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Post Info TOPIC: compression/engine start issues.


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compression/engine start issues.


Hey All

Well it has finally come time to try and fire up the 239 in my 49 Pontiac I've been working on.Still lots to do but most of the big stuff is finished.So I have fuel and got rid of the last fuel leak by installing a new fuel bowl/filter assembly,fuel now going to the rebuilt carb.The motor turns over and I seem to have spark although it seemed a bit weak at first.I did replace the wire from the ignition to the coil as it was frayed in a few places and that seemed to help.I have turned the motor over a couple hundred times now and just won't fire.I do get smoke out of the oil breather but no start.Dist is new,wires are new,plugs are new,rechecked the firing order and made sure it is pointing to cyl 1 at tdc.So someone suggested a compression test so did that tonite.Keep in mind this motor has not run in at least 5 years if not more.I did have the head and oil pan off and the cyl's looked decent.So googled the comp ratio and came up with 110 psi,hope that is correct.First test dry test.

cyl 1 65psi

cyl 2 60 psi

cyl 3 20 psi

cyl 4 45 psi

cyl 5 40 psi

cyl 6 60 psi

put a tablespoon of oil down each hole and tested again

cyl 1 70 psi

cyl 2 70 psi

cyl 3 30 psi

cyl 4 65 psi

cyl 550 psi

cyl 6 90 psi

figured matbe the rings are stuck a bit so dumped in some more oil and let sit for 1/2 hour

cyl 1 100psi

cyl 2 85 psi

cyl 3 50 psi

cyl 4 70 psi

cyl 5 60 psi

cyl 6 90 psi

I turned over the engine to blow the excess oil out and installed the plugs and tried again,much more smoke out the breather and exhaust but still no fire up,seemed like it wanted to a couple times.I took the plugs back out and dumped a medicine cup of oil down each cyl.Going to let sit until I get home tomorrow and check the compression then.I am really hopeing the rings are just a bit sticky but I guess the other final option if this motor is no good is to pull the motor out of the 54 since I have it torn apart while I search for a body replacement and install it in the 49.One is an automatic so not sure what is all involved in mounting the standard to it to make it work in the 49.Any suggestions guys,sometimes at my wits end with this project but I know its 70 percent to done at this point.Hearing the motor fire up would be a great motivator at this point.

 



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Canadian Poncho Superstar!

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Im probably the least qualified to comment here but just a double check for you on your tdc. Mistake is sometimes made when it is at the top for the exhaust stroke instead of the compression. Otherwise usually you at least get a few back fires. Sure some of our experts will pipe up.

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Jerel


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I have been told that it may be a sticking valve situation as well so I will remove the valve covers and lube the valves/lifters as well as see if that helps.Thinking about it this motor may have sat for more like ten years since it ran last but it was running and driving at one point,I did pull the head and oil pan on it and everything looked to be in ok shape.I don't think this one even has 65000 miles on the odometer.

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ok working on it now,did a quick compression test after work and number 1 cyl is up to 120 psi today.others seem to be 80 ish now.removed the valve covers and checked the valves and they all seem to be free as I can rotate them with my fingers,Got it turning over and now getting backfire up through the carb.So I believe I need to find tdc number 1,remove the dist,rotate the motor over until I hit compression again and re stab the dist? I think I may be on the exhaust at tdc and not compression at tdc? Hope I am correct,will post a video later tonite,either it will be running or still puffing through the carb.

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ok working on it now,did a quick compression test after work and number 1 cyl is up to 120 psi today.others seem to be 80 ish now.removed the valve covers and checked the valves and they all seem to be free as I can rotate them with my fingers,Got it turning over and now getting backfire up through the carb.So I believe I need to find tdc number 1,remove the dist,rotate the motor over until I hit compression again and re stab the dist? I think I may be on the exhaust at tdc and not compression at tdc? Hope I am correct,will post a video later tonite,either it will be running or still puffing through the carb.Or do I just have to find tdc pull the dist back,rotate the rotor 180 degrees?

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well no start,puffing at carb,a few big backfires out the exhaust.I will let it soak in some more oil tonite.Timing seems to be correct maybe valve issues? Sorry won"t let me upload the video



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Poncho Master!

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Two things I would check.
1 - TDC compression stroke. Pull the plugs and place your thumb over the #1 plug hole. Have someone bump the engine over until you feel compression building in the cylinder. Now that you are close use a welding rod or coat hanger through the plug hole to find TDC. Align distributor to have one of the towers on the cap inline with the rotor.

2 - Confirm distributor rotation. Place plug wires to spark plugs in firing order and in consideration of rotor rotation.

Best of Success!

