No compression on #3cylinder


#1

Good day everyone. I am driving a polo 6r 1.4 2010 clp engine, I recently did the engine overhaul. The car at would at first would not idle, when I start it I had to put the foot on the gas panel, I drove it to the mechanic to do diagnose it, the results came out saying its the crankshaft position sensor. I have put a new sensor but it still hesitated to start… Until it could not start anymore. Last evening I did a compression test and this is what I gotUpl20190213_194601-COLLAGE.jpg…
Cylinder #3 does not have compression at all… Could it be a faulty coil pack, burnt valves or piston rings? PLEASE HELP


#2

Not coil pack. Burnt or misadjusted valves are possible. Something wrong with installation of piston rings seems less likely but could happen.


#3

You yourself or you paid a mechanic to do this? If you paid to have it done, take it back to that person because they screwed #3 up.

It is NOT a coil pack. It could be pistons rings or a bent valve or a burnt valve - no matter, the engine must be opened up to find the reason. Soooo the person who rebuilt it needs to re-rebuild it!


#4

Do a leak down test on cylinder #3 to determine why there’s no compression.

Tester


#5

In almost all cases when a cylinder has no compression at all it is related to a cylinder head valve issue.


#6

When you say you rebuilt the engine, be more specific. What did you do, and why did you do it?


#7

It may be one of the valves in that cylinder is sticking slightly open for some reason. Could be something simple, in concept anyway. But may require removing the head to fix, don’t know. We don’t get the VW Polo here in the USA, the most similar model here is probably the VW Golf, but that only comes in 2L turbo or 2.5 normally aspirated engines here. A little googling shows that’s a pretty common engine and there are quite a few rebuilt versions available for sale, so that’s a potential backup. Some shops may have an imaging tool that allows them to insert something into the spark plug hole and see the valves. If you want to do something yourself, remove the valve cover and see if you can see anything weird happening with the cyl number 3 valves and camshaft lobes. Measure the valve clearances for example.