Multiple cylinders with no compression.

[dcj63000]

I have an AE 1600 1971 engine and cant get it to start. Engine fires and sounds SO CLOSE but just wont go. Running a Bosch 009 and 34 PICT3 carb. Carb has been rebuilt and I have compufire electric ignition.

I went to do a compression test and got terrible results. Cylinder 1 had compression, ~140 psi. Numbers 2 3 and 4 did not even register on my gauge, didnt even move. I tried them multiple times wet and dry. The valves have been set to .006. Pulled the heads to have a look at the pistons. Running 90.5 Mahle Pistons. No damage to the piston heads and the rods look good. No valves are sticking and seem to be seating well.

Thoughts? Thank you for any ideas.

[BUGGUTZ]

Back your rockers off completely and try. Do you hear any hiss? Turn by hand and listen to the oil fill, carb and exhaust.
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66 Baja
73 standard
14 Jetta TDI
95 Escort
89 CUMMINS in whats left of a dodge body

Everyones gotta be somewhere!

[enjoyther1de]

Tourqe your heads while your at it.
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HBB took me to BBV.

[Mal evolent]

squirt oil into the non performers. if you get compression back, it's rings.
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73 Beetle Baja, Ghia front brakes, Type 3 rear brakes, 2220 ( 94 X 80 ), Weber Progressive, Bosch SVDA, '97 Mustang seats

Baja Bugs for Volkswagen Virgins: Index

[dcj63000]

Should have mentioned, I currently have the heads off to inspect the cylinders/pistons. Everything looks* normal. I am going to put the heads back on this weekend, I will torque them to spec and try backing off the rockers like suggested.

I did try the wet test with no change.

Ill post up if I figure anything out, Thanks!

[dirtslinger]

If you have the heads off, why not throw some new cylinders and pistons on it. Or at least rings.

[dcj63000]

Put the heads back on without the rocker arms so the valves would be fully seated. Ran some air through the spark plug holes and could not feel any leakage through the intakes, as well as through the exhaust, still no air escaping.

Seems like valves are seating fine.

I would love to replace the pistons and cylinders (cylinders are rusty on the outside) I just want to be sure they are the problem before I drop that much money.

Possible rings are stuck/sticking?

[phoenixragtop]

you can do a leak down test with motor out of car. That will show what the problem is.
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http://www.youtube.com/watch?v=7Wp3Quepf6c

[dcj63000]

Put the rockers back on and all, adjusted valves again, did another round of compression testing. Number one was still fine.
2 - 0, 15 wet
3 - 15, 60 wet
4 - 0, 20 wet

Looks like pistons/rings are the winner. maybe i didnt have enough oil the first rounds of the wet tests

[dcj63000]

So I replaced the rings and cleaned everything up and still have 0/little compression in 2 3 and 4. I made a leak down adapter:
https://www.youtube.com/watch?v=fmavwDldl8M

There is air coming from the #2 intake Need to replace valve.

On all the other cylinders the air escapes from the push rod tubes, I plugged them with paper towels and the air escapes from the oil filler.

Is there any point to buying the actual leak down tester and checking percentages or should I just replace the full P&C set?

Also...when replacing the rings i noticed that the pistons were able to slide out of the bottoms of the cylinders with the rings on. Is this normal or an indication that the cylinders are no good?

[Dale M.]

Air coming out of pushrod tubes or oil filler means you have "leakage" past your rings.... IF rings are new and not seated, results will be alarming.....

You can throw way the concept in YOUTUBE video as its very crude...

Try this the with parts you have...Plus a few additional ones...

http://vmaxoutlaw.com/tech/leakdown_tester.htm

Yeah I know its from a motor cycle page but concept is exactly same....


Dale
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"Kellison Sand Piper Roadster" For Street & Show.
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All suggestions and advice are purely my own opinion. You are free to ignore them if you wish ...

[dcj63000]

Is it possible that the rings on #2 #3 and #4 are simply not seated yet but #1 is?

I have not tried to start the engine, just did the compression test after I got it all put back together.

[Dale M.]

[I Ride Sand]

How are you sure the valves are actually seating correctly? You said there is air coming from the number 2 intake, whats been done to address that? Just throwing in a new valve probably wont fix it as the seats wont match of its ever been reground.

