Glow plug system

[T J]

Hi
I have a 1993 Mitsubishi MT15 D diesel tractor, 3 cylinder I recently bought. Used of course. I turn the key on, the glow plug light comes on, I let it be for a minute, then try to start. I was told to just turn the key on (there is not another glow plug "switch" nor do you turn the switch the opposite direstion to heat glow plugs) and wait a minute. It takes several cranks before it starts. I tested the glow plugs. The glow plugs are good. I don't know if the relays are good. and don't know how to test.
I have a Mitsubishi D2350 and it starts right up after using glow plug part of switch.
I also have a Bolens diesel and it has a seperate glow plug "switch" you turn and hold for 30 seconds or so to heat the glow plugs.
Suggestions welcome.

 

[ericm979]

Many newer tractors have a glow plug timer that comes on automatically when you switch the ignition on. The timer may measure engine or ambient temp to determine time, or it ma be a fixed time. They usually have an indicator on the dash which lights when the plugs are on and turns out when they go off. It sounds like yours does not have the indicator. You might look for an owners manual to find out.

A minute is probably too long to wait though, and may be why it's hard to start. Try 20 seconds.

 

[T J]

Thank you. This is a 1993, so I don't know if this is considered newer? I tried about 30 seconds and about one minute. Seller told me wait about a minute. but I don't think he know for sure either. I'll try your suggestion.

 

[LouNY]

Do the glow plugs get hot to the touch ( be careful could burn),
or check for voltage to the glow plugs with the key on.

 

[T J]

Yes they checked out okay. What should the voltage be to the glow plugs. I aSSUME YOU WOULD JUST PUT THE POSITIVE LEAD ON THE GLOW PLUG STRIP AND OTHER LEAS ON GROUND TO MEASURE?

 

[LouNY]

Yes that is a quick easy way, most you will get 6-8 volts to ground.

 

[Hay Dude]

Yes they checked out okay. What should the voltage be to the glow plugs. I aSSUME YOU WOULD JUST PUT THE POSITIVE LEAD ON THE GLOW PLUG STRIP AND OTHER LEAS ON GROUND TO MEASURE?

When you say they checked out good, do you mean they get power, or are they actually getting hot?
They could be getting current, but the element itself not working. A 1993 is a pretty old tractor and could need new GPs

 

[T J]

I tested the glow plugs individually and all were okay.

 

[DonRybak]

TJ, when you say they tested good individually do you mean you removed the wire from each and measured the resistance of each one or that they each are getting hot?

 

[LittleBill21]

put an amp meter on them. should pull over 10+ amps, easiest way to confirm

 

[T J]

I tested the glow plugs individually and all were okay.

I checked each of the three individualy

 

[T J]

Dude. this morning I connected volt tester ground to battery ground, put positive end on bar that conncts the three glow plugs, turned on switch. Glow plug light lite, no voltage to glow plugs.
any more suggestion.

 

[rScotty]

Sounds like your glow plug relay has two contacts inside - one for the glow plug indicator light and one for the glow plug voltage.

The glow plug side is probably fused, so check the fuses first. That will probably be the biggest rated fuse in the fuse holder. If the fuses are OK, next thing to check is the glow plug relay. Those glow plug relays go bad; they don't last forever.

To find the relay, trace the wire that connects to the bar feeding voltage to the three glow plugs. Follow that wire and make sure it is good & not burnt up. Following that wire should be easy as it has to be a fairly heavy gauge wire.

Anyway, check that wire back to the relay which is a pill box size box probably under the dashboard. That under-dash box ought to be the glow plug relay.

Expect that relay box to have 4 wires: the one to the glow plugs, another heavy gauge wire back to the fusebox, a smaller wire up to the glow plug light, and a medium wire to the ignition switch to power up the whole system when you turn the key.

When you turn the key, putting the negative voltmeter lead to the frame, and the positive meter lead on any those other wires should show 12 volts give or take an volt. If one of them doesn't show voltage either the relay or the wire - or the key switch itself - is bad.

rScotty

 

[T J]

TJ, when you say they tested good individually do you mean you removed the wire from each and measured the resistance of each one or that they each are getting hot?

Yes

 

[T J]

Scotty
Ill try that Monday, thamks

 

[rScotty]

Scotty
Ill try that Monday, thamks

Sure enough. The other check is to make sure the battery is a good one with good connections to the battery cables.
If the temperature is about 30 or 40F or above, even a worn diesel should start right up if the starter cranks it over at normal speed. It should start without needing any help from the glow plugs at all.

 

[skipmarcy]

Sometimes, as on my Mahindra, the power to the glow plugs is protected by a fusible link, not a fuse. A fuse protects the RELAY control side but not the power wire to the glow plugs.

 

[WranglerX]

Trace wiring back from buss bar on GP's to source of power for GP's (key switch) ... Some where along the way you will find a malfunction (bad relay/bad fusible link/bad fuse/loose connection)... Wiring diagram from factory service manual would be big help....

 

[T J]

As to my Mitsubishi MT15D tractor. I am still working on glow plug issue. I have checked all that has been posted, and then some. Thank you
However, still not functioning. The person I bought from installed a new ignition switch. I do not know if it is wired correctly. I have Southern Global MT15+ book, with a wiring diagram.
So, the question I have today is: Did this original ignition system switch have a turn back position for glow slugs, or did the key turn to start position, wait a few moments and then start engine?
Currently, when I turn switch on, before starting, the glow plug light does not light. I wait a few seconds and it cranks and starts but takes several cranks to do so. I have two other tractors so am used to diesel operation.

 

[LouNY]

On my older F2000 mower the glow plugs are activated by the key switch being held inbetween the run and start position.