F25 Sudden Compression Loss

AGENT 37

Petty Officer 1st Class
Joined
Mar 2, 2007
Messages
319
After running fine for five hours, my 2002 F25 missed for a few seconds at half throttle, quit running when I slowed down to investigate, and would not re-start.

Compression was an even 140psi prior to the issue, it is now an even 90psi on both cylinders.

I've verified good spark, fuel, and proper oil level. The carburetor is new. The timing belt is also new. I will check alignment marks later to make sure timing didn't jump but don't suspect that. I replaced the belt because the old one deflected beyond 13mm indicating that it was worn out.

Can somebody please explain the compression release function utilized during starting and tell me whether or not this may be the culprit?

Aloha
 

AGENT 37

Petty Officer 1st Class
Joined
Mar 2, 2007
Messages
319
Pulled the cylinder head off today and found water inside the cylinders but no scoring. Also found three fins of water pump impeller busted apart. All valves are operating smoothly. Hoping the head gasket is all that went with the impeller failing.
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
need to fix the alarm system also if it did not alert you about the overheat
 

AGENT 37

Petty Officer 1st Class
Joined
Mar 2, 2007
Messages
319
I wound up putting a new impeller, head gasket, and rings in this motor and it is running better than ever. I have not seen a horn on this motor, is it possibly that it is just the indicator light?
 
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