Car Has No Compression On #4, ...can I take the valve cover off without draining oil? |
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
Car Has No Compression On #4, ...can I take the valve cover off without draining oil? |
7TPorsh |
Jun 30 2016, 12:30 PM
Post
#1
|
7T Porsh Group: Members Posts: 2,691 Joined: 27-March 06 From: Glendale Ca Member No.: 5,782 Region Association: Southern California |
A problem has recenly developed and I can't figure it out. The car starts up easy and on the first crank. I let it warm up a few minutes and drive....It drives fine as it's warming up.
Then after about 15 or 20 minutes the engine starts developing a shudder. Idles fine but and can run ok under low load but under some load the #4 cylinder starts popping and firing up through the carb. feels like it's running 3 cylinders and wasting gas. It's been suggested I do a compression test but I'm thinking if the engine runs great cold and while warmin up; the compression should be ok. Is there a case where comprression is ok when cold but low when hot? Can't figure out why car runs great when starts f'n up. 1.7 with dual weber 40 IDFs |
Dave_Darling |
Jul 8 2016, 02:49 PM
Post
#2
|
914 Idiot Group: Members Posts: 14,991 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California |
Look at the valve tips when each cylinder is on TDC. If one of the valves on #3 is sitting with the tip closer to the head, it's a dropped valve seat.
With zero compression, the problem is almost certainly serious enough that to fix it you will need to drop the engine and remove the head. At a minimum. --DD |
jcd914 |
Jul 8 2016, 05:16 PM
Post
#3
|
Advanced Member Group: Members Posts: 2,081 Joined: 7-February 08 From: Sacramento, CA Member No.: 8,684 Region Association: Northern California |
Look at the valve tips when each cylinder is on TDC. If one of the valves on #3 is sitting with the tip closer to the head, it's a dropped valve seat. With zero compression, the problem is almost certainly serious enough that to fix it you will need to drop the engine and remove the head. At a minimum. --DD (IMG:style_emoticons/default/agree.gif) Several things can cause low compression. Not many things will cause NO compression. Worn out rings won't give you 0 compression. A tight valve won't give you 0 compression. Carboned up, poor seating valves won't give you 0 compression. Dropped valve seat will. Badly burned valves will. Hole in a piston will. Leakdown can help you find where the leak is and then you can figure out what happened. Jim |
Lo-Fi Version | Time is now: 17th June 2024 - 09:41 AM |
All rights reserved 914World.com © since 2002 |
914World.com is the fastest growing online 914 community! We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ... |