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1987 Crusaders 270HP Year long running issues.

S

stslicker

New member
Motor will start up and run great for anywhere from 20 minutes to 2 hours. Running about 3000 rpms and it starts missing and shuts down completely.
Let it set for 10 to 20 minutes restarts and runs sometimes up to 2 hours or more. I have replaced cap, rotor, plugs, coil, wires, ballast resistor and Mallory internal pick up. Replaced all gas filters last year, pulled filter yesterday, no water or sediment. Trying anti siphon today.
 
When we toss a whole bunch of parts at an issue all at one time, one of them may fix the problem. However, we may not know which one did the trick!

Try using the tried and proven P of E (process of elimination) making certain that you test/check/replace only one item at a time.
This is much more fruitful, leaving us better educated and prepared for a future similar issue! :)


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nothing beats an accurate diagnosis.......first question I'd ask is "Does the engine quit from lack of fuel or spark?"
 
RicardoMarine said:
When we toss a whole bunch of parts at an issue all at one time, one of them may fix the problem. However, we may not know which one did the trick!

Try using the tried and proven P of E (process of elimination) making certain that you test/check/replace only one item at a time.
This is much more fruitful, leaving us better educated and prepared for a future similar issue! :)


.
Click to expand...
All of the parts listed have been added one at a time.
 
I suppose it could be a clogged fuel tank vent. If the short runs before shutdown (20minutes) are when the tank is full and the longer runs (2 hours) are when the tank is down a ways, then that would be further evidence to look here. Or if you find that upon shutdown you can loosen the gas cap and it immediately starts up, then that is the problem.

Long shot (never met anyone that had the issue) but easy to check.
 
or crud in the tank accumulating on the screen until it shuts down.....at which point it drops off and the cycle repeats.....
 
Time for serious troubleshooting. Recommend temporarily plumbing in a pressure gauge between the fuel pump and carb. All the necessary (inverted flare) fittings,clamps, and hose is available at most car parts stores. Pressure should be about 7 psi at all rpm ranges. If a clogged fuel line is suspect, the gauge should be plumbed in before the fuel pump. Suction should not exceed 5.0 In-Hg. Might also monitor ignition voltage by tapping in a voltmeter ahead of the coil. This would help identify a wiring breakdown between the battery/alternator and coil which would also include the ignition switch. A long shot would be the tach shorting to ground – rare, but it happens. Sounds like something electrical is heating up and shorting out but fuel is also a major player. I had the exact same presentation on a 454 which turned out to be a slow failure of the oil pressure switch which powered the electrical fuel pump. Please share the solution when the problem is solved. Good Luck.
FL Panhandle
 
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