303.5 glow plug operation?

Hi Matt, It looks like the glow plug indicator in the monitor display is taking it's signal directly from Wire 877 F51 this goes through the 5a fuse switching to wire 439 F47 and onto the monitor. So in reality if the glow plug light is coming on in the monitor the timer should be activating the relay.
I would check for voltage at the glow lugs when you you turn the key on. If you get a flash the circuits should be OK.

The next thing is the logic used in the timer as Ken mentioned. I would assume the timer has the ambient temp sensor incorporated into it. The other thing is that temps here have been unseasonably warm and the timer may not be calling for the glow plugs. Depending on the engine used that could be fro 45-30F and usually it only comes on for a brief time and timer then extends the duration according to decreasing temps.
It can be difficult getting that info from the product group if it is not easily available to the dealer. I Have been through that when I worked in Syr.

Is your father named Matt as well and lives on South Hill?

Matt the connections on the releay should as below

#3 - 200 Ground
#4 - 308 Should have voltage with key on
#5 - 306 Should have voltage with key in start position
#6 - L987 should b e ground when glow plugs are activated.

So make sure pin 4 is hot with key on and pin 5 is hot with key at start

By jumpering the ground contact on the relay it makes the circuit work like it should and the dash light comes on with it. I didn't happen to notice if that rental unit had a Mitsubishi engine in it. Mine appears to be. It's got the 3 diamonds logo on a sticker on top of the valve cover. And no. That's a different Matt eaton. Not to far away. I do know them.

Ben Witter said:

The next thing is the logic used in the timer as Ken mentioned. I would assume the timer has the ambient temp sensor incorporated into it.

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Never thought about that, there could be a sensor built into the timer "Brain box"!

Well that was a surprise, just for fun I checked the price of the timer # 119-9896 and it is only a bit more than the relay $95.53 and one is sitting in the Syracuse store.

Now all we need to do is figure out which one Matt needs.

Seems if there is power to one of the white #18 wires on the relay and when a jumper is used to ground the other terminal that has the other #18 wire on it and if that powers the glow plugs that would say the relay is functioning, if not then the relay is at fault.

Does that sound right Ben? Just don't want to spend any more of Matt's money than we have to!

OK maybe you're the Eaton's from Cincy way then? I am just over the hill (or 2) from you

Does sound like a Mitsu. Like I said depending on the logic/strategy of the glow plug operation it may not even be calling for operation at these temps. Maybe in the next few days it will get cool enough to see if they will come on for longer .
Are you having issues getting it started now?

Yeah that's us. Willet. It has always started. But I thought it always seemed sluggish on the cranking and the crank time. I've only owned it a few months. When I used the rental 303 in town it started like a gas engine on a car. Easily twice as fast as mine. And I noticed the glow plug indicator cycling. Which mine doesn't do. I'd like to get whatever I need and a cat battery in it before it actually doesn't start when it's cold.

I think if any thing is faulty it is the timer. But I would rather he wait for cooler weather or Use something to cool the timer down and see if glow plug activation time increases. You could always shoot it with a CO2 fire extinguisher or take it off and put it in the freezer for awhile then try it to see if it works better.

Of course I would have probably have to set it in my cooler full of cold beer to do this....LOL

I've just got the two beer fridges. Don't have a cooler out. And I'm not the only one thinking of shooting it with a fire extinguisher. Saw it on myth busters. But I'm not going to do that. Would cat be able to tell me the range if there is one for the temperature

Of course if you don't want to pend $100 or more by the time your done. You can always put in a push button and run the L987 wire to that and the other side to ground. That way you can call for glow plugs anytime you want. Besides that would tell you if you get an improvement in starting with increased glow plug time

I was thinking of that already if it's going to ne an issue. I wonder what just a new battery would do. There is a "Deka ultimate" battery in it. 850cca. Ever heard of that? Looks like a $50 Walmart battery to me. Looks new. Ish.

Maybe. The guy to talk to is Todd. He is like their technical expert. Or at least he was there last I knew. Things have changed quite a bit in 15 yrs.

He still may have a tough time getting the info.

How do I really tell if the glow plugs are good. Test light lights up on the connecting post of the glow plugs, when I jumper the ground. Should in be able to feel them getting warm on the outside after 15/20 seconds.

I would think you should feel them but if they are long enough you may not. You can measure them with an Ohmmeter from the connector to engine ground and compare them to each other or I am sure that Cat has a spec for them.

You can wait til the morning and just ground the relay for 20 sec. then start it and see what if any difference it makes.

Also comparing one machine to another even of the same model may not be an accurate measurement. Engines and systems can change and results will vary

Hi Guys,
Its been my experience you cannot test them using ohm meter.
What seems to happen to them is the resistance wire in the tip of the glow plug gets thinner over time and even though they measure the correct ohms with a meter, when a current is applied the current draw is way down from original due to the wire being thinner .
As a quick test we use a non intrusive amp meter which goes over the main wire as a test.
Usually they are wired in parallel so better test is to disconnect each one and apply power and test current draw.
A lot of people go around in circles with glow plugs being side tracked by the fact that they are drawing current.
The fact is they must have the full design current as they only have seconds to get hot sometimes glowing red hot at the tips.
So even half original current affects there performance dramatically.
Word of warning if you are applying power manually and your plugs are old and weak they sometimes pop and finishes them off so don't take all day making your current draw test.
You mentioned somewhere it was not cranking as sprightly as the rental.
The battery, cables, and starter have to be tip top in cold weather.
A weak battery will reduced cranking speed and reduce your heat off compression and also supply less current to your glow plugs reducing there effectiveness.
Its hard some times to find what the current draw should be and some times you can get it from the plug itself.
Good Luck.

Some good points there. I'm getting a timer today so tomorrow morning I'll see if it's any better. Go from there if something else is suspect. Thanks for all the help and comments.

The timer brought the system back to life. Indicator comes on, starts way better. I've tried it a few times so far. Not been super cold but already notice a huge difference. Thanks for the wiring diagram and the pointers.

Matthew Eaton said:

The timer brought the system back to life. Indicator comes on, starts way better. I've tried it a few times so far. Not been super cold but already notice a huge difference. Thanks for the wiring diagram and the pointers.

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Don't worry by the end of the week you should see overnight temps in the low 40's to middle 30's! to test those glow plugs!

Glad that it seems to be working now!