UNiversal starting problems resolved!

After nay years and many suggestions ( even from the Mfg) I have finally solved my starting problems! From new batteries to new cables and upgraded wiring as well as a solenoid replacement, nothing fixed the problem of starting my MD 12 ! Finally a month ago I replaced the start and glow plug buttons and the ignition ( key) switch , and now she starts like brand new.....Best $60 bucks and 30 minutes I ever spent!

Pass it on!

I have also replaced both of those switches, and found it helped. But the other great modification not to forget is listed on this site under "Owners & Projects," and has to do with altering the wiring a bit to allow the ignition to be hot without engaging the glow plug switch. This is not just a convenience, it also helps starting, as more amps are now available for the starter motor. My engine was that hard to start, but I made the modification just because I got tired of always having to explain to guests and yard folks that the reason my engine wouldn't start was that they weren't holding down the glow plug!

Watch the gauge

I have always observed my battery meter on the engine panel when I hold the glow plug button in. It had better set the meter down to +- 10 -11 volts, or I know there not working. 15-20 secs then she starts everytime cold.

Steve E35-3

Listen to that blower

I use a similar method of making sure the glow plugs are working. I flick the engine compartment blower on. The blower itself is not as necessary on a diesel as it is for a gasoline engine but it can't hurt.

When I push the glow plug switch I can hear the pitch of the fan distintly change as the plugs pull down the voltage.

I don't think it is that simple. Here's the reply from the Torreson site on an inquiry about checking glow plugs:

"1. Check the glow plug with a multi meter for resistance. Should get a reading of 1.6 ohm.

2. Check for current draw. Draw should rise up and then decline. However, if there is a short it will simply peg and stay."

Geoff,

Yes, that's the way to definitively check the glow plugs. Watching the voltmeter drop or listening to the blower slow is just a quicky that generally tells me if my plugs are drawing significant current, before I start pulling out the multimeter.

If I'm having a hard time getting the engine to start and I don't hear the fan speed sag, my best guess is that a glow plug is bad and I'll pull out the multimeter and do the detailed checks you mentioned and look for a possible bad connection in the circuit.

If I hear the fan motor sag with the plug button pushed I'm probably going to look elsewhere first for the starting problem. I'll start with the easiest and most likely culprits, like no fuel (never skip what should be completely obvious), shut fuel valve, air in the line, clogged fuel filter, etc., moving on up to bad fuel injectors, etc. By then I've got my head pretty well stuck in the engine compartment and will probably be checking the glow plugs while I'm at it.

Actually, I was referring more to Point 2, namely that the current draw will rise and then decline. Maybe somebody can explain to me the electrical principle behind this observation (is it because resistance increases with temperature?), but this thread seems to be assuming that a rise in the current draw by itself indicates properly operting glow plugs, when, in fact, there may still be a short.

Geoff,

Yep, you got it about the change in current draw. Most materials increase resistance with temperature. This is a useful phenomenon. In the case of a glow plug it will draw more current until it heats up. The hotter it gets the higher resistance and the less current it draws until it reaches a balanced steady state. Incandecent light bulbs do the same thing although they come up to operating temperature so quick you'd have to use an oscilloscope to pick up the initial inrush of current.

Just think if the opposite (resistance decreases with temperature) happened. Initial current would heat the element, lowering its resistance, increasing current, heating it even more. You're now in a runaway situation until you burn out the element, shutting down the circuit.

With a glow plug the most likely failure mode is a burn out of the element and an open circuit with no current draw when you press the button. If you have a short you'll pull too much current, opening the circuit breaker or blowing a fuse or fusible link. Again, no draw of current and no sagging voltage or slowing blower motor.

However, that brings up a good point. Off the top of my head I don't know how that starting circuit is protected. I'll have to check the diagrams when I get down to the boat.

So what is the life expectancy of a glow plug? At $57 each, they should last forever.

Never had to replace one of mine in the six years I've owned the boat. The boat came with a spare plug (and injectors) but never had to use them. Only problem I've had with the system is a loose connection that only took a few minutes to fix.

Haven't got to the boat yet but found in the Universal Owners Manual that the starting circuit is protected by a 30 amp fuse plus a 20 amp fuse just upstream of the starting solenoid. Will have to stick my head in and locate them. Sounds like something else to keep as spare. Hope they're not $57 each.

Looking at the diagram I also noted something else. Since there are two plugs (at least on my two lunger) I could have one bad and maybe not notice on my quicky check. My guess is that if one was bad you might have a little harder time starting since only one cylinder would start firing. However, after one cylinder carried the other for a few seconds I would guess that the second cylinder would fire off since it would start to be heated by the compressing air.

Yes it would be a good idea to have a few of the 20 amp mini fuses on board. (They're cheap.)

In the last 10 years there have been three times when my engine wouldn't start, and each time it was the 20 amp fues that had blown. The last time it wouldn't start even with a new fuse, and I found out that the in-line fuse holder had gone bad. I jury rigged it by just soldering the fuse in-line till I could buy a replacement fuse holder, and now keep a spare in-line fuse holder on board too.

Steve,

I bet it was that fuse holder which caused the earlier fuses to blow. If the fuse holder's contact to the fuse is weak there is a poor, high resistance contact. When current flows it causes heating. That heating plus the normal heating of the fuse when the load current flows makes the fuse blow at less than it's rating.

Spare fuses, then fuse holders. Before you know it I'll end up with a complete spare boat.

Jim,

I hadn't thought about it, but I bet you're right about the fuse holder itself being the cause of the problem. It lives in a pretty terrible environment for anything electric.

As for spares, I like to have lots on board (spare electric fuel pump for example). But my wife has a more fatalistic approach. She feels that something WILL fail, and that it will NOT be something for which we have a spare. There fore having all of the simple spares aboard is tempting fate, meaning that the failure will have to be something big like a piston of cylinder head.

Still, I find it very hard, when something breaks down, not to buy a replacement AND a spare. Could that be why the waterline hasn't been seen in years?