compression test how to - Moderated Discussion Areas

  ContinuousWave
  Whaler
  Moderated Discussion Areas
  ContinuousWave: Whaler Repairs/Mods
  compression test how to

search | FAQ | profile | register | author help

Author Topic:   compression test how to

Cpt Quint posted 10-30-2002 02:04 PM ET (US)
sorry,i cant find post specifically telling me where to pick one of these gadgets up and then how to use it to determine if all okay. Also mines an 89 spl 88 rude so what reading am I looking for??
please post thread if more applicable
JBCornwell posted 10-30-2002 02:23 PM ET (US)
Ahoy, Cpt. Quint.
Any auto supply store can sell you a compression tester guage. Be sure to get the type that screws into your spark plug holes.
1. Warm the engine up.
2. Remove all plugs.
3. Leave ignition off and spin engine by jumping the starter.
4. Turn engine at least 5 times for each cylinder.
Exact reading is not very important as long as it is over 100psi.
It is important that all cylinders read within 15% of each other.
Good luck.
Red sky at night. . .
JB
Bigshot posted 10-30-2002 02:43 PM ET (US)
Any auto parts store $20-25. Engine can be cold as well. I like to do both ways. Turn over 5-8 times until needle basically peaks. Reset and do #2, etc. Write it down and keep so you can compare next year etc.
tuna1 posted 10-30-2002 02:47 PM ET (US)
To add to JB info. 1-Make sure you have a fully charged battery so the voltage won't drop during testing and change the cranking speed,jump off a runnig car. 2-Make sure the throutle is wide open-so maximum amount of air is ingested into the engine. 3-Watch how fast the compression builds up-it shows the tension on the ring set or sticking rings. 4-do a wet test-add a little oil in the cylinder prior to testing again to see how well the rings are sealing.A Good test is less than 10% diference between the highest and lowest,but watch out for high numbers than it should be- the result of alot of carbon buildup in cylinders. Tight Lines...
Cpt Quint posted 10-31-2002 04:51 PM ET (US)
oops, now I have to show my mechanical ignorance.... by jumping the starter does that mean turning the ignition with the kill switch off (so it cant fire over) or something else???
JBCornwell posted 10-31-2002 05:02 PM ET (US)
There are several ways to do this, Capt. Quint, but all involve temporarily connecting the Battery + to the starter motor without turning on the ignition.
The easiest way is to connect a short piece of wire to the small terminal on the starter solenoid. When you need the starter to spin with ignition off, touch the other end of that wire to the big terminal that has the battery cable on it.
Good luck.
Red sky at night. . .
JB
andygere posted 10-31-2002 05:58 PM ET (US)
With all the spark plugs out, the engine won't fire, so just use the keyswitch as if you were starting the boat. If you are worried about arcing, put a small strip of electrical tape across the plug boots. No need to jump the boat battery from a car etc. if it has a decent charge. The starting battery on a boat should be able to crank for a long time without slowing down appreciably. Also, if you give the carbs full throttle, make sure the shifter is in neutral or the safety switch won't let the engine turn over. It's easy and only takes a few minutes.
63WHALER posted 10-31-2002 06:41 PM ET (US)
Another way to check is to simpley remove the safety lanyard, which will keep engine from firing while turning over. This way you won't have to jump the starter.
prj posted 10-31-2002 06:53 PM ET (US)
Superior information gentlemen. Thanks for asking Cap'n.
Now for the biggest question that i need to overcome personally: Do i really want to know? Hypothetical, no need to convince me with a myriad of valid reasons. Ive got to work through this one myself.
JBCornwell posted 10-31-2002 08:41 PM ET (US)
Do not turn it over with the ignition on. It will destroy your powerpacks.
Red sky at night. . .
JB
JBCornwell posted 10-31-2002 08:50 PM ET (US)
Um, Ahh. Don't turn it over with the ignition on unless it is going to fire the plugs. The CD** SCRs* can't stand a no-load situation.
** Silicon Controlled Rectifiers That *Discharge the Capacitors.
Red sky at night. . .
JB
Bigshot posted 11-01-2002 10:25 AM ET (US)
Have no clue to what you guys are talking about. Yank the lanyard so no fire, pull the plugs out, insert guage and do the darn test. Without plugs there is no compression and that thing will spin like the dickens. Lets not complicate this.
On certain engines and most newer ones, I think what JB is talking about is if you ground the spark plug to check for spark, you can burn the electronics. Suzuki was the first to have this happen.
Just yank the lanyard and go. You can do more damage by jumping the solenoid. I have seen people weld screwdrivers to stuff from the current.
Cpt Quint posted 11-01-2002 03:32 PM ET (US)
Thanks for each input...in keeping the piece I think this is another example of how certain tasks are achieved differently on this forum. Its good to get different levels of precaution to fit your comfort level.
Personally Im an "easy go" route on cosmetic stuff but normally play it safe on the engine. thanks to all.

