Can bad compression prevent my e34 from starting?

[gmannino]

I tested cylinder 1 thru 5 at around 60 psi. Cylinder 6 is at 140 psi. I still cannot get my car started, would this be due to low compression?

[winfred]

60 is not enough to run 160 would be around normal, very unsusal for a m20 motor to loose compression, it just up and die? what's the story? i may be able to direct you with some more info

[632 Regal]

probably fuel wash, pour a tablespoon of trans fluid in the low cylinders to help seal the rings back up.

[grave77]

60 is very low, u might have cracked head, does it keep pressure when u check it? if it's leaking then a crackdown is there. a bad AFM would cause a bad start for normal engine, so with low compression it would be wors. as the vacuum required for efi to work would be not enough.

[ajt3nc]

I agree that that sounds like a gasket on the good side or a warped head.
Even if the rings were wasted you should hold more than that.
THE BIG QUESTION,,,, have you done a leakdown test?

[632 Regal]

you cant check compression or a leakdown with a fuel washed cylinder.

I agree that that sounds like a gasket on the good side or a warped head.
Even if the rings were wasted you should hold more than that.
THE BIG QUESTION,,,, have you done a leakdown test?

[gmannino]

What is Fuel washed? elaborate on that?? The cylinder head is brand new. It ran fine for about 4 hours. Then i had a coolant hose break, now my car wont start. here is the thread with more details and some of the stuff i already troubleshooted.

http://www.bimmer.info/forum/showthread.php?t=20862

[632 Regal]

fuel wash is where fuel is getting into the cylinders but it isnt being fired. It washes the oil from the pistons and compression rings creating a visious circle where more fuel dumps cause it thinks its going to fire. After a while you should be able to smell fuel in the oil.

Adding a tablespoon or so of trans fluid usually temporarily seals the rings enough for the engine to start and get its own oil up there sealing things.

Good luck!

[grave77]

mate, a yellow spark is a good spark, it means that it has good temparature. you sais that the water hose blew up then you had this problem. I'm afrade that M20 Engine is very vragile to heat issues, most probably you need to check the oil / water leaks ( chocolate colore mixutre ) your new head might got bent too ... that depends on how much ur engine heated up. the way you explained the compression rating seems to show gasket problem or head got twisted. try to listen more to the engine sound when it cranks ... does it sound smooth easy or rough? twisted head will make the engine sound smoother when u crank it and faster. more compression will make it crank slower and rougher.

[E34-520iSE]

Fuel wash is so easy to do on an M20 (and M50, my father in law did it yesterday in his 520i. I did laugh). I can tell you how to get it to happen on command if you're really interested. The resulting low compression will fool you into thinking the head gasket's gone! Pull the plugs out, pour a bit of light oil in each low cylinder, put the plugs back. Crank it and -vroom- it's running!

Easy peasy,

Shaun

[gmannino]

I will try to pump some ATF into those cylinders as soon as I can.

As far as how it sounds when I try to start it, it sounds like it wants to fire but doesnt. You can't really hear the engine turn over but it does sound like its trying. It even hiccups if you crank it long enough but it never grabs enough to fire up.
I noticed the day after that I cranked it and it fired up but quickly died on me. After that I never got it started again. Since i'm getting compression, the crankshaft is obviously turning, and all the belts are turning as normal during crank. The cam and valves are moving by peeking into the oil fill.

I can see some fuel on the spark plugs but I am not 100 percent certain that enough fuel is getting into the cylinder. How can is tell definetly, that sufficent fuel is getting into each cylinder?