While you have the motor out and the heads nearly off anyway, pop out the valves and really give the heads a good inspection. Check the play in the valve guide, too much here will let the valve close without seating properly. If they all check out, buy some machinists dye and some lapping compound. Put a thin layer of dye on both the valve and the seat and use a very small amount of lapping compound and spin the valve against the seat by hand. after about 30 seconds, pop the valve back out and look and see if the dye is gone completely from both valve and seat, is yes, move on, if no have a valve job done on it.

There is really a lot more to be on the look out for when checking the seats such as contact width, pitting, contact location, seat and valve wear, but this should get you a better idea what is going on. if there is a funky valve or three, it would cause a low compression. If your rings are worn it just adds to the problem.

lets say the valves check out. lets move on to cylinders. I see you have put new rings in trying to find the problem. no bueno... the rings and the cylinders have to wear in together before they will seat. Thats why a good hone on the cylinders is soooo important. The hone marks actually act sort of like a file to very slightly cut the rings to sit 100% against the cylinder across its entire circumference. So, how worn are the cylinders? do they have a ridge at the top where the ring stops moving upward, or are they dead smooth? the ridge may be livable as long as it is within spec, but i cant remember the spec.... someone else probably knows it. Do you have the tools to check for roundness of the cylinders? This will be a bore gauge and a micrometer. An oval cylinder wont seal to a circular ring. Also check the clearance between the cylinder and the piston. Too much here and you may be wasting your time with those barrels and pistons anyway.

Another thing to check is to see if the cylinders are the same height. I actually bought an engine that had been thrown together from junk the guy had laying around, and a missmatched set of cylinders had been used. It had two 87mm cylinders, and two 85.5mm cylinders. the 87's had been cut down to bump compression, and the others were not. They put one 87 and one 85.5 on each bank, causing the heads to not sit flat. I could not figure why the thing ran like crap for 3 days after I bought it until I saw smoke coming from between the cylinders and heads...

You want to make 100% sure it will have compression the next time it goes together?

Step 1: have valves ground.
Step 2: new piston/cylinder kit.
Step 3: put it together.

[I Ride Sand]

double post

[dcj63000]

I am building the leak down tester today. I know the #2 valve needs work before I move on. I am thinking to have the heads checked out at a local shop.

I verified all the cylinders matched part numbers and they still had the cross hatch marks on the insides so i did not hone them. Before placing piston rings I checked ring end gaps and they checked out to .006. I did not measure them with the mentioned tools so it is deff possible they are out of shape at some point. I did not check the ridge. Thanks for the input!

[EnjoyNukaCola]

What does a hiss tell you when turning by hand?
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"when i go to drive it i get to like 5-10 mph it is at high rpms and gets higher the faster i go when i shift up to second the rpms drop is this normal or what and this is my first vw please help"

[I Ride Sand]

[Dr OnHolliday]

Its your cam, valves or head to cylinder leakage. Engines will run with some really marginal
rings.
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1965 Type 1 sunroof Baja / about 70k miles on self-rebuilt '74 1600 and counting / SP heads and aftermarket valve keepers / non-doghouse shroud with external cooler and filter / 1.5 qt extended sump / Weber 32/36 DFAV progressive carb / 009 dist with Pertronix / 1.25 ratio rockers and ball adjusters / 1.5" stainless steel J-pipes and carbon steel baja exhaust

[dcj63000]

Took the head to local shop and they said they fixed the sticky valve. Said all the other valves were in good shape. They went to hone the cylinders and said they were warped. Bought a set of 92 P&C's. Finally had time to get them installed yesterday.

Set em up with .006 valve clearance and had 0 compression reading on all cylinders. Backed them all out to .008.... 1 and 2 show 0 lbs while 3 shows 60 lbs and 4 shows 15 lbs. Read the same with 2 different testers.

I know all the rings are staggered, I pulled all the pistons out to check before install......

Pressurized the cylinders and #2 Intake still leaking a small amount of air at TDC. It seems the shop I went to did not fix that valve (?). 1 3 and 4 not leaking air but still not correct compression.

Anything need to be set up differently with bigger pistons? I dont know.