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that's what I have been doing,i pulled number 1 plug,i can turn the motor over by hand with the fan and putting my finger over the plug hole to find compression.Then I can look down and see the timing marks on the crankshaft and I am lined up with the udc mark.Pulled the cap and I am lined up with number 1,approx 4 o clock position,lined up with number 1 on dist cap tower.rotation on dist is ccw and have firing order right.All wires have spark I checked,checked the points gap.I am still suspecting ring issues as it seems to be getting better the more I turn it over but still have low compression on 2 and 3 cyl.I may have to re pull the head and check the actual valves and seats.

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I hate to say it but from my experience even a real tired engine with a cylinder or two with real lousy compression should still start. It will just run very poor. If I was betting I would still say distributor position. A second set of eyes can sometimes really help too. Continued good luck.

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Jerel


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Without being able to lay hands on it will be difficult to trouble shoot.

I don't trust timing marks, hence the reason to confirm tdc.

If you have a dwell meter check your point dwell. Even with factory gap setting the dwell maybe off. Adjust the points to meet recommended dwell.

Is the coil healthy?
Is the capacitor good?
Can you power coil with a separate lead direct from the battery to insure full voltage under load?
I'm sure cap, rotor, points, plugs etc are all good??

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The Projects:

1935 Chev 3 Window Std Coupe

1967 Mustang Convertible

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1969 Camaro X11-V8

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1969 2+2 was a 396

1969 2+2 427

1978 Chevy Short Box Step Side 4x4

1980 Harley FXWG

1986 CJ7 Jeep

 



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With all that oil down the bores a hotter set of plugs might fire it up. Worked for me on a tired 283 that had standard plugs.

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Canadian Poncho Superstar!

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Like Jerel said..don't worry too much about compression. Just make sure you have good spark(blue) and fuel. Like Eric said comp at TDC and firing order in the right rotation. Once timing/firing order is set you can pull the coil wire out of the distributor and hold 1/2" away from ground..should get a blue arc when cranking. If it's orange bad coil or coil hooked up backwards(neg goes to dizzy),next I'd check that the accelerator pump is working. With key off and air cleaner removed,pump the throtle by hand,should see fuel squirting out of carb(may need to hold choke open to see). If you have fuel,spark, compression and your timing is right she should flash. Also,all that oil you've been dumping down there is going to hinder start up,it will burn and mix with air/fuel when the cyl fires. Make sure plugs are clean and dry,could also put in some higher octane fuel to help. Good luck and keep us posted. There's nothing like bringing an old girl back to life.



-- Edited by hawkeye5766 on Thursday 31st of May 2018 01:08:21 AM

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hi guys,thanks for all the help as I am quite baffled by this at the moment.My other motor in the 54 fired up quite easily so this one is being a little frustrating.Yes I can pump the carb by hand and I can hear fuel squirting.The carb is a complete rebuild and was tested and tuned before shipping so they say.I know the oil isn't the greatest for it so I did remove all the plugs and turn the motor over a bunch before cleaning and reinstalling the plugs.I am going to drain the fuel tonite and put in fresh gas this stuff,about a jerry cans worth has sat over the winter,maybe its gone bad.It seems so close to firing,i have smoke which tells me some sort of ignition is happening,i have had 3 or 4 backfires out the exhaust and puffing of smoke out the carb so now thinking maybe valve issues?This motor only shows 66,000 on the odometer my 54 has 77,000 and runs like a top.Try some things tonite after work.

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Poncho Master!

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I think you should remove the distributor and rotate it 180 degrees. I had the same problem with a 1950 239 that has sat for years. The engine would almost fire but it would backfire out the exhaust. Check the oil and make sure it is not saturated with gas and washing the cylinder walls. If the oil smells like gas change it. I still have a problem with the 239 as it has a roll to it at idle and think it is a carb problem as when I put my hand on top of the carb it idles a lot better.

Al


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Poncho Master!

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It does sound like an ignition timing issue.

To verify #1 is on the firing stroke pull the valve side cover off again.

Slowly rotate the Engine and watch the valve movement on # 6.

As the exhaust valve is finishing closing the intake valve starts to open.

This point is referred to as the valve overlap position, both valves slightly open.

Both #1 and # 6 will be at TDC but only # 1 will be firing as # 6 will be on overlap.

It can take a few tries to exactly find the overlap position.

At this point your timing mark should be at zero and the piston at TDC.

This is also how you verify cam timing if one suspects a timing chain has jumped.

If the cam is on overlap and the piston isnt at TDC there is a timing chain issue.

With # 6 on overlap, install a plug in the #1 wire and rest the plug on the head.

"Jiggle" the distributor back and forth with the ign you should have the #1 plug fire each time you jiggle.

From there rotate the distributor about 1/2" against rotation to give the ign timing some advance.

It should fre right up !!

