190e 2.5 16v - no oil pressure or combustion pressure after part rebuild - Help! - PeachParts Mercedes-Benz Forum

Uk Merc Man · #1 05-25-2007, 02:44 PM

hi all....well a bad day today...

a while back my main chain rail plastic bit busted up on start up.....i stripped the engine and replaced chain, tensioner, upper/lower guide rails and have obviosuly removed/replaced the associated bits and pieces to get to it...today I got the car to a point where I could try to start it.....

Filled it with oil, water, ps fluid, etc, etc - plug out and leads off, cranked and no oil pressure on gauge in car......cranked for ages, nothing!

Attached pressue gauge to do a compression check on the pistons - NOTHING! The needle didnt move AT ALL on any of the 4 cylinders!!

The engine is spinning and the cams are going round.....I haven't had the head off but with both manifolds removed during the rebuild I could see the valves and they looked fine......??

I had a timing chain failure.....could I have the cam timing SO FAR OUT, that the engine has no piston compression?

The engine is rotating, it sounds fine, the cams are turning and from what i can see through the oil cap, the valves are opening/closing....

Any one care to point me in the right direction?

Cheers!

jhodg5ck · #2 05-25-2007, 04:09 PM

Sounds like your oil pump has lost it's prime.. I've been down this road before w/ quite a few other MB engines and the only sure fire way I have found to remedy it is drain the oil, drop the pan, drop the pump and fill it w/ Very thick oil (ie, motor honey/STP/lucas heavy duty oil stabilizer etc, etc..). Re-install everything as quickly as you can (I usually only install 1/4 of the pan bolts just to get oil back in the pan and get the car cranking ASAP). Once I have pressure (which should come up in a matter of seconds) re-install the remainder of the pan bolts etc..

As for no compression, I imagine it's possible to have the timing that far off, but my concern is I do not think it possible to have the timing that far off and not have piston to valve contact. I would pull the head and make sure when you turn the engine over by hand that you are not getting excess clearance b/w the cam and lifter.

Hope it works out for you!

Jonathan

Uk Merc Man · #3 05-26-2007, 12:18 PM

UPDATE: now have oil pressure

but still no combustion chamber pressure...

I swapped the cam timing 180d just in case but nothing, the pressue gauge doesn't move, not even a little bit...

ideas?

jhodg5ck · #4 05-26-2007, 12:47 PM

If that's the case sounds like you have bent valves :-/

Jonathan

Uk Merc Man · #5 05-26-2007, 01:23 PM

i'm guessing that but i wanted to know a couple things before pulling the head off....

(1) is it possible for the cam timing to be so far out it would give zero compression? and i mean zero, the needle on the gauge doesnt move AT ALL! (i have tested the gauge on a working engine and its fine)

(2) again, with the valves, would it be possible for every single one to be damaged to the point of zero compression? if it was low pressure i could get it - but none at all?

Please advise before i start pulling it all aprt again

Chas H · #6 05-26-2007, 02:38 PM

Yes to both questions. But it takes only 1 valve/cylinder to be bent to make for no compression. Before you pull the head, do a leak down test. If a valve is leaking you will hear it.

jhodg5ck · #7 05-26-2007, 03:45 PM

It's a little surprising that you have no compression @ all but I'd wager you have managed to tweak the valves just enough as to prevent them from closing fully. Again, pulling the valve cover and turning the engine over by hand/checking the rockers will tell you if they are indeed closing or not.

Jonathan

Tomguy · #8 05-26-2007, 04:04 PM

You said your chain failed. If your timing chain failed, your valves hit your pistons. Either your valves are bent or cracked, or your pistons are. I'd imagine the 2.5 16v is an interference engine, just like all other Benz engines I can think of made with overhead valves.

Uk Merc Man · #9 05-26-2007, 04:36 PM

the chain didnt fail....the plastic cover on the longest guide rail broke up on start up, the engine was immediatley turned off, the chain was in one piece and after closer inspection i would have said the chain maybe skipped a tooth.....on the exhaust cam

barry123400 · #10 05-26-2007, 05:47 PM

I am not much of a mechanic so allow. I would put the engine on #1 top dead centre. Check my valves to make sure the cam is clear of them on the number one cylinder. Inject a little air.
This would separate the chain timing issue from bent valves quickly. Or if either valve is open on top dead centre you either have the valve timing messed up or you have to rotate the engine one more time as you are on the other stroke. I assume your car has a rotor in the distributor so you can verify the power stroke top dead centre as well.
Should not take a lot of effort to figure what is going on. I also assume your compression gauge is functional.

Uk Merc Man · #11 07-01-2007, 08:12 AM

well. update on this. pulled the head and it turns out i had 8 bent valves! replaced them all, got the car back together and took it for a spin yesterday. all good, oil pressure pegged at 3 bar, good oil and water temps - all good.

anyway.....today, the oil pressure has gones walkies again.

have checked obvious stuff like the wire to the sender and its good.

when i remove the pipe from the base of the oil filter to the turbo nothing comes out when i crank - the only oil related thing I touched during the rebuild was the crank nut to allow removal of the timing chain cover - would not doing this back up tight enough (what is the touque, i just did it tight as i could) give me no oil pressure?

what things should i check next?

thanks all