The glow plugs in my D6c (3306 PC) have a habit of burning out. Using them for short heats (20-30 sec.) works fine but in colder weather where you heat longer they start burning out and popping the circuit breaker. Have had it happen several times. Not sure how long is too long to heat them... I've read up to 2 min in cold temps but I haven't gone near that long. Any idea what's causing the problem?
Try cycling them.. instead of a constant "on" heat.. Try counting to 20 seconds several times on for 20..off.. on for 20..off.. back on for 20.. start.. PLUS,, u may have a fuel supply issue.. is it "smoking white" when u try to start it..?? That's usually an indicator you ARE getting fuel & its just a cold cylinder.. BUT if your NOT smoking white, then u may have a supply issue.. & not a "heat" issue..
Do you replace all of the glow plugs at the same time?
Where are you getting the glow plugs from? On the old machines I've worked on many times I've had them on for three minutes or more and never had one short through. They should pull between five to seven amps each so total draw on a six cylinder engine would be between 30 to 40 amps. How did you check to see that they were were burned out?
I did some digging on SIS with no luck finding spec's for glow plug and only found torques of 120 inch lb. So I dug out an old manual I have and found my notes for at least one glow plug and it was the 1P7324 which is one of the numbers used in a 3306 among other engines. One note says 4.5 Ohms which at 24 volts would be 5.3 amps The other note says apporx. 6.5 amps which at 24 volts would give a resistance of 3.7 Ohms Both of those are right in line with John C.'s spec's
Both of my same era Cat machines with direct electric start require up to 2.5 to 3 minutes below 20F. 2 minutes above that. That's from the operations manuals along with the amp draw. Much less amp draw than from the starter spinning. They should hold up to holding them on that long. Are they Cat glow plugs?
Last time I replaced all the plugs at the same time. I bought Cat plugs so I hoped that would solve the problem. A couple of days ago I had one fail. I'd started a couple of times, heating about a minute, but the last time it failed after heating for only a few seconds, popping the circuit breaker.
Did you check the plugs with an ohm meter? I've only had trouble with then when the top connectors are bent and pushed over the insulator or when the tips of the plugs are burned off. Most of the time the problems are in the harness and connectors.
I fail to see how any mode of electrical failure could cause these glow plugs to burn out. 24 volts is all it is. Maybe they got a bad batch. I would be returning them to the dealer ASAP so they can try and figure out what the problem is with their plugs.
I'm not familiar w/ the set-up.. They're obviously push button operated, if everyones count is different, right? Then whats after the button? Does it go thru a relay? D6, have u checked to MAKE SURE your button isn't stuck ON.. cuz that'll do it in a heartbeat.. or partially ON.. feeding voltage to the plugs after its started.. I'm just thinking outloud.. because I haven't seen any indicators that u checked anything.. just keep replacing them.. A simple volt/ohm meter or even a 5.00 testlite will show u what's up..
Hopefully you’re not getting 12 volt glow plugs. Check them with an ohmeter to see If they have the resistance listed above.
Seems like junk manufacturing. They only produce about 120 to 150 watts of heat each. Old school recommendation was anything below 32 deg. F. was two minute heating plus ether.
Dam good point Mobiltech..!!
Any chance you have the part number off the ones that failed? Back in the day when just about every Cat at the quarry had glow plugs and up till I retired and there were a few still running them I can only think of maybe a hand full of failed glow plugs. Most of the failed ones just plain did not heat seldom had a broken tip! More often the problems were bad connections where the wire clipped on the top. Actually the last one I did work on was in a D6C dozer and only problem was the wire harness attached to the to of VC.
Well about all the Cats with glow plugs I recall had a dual function switch, turn counter clockwise to power glow plugs and clockwise to work the stater. So it would be hard to accidentally leave glow plugs on. And as these plugs should be able to be operated for minutes and not seconds I kind of doubt someones timing is the problem. Usually my had would get tired long before the allotted time had passed as that switch had a strong return spring! That said I would not rule out the possibility of a faulty switch, never saw it happen but never say never!. Seems as though it would be obvious if switch was sticking in the "heat" position as if the disconnect switch was turned on the amp-meter should swing way over to the "discharge" side. Even if it only acted up after running I believe the electrical load from the glow plugs would cause the amp-meter to show a discharge at anything below high idle.
Okay took lots of digging on SIS but finally found the instructions for how to start using glow plugs. Not the last half of the first sentence.
Normally if a glow plug burns out it stops making a connection never had a glow plug pop a breaker before have you checked your harness to make sure there is not a short
I did have a glow plug short on me last year, it had one of those little glow heat indicators in series on the machine and it would burn up whenever you tried to use the glow plugs, expensive little guy too. I ohmed out the plugs, due to the low ohms of everything it was hard to tell but I replaced just the one that showed low, and it has been happy ever since. I was disappointed in the guy who sold it to me, he had warmed up the machine before I inspected it (twice) presumably to hide the problem from me. Glad it was not worse.
My old 10K D6C is a real good starter when cold. At 20f it only requires about 30 seconds & away it goes...…….At 0f I will heat for about 75 seconds & it starts right up. It has the D333C in it.
They don't normally short out, just the heating element (resistance coil) burn out.
That's a great illustration OM. Does the insulation portion glow red when they heat?
Everything that is colored a dark red in that picture that is about 1/8" below the end of what is labelled plug body will glow red/orange when heated up.
They're definitely 24v but I don't have the part no. handy. I do know there are two different plugs listed, depending on arrangement no. Every time I've had one fail they've always shorted and popped the circuit breaker.... otherwise I wouldn't know I had a bad one.
Not sure but thinking the different glow plugs might be because of the size of the terminal the wire hooks on to. Most of the ones I dealt with had a terminal that looked like the top of a spark plug and then the newer machines had a small stud about 1/8 inch or smaller for the wire to slip on.
Correct glow plugs would be a 1P7324=3T9652=3S9624=4S7824=7M1634=9H4577 Terminal end looks like spark plug terminal. Alternates would be: HKT RK98 NGK Y171 Bosch GPC921