Mitsubishi 4dq5 engine not starting when cold

stonny9 · May 23, 2013

My uncle traded for an older tractor last year. He was told it was a grey market tractor by the previous owner who bought it used a few years before and hadnt touched it in years. It has a Mitsubishi 4dq5 4 cyl diesel engine and from my research looks to be a 2wd MT4501 or MT43. Has 9 forward gears and 3 reverse

It doesnt seem to turn enough rpm to start when cold in 70-80 deg weather even when using starting fluid. Put a brand new 1000 crank amp battery and cleaned/greased the starter which didnt look bad at all and no change in starting rpm. It fires right up when pull starting in high gear and starts when hot but the starter acts more like a booster and the engine combustion brings it to idle rpm. Starter turns it over about 50% of the idle rpm which according to the dual needle gauge is 500 rpm starting and 1200 rpm idling. Seems kinda high and I am reading the top half of the gauge.

Is it supposed to have a preheater system? I have looked but didnt see anything and there doesnt appear to be any lights to indicate one. Tractor is 1.5 hrs away and wont be used until next winter.

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Kernopelli · May 23, 2013

I would be surprised if that model didn't have glow plugs, although I doesn't appear to have a "heater" window on the dash. You can always look at the engine and see if plugs are there. If so, turning the ignition key counter clockwise from the off position generally is how the Mitsