Motor dies after startup.

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You did a good test to isolate the misfiring cylinders. To check the 2 plugs either:
1) Swap out 2 other plugs in 2 of the working cylinders to 4 and 5 and see if the problems stays in 4 and 5 or moves to the other 2 cylinders.
2) Or, use the resistance setting of a voltmeter if you have one and check the resistance through the plugs and from the plug cap to the metla body. There should be very high resistance form cap to metal body, and no more than around 3000 or 4000 ohms (3k or 4k ohms) through the plug form the connection 'knob' to the firing tip.

You can do either of the same tests to check the wires to 4 and 5. Through resistance will vary from wire type to wire type. It should be less than 5 k ohm for a new resistance wire. Make sure the wires on the distributor are arranged around the distributor ca; if it is up near 10 k, it is time to replace. You can compare meter readings for all 6 wires.

Make sure the wires area all connected to the distributor top in the proper firing order, just in case you swapped 4 and 5 by mistake.

Let us know what you find. Isn't the shock fun?? Too hard on my old joints anymore! Pulling the wires at the distributor end lowers the chance to get zapped, BTW.

If it is bad plugs, then yes, replace then all. Too inexpensive to not do so.

If the plugs and wires are good for cyliinders 4 and 5, then it is time to see if the valves are working right, and then check compression on the cylinders.

What year is your car? The distributor advance vacuum hose for the older cars should be connnected to a port at the base of the carb below the throttle plate, not to a port up on the side of the carb body. But the later ones will be connected differently and the vaccum to the distributor advance may go through a temp controlled valve and another valve. We need to know the car's year and the situation with the emissions controls being intact. The vaccum situation is likely much less important than why cylinders 4 and 5 are not firing at this time.

BTW, how old is the gas? Is it old mixed with new? (And it hleps to get answers to all questions; there are reasons to ask them.)
 
My mechanic friend came over to help me diagnose.

When we pulled plugs 4 and 5 and the plug cylinders I noticed there was a rod sticking out. My friend feeled on the inside, we pulled the valve cover, and realized the reason why 4 and 5 are not firing is because I have two bent pushrods.

So I'm going to pick up a feeler gauge and a couple of pushrods, read up on valve adjustment, and see if I can fix this myself. I'm looking thru the service manual right now but offhand if I can't find it does anyone know the feeler gauge size I need to put it at the correct rocker setting?

Good lord.


Incidentally we swapped 4 and 5 just to see what it would do with a good plug from 2. All 6 plugs appear to be firing. I think the bent pushrod was the culprit. What good is a spark if the valves won't move.

While it was sitting I only had a little in the tank. The tank was more recently filled and the fuel at the pump smells new.
 
mattmatthew said:
My mechanic friend came over to help me diagnose.

When we pulled plugs 4 and 5 and the plug cylinders I noticed there was a rod sticking out. My friend feeled on the inside, we pulled the valve cover, and realized the reason why 4 and 5 are not firing is because I have two bent pushrods.

So I'm going to pick up a feeler gauge and a couple of pushrods, read up on valve adjustment, and see if I can fix this myself. I'm looking thru the service manual right now but offhand if I can't find it does anyone know the feeler gauge size I need to put it at the correct rocker setting?

Good lord.


Incidentally we swapped 4 and 5 just to see what it would do with a good plug from 2. All 6 plugs appear to be firing. I think the bent pushrod was the culprit. What good is a spark if the valves won't move.

While it was sitting I only had a little in the tank. The tank was more recently filled and the fuel at the pump smells new.
Click to expand...

The litttle left in the tank IS a problem, maybe THE problem. If it gets old and evaporates off a loT of the light components, you are left with what is called varnish. The new gas will carry this into the engine. Carb will be gunked, plus the problems you see with the valves stuck. (It is even wose on a fuel injection engine.) And it will detonate like crazy and be hard on things and even tear things up. So you gotta be ready to clean the fuel system IMO.

Check the thread on this forum about 'Bending rods'; they bent for a reason that has to be run down. And read up on how to work the valves loose in the guides with Mystery Oil or SeaFoam and a mallet; very good info there. Be careful with the mallet; I would use a bit of 2x4 and be careful to push or knock STRAIGHT on the end of the valves so that you do not bend the valve stems.

Well, at least you ran it down! Just where was this 'rod sticking out'?
 
Ah yeah the tank will have to be dealt with eventually. I want to get a new tank anyway. The old one is a little beat up from bottoming out on too many driveways.

I think for now this fix will get me going but this is a work in progress so when I have time I'll drop the tank.

My friend used a mallet to loosen up the valves. Also I noticed one of the spacer nut/washers on the rocker shaft was loose. Will have to tend to that as well. It doesn't look like the rockers have been adjusted in awhile, some are really loose. I'm wondering if excessive play caused the rods to bend.

They were just sitting in that area where it has the holes that go down to the bottom of the head.

I'm also having some problems figuring out what the adjustment for the rockers is supposed to be. Looking thru the manual right now and I don't see anything.

[Edit: I'm seeing this at 0.010 in on the intake valves and 0.020 in on the exhaust valves? That sound right?]
 
Matthew, I typed this before I read your latest posts. I stand by what I wrote, but as you said: "What good is a spark if the valves won't move."
The answer, of course, is NONE! First things first, grasshopper.

mattmatthew said:
......................

i figured, if any of the spark plugs weren't working, then if i pulled the wire, the bad plugs would be the ones that didn't produce a change in the sound. plugs 4 and 5 didn't give me any change in motor sound / vibration. maybe these are bad?
Click to expand...

All good up to that test, and it's a good one. Good spark, but no change in engine with wires off - could just be a couple of fouled plugs. I'd change all six of 'em.



mattmatthew said:
,,,and i shocked myself. heh. i know you're not supposed to do that but i figured it was a quick and easy way to see which cylinders may or may not be firing.
Click to expand...

Like that old Hank Williams song ... "I saw the light - I saw the light...."

mattmatthew said:
...i don't have a vacuum tester (perhaps i should get one) but i pulled the hose at the vacuum advance side to see if it was drawing any air (to make sure i had it hooked up to the right carb inlet). it didn't feel like anything was sucking so i moved the hose onto one that was that wasn't being used for anything.
Click to expand...

Vacuum pump is mighty handy and can be used for bleeding brakes, too. But you won't really use it very much. I usually just do the suck test, 'cause I'm right there and the vac pump is not. (don't suck on a gas hose, though! That gets nasty real quick. Don't ask me how I know this!) The vacuum port you said was "not being used for anything" ... I hope it had a cap on it! With the engine idling you should have vacuum at one port and not the other. The one with the vacuum is the "manifold vacuum", and needs to be capped if not used. If that port does have a hose on it, I would just cap it off and address it after we get the idle and power situation fixed. The port with NO vacuum at idle should begin to pull vacuum as you open the throttle. That is "ported vacuum" and it goes to the distributor advance mechanism. Be sure that hose (and all hoses) do not leak, and if it does NOT pull vacuum when you open the throttle I'd bet you've found the problem.

BC
 
64ragtop said:
The port with NO vacuum at idle should begin to pull vacuum as you open the throttle. That is "ported vacuum" and it goes to the distributor advance mechanism. Be sure that hose (and all hoses) do not leak, and if it does NOT pull vacuum when you open the throttle I'd bet you've found the problem.
Click to expand...


Yeah my friend said that port only has a vacuum as RPM increases. Well, makes sense, since I read last night that the vacuum advance was to compensate for changes in load on the motor. I guess I didn't put two and two together.

And yeah, I capped off anything that wasn't being used.

Anyway, picked up 2 push rods and some spares, also a new fuel filter as well since the tank can't be dropped or cleaned just yet. That'll be next on my list of things to do, provided everything works after the rods are replaced.

Also going to put in some fresh plugs. There was a little bit of oil build up on the plugs, possibly due to the rods not being in the holes they were supposed to be in. The old plugs have spark still so might keep those as temporary spares.
 
So I put one of the rods in, but the other won't stay in. It looks like the valve is sticky (probably caused by old oil, old gas, sitting still for 5 years, or a combination of all) and goes into the open position ok but is slow to close (come up). As a result, when the cam brings the push rod down, the rocker doesn't respond fast enough, and the push rod falls out.

I've tried to soak it in PB Blaster (both from the top and through the hole where the spark plug goes) and tapping it with a hammer or hammer/punch. Still comes back up really slow.

Any advice for loosening up a stuck valve without removing the head? Where does it commonly bind up, where the valve seats or on the stem where it passes through the block?



[All this makes me wish I just dropped the damn tank, or at least emptied it while it sat. Except I didn't know any better.]
 
UPDATE

So my friend stopped by after his clutch job and we worked on it together. I moved the fan belt back and forth to free up the stuck valve while he held the rocker on the push rod. The valve was still stuck and we talked about various options like pulling the intake to shoot penetrating oil in.

After looking for a straw to shoot the PB (I lose mine all the time), I found a straw on some carb cleaner, and asked if he wanted to use the straw for the PB. Instead he bent the straw upward at the tip, and used the carb cleaner on the valve in the open position, via the spark plug hole. And with him holding the rocker on the push rod I cranked the motor at the starter relay, and we start to see the valve coming up faster and faster.... Put the sparkplugs back in, let it idle for awhile to see if the push rods would fall out... Put a little more gas on it... And now that thing runs like nobody's business.


Tomorrow I'm going to use the feeler gauge to set the intake and exhaust rockers to the correct gaps.

And hopefully, a test drive. :)

I learned more about my motor today in 9 hours than I have in the entire time I've had this car. It's not over yet.
 
I am doing the same thing tomorrow. I had two bent pushrods that I bent back straight and adjusted as far as they would go. I ran out of adjuster so it has a rough idle, but good enough to drive the 1.2 miles to work each day. I reallllly wish I had your weather, however. Its funny, out of the many slant sixes i've rescued over the years this is the first one i've had sticky valve problems on. All the rest i've been able to cycle a few tanks of gas thru to get the old crap out but that was back in the early 90's. Hell, some of those cars had weeds growing above the roof with the last year of vehicle tabs being in the mid 1980's.
 
Here's a pic I drew of how we got the valve unstuck...

valves_zpsbfe959b1.jpg
 
Just for the future, I don't think I would use PB Blaster inside an engine. Use something with some lubrucating ability. Glad you got it going! The valve would have been stuck in the guide (where the stem comes up).

Newer gasolines (maybe in the last 10-15 years??) are a lot worse about deterioriating from even a few months of sitting.
 
Got my valves adjusted. There was a stumble off idle when pressing the gas like when you're leaving a stop light. The valve adjustment fixed that (I knew the accelerator pump was working as I could see a steady shot into the carb). Also finally installed the offenhauser valve cover after trimming the inside of the cover (the head bolts were keeping it from sealing on the ring around the head). Tomorrow will see one half of the dual exhaust from my 73 duster installed on the 75. Save money, earn chicks!

MattMatt, where are you on your valve adjustment? How'd it go?
 
If by valve adjustment, you mean using the feeler gauges to set the correct distance between the rocker arm and the valve stem, I set the exhaust to 0.020 and the intake to 0.010 after running the car for 10 min and warming up the block.

I took it on a test run today around town. A little bit of stumble on the idle but it accelerates nice and smooth.

Tomorrow I'm going to pull the valve cover and make sure those rods stayed in place. And then test drive it again.

Cooter did you take a pic of your motor after installing the offy?
 
^^thats sexxxy lol

so today, I pulled the valve cover to check my rods after the test drive yesterday... rod had fallen out of cylinder 2 exhaust, and one of the new rods i put in yesterday was bent slightly. not sure why the new one bent, perhaps it was not seated properly at the bottom. and doubly not sure why No. 2 came out either.

(any thoughts why this might've happened?)

when i adjusted the valves yesterday i ran the motor for 10 min, then shut it off and used the feeler gauges to make adjustments.

today i tried slant six dan's advice to do it while running (10-15 min of low to high idle warmup), it was tricky but i think it's seated better now. i also tried to get more consistency between the exhaust and intake adjustments across the cylinders by using the feeler 0.002 above 0.010 and 0.020 inch. i figured the 0.012 and 0.022 should not fit at all, while the 0.010 and 0.020 would just barely fit.

hope i did it right. took a few quick spins around the neighborhood and popped the valve cover to see if anything moved, but so far so good. gonna attempt to drive it to work tomorrow hopefully everything stays where it should be.
 
