Explanation of the two rectifiers in start circuit

Need explaination of what the

Need explaination of what the two rectifiers do in the start circuit. Looks like they prevent back feeding.What trouble do they cause?

Engine model? Year?

Engine model? Year?

Thanks E P but I figuired it o

Thanks E P but I figuired it out. One rectifier is used for "start" and the other one is for "RUN".The rectifiers separate the common load from each function.

"A rectifier can be diodes use

"A rectifier can be diodes used to check D/C current flow direction.
What are you speaking of that would be used in a starter circuit?
Are you talking about part of the ignition sourced alternator field circuit?
If so, occasionally a bad circuit can cause back feed to an ignitioin system (gasoline Volvo Penta engine) causing the engine to continue running with the ignition switch OFF.

Just curious...... What year/model/engine/drive?"

"BTW, that usage of the word &

"BTW, that usage of the word "Check" is as in; "one way" current flow, or as in "check valve". "

"The diodes are connected to a

"The diodes are connected to a common load, in this case the electric fuel pump. On "start" 12v is routed thru Diode (1) directly to the fuel pump for starting and bypassing safety interlocks and Diode (2)blocks 12v from going back thru safety interlocks.AFTER starting 12v is supplied thru diode (2) thru the oil pressure sensor but blocks the 12v from going back to yellow/red 'crank" circuit which would keep starter cranking."

"Just to be clear.... a "D

"Just to be clear.... a "Diode" can be though of as an electical D/C current one-way valve. When A/C current is applied, they can "rectify" allowing only one direction of current flow.
I believe that you are speaking of relays or relay switches... not a diode.

During starter activation, current is supplied to the electric fuel pump to circumvent the open oil pressure switch that is part of the loop, so to speak..... of which is a safety requirement!

Once the engine is running, the starter motor "by-pass" circuit opens, and the oil pressure switch circuit closes allowing the fuel pump to have power and continue operating.

When/if the engine should stop running, the loss of oil pressure opens this circuit again, disrupting the fuel pump power supply!
Again, this is a safety requirement.

The yellow starter motor solenoid circuit should be in-active once the key switch is released and springs back to the run position.
Any unwanted power here would be a result of a bad solenoid or solenoid circuit, IMO.
Is there something that I am missing here?

Just what is it that you are in need of checking and/or replacing?

."

"Absolutely nothing. In my sec

"Absolutely nothing. In my second response I corrected myself and said that I had figuired out what the RECTIFIERS pupose was. They are not relays although they could be wired in that configuiration.The original problem was a "starter" problem that grew into a starter continuing to run after start and then a starter energized in the KEY position, "RUN".The owner brought the "Problem" to a round table after several marine mechanics had not fixed the problem. The electrical diagram that he brought showed two rectifiers connected to the fuel pump. One was powered by the Y/R crank wire and the other by the Purple ignition wire. A marine mechanic had told him that they alternate and that could be the trouble so I wanted to know what he was talking about since he didn't explain.
Your explaination is in agreement with what I said except they were rectifiers and not relays.

On Wed, Oct 7, 2009 at 11:17 AM, MarineEngine.com Message Board <[email protected]> wrote:"

"Somehow lost the wiring diagr

"Somehow lost the wiring diagram trying to upload.oops to large, try this . elect diagram

"OK, now you tell us that this

"OK, now you tell us that this is EFI! LOL
This may be a question for a Volvo Penta dealer."

"We discussed something simila

"We discussed something similar for a carburated engine not long ago. The mission of the diodes is the same whether the engine is carburated or EFI.

http://www.marineengine.com/discus/messages/12487/293923.shtml"

"Well, if 28 and 29 are what w

"Well, if 28 and 29 are what we are discussing, I find it hard to call these "rectifiers". Schematically, and from the task that they appear to be performing, they would appear to be "relays" in my book.
This may have something to do with language translation.
What say yee, Eduardo????

It's sort of the language useage of the words Motor vs Engine thing, I suppose! Don't get me started on that one! "

"Look at the last drawing, not

"Look at the last drawing, not at the first one....."

Although they are represented

Although they are represented as squares and can be mistakened as "relays" they are Rectifiers.(also not diodes). Note that there is no (-12v) connection to be a relay.