Hop to:

Contact Us | RETURN to ContinuousWave Top Page

Powered by: Ultimate Bulletin Board, Freeware Version 2000
Purchase our Licensed Version- which adds many more features!
© Infopop Corporation (formerly Madrona Park, Inc.), 1998 - 2000.

Author	Topic: compression test how to
Cpt Quint	posted 10-30-2002 02:04 PM ET (US) sorry,i cant find post specifically telling me where to pick one of these gadgets up and then how to use it to determine if all okay. Also mines an 89 spl 88 rude so what reading am I looking for?? please post thread if more applicable
JBCornwell	posted 10-30-2002 02:23 PM ET (US) Ahoy, Cpt. Quint. Any auto supply store can sell you a compression tester guage. Be sure to get the type that screws into your spark plug holes. 1. Warm the engine up. 2. Remove all plugs. 3. Leave ignition off and spin engine by jumping the starter. 4. Turn engine at least 5 times for each cylinder. Exact reading is not very important as long as it is over 100psi. It is important that all cylinders read within 15% of each other. Good luck. Red sky at night. . . JB
Bigshot	posted 10-30-2002 02:43 PM ET (US) Any auto parts store $20-25. Engine can be cold as well. I like to do both ways. Turn over 5-8 times until needle basically peaks. Reset and do #2, etc. Write it down and keep so you can compare next year etc.
tuna1	posted 10-30-2002 02:47 PM ET (US) To add to JB info. 1-Make sure you have a fully charged battery so the voltage won't drop during testing and change the cranking speed,jump off a runnig car. 2-Make sure the throutle is wide open-so maximum amount of air is ingested into the engine. 3-Watch how fast the compression builds up-it shows the tension on the ring set or sticking rings. 4-do a wet test-add a little oil in the cylinder prior to testing again to see how well the rings are sealing.A Good test is less than 10% diference between the highest and lowest,but watch out for high numbers than it should be- the result of alot of carbon buildup in cylinders. Tight Lines...
Cpt Quint	posted 10-31-2002 04:51 PM ET (US) oops, now I have to show my mechanical ignorance.... by jumping the starter does that mean turning the ignition with the kill switch off (so it cant fire over) or something else???
JBCornwell	posted 10-31-2002 05:02 PM ET (US) There are several ways to do this, Capt. Quint, but all involve temporarily connecting the Battery + to the starter motor without turning on the ignition. The easiest way is to connect a short piece of wire to the small terminal on the starter solenoid. When you need the starter to spin with ignition off, touch the other end of that wire to the big terminal that has the battery cable on it. Good luck. Red sky at night. . . JB
andygere	posted 10-31-2002 05:58 PM ET (US) With all the spark plugs out, the engine won't fire, so just use the keyswitch as if you were starting the boat. If you are worried about arcing, put a small strip of electrical tape across the plug boots. No need to jump the boat battery from a car etc. if it has a decent charge. The starting battery on a boat should be able to crank for a long time without slowing down appreciably. Also, if you give the carbs full throttle, make sure the shifter is in neutral or the safety switch won't let the engine turn over. It's easy and only takes a few minutes.
63WHALER	posted 10-31-2002 06:41 PM ET (US) Another way to check is to simpley remove the safety lanyard, which will keep engine from firing while turning over. This way you won't have to jump the starter.
prj	posted 10-31-2002 06:53 PM ET (US) Superior information gentlemen. Thanks for asking Cap'n. Now for the biggest question that i need to overcome personally: Do i really want to know? Hypothetical, no need to convince me with a myriad of valid reasons. Ive got to work through this one myself.
JBCornwell	posted 10-31-2002 08:41 PM ET (US) Do not turn it over with the ignition on. It will destroy your powerpacks. Red sky at night. . . JB
JBCornwell	posted 10-31-2002 08:50 PM ET (US) Um, Ahh. Don't turn it over with the ignition on unless it is going to fire the plugs. The CD** SCRs* can't stand a no-load situation. ** Silicon Controlled Rectifiers That *Discharge the Capacitors. Red sky at night. . . JB
Bigshot	posted 11-01-2002 10:25 AM ET (US) Have no clue to what you guys are talking about. Yank the lanyard so no fire, pull the plugs out, insert guage and do the darn test. Without plugs there is no compression and that thing will spin like the dickens. Lets not complicate this. On certain engines and most newer ones, I think what JB is talking about is if you ground the spark plug to check for spark, you can burn the electronics. Suzuki was the first to have this happen. Just yank the lanyard and go. You can do more damage by jumping the solenoid. I have seen people weld screwdrivers to stuff from the current.
Cpt Quint	posted 11-01-2002 03:32 PM ET (US) Thanks for each input...in keeping the piece I think this is another example of how certain tasks are achieved differently on this forum. Its good to get different levels of precaution to fit your comfort level. Personally Im an "easy go" route on cosmetic stuff but normally play it safe on the engine. thanks to all.