195 fw 4.3l omc 1992 diode?

[Ortonville]

What would cause both diodes to become open(NO CONTINUITY) on fuel ignition system?

 

[Don S]

Re: 195 fw 4.3l omc 1992 diode?

What makes you think they are both open?

 

[Howard Sterndrive]

Re: 195 fw 4.3l omc 1992 diode?

diodes aren't usually checked for continuity.
on most meters, you need to use the "diode check" function on the meter and it reads a voltage drop, not resistance

 

[Ortonville]

Re: 195 fw 4.3l omc 1992 diode?

The book says that there should be continuity in one direction and reverse meter probes and no continuity. I had no continuity in either direction. I removed the wiring harness and bought new diodes. Even though the meter doesn't sound off with continuity it does show resistance one direction on both old diodes and new ones. The whole problem started because I changed fuel filter and took the boat out and it wouldn't start. Got it home and there was no fuel in the new fuel filter. I measured the voltage to the pump with one battery that was tired and only got 8 volts. The battery itself read 12 volts. The other battery was charging. The book states 11-13 volts so I assumed that I had an electrical issue other than a pump issue.

 

[Howard Sterndrive]

Re: 195 fw 4.3l omc 1992 diode?

The book says that there should be continuity in one direction and reverse meter probes and no continuity.

the book that came with your multimeter?
note the range used on the multimeter in this clip
http://www.youtube.com/watch?v=hRKzZTk27Ug&feature=related
I see a lot of people using the 20 ohm or 200 ohm scale and getting invalid readings on diodes- usually the 2K scale is the diode check, but read the manual for your meter or look for the diode symbol on your ohmmeter range settings
again, as shown in that video, you should read a number, but NOT a resistance reading. Good diodes don't have resistance, but they require voltage to pass current in fwd bias. It is a VOLTAGE DROP reading on the meter.
and the battery in your meter has to be good

 

[bruceb58]

Re: 195 fw 4.3l omc 1992 diode?

Most good meters check resistance with a voltage lower than the voltage needed to forward bias a transistor or diode so your meter typically has a diode check setting.

 

[Ortonville]

Re: 195 fw 4.3l omc 1992 diode?

The boat manual was what I was referring to. The diodes were both good. The battery that I tested the fuel pump power supply with registered 12 volts. At the fuel pump only was getting 8 volts. Would a not fully charged battery drop voltage?

 

[Don S]

Re: 195 fw 4.3l omc 1992 diode?

I measured the voltage to the pump with one battery that was tired and only got 8 volts.

How and where did you measure the 8 volts. where was the positive and negative leads from your meter. Many times on this forum meters have been used improperly, giving a misleading reading.

 

[Ortonville]

Re: 195 fw 4.3l omc 1992 diode?

The plug that attaches to the fuel pump. Black and red.

 

[Don S]

Re: 195 fw 4.3l omc 1992 diode?

Was this while the engine was running, with the pump running, or was it unplugged? If unplugged, I would guess you was cranking the engine over. If so and you show 8 volts, then you have loose or corroded connections, probably at the relay where it plugs into the socket.
A blown (open diode) would give you no voltage at all, not low voltage.

 

[Ortonville]

Re: 195 fw 4.3l omc 1992 diode?

It was cranking and unplugged. I could barely move a wire on the 12.5 circuit breaker. Noticed this after I tested voltage on the pump voltage supply. Tightened and cracked the breaker. Getting another hopefully tomorrow. I hope that is the problem instead of the pump. Thank-you for your input. Will let you know

 

[Ortonville]

Re: 195 fw 4.3l omc 1992 diode?

The problem was the connector to the fuel pump. I cleaned it and the old fuel pump would work but the new one would not.