86 Scottsdale - No start

[BAChevyMan]

Originally Posted by cadillac_al

If you really want to start at square one, you should do a compression check. Then check your timing tab/balancer marks. It does kinda sound like the timing chain jumped a tooth but personally I don't believe chevys jump time as easy as other engines. I had a 305 that the timing chain got so loose it wore a hole clean through the timing cover. With good compression and an accurate timing mark it should fire right up.

I was a little confused about a previous post about holding it to the floor to start it. That should not be necessary unless it is really flooded. It is harder on the starter to crank it with the throttle open.

Well the reason I was holding the accelerator to the floor is to try to start it, basically testing if its flooding. My timing light fires off every cycle so I have spark, and if I crank long enough I see clouds of unburnt fuel out of the exhaust. So... I have spark, and I have fuel. There are no air leaks, I already fixed any air leaks I did have. So pretty much at this point... its gotta either be timing or compression. My compression tester is at work though so I am gonna have to do that later. But I am probably going to do compression test and if that's not revealing, going to rip apart the front of the engine to verify timing.

[my86lb]

replace you magnectic pick up coil
you will need to remove your distributor
to replace

[BAChevyMan]

Originally Posted by my86lb

replace you magnectic pick up coil
you will need to remove your distributor
to replace

Aint that what controls the spark? Because if so... spark is not my issue. If I connect my timing light it flashes rhythmically without fail.

[geezer#99]

I believe He already did!

Why tear apart the front of the engine to verify timing.
30 minute job with a piston stop.
Info here.


https://www.crankshaftcoalition.com/...op_dead_center

[BAChevyMan]

Originally Posted by geezer#99

I believe He already did!

Why tear apart the front of the engine to verify timing.
30 minute job with a piston stop.
Info here.


https://www.crankshaftcoalition.com/...op_dead_center

I have just never heard of a piston stop, not even sure how it works. Nor do I have one. It does give me an excuse to chrome out my timing cover. For $120 I could always delete the chain and convert it to gear timing... lol, jk. I'll look into that link you gave me, or find a video, that typically works better for me.

[geezer#99]

You can buy a piston stop at summit racing or make one from an old plug.
Just knock the porcelain and electrode out, thread the hole for a bolt and locknut and have at it.
New or different timing cover still doesn’t remove the need to check your timing marks.
Gear drive doesn’t change that need either.
Pic a video or two.

https://www.youtube.com/results?sear...+stop+on+a+sbc

[BAChevyMan]

Originally Posted by geezer#99

You can buy a piston stop at summit racing or make one from an old plug.
Just knock the porcelain and electrode out, thread the hole for a bolt and locknut and have at it.
New or different timing cover still doesn’t remove the need to check your timing marks.
Gear drive doesn’t change that need either.
Pic a video or two.

https://www.youtube.com/results?sear...+stop+on+a+sbc

still slightly confused on where to set the stop tool... but it seems like it doesn't necessarily matter because the piston is stopping somewhere near TDC but not at TDC since TDC is in the middle of the two. Is that accurate?

[LS short box]

As I said above screw in the piston stop and turn the engine over with a wrench until #1 piston hits the piston stop. Pull all the plugs so you easily turn the engine over. Should of said that before. Mark the balancer. Then rotate the engine in the opposite direction until it comes up against piston stop. Again mark the balancer. Top dead center will be half way between the two marks.
A piston stop is typically used to degree in a cam.
Another thought. OP said he knows he has spark because his timing light flashes when he cranks it. Doesn't mean its good spark. A properly working HEI should create a really nice blue spark that will easily jump 1/4" to ground. Back in the day we had a Sun machine and a HEI would put out 40,000 volts to the plug. Just a thought.

[geezer#99]

Yup!

[cadillac_al]

Dude, I hate to be a dick but you can't call yourself a mechanic if you don't know what a piston stop is. That's why I mentioned there aren't many mechanics left anymore. No problem though, that's why everybody is trying to walk you through this basic stuff. You're getting there.

Personally I never needed a piston stop because I don't need to know the exact degree where TDC is. If it's off an inch or more then I can see the problem. This only comes up with mis-matched balancer and timing cover issues (which you may have). I can use a pencil and get it close enough for my needs. If I was actually degreeing a radical cam I would worry more about accuracy.

[BAChevyMan]

Originally Posted by cadillac_al

Dude, I hate to be a dick but you can't call yourself a mechanic if you don't know what a piston stop is. That's why I mentioned there aren't many mechanics left anymore. No problem though, that's why everybody is trying to walk you through this basic stuff. You're getting there.

Personally I never needed a piston stop because I don't need to know the exact degree where TDC is. If it's off an inch or more then I can see the problem. This only comes up with mis-matched balancer and timing cover issues (which you may have). I can use a pencil and get it close enough for my needs. If I was actually degreeing a radical cam I would worry more about accuracy.

Whatever dick, I have a certificate from an automotive school that dont teach you **** about piston stops or how to use them. Or to work on classic cars. I am ase certified, have 4 years of experience. I also did 2 head gaskets in a 98 malibu 3.1, and a 2006 saab 9-5 before I became a mechanic. So **** you on saying I'm not a mechanic because of not knowing what a piston stop is or how to use it. Also, I have never needed a piston stop.

[my86lb]

Originally Posted by BAChevyMan

Aint that what controls the spark? Because if so... spark is not my issue. If I connect my timing light it flashes rhythmically without fail.

how old is your distributor? yes you can a spark but it will be very weak

[BAChevyMan]

Originally Posted by my86lb

how old is your distributor? yes you can a spark but it will be very weak

My spark tester and compression tester are both at work so I cannot verify compression and spark until I bring them home. Also gonna see if the tool trucks have a piston stop. For all I know the distributor could very well be as old as the truck its self.

