B5 Fanboy

Hey guys, I'm having some problems with this A4 I just purchased. I bought it not running. It cranks, almost fires but it doesn't quite get there. It has spark, and fuel. Starting fluid does nothing. I did a compression test and here are my results.

Drivers side head:
180
180
180

Passenger side head:
122
121
123

I heard the compression is supposed to be at 150PSI. Why the heck is it at 180? I don't have any timing codes. Anyone know what might cause the no start? Or the high compression?

Also, this is the 3.0L V6.

Brian Cecil

High compression can be caused by a buildup of deposits in the combustion chamber or on the piston crowns. Or by milling the bottom of the head which reduces combustion chamber volume. Warped cylinder heads are often milled after an episode of overheating to flatten their bottom surface and provide a good seal for the head gasket.

B5 Fanboy

There is also a code for P0321 engine speed sensor implausible signal. The sensor itself is new, the previous owner replaced it. I double checked to be sure, the sensor looked brand spankin new. I figured this might be why it doesn't run, but what else would make it have an implausible signal?

Lornnn

The video shows both low and low-quality coolant. That definitely isn't G12 or the like.

Maybe head gasket issues led to your compression problems.

Also Ross-Tech says this about the P0321:
"When an engine will not start due to mechanical timing or spark/fuel related issues it is not uncommon to set G28/G40/G163 fault codes. The basics should be checked if this code returns after extended craning and a no-start with a new sensor installed."

Prospeeder

um id be more worried the low compression on the other side. Like cam timing on that side is off, or the lobes on the cam are wearing. The 180 could just be your tester, they arnt usually accurate. And 150lb is the minimum limit, not Max. 180 is a healthy number for these higher compression non turbo engines.

B5 Fanboy

Update: car is now running. Timing belt was opened up and guess what? It was ALL brand new. Belt, pump everything. Upon closer inspection, we realized the passenger head was a full turn off, causing a backfire. Some idiot didn't set the timing up right. We didn't have the tool to use on these 3.0 engine so we did it the old school way with a long screwdriver. Put it all back together, and it started right up. It runs smooth as butter. I have taken it up to 6000 rpms to make sure the variable valve timing was working properly, and it seems as though it is! It runs great. So far I'm on my second day of daily driving, no issues. And the best part? I didn't have to spend any money on parts. I can't believe none of the valves weren't bent.

Prospeeder

Great job, carful, everyone here will accost you for not using all the special tools lol. I love how this worked out perfectly without them.

lyleswk

Good troubleshooting. Looking back on this, it is easy now to see why each bank was behaving the way they did.