Gonna do a compression test on the motor today can someone tell me where the fuse or the relay for the fuel pump is please. It's a Leon 1.8 t
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Compression test
- Thread starter Mattyboy1
- Start date
Thats the way i did it on my MK2 Golf ABF, the results showed a large drop on cyl 2 & 3 so had to change the head gasket, changed the piston rings and full head rebuild while i was there.
EDIT - 1.8T guide differs a little lol
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Compression Check DIY for a 1.8T
You'll need: Flat head screwdriver, 3/8" ratchet with 6" extension, 5mm Hex drive or allen wrench, 5/8"spark plug socket, compression check gage with hose, and about 30 minutes.
1. On a warm engine, open the hood andlocate the 3 plasticfasteners on the enginecover.
2. Using a largeflat head screwdriver, turn the fasteners counter clockwise. They should pop up. They do not come out all theway,so don'ttry topull them out completely.Then remove the plastic engine cover.
3. Using a 5mmhex drive or allenwrench, remove the8 socket head cap screwsholding in the ignition coils. Place these to the side,so the don't end up falling into one of your cylinders later.
4. Gently pull the ignition coils out,and your spark plugs will bevisible.
5 Using a standard 5/8" spark plug socket, remove the spark plugs. Now would be a great time to check your plugsto see if they need to be replaced. Also, (optionally) you can disconnect the electrical connectors to the fuel injectors, so that yourinjectors don'tsprayduring the compression check.
6.Connectyour compression gagein the first cylinder,turningthehose until the o-ring makes a good seal and is tight.
7. Crank the engine over,about 8-10 turns isplenty.The engine will turn over quietly and with much less effort since there are no spark plugs in the other cylinders. CAUTION: DO NOTATTEMPT TO CRANK THE ENGINEBEFOREREMOVING THE COILPACKSFROM THE OTHER CYLINDERS - YOU DON'T WANT TO ACTUALLY START THE ENGINE.
8.Check your compression gage.The needle should remainat the highest PSI levelachieved in that cylinder.If it seems toolow, check to make sure that it isconnected tightly enough for theo-ring to seal properly.Hit the release valve on the gage and crank the engine again to double check the compression, if you're having doubts. Write down the PSI.
9. Repeat this for the other 3 cylinders, and you now know the compression of all your cylinders.
10. Put your old plugs back in (or new ones) and put the coil packs back on (torque 5mm socket head cap screw to 7 ft-lbs - if you're the kind of person that needs a tq wrench for everything). It is also a good time to wipe out any dirt or crud that might have built up around or under your oil cap. Put the plastic engine cover back on, and you're done.
The service tech at my local dealer told me the compression should be about 180 psi for at 1.8T or 2.0T, and 160 psi for a 2.8 or 3.0 (normally aspirated). Cylinders should all be within 10% of each other. Ideally, thecloser they are in range, and the higher the compression, the better.
A fresh 1.8T engine should be atabout 200 psi, and lower than 140 psiis considered the lower extreme. Anything less thanthat, and you might want to consider checking into why it isreading low.
Trouble Shooting
If it reads low - firstmake sure your gage is reading accurately.
1. Make sure you read the compression while the engine is still warm. It needs to heat up to get to maximum compression. If the last of the cyclinders you check are lower than the first, it could also be because the oil is leaking by the piston rings from cranking the engine.
2. If it still reads low, put a little motor oil (5w30 synthetic or whatever you use) into the cylinder through the spark plug hole. This will help make a betterseal between the cylinder walls and the piston rings. If the compression now increases, it is a sign that the cylinder walls/piston rings are worn, and you're due for some cylinder honing and new rings.
3.If the compression still reads lowwith a little oil added into the top of the cylinder, itcould besign that air is leaking from the combustion chamberthrough the valves.Try some trusty valve / injector cleaner in your tank, or ifit's really bad,you mightbe in for somehead work.
Please check your engine specifications foryour acceptable compression ranges, and usethis only as a guideline for general information.
HTH
You'll need: Flat head screwdriver, 3/8" ratchet with 6" extension, 5mm Hex drive or allen wrench, 5/8"spark plug socket, compression check gage with hose, and about 30 minutes.
1. On a warm engine, open the hood andlocate the 3 plasticfasteners on the enginecover.
2. Using a largeflat head screwdriver, turn the fasteners counter clockwise. They should pop up. They do not come out all theway,so don'ttry topull them out completely.Then remove the plastic engine cover.
