compression check

Irish Rob

Cadet
Joined
May 26, 2005
Messages
17
Ok, I got instructions on how to do a compression check from my previous posts, but I still have a few questions which might seem obvious but I want to make sure. Here are the instructions <br /><br />Purchase a compression guage at most any auto parts store or Sears (about $25-$35). Put on the muffs, start motor and run at idle until warm. Shut off the motor, remove both plugs and ground them to the power head. Rig jumper wire across neutral interlock switch. Place throttle in WOT postion. Screw compression gauge into cylinder #1. Crank engine about 4-5 complete revolutions until max compression reading is obtained. Write down the number. Screw compression guage into #2 cylinder and crank 4-5 revolutions. Write down the number. Compression should be at least 110 psi and no more than 10% difference between cylinders. <br /><br />Question 1: how do I ground spark plug wires to power head. By taping the wire glove to the power head?<br /><br />Question 2: If I am removing the sparks plugs, do I still crank the engine by using the key in the ignition? I never tired, so I want to cover bases.<br /><br />Question 3: Rig jumper wire across neutral interlock switch. How do I do this? The service manual does not mention this part.
 

novicetech

Petty Officer 1st Class
Joined
Jan 19, 2004
Messages
267
Re: compression check

1) I usually just disconnect the ignition wire coming from the ignition switch.<br />2} Yes you use the key and let the starter do the work.<br />3)If you only jump the neutral saftey switch your motor will be in gear when trying to crank starter, Does your control have a throttle only postion? There is usually some kind of pull out button on chrysler and us marine force motors.
 

Irish Rob

Cadet
Joined
May 26, 2005
Messages
17
Re: compression check

3) It has push in button on throttle lever. When pushed in the throttle lever can be pushed forward without motor going into gear. Does this mean motor has to be cranked while in gear and not neutral to get compression check?
 

eurolarva

Rear Admiral
Joined
Jun 24, 2003
Messages
4,182
Re: compression check

Dont worry about the interlock switch. I doubt you will see a diffence in the compression between WOT and neutral. If you are commited to WOT test most interlock switches have connectors that pull off. just remove the leads from the switch and black tape them together. Be careful that no bare parts contact the motor because they carry 12 volts.<br /><br />You can buy a test jig for the carbs. I use wire wrapped around the plug threads and tie one end of the wire to a screw or the negative lead of the battery.
 
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