All this work and low Compression - PeachParts Mercedes-Benz Forum

RC4U12 · #1 03-06-2009, 10:28 AM

I dont know why i didnt check compression first..but after all this work i have done to the car i finally checked and 95-100 per cyl.,,or will this goe up as its been sitting for 2 months not started????.oh well ..
.I did get my chain all installed and rewired the injectors which are from my 350slc as the others are so big for Mega Squirt..it will have to do for now.i figure this engine has many miles bing this is probably 3rd chain and the tranny pan was punded out from inside and the tranny filter was just awfull,,i dont know how it sucked fluid and all the dirt fine stuff at the bottom....Jeff

RC4U12 · #2 03-06-2009, 07:12 PM

I rechecked the compression and 1 has 125, 2 has 65, and 3 has 95 and 4 has 95..cyl 5-8 has 155

after oil 3and 4 has 120adn 140 but 2 only 75

seems strange and this is cold and not run for a while..i assume broken rings?? i hope i cna run the car until next winter and take out and redo the 3 cylinders ..Jeff

TOPGUN · #3 03-06-2009, 10:13 PM

The four low values are all the same bank. It could be valves. Timing chain trouble? Before or after install. Just a guess. Good Luck.

RC4U12 · #4 03-06-2009, 11:02 PM

i just changed the timing chain.and it is on the marks and 2 degrees advanced like its supposed to be..Jeff

JonL · #5 03-06-2009, 11:09 PM

If it has hydraulic lifters they could be not fully pumped up yet. It could have carbon or rust on the valves where they seat. It could have a little rust on the valve stems causing the valves to close a little slowly. It could have some sticky rings. All of these things can improve from running a little while. It could also be something much worse, but I would try not to worry until you've run the engine for a while, then check the compression hot. Don't forget to check it with the throttle held wide open. Good luck.

RC4U12 · #6 03-07-2009, 12:37 AM

'74's have solid lifters and its only been 6 or 8 weeks since ran not years..but i am hoping valves as heads i was going to do next winter ..Jeff

JonL · #7 03-07-2009, 12:55 AM

Didn't know the year of your car. Also check for tight valves.
Two months is enough time for things to get a little rust on them, or get a little sticky.

RC4U12 · #8 03-07-2009, 10:02 AM

i updated my profile..should have done that ..anyway i did adjust the valves when i installed chain and only a few minor adjustments needed..i think it's bad valve on #2 and rings on 3-4 ..Will running with bad or broken ring wreck cylinder or probably ok to run till next winter? Jeff

JonL · #9 03-07-2009, 10:21 AM

If it was running fairly well before, I think it is unlikely you will do any damage by running it some more. I still think it may "get better" after you run it a while. Of course if things don't seem right after you start it (unusual noises, smoke, etc...) then DON'T run it for long, and investigate further.

RC4U12 · #10 03-10-2009, 10:59 PM

WOW today i bought new plugs and before installing i moved the compresion testor and noticed the O-Ring was tore{very old} ..thats why the last bank was low compression..retested today and all are the same within 5 at 155....and after finaly starting itran just slightly rough after tuning megasquirt..put the fule pressure guage on and only 18 psi ....That doesnt work i tried turning nut on regulaterand nothing.. put the one from the '73 on and THERE it is 39 psi..but it leaks down right away..bad fuel pump?? as the cold start is not hooked up as dont need it. But idles so nice ohhh..just strange that most are rich at idle and my engine shows 14AFR and below to get nice smooth idle..Jeff