Check the compression. It loses power under load? Timing chain perhaps? Bad distributor? These Are things to check. I would suspect the last major thing you changed. Just because it's new doesn't mean it can't break! Smelling oil...blow by perhaps? This would suggest a timing problem.
 
And you may still have crud casuing sticking vavles in the guides. Have you added anything to the fuel or oil for cleaning the guides further?
 
my mechanic friend suggested cleaning out the oil by replacing it with transmission fluid as a way to flush the crud out. and then putting fresh new oil inside.

man i'm totally stumped. i've bent 3 push rods that i know of, the car was fine last night, adjusted the valves while hot, drove it to work this morning, and the car sounded absolutely awful coming home, probably bent more push rods... :(

i haven't added anything to the fuel. i did wonder if it was a timing issue, did a general search on the forum last night. like maybe a worn timing chain or maybe the tick marks are off, but i would think that if they were off, i'd have problems on all cylinders, no? what do you guys suggest adding to the fuel?
 
Sreyno said:
Check the compression. It loses power under load? Timing chain perhaps? Bad distributor? These Are things to check. I would suspect the last major thing you changed. Just because it's new doesn't mean it can't break! Smelling oil...blow by perhaps? This would suggest a timing problem.
Click to expand...

you know what, i have been smelling oil. and the car was shuddering really bad on the way home today — no doubt i bent more rods. last night after i made my adjustments the valves were working nice and smooth, idle was good, power was really good.
 
I should add that while I'm testing it and the engine is warm I can do idle and throttle with no problems. But once the motor cools down and sits, say, overnight, the moment I start it in the morning it starts having a really rough idle and then shakes more than usual. This morning startup was a little rough but power was OK... on the way home I was severely lacking torque and power. and the shaking was really bad, plus the smoking.

Maybe you guys are right, when the motor gets cold the gumming up gets worse and thicker.
 
Look for the suggestions on the thread about Avblend...SeaFoam and Marvel Mystery and the auto fluid before the oil change seems to be popular......My neighbor's dad used Rislone down the carb!

You're bending the push rods for a reason; either the rockers are binding really hard (not at all likely). Or something is binding the valves in the guides. Or something is hitting the valves in the cylinders (Bolts in the cylinders? Squirrels hiding their winter larder in your engine? Not likely). #2 seems most likely from all the comments from those in the know.

And 'varnish' may still be slowly coming in from the tank and replenshing the gumminess.

Have you removed the valve cover in the AM and see if all the valves will move? Any recent fill of fresh fuel? Does the engine smooth out after warming up or just get worse? (Sounds like the latter.) The smoking may be from fuel going right through a cylinder via an open exhaust valve into the exhaust.

But my concern is that there is still varnish in the tank/fuel ALONG with the old, bad fule that is detonating and could damage a piston. (That could explain the sounds and the oil smell.) If you can free up the valves and replace pushrods and everything runs smoothly again, then you are OK....for now. But that is why the old gas HAS to be gotten out. I have damaged an engine with bad fuel to where I had rebuild it. All the additives in the world can't fix really bad, old fuel.....
 
Hmm,a Pennzoil motor perhaps? From what you're describing, it seems you need the cylinder head done. If the valves are sticking bad enough to bend pushrods there is something wrong with the head. The valves should be adjusted with the motor warm. It is a solid lifter cam in those engines. There is no give at all.
 
The old fuel and varnish will definitely continue to seize the valves in the valve guides. I assume your two bent pushrods were probably for the two middle intake valves, or at least for two intake valves. I had to compress my springs, remove them with rope in the cylinder, remove the valve seals, soak them in chrysler penetrant for days to get mine free. I also pounded them down too far to get the springs back on and had to yank them back out with the valve keepers back on the valves and a vice grip on the keepers and a rope tied to the vice grips and the other end to a hammer slide. Fun times. Get a new tank and a fuel line from right stuff detailing, stop wasting your time.
 
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