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Rb25 no compression in any cylinders

3922 Views 5 Replies 4 Participants Last post by  robbie2883
I just recently did a rb25 swap into my r32, I cannot get the car to start, turns out there's no compression in any of the cylinders, there's spark and fuel, I purchased the motor from a reliable seller who says they tested the compression and replaced the timing belt and all was good.
I didn't mess around with the timing or remove the cams so I don't believe there is any possible way I could have bent the valves, let alone all of them. the only thing I did mess around with while trying to get it started is the cas, is it possible that's the cause of no compression? and if not does anyone have an idea what else could be causing the problem? I have yet to pull the head off to check the valves.... Also its a series 2 rb25 and it has hydraulic valves

Any help would be greatly appreciated

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Well you would probably bend all of the valves if it was a timing issue. You dont usually just bend 1 or two..

CAS would have nothing to do with it.

So ya have these general possibilities
-headgasket (doubt it- usually doesnt fail on ALL cylinders @ once)
-Valve seals (again, doubt it- usually you will drop compression on a cylinder at a time, they usually dont all go out at once.)
-Rings and or pistons (very good possibility when buying used shit if its been detonated and overheated like fuck.)
-Timing belt is off enough to open valves during compression/exhaust stroke. Hopefully its not enough to bend the valves.. (maybe?)
-If he has had head work before he sold it, its possible that the valves were cut wrong etc causing improper seating and no compression

Did he replace the timing belt and drive it or replace it and sell it right away?

I would reccomend doing a leakdown test next. A very easy cheap way to determine if its a head/valve issue.

Check the timing (if you already know how to do it, just ignore me...)
pull the front cover off. there are single dots on the front of each cam gear. make sure the motor is at top dead center by lining up the third mark on the crank pulley (15degreees) with the line on the lower front cover (its located at about 2 o'clock if i remember). once thats lined up and you are on the right stroke, the dots on the cam gears should line up with the hash marks on the metal plate behind the cam gears. If they all line up your timing is all G.

Hope that helps. Sorry for the rambling. damn coffee this morning...:)
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I tried it throttle open and closed, i have yet to pull the head off but I pulled the valve covers off and the exhaust valves are all stuck open slightly and all the intake valves are closed and in perfect condition, all the valves move, cams spin and its all timed correctly. Is it a common thing for an engine thats been sitting for 6 months or w.e it is to have valves stick for any possible reason, I want to leave pulling the head as my last resort assuming the exhaust valves are bent...

Thanks alot for your help
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it might have been mistimed before they ever replaced the timing belt. might be why they were getting rid of it in the first place
You try putting oil in the cylinders yet? It is common for the rings to unseat in an engine that has been sitting for 6 months. We had a mazda rx-8 in the shop fairly recently that had flooded out and we had to put trans oil in it and crank it for a good 30 minutes to get it to fire up. Rotary engines are a bitch when the rings are washed out.
rotary engines don't have rings, they have apex seals and work on a WHOLE different principle which is why the trans fluid worked.
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