sleep or food trying to get this damn thing running. So I changed the condenser and the coil and I am not having any luck what so ever. I took the valve cover off and visually inspected the closing of the intake valve to the timing mark on the damper. I also can crank the engine over and see that after all my fiddling around my timing is 5-8 BTC. Not optimal I know, but it should still run. I set the dwell to 40-43 deg. I can sometimes get it "running" Which means my foot has to be planted on the accelerator, and the engine is still stumbling on itself. No matter how I fluctuate the throttle it will always die and doesnt start again. I have a spark tester and I verified that all 6 plug wires are seeing spark. What am I missing?
Could I have shaken something lose in the distributor when I was shaking it? Which doesnt make sense, it was bucking and wouldnt start before I fiddled with it.
Could of it jumped timing? I dont believe so, but I guess anything is possible. This issue started out very faint than got worse. I was driving at a constant speed at the time this started so I dont see how the timing chain could of jumped.
Does anyone have any ideas on what I am missing? The old man says it could be cap, rotor or plugs. But all of that was changed. I didnt see any cracks in the cap.
I really dont have the money to keep buying the same tune up parts over and over again, so I would like to have a better idea of what the problem is without continually throwing money at it in hopes it rights itself.
I will be away from the car the next few days, which is probably a good thing, so I will be a little delayed with some answers to suggests/tests suggested.
Thank you from a defeated A body Owner...
This is a classic low speed circuit issue.
Normally I would suggest polluted gas, as in water in the gas; but after all this goofing around, the water should have worked it's way out
Now the low speed circuit starts at the gas tank, same as all the other circuits. If you are sure that there is actually gas in the carb, that is half the battle. With known-to-be-good and pure gas in the carb, then, the rest of the circuit looks like this; float level,main well, idle well, emulsion tubes, idle air bleeds, transfer slots and idle discharge ports. Also included and very important is air/vacuum leaks,as well as valve lash.
Air/vacuum leaks are the most likely place to start, but with a non-running engine, this is supremely hard to test. So in this case I would check/adjust the valves first and follow it with a compression test. If an exhaust valve is burned up, then during cranking, the piston will suck air up the tailpipe cuz it's way easier for air to come in there than thru the carb. So if you get some low numbers with the compression tester, then have a helper crank the engine while you go put your palm over the tailpipe. If you feel the engine sucking on your palm, then the jig is up; time for a valve job. This only works if the exhaust system is reasonably tight as to leaks.
So after you have proved the compression is at least 110 at the minimum, and no valves are tight, try again.
If it still won't start, then I would check the cam timing. If the valves get out of time, then the ignition timing goes out with it, and then you get symptoms in red above. If you are able to reset the ignition timing but the valves are still late, you may be able to get it running with a lot of throttle, but it will have no power.But a simple test is to pinch the PCV shut, and the booster hose too, and disable the ignition system by disconnecting the ballast resistor.. Then have a helper open the carb about 1/4 throttle and crank the engine, while you put your hand over the airhorn. Only crank for 2 or 3 seconds. The engine should try to suck your hand down into the carb, and it should be sucking gas big time. Go dry off your hand. So if suction is strong then the cam timing is probably good.
So after the cam timing is proved to be correct, try again.
If it still won't start or it will with a lot of throttle, now we are left with a carb problem. So, go disconnect the choke system and make sure the valve stays open. Then splash a tablespoon of gas straight into the throttle valves. Then floor the pedal and twist the key. With just a bit of cranking the engine should spring to life, and rev right up. While it's clearing itself out, rev it up a couple of times.Then, back off gently so you don't blow it up, and keep it at a high idle, maybe 2500 for about a minute.See if she will take throttle; gently rev it up to 3500/4000. This will probably get her on the mainjet. If she takes it, then we know that the engine is probably OK and the main circuit too. Then begin to lower the rpm back to 2500.
But if she bucks at 3500, abort the test.
Continued in post #35