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1.7 boxer engine, 2 cyl with no compression

3K views 17 replies 6 participants last post by  Red156Ti 
#1 ·
Looking at the front of the engine the LEFT Front & RIGHT Rear have compression. The 2 without are Left Rear & RIGHT Front

0 bar <--> 6 bar
6 bar < --> 0 bar

The battery I was using was weak & therefore not turning over the engine very fast, i reckon that's why the 2 are showing 6 bar, would have expected nearer to 10bar

Could it be something simple, such as lack of oil in the hydraulic tappets [ if they have Hyd tappets ] or will it more likely be badly seated or bent valves?

The 2 heads had been removed & re-fitted by another person, from whom I bought this engine.

Ideas or suggestions appreciated :thumbs:
 
#4 ·
Comp tests must be done on a hot engine (drive it around a while), then after with all plugs out, wide open throttle.

A wet test should always be done.
This means squirting about a teaspoon of oil into the cylinders via the plug hole (in turn of course..) and repeating the comp test; that is a great way to 'wet-up' the rings and make them seal (better/properly!). Thus a wet test really can indicate whether rings or valves are the problem. If the wet test gives much higher values than the 'dry' then the rings are worn out.
 
#5 · (Edited)
Brit, thanks for the advise, kinda hard to get it warm when the engine lying on the ground, removed form a car...... i'm looking for possible reasons why there is no compression. could it be a re-assembly error? bad timing?

from the symptoms described does it give any indication as to what may be wrong?
 
#10 · (Edited)
all i did was I bought an engine which another person had replaced the 2 head gaskets on. he claimed it was running but mis-firing due to a faulty coil pack :rolleyes:

Before usng this engine I decided to do a compression test, to find 2 of 4 cylinder are without compression.

As for strippig it etc, yes I have the tools & skill required to do so. Its just I'm not familiar with the boxer engine. i was hoping some-one might say if Cyl A & Cyl B have no compression its means =???

It'll be a few weeks before I'll look at it in any detail. Thanks for all the replies.

To clarify, the engine is NOT fitted in a car at present, its under a work bench.

BTW its a '92 1.7 16V engine from an Alfa33 P4, i assume Hydraulic tappets? or if they are mechanical what is the measurement for the clearance gap
 
#7 · (Edited)
If there is no compression at all then something is drastically wrong.

First thing that comes to mind is that those valves are not opening/closing properly (seating badly or damaged seat), hence the compression issue. That will run horribly on 2 pistons if it runs at all.

Check the timing - if that looks ok take the heads off.

Take the heads off and turn the cams by hand to see how the valves lift. Looks like a rebuild - do it yourself this time!

Mech or hydraulic tappets?
New cams?
 
#8 ·
At that rate Id pull the heads anyway and give it a good look over. I assume its history is unknown as it came as parts so its worth splitting it and having a root around before you put it into a shell. It sounds to me like the pistons and valves may have met at some stage.
 
#9 ·
agree.

6 bar = 87 psi is extremely low also. (I get 190 psi - this was before my current rebuild).

150 psi is the benchmark.


I'd begin with a complete rebuild IMHO as you have the engine removed.

Do you have the tools/skills? (easy to learn):thumbs:
They are nice engines to work with.
 
#11 ·
#16 ·
Just looking at the cylinders which have compression (1 and 4) and those that don't (2 and 3), I would say that something is 180° out of phase somewhere - did the correct camshaft go on the right cylinder head? Hydraulic cam housings are pretty symmetrical looking?
 
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