Prestolite troubleshooting.

[ski_king]

I have an 89 Force 125HP which has some ignition issues. I have a repair manual which outlines the procedure to troubleshoot. However it calls out for a peak hold voltmeter which I do not have. I tried using my regular DVOM and it doesn't react fast enough to see the voltage levels. Any suggestions as a work around?

 

[JDP]

Re: Prestolite troubleshooting.

Are you just looking to check spark? I don't have the meter your talking about either. I used the old pull the plug and ground it to the head and turn the motor over and look for spark. Just be careful to not let the motor start and don't rest your forearm on the edge of the motor casing. You'll find out real quick if you have spark. My arm was tingling for about 5 minutes after that one.

 

[ski_king]

Re: Prestolite troubleshooting.

I've checked for spark and I have spark on all plugs. However the boat won't exceed 2000 rpm under load. The plugs on cyl #3 and #4 are badly discolored compared to #1 and #2 which are clean. I'm thinking the voltage to the plugs isn't enough to fire under load and I'm going through the troubleshooting procedure in the manual that calls for the peak hold voltage. I'm guessing the voltage from the stator or the output voltage from the CD unit is low.

 

[QuadManiac]

Re: Prestolite troubleshooting.

Have you performed a compression test?

 

[4runneradam]

Re: Prestolite troubleshooting.

You can check resistance values with a regular VOM. I did and found out my stator was bad.

 

[ski_king]

Re: Prestolite troubleshooting.

Have you performed a compression test?

Yes.... 130 PSI across the board.

 

[ski_king]

Re: Prestolite troubleshooting.

You can check resistance values with a regular VOM. I did and found out my stator was bad.

I Ohm'd out my stator, both sides had approximately 750 Ohms.

 

[Scaaty]

Re: Prestolite troubleshooting.

Motors well know for this proplem..bad Stator, cuts in and out on a Module (one or both Powerpacks might be affected)
Start at the Stator
.

 

[QuadManiac]

Re: Prestolite troubleshooting.

You can significantly close the gap on plugs for the affected cylinders. If it's weak spark, this will help as a temporary fix/troubleshooting step.

 

[ski_king]

Re: Prestolite troubleshooting.

Motors well know for this proplem..bad Stator, cuts in and out on a Module (one or both Powerpacks might be affected)
Start at the Stator
.

The original stator was bad resistance between #1 and #2 was 1.2 Mohm. I have a parts motor where I swapped the stator from and it made no difference. The resistance on the new stator was 750 ohms between #1 -#2, and #3-#4. Magnets on the flywheel are tight and easily held a screw driver. The new stator could be bad as well but I'm shooting in the dark without having the DVA tester. I ordered one off the internet but it's on back order. Hopefully I'll get the tester this weekend so I can determine the problem.

 

[MikDee]

Re: Prestolite troubleshooting.

You don't think cyl. #3, and #4, have crossed wires do you? due to crossed wiring going to the coils?

 

[Scaaty]

Re: Prestolite troubleshooting.

If your getting crummy plug reading on two plugs, try switching the power packs, and see if it follows..

 

[ski_king]

Re: Prestolite troubleshooting.

You don't think cyl. #3, and #4, have crossed wires do you? due to crossed wiring going to the coils?

I'm pretty sure I have them correct. Orange wire off the CD goes to #3 coil and red goes to #4 coil.

 

[ski_king]

Re: Prestolite troubleshooting.

If your getting crummy plug reading on two plugs, try switching the power packs, and see if it follows..

I need to swap them and try this. But I have to put it in the water for a wet test. Running on the muffs the plugs look fine, only under load is when they look bad.

 

[activa]

Re: Prestolite troubleshooting.

Any luck with your problem?

I think I must have the same problem. On my '87 Force 85, one CD module output was bad, but since mine is a 3 cyl. I had an extra output, which I figured how to use (I had to swap stator outputs around). All cyls around 125psi, rebuilt the fuel pump and cleaned up the carbs, I get a spark on all cylinders but it just seems to miss. I checked all ignition parts for resistance and all seemed ok.

Lots of advice pointing to the stator, but I'd rather have some proof before I drop $150 for the stator, not to mention the socket and puller I'll have to buy. I get a spike on the VOM when I turn the flywheel by hand, so I have trouble believing its that.

 

[Scaaty]

Re: Prestolite troubleshooting.

I need to swap them and try this. But I have to put it in the water for a wet test. Running on the muffs the plugs look fine, only under load is when they look bad.

Yep, do that..(clean the plugs, and also move them with the power pack..this will isolate any internal problem associated with anything but ignition

 

[eurolarva]

Re: Prestolite troubleshooting.

The plugs on cyl #3 and #4 are badly discolored compared to #1 and #2 which are clean.

From this description I would be focusing on plugs 1 and 2 as your problem. Clean plugs are typically from a blown head gasket or not firing. The discolored plugs you mention tell me those plugs are firing for you. What color is the stator you currently have? Red or Black? If you have dual carbs and one is fueling units 1 and 2 try spraying some gas premix into that carb while motor is running in a tub of water. Swap plugs 1 and 2 with plugs 3 and 4 and see if the plugs in 1 and 2 clean up. If they do you might have a blown head gasket even though compression numbers disagree.

 

[ski_king]

Re: Prestolite troubleshooting.

I'm thinking this could be a head gasket problem. I went through the ignition and it seems to be good. (Too much typing to describe all the troubleshooting).

I'm open to suggestions because I'm about to fix this boat with some gasoline and a match!

Here are some pictures of the plugs.

 

[Delta 1]

Re: Prestolite troubleshooting.

If you have a bad head gasket it should show on compression test (1 or 2 cylinders low) did you do the comp test with all the plugs out? Have the carbs been touched? Vacuum leak? Just some ideas off the top of my head.

 

[MikDee]

Re: Prestolite troubleshooting.

Plugs on #1, & #2, look like they've been washed, and dry cleaned (typical of water intrusion) probable head gasket? Don't know where else you'd get water intrusion? #4, don't look much better, #3 looks like the best of the bunch.