Josh B

Well - bolted everything back together and it still won't fire. I pulled every single plug and I could smell fuel on each one. (brand new plugs) Grounded each one to the intake and got a nice strong spark. I have good oil pressure (5 bar) and the tach is bouning but the car just won't start. Timing marks are exactly on. So frustrated!

Tom M'Guinn

So sorry it's being a pain. Might try a compression check now that it's together, to confirm that leak down issue.

ilikemy944

When you say you got better numbers on the other block - what were the numbers?

brad-cam

Just double checking, when you say timing marks are exactly on, you mean *both* the one on the cam gear and the one on the flywheel through the slot on the bell housing, right ? Also, check to make sure the reference sensor connectors are tight.

Josh B

Leak down on one and two on the other block was closer to 20% and then three and four were more around 30 to 40% with air coming out of the exhaust ports.

That short block probably hasn't been touched in a year at least.

Yup - Cam gear and flywheel marks are right on. Reference sensor connectors are tight.

fast951

Josh, Have you done a compression test? In order to run the engine needs: Spark, Fuel and compression. It sounds that you have Spark and fuel.
If you have compression, I would change the spark plugs just to eliminate a variable. then examine the engine temp sensor wiring, injectors wiring.

Racing Porsche

Josh,

Was this head the same one you had on the car when it was running? If not I would really be looking at that head. It seems to be the only new part. Why did you remove the head?

Sorry to hear this.
Mitch

Papamurphdog

Look for a short in the injector harness. If I remember, you replaced them yes? Even so, it sounds just like the IH issue I had. Even if compression was in the toilet it would still fire and just run crappy. Noid light them and see what you get... if you need and extra hand I can stop by with the noid kit...

theedge

Are your plug wires on in the right order?

Speed and ref sensors both gapped correctly?

Tach bounces? You could try switching the speed and reference sensor plugs anyway. Worst thall happen is nothing.

Fuel pump runs while cranking?

Josh B

Ok - did compression test and the numbers from one to four were 52, 52, 87, 52. When the car was running and I checked them last with the same tester they were at 135 +/- on all four.

I did a leak down test on number 1 with the crank and cam at TDC. I put a rubber latex glove around the opening to the MAF and on the exhaust tip to show me where air was going. Also I left the cap off the AOS. At 100 PSI I had 80 percent leakage. There was nothing coming out of the exhaust and nothing out of the MAF but lots out of the AOS. If I put the cap on the AOS then I got air out of the MAF. I disconnected the line from the AOS to the j pipe and got the same result.

I bolted this same head to my spare block and got only 20% leakeage on cylinder one so I don't think it is the head. I guess I have some sort of major failure in my block. I can't figure out how that can be without major scoring on the cylinder walls - they look fine!

Van

I don't usually quote myself, but you never answered these questions...

Quite clearly you have a combustion camber sealing problem. Either you deck isn't flat, your head gasket is damaged, your block is cracked or your head isn't flat (although it does sit *better* on the other block).

Josh B

Hey Van - sorry - I do appreciate the help.

I think I can narrow those four scenarios down to at least two (deck not flat or block cracked) as I bolted this same head and gasket to a different block and got an acceptable leak down number on cylinder one.

I took a flat edge to the head around the o rings but didn't use the cellophane - just sort of eyeballed it and looked for a high spot but I couldn't find anything.

What could cause the deck to go out of flatness or the block to crack? How could the block crack in such a way that it affected all four cylinder chambers?

Josh B

Also - o rings sit proud only very slightly - maybe like 4 or 5 sheets of office weight paper squished together?

Van

paper is about 0.003" thick, so that would make it 0.012" - 0.015" thick. (I don't know what's recommended for a stock or wide fire ring head gasket.)

You're right - a cracked cylinder usually only affects that one cylinder.

Could there be some deformation, burr, scratch, or bending that's keeping the head partially lifted up? Did this block ever fall and hit the ground? Or have anything heavy drop on it?

Tom M'Guinn

How about the dowel alignment pins? Any chance one of them is cockeyed and/or that there's something in the receiving hole?