3. Using a 5mmhex drive or allenwrench, remove the8 socket head cap screwsholding in the ignition coils. Place these to the side,so the don't end up falling into one of your cylinders later.
4. Gently pull the ignition coils out,and your spark plugs will bevisible.
5 Using a standard 5/8" spark plug socket, remove the spark plugs. Now would be a great time to check your plugsto see if they need to be replaced. Also, (optionally) you can disconnect the electrical connectors to the fuel injectors, so that yourinjectors don'tsprayduring the compression check.
6.Connectyour compression gagein the first cylinder,turningthehose until the o-ring makes a good seal and is tight.
7. Crank the engine over,about 8-10 turns isplenty.The engine will turn over quietly and with much less effort since there are no spark plugs in the other cylinders. CAUTION: DO NOTATTEMPT TO CRANK THE ENGINEBEFOREREMOVING THE COILPACKSFROM THE OTHER CYLINDERS - YOU DON'T WANT TO ACTUALLY START THE ENGINE.
8.Check your compression gage.The needle should remainat the highest PSI levelachieved in that cylinder.If it seems toolow, check to make sure that it isconnected tightly enough for theo-ring to seal properly.Hit the release valve on the gage and crank the engine again to double check the compression, if you're having doubts. Write down the PSI.
9. Repeat this for the other 3 cylinders, and you now know the compression of all your cylinders.
10. Put your old plugs back in (or new ones) and put the coil packs back on (torque 5mm socket head cap screw to 7 ft-lbs - if you're the kind of person that needs a tq wrench for everything). It is also a good time to wipe out any dirt or crud that might have built up around or under your oil cap. Put the plastic engine cover back on, and you're done.
The service tech at my local dealer told me the compression should be about 180 psi for at 1.8T or 2.0T, and 160 psi for a 2.8 or 3.0 (normally aspirated). Cylinders should all be within 10% of each other. Ideally, thecloser they are in range, and the higher the compression, the better.
A fresh 1.8T engine should be atabout 200 psi, and lower than 140 psiis considered the lower extreme. Anything less thanthat, and you might want to consider checking into why it isreading low.
Trouble Shooting
If it reads low - firstmake sure your gage is reading accurately.
1. Make sure you read the compression while the engine is still warm. It needs to heat up to get to maximum compression. If the last of the cyclinders you check are lower than the first, it could also be because the oil is leaking by the piston rings from cranking the engine.
2. If it still reads low, put a little motor oil (5w30 synthetic or whatever you use) into the cylinder through the spark plug hole. This will help make a betterseal between the cylinder walls and the piston rings. If the compression now increases, it is a sign that the cylinder walls/piston rings are worn, and you're due for some cylinder honing and new rings.
3.If the compression still reads lowwith a little oil added into the top of the cylinder, itcould besign that air is leaking from the combustion chamberthrough the valves.Try some trusty valve / injector cleaner in your tank, or ifit's really bad,you mightbe in for somehead work.
Please check your engine specifications foryour acceptable compression ranges, and usethis only as a guideline for general information.
HTH
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Right just done the compression test . I let the car idle until temp gauge was reading 90 then I removed all coil packs took the spark plugs out. Disconnected the plugs for the injectors. Then put the compression tester in cylinder 1 turned the car over for ten revolutions with my foot flat down on the accelerator then I took the reading . Reset the compression gauge and done again just to double check and then repeated this on all the other cylinders. And these are the results
Cylinder 1. 200 psi
Cylinder 2. 200 psi
Cylinder 3. 198 psi
Cylinder. 4. 198 psi
So am I right in thinking all is good there.
Cylinder 1. 200 psi
Cylinder 2. 200 psi
Cylinder 3. 198 psi
Cylinder. 4. 198 psi
So am I right in thinking all is good there.
Fair dos pal, unless there was a variation of 20+ psi then there tends to be no issue. It's when you get one like the 1400 turbo multi air Alfa mito I checked the other day where 1,2&3 had 180 and 4 had 0.0! That's when you know there may be an issue!
Italian crap, 2 years old 15k miles and a fudged engine already or the multi air unit had failed.
Italian crap, 2 years old 15k miles and a fudged engine already or the multi air unit had failed.
Excuse my ignorance in advance but how do you actually turn/crank engine over for this test? Is it turning key as usual as though starting car or physically turning something manually round to get it to turn the engine over?
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