power pac isolation diode tests bad

[fast_c_class]

1983 115 crossflow v4<br />power pac isolation diode tests bad according to the test procedure in the clymers manual. any ideas what would cause this to happen? i dont want to replace these powerpacks if they are going to blow because of something else upstream taking them out.

 

[Joe Reeves]

Re: power pac isolation diode tests bad

The diodes in both powerpacks are bad?<br /><br />Are you checking, with an ohm meter, between the black/yellow wire and the white wire of the powerpack? A good diode will give a reading in one direction but not the other.<br /><br />How are you checking and what readings are you obtaining.

 

[fast_c_class]

Re: power pac isolation diode tests bad

yes both check bad.<br /><br />checking between the black\yellow stripe wire and solid white wire with an ohm meter. checking both directions. <br /><br />the ohm meter is showing it as an open circuit both directions.<br /><br />i still get spark on all 4 cyl and the engine will idle (but rough) but as soon as throttle is applied the engine will die.

 

[Joe Reeves]

Re: power pac isolation diode tests bad

I don't know what kind of ohm meter you're using but you are definitely obtaining a false reading. If those diodes were faulty, the engine wouldn't run at all and you would have the combustion firing out thru the exhaust area.<br /><br />Your explanation of the problem as per the last sentence of the above post (dies when throttle is applied) indicates that either the carburetors are fouled, fummed, clogged (lean mixture) or the timer base under the flywheel is sticking (retarded spark advance).

 

[CATransplant]

Re: power pac isolation diode tests bad

Hmmm....are you sure your meter is set to measure resistance. Check your switch. Then touch the two probes together. The meter or display should show zero ohms or close to zero, anyhow. <br /><br />As Joe said, if they showed open circuits in both directions, your engine would not run at all.

 

[fast_c_class]

Re: power pac isolation diode tests bad

catrans.. you are right somewhat, i didnt have the meter set to the diode setting (i didnt know it had one) turns out THEY ARE OK<br /><br />however a problem still exists and here it is:<br /><br />1 engine has good spark outside the cyl on all 4.<br />2 idle is slightly rough<br />3 engine runs rich<br />4 as soon as throttle is applied engine kills.<br /><br />what i have checked<br /><br />1 coils = good<br />2 power packs = good<br />3 carbs = recently rebuilt <br />4 all new fuel line and fuel pump (bulb stays hard)

 

[Joe Reeves]

Re: power pac isolation diode tests bad

Either you've overlooked something within the carburetors.... possibly not manually cleaning the four high speed jets that are located in the bottom center portion of the float chambers, or to quote myself....<br /><br />Your explanation of the problem as per the last sentence of the above post (dies when throttle is applied) indicates that either the carburetors are fouled, gummed, clogged (lean mixture) or the timer base under the flywheel is sticking (retarded spark advance).

 

[fast_c_class]

Re: power pac isolation diode tests bad

im pretty sure its not the carbs, i have 3 sets of them, all are in good rebuilt condition. ive taken them apart, sprayed with carb cleaner, soaked them in it, run small dia wire thru the jets, low and high speed.<br /><br />it has new fuel pickup in the tank <br />all new clamps <br />all new fuel hoses (every single hose tank to carbs)<br />new fuel pump<br />reeds are good<br /><br />i made a ground wire harness tonight that ties every ground wire together and ran it to the neg battery term. i'll see how she runs tommorow

 

[Xcusme]

Re: power pac isolation diode tests bad

FYI: <br /><br />Testing a diode with a DIGITAL multimeter<br /><br /> * Digital multimeters have a special setting for testing a diode, usually labelled with the diode symbol.<br /> * Connect the red (+) lead to the anode and the black (-) to the cathode. The diode should conduct and the meter will display a value (usually the voltage across the diode in mV, 1000mV = 1V).<br /> * Reverse the connections. The diode should NOT conduct this way so the meter will display "off the scale" (usually blank except for a 1 on the left). <br /><br />Testing a diode with an ANALOGUE multimeter<br /><br /> * Set the analogue multimeter to a low value resistance range such as × 10.<br /> * It is essential to note that the polarity of analogue multimeter leads is reversed on the resistance ranges, so the black lead is positive (+) and the red lead is negative (-)! This is unfortunate, but it is due to the way the meter works.<br /> * Connect the black (+) lead to anode and the red (-) to the cathode. The diode should conduct and the meter will display a low resistance (the exact value is not relevant).<br /> * Reverse the connections. The diode should NOT conduct this way so the meter will show infinite resistance (on the left of the scale).