Don't start Pb compression

[fathi]

Hi,
I have restore a motor (8 valves) : refection of the valves, refection of the head gasket.
After that the motor don't start ; so i had take the compression and obtain :
1 cylinder -> 8 bars
2, 3, 4 cylinders -> 2 bars
The alignement of the distribution is correct.

Somebody had the same problem ?

i had think for a probleme of segmentation at piston but i don't think that it will give so less as 2 bars!

Somebody have a sugestion ?

[EntonoX]

What did you restore on the engine?

- bored the cilinders?
- new pistons / compression rings?
- new valve seats / valves?
- new head gasket?
- head mounted correctly?
- valve clearance ok? if no valve clearance, valves stay open and no compression.

So it can be lots of things, please give us some more info on what is new and what you tried.


TR7, ACG 2700L

[fathi]

Hi,
Thanks for your reply.

new valve seats / valves
- new head gasket
- head mounted correctly
- valve clearance ok
- distribution ok

[Howard722]

8 bar compression is just about OK, but 2 bar is very very low and fuel will not atomize=flooding of spark, are plugs wet with fuel? Re-check compression after putting good shot of cold engine oil into cylinders via spark plug hole-if compression goes high suspect piston rings/sizes etc.? If compression about the same indicates problem is valves not shutting/sealing?


Enjoy& regards

[john 215]

Hi Fathi,
Dont want to put doubt in your mind,but, you did put the inlet valves in the right port [:0] and not mixed the two up. Please forgive me if that sound obvious but you would'nt be the first.
Cheers John

LIVE LIFE A QUARTER OF A MILE AT A TIME!
1979 3.5 FHC(STATUS PENDING!!)

1982 2.0 DHC NOW A 4.6 WILL BE ON THE ROAD VERY SOON!
Read My Blog http://www.waringstowntr7s.co.uk/blogs/ ... hp/John215

[Beans]

Could also be sticky valves (valves being to tight in the guides) so they don't close properly.

Also how did you check/measure the compression?

<center>
<font color="blue"><i>1981 TR7 FHC Sprint (better known as 't Kreng)
1981 TR7 DHC (not very well known yet, but back on the road)
Also a 1980 TR7 DHC, 1980 TR7 DHC FI, 1981 TR7 FHC
http://tr7beans.blogspot.com/</i></font id="blue"></center>

[fathi]

HY,
IN FACT MY PROBLEM COME FROM A LEAK AT THE PISTON FOR 3 OF THE 4.
I HAD FIND IT AFTER HAD PUT SOME OIL AND HAD OBTAIN BETTER BETTER COMPRESSION.
IS SOMEBODY HAD THE SAME PROBLEM ?

REGARDS

[john 215]

Hi Fathi,
How much did the compression rise, it will always go up a little even on a good engine. Did it run ok before you carried out the work [?]
Cheers John.

LIVE LIFE A QUARTER OF A MILE AT A TIME!
1979 3.5 FHC(STATUS PENDING!!)

1982 2.0 DHC NOW A 4.6 WILL BE ON THE ROAD VERY SOON!
Read My Blog http://www.waringstowntr7s.co.uk/blogs/ ... hp/John215

[fathi]

Hi,
I had put some oil in the cylinders and had obtain good compressions ; so normaly i think it's the rings on the piston that are stick.Is somebody had the same problem ?
Is it possible to get out the piston from the sump pan ?
Do you know if it's a special tool to dismount the nut con rod and the nut crankshaft cup.
Thanks in advance for your reply.

[john mc nulty]

Hi you can take the piston out from the sump do not think you need any special tools.but it involves a bit of work you have to lift the engine up a bit to remove the oil pan you also have to remove the cylinder head so quite a bit involved in it. The workshop manual is on here somewhere do a search and you should be able to find it or someone will give you the link

[fathi]

Thanks for your prompt reply ; the motor is ona table and not in the car. I have allready put out the oil pan and i can see that there is special bolt.
If somebody hs allready done the job please advise ?

[john 215]

Hi Fathi,
Do you mean the 'Big End' nuts that secure the caps onto the conrods?
These are 'bi hexagon' ie. 16 side so will req such a socket, cant remember but think they are 9/16 of an inch, but easy to obtain, been a while since i had one apart. Sure you know but <u>mark them well and dont for which rod and direction not mix them up</u>
Cheers John

LIVE LIFE A QUARTER OF A MILE AT A TIME!
1979 3.5 FHC(STATUS PENDING!!)

1982 2.0 DHC NOW A 4.6 WILL BE ON THE ROAD VERY SOON!
Read My Blog http://www.waringstowntr7s.co.uk/blogs/ ... hp/John215

[fathi]

Hi,
Thanks for your reply.
I had dismount the oil pan and had see that for the first piston, that had good compression, there is oil between the piston and the cylinder ; but for the over that don't have compression there is no oil.
Somebody know how the oil come between the piston and the cylinder ; do you know if there is an oil gallery in the piston head and where is it.
Normaly i think that the cylinder are oil by projection ?

Thanks in advance for your reply.

[Chunk]

Sounds like a sticking piston ring, or even a broken piston ring on that piston/cylinder. You will have to remove piston to check.

1979 TR7V8 FHC 3.9 Litre
19 years of tinkering and tuning...... So Far!
Better to burn out than fade away.

[terryjm1]

While I am not certain it is impossible to remove the piston through the sump, I can assure you it is definitely the more difficult route. You need to pull the head and do it the standard way.

Terry Merrell
St. Louis, MO