[my86lb]

Originally Posted by BAChevyMan

My spark tester and compression tester are both at work so I cannot verify compression and spark until I bring them home. Also gonna see if the tool trucks have a piston stop. For all I know the distributor could very well be as old as the truck its self.

you can have a very weak spark once you replace the pick up coil you will have covered everything in the distributor. yes you have replaced the ignition coil but not the pick up coil.

[LS short box]

Just a note on compression testing and you may know this. All the spark plugs should be out and the carb butter flies should be blocked to the wide open position.
Up here in sunny MN back in the day when carbs were typical many times cars were brought into the shop when it -20 plus out and because the chokes weren't set properly flooded the engine with gas. Standard procedure was to drain the oil to get the gas out of the oil.
Then pull all the plugs, crank it over a bit to clear the gas. Be careful and pull the 12 volt lead off the distributor so you don't get a spark and start a fire from the gas out of the cylinders. Ask me how I know!. Then squirt a bit of oil into each cylinder to get compression back because if you really had a flooded engine the over load of gas washes the rings and you lose compression. Crank it over a bit and then reinstall the plugs and give it a shot. Easy to do and doesn't cost anything except the oil change.

[BAChevyMan]

Originally Posted by LS short box

Just a note on compression testing and you may know this. All the spark plugs should be out and the carb butter flies should be blocked to the wide open position.
Up here in sunny MN back in the day when carbs were typical many times cars were brought into the shop when it -20 plus out and because the chokes weren't set properly flooded the engine with gas. Standard procedure was to drain the oil to get the gas out of the oil.
Then pull all the plugs, crank it over a bit to clear the gas. Be careful and pull the 12 volt lead off the distributor so you don't get a spark and start a fire from the gas out of the cylinders. Ask me how I know!. Then squirt a bit of oil into each cylinder to get compression back because if you really had a flooded engine the over load of gas washes the rings and you lose compression. Crank it over a bit and then reinstall the plugs and give it a shot. Easy to do and doesn't cost anything except the oil change.

Well I kenw most of that, but thanks for making sure... that bit about the butterflys being opened I didn't know since I haven't worked on many carburetored vehicles. On another note, think I should pull the fuel line off the carb and put the other end into a gas can? Can't exactly disable a mechanical fuel pump.

[LS short box]

Ok one more thing. This a bit of a "Bubba" fix thing but I use it all the time when I'm changing valve springs on a LS build. In lieu of using compressed air to hold the valve up while I replace the valve spring I thread in thru the spark plug hole small length of cloth line rope and the bring the piston up against the rope to hold the valve in place while I replace the valve spring. Works great.
So in lieu of a proper piston stop the the cloth line rope could be a cheap piston stop. Not quite as accurate as real hard stop piston stop but it will get you close.

[LS short box]

The needle and seat in the carb should prevent more fuel into the engine as you crank it. Holding the butter flies open don't affect the needle and seat operation. But having said that crank it and see if it's dumping fuel into the engine.
Again back in the day I don't recall disconnecting the fuel line but it's been 30 plus years.

[BAChevyMan]

Originally Posted by LS short box

The needle and seat in the carb should prevent more fuel into the engine as you crank it. Holding the butter flies open don't affect the needle and seat operation. But having said that crank it and see if it's dumping fuel into the engine.
Again back in the day I don't recall disconnecting the fuel line but it's been 30 plus years.

Yeah, I am used to pulling fuel pump relays... about the oldest vehicle I touch now is around a 1992. Nothing carbureted though.

[BAChevyMan]

Well thanks to everyone that threw in their 2 cents to help my no start... my conclusion is low compression because of washed cylinders. I only got compression on 2 cylinders before my compression tester stopped holding pressure. Gonna see if replacing the Schrader valve in the tester. Plugs smelled fuel fouled this time when I pulled them out. I threw in the old plugs that I pulled out of the truck and it fired right up. So I reset my carb and got a new set of ACDelco's to put in. Had NGK's (Figured they were alright since its the only spark plug used in my SAAB), gonna swap them in once the truck cools down.

[Palf70Step]

Glad you got it running again

[1976gmc20]

Originally Posted by BAChevyMan

Well thanks to everyone that threw in their 2 cents to help my no start... my conclusion is low compression because of washed cylinders. I only got compression on 2 cylinders before my compression tester stopped holding pressure. Gonna see if replacing the Schrader valve in the tester. Plugs smelled fuel fouled this time when I pulled them out. I threw in the old plugs that I pulled out of the truck and it fired right up. So I reset my carb and got a new set of ACDelco's to put in. Had NGK's (Figured they were alright since its the only spark plug used in my SAAB), gonna swap them in once the truck cools down.

Chicken and egg ?????

I once put two brand new Champions in a Cat pony motor and it wouldn't even putt! I don't remember what the deal was with the ones I pulled out, but somebody gave me a couple of old Autolites out of a junk bucket, and it fired right up. I think they were still in there when I traded off the Cat.

Some brands of plugs just don't work in some engines. Doesn't make sense, but ......

[BAChevyMan]

Originally Posted by 1976gmc20

Chicken and egg ?????

I once put two brand new Champions in a Cat pony motor and it wouldn't even putt! I don't remember what the deal was with the ones I pulled out, but somebody gave me a couple of old Autolites out of a junk bucket, and it fired right up. I think they were still in there when I traded off the Cat.

Some brands of plugs just don't work in some engines. Doesn't make sense, but ......

Funny thing is... it was autolights that I put in that made it start. I even cracked the insulator on 2 plugs going in and it still rolled down the road like a champ. It dont start worh a damn in the cold though. I think I need to check the instalation of my electric choke.