I have read this thread with interest, but I have a Yanmar, and realize that they are going to be different, however, there are principles which should apply to all engines...so, to those more knowledgeable than me, what should I be looking for on my 3HMF Yanmar? (and, thank you to all who have gone to such lengths to make sure we who are not so mechanically inclined can understand and benefit from this discussion!)
Richard 1985 C&C 37, CB, Ohio River, Mile 584.4; Richard N. Bush 2950 Breckenridge Lane, Suite Nine Louisville, Kentucky 40220-1462 502-584-7255 -----Original Message----- From: Rick Brass via CnC-List <cnc-list@cnc-list.com> To: cnc-list <cnc-list@cnc-list.com> Cc: Rick Brass <rickbr...@earthlink.net> Sent: Tue, Aug 11, 2015 11:17 am Subject: Re: Stus-List Universal Engine panel wiring David; Previous owners, shade tree mechanics, and inexperienced/inexpensive mechanics often make repairs or modifications that are ill advised or less than optimal. For example, I recently helped one of the boaters on our City Docks diagnose why his recently replaced fuel gauge did not seem to work reliably. Turned out the guy who replaced the gauge had gotten power from the glow plug button – the downstream side of the glow plug button – so the fuel gauge was only powered up when the glow plug button was pushed. Universals and Westerbekes are designed to be wired and started in the manner described in the owner’s manual. I would restore the wiring to what is shown in the wiring diagram, for a couple of reasons. Regarding the 8V at the starter solenoid terminal: You saw battery voltage (about 12.6v) on the hot side of the starter button with the button not pushed, 0v on the output side of the starter button with the start button not pushed, and then 8v at the solenoid terminal when the button was pushed. When you push the button you are energizing the coil of the solenoid and creating what is almost a dead short across the solenoid. What you were measuring between the solenoid terminal and ground is the voltage drop that results from resistance in the coil, resistance in the metal of the starter, resistance across the bolts holding the starter in place, and resistance in the metal of the block as the current travels from the solenoid terminal to the ground wire. 8v is a bit lower than I would expect, but I see nothing unusual in such a reading. Your starter and solenoid are fine. As Neil pointed out, pressing the glow plug button does a lot of things. Of course it powers the glow plugs, which are in essence a high resistance short in the wiring, and the voltage at the output side of the glow plug button will drop into the 11.5v to 12.0 v range. Powering the glow plugs heats the air flowing into the combustion chambers, which is needed for a cold start and improves starting during hot starts. In indirect injection diesels (where fuel is injected into the airflow before the intake valve instead of directly into the hot compressed air just before the conclusion of the compression stroke) the glow plugs are needed to get good initial combustion. Hot air makes the starting easier and faster, reduces the load and cranking time on your starter, and ultimately how much current you draw from the battery to start the engine. The glow plug button also powers the electric lift pump that supplies fuel at 4 or 5 PSI (it might be as high as 7 PSI, but I don’t recall exactly) through the engine fuel filter to the inlet of the high pressure injection pump. That lift pump coming up to pressure is the rapid clicking sound you hear for the first few seconds after you push the glow plug button. After the engine starts, the pump is powered off the oil pressure switch as Neil described. In a hot start situation without power to the lift pump, the high pressure pump will supply fuel to the injectors for a few engine rotations. But if the engine does not start the pump will be starved for fuel and the engine will not start. Fuel starvation becomes more likely as your fuel filters get plugged over time. As I said, I’d put the wiring back to what it was supposed to be according to the manual and the wiring diagram. Rick Brass Washington, NC From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of David Knecht via CnC-List Sent: Monday, August 10, 2015 11:16 PM To: CnC CnC discussion list <CnC-List@cnc-list.com> Cc: David Knecht <davidakne...@gmail.com> Subject: Stus-List Universal Engine panel wiring Since I got my boat, I have been bothered by the fact that the engine will not start in the way it is described in the manual unless plugged into shore power. The manual says to hold the glow plug button for about 30 seconds and then while continuing to hold that button in, push the start button. When I do that, the starter does not turn over. If I release the glow plug button and push the start button the engine starts fine. My father (retired electrical engineer) and I (genetic engineer- useless in this case but sounds good) spent some time trying to diagnose the problem this weekend and found two interesting things: 1. The buttons both tested fine in terms of their switch function. We then tested power at the engine. There is a heavy red cable coming from the battery to the starter measured 12V. The red-yellow wire from the start button is attached to what I am presuming is the solenoid (the wiring diagram in the manual does not show a solenoid). We only measured 8 volts at the solenoid when the button is pushed, but 12 volts everywhere else. So that probably explains the fact that both the glow plugs and starter won’t work at the same time because we appear to be losing 4 volts in the solenoid. I will pull the starter next winter and have someone test it unless someone has an alternative suggestion. 2. The wiring diagram in the manual (Fig 2 on page 13) shows the power from the key switch coming into the glow plug button and then a wire from the other lead to the start button. The manual shows that wire running from the downstream side of the glow plug switch so that the start button should only be energized when the glow plug button is pushed (as the manual describes). If that were the case, the I would not be able to start the engine with only the start button. Nevertheless, it does start the engine. Tracing the wires, we found that the bridging wire actually came from the hot side of the glow plug switch, so that either button will work independently as both are always powered. What I don’t understand is why you would wire it the other way (as the manual shows) since that would remove the ability to start the engine without the glow plugs (as in an already warm engine). I don’t know if the PO or some yard mechanic made that change or if it is indicated wrong in the manual, so I am curious how other Universal panels are wired. The way it is actually wired makes more sense to me than what is in the manual unless I am missing something. Thanks- Dave Aries 1990 C&C 34+ New London, CT _______________________________________________ Email address: CnC-List@cnc-list.com To change your list preferences, including unsubscribing -- go to the bottom of page at: http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com
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