Thanks
Randy







-- Edited by GLHS60 on Thursday 31st of May 2018 01:02:08 PM

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well had a little time to work on it tonite found tdc again,and then switched dist 180 degrees.It was much worse for backfiring out the exhaust.Found tdc again and put it back how it was.Checked compression again as I pulled the plugs to check for oil fouling.Now number 6 is up over 110 psi as well like number 1,5 and 4 are decent at 89 psi but 2 and 3 are still low.It acts like it wants to fire,lots of smoke.Anyways drained the fuel and will try with new fuel tomorrow.If not them I am going to pull the head this weekend and check the valves,cylinders again.

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hey all,well still no start even with fresh gas,lots of smoke,a few puffs,a few bangs.Anyways I ended up pulling the head just to dry out the cylinders and take a look.I let someone who knows better then me but I pretty sure the piston and valves on number 3 may be toast.So now if the motor needs rebuilding I guess the option is to pull the motor out of the 54 as I know it runs and drives.Although it is an automatic and this car is a standard.Are the rear of the blocks the same so one can undo the automatic and install the standard? Take a look at the pics and give me your opinion.



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Canadian Poncho Superstar!

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Well Im not trying to be the devils advocate here but I think if your wiring and distributor are good and your carb is working half assed that engine should run no matter how bad a cylinder or two is. I think you are putting too much emphasis on the compression problems. They may well need to be dealt with after but Ive fired some pretty weak engines over the years but am in no way an expert.

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Jerel


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jmont64 wrote:

Well Im not trying to be the devils advocate here but I think if your wiring and distributor are good and your carb is working half assed that engine should run no matter how bad a cylinder or two is. I think you are putting too much emphasis on the compression problems. They may well need to be dealt with after but Ive fired some pretty weak engines over the years but am in no way an expert.


 x2  Now with the head off roll over by hand until intake on #1 opens on downstroke,bring back up to TDC and see where your rotor is pointing. Check #1 plug on cap and see if they line up. Do you have a remote starter switch? Handy little tool! Me..I'd put the head back on...she'll run. Did you check for good spark before removing and get new plugs? Tripple check rotation of rotor and firing order on the cap. I have also poured a couple of tablespoons of fuel down the carb to get flashed.  Keep us posted.

31bGQOOuhNL._SY450_.jpg



-- Edited by hawkeye5766 on Saturday 2nd of June 2018 01:01:19 AM

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Poncho Master!

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Just looking at your compression readings. After you added oil especially the amount you did your readings should have surpassed new spec. That tells me valve issue. Possible tight clearances. Definitely worth a recheck on your gap settings.

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Poncho Master!

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hawkeye5766 wrote:
jmont64 wrote:

Well Im not trying to be the devils advocate here but I think if your wiring and distributor are good and your carb is working half assed that engine should run no matter how bad a cylinder or two is. I think you are putting too much emphasis on the compression problems. They may well need to be dealt with after but Ive fired some pretty weak engines over the years but am in no way an expert.


 x2  Now with the head off roll over by hand until intake on #1 opens on downstroke,bring back up to TDC and see where your rotor is pointing. Check #1 plug on cap and see if they line up. Do you have a remote starter switch? Handy little tool! Me..I'd put the head back on...she'll run. Did you check for good spark before removing and get new plugs? Tripple check rotation of rotor and firing order on the cap. I have also poured a couple of tablespoons of fuel down the carb to get flashed.  Keep us posted.

31bGQOOuhNL._SY450_.jpg



-- Edited by hawkeye5766 on Saturday 2nd of June 2018 01:01:19 AM


 And, at exactly the same time, #6 valves will be on overlap, if the timing chain hasn't jumped !!

 

Thanks

Randy



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well hate to say it but I have all but given up on this motor.Had the head off,did the tdc thing,i have valve overlap on 6 ,the dist was slightly off so I turn ed it so it was perfectly lined up on one.Unfortunetly after all that the motor still refuses to fire.I have tried 2 distribiutors,2 coils,have spark at coil,have spark at plugs,have fuel.It just will not fire.Going to try my other carb,but don't think that's the issue.So frustrated at this point,going to sleep on it do some reading,see if I don't have something wrong somewhere.

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Poncho Master!

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Sounds like you need to host a CP garage coffee get together. More eyes the better. Before the beer of course. Lol. 



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omg guys sorry I did the blond thing.So as I sat reading first I thought what valve did I time it off?.Took the head off again and timed it to the intake valve because I was thinking maybe I did the exhaust on number one instead.Then checked the dist again,then as i'm putting the cap back on I realize that hey dummy the dist turns ccw not cw like a normal engine.Sure enough had the wires on backwards.Changed it around and after some more gas pumping and lots of turning over it actually fired up and ran for 5 minutes.Really smoky but hey it hasn't run for at least 15 years of more.Thanks for all the help,sorry for the bitchin,its time for a beer!!!!!!!!


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Poncho Master!

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You better go buy a new bigger shirt with your chest all puffed up from success!!

Congrats

Thanks
Randy



-- Edited by GLHS60 on Saturday 2nd of June 2018 08:35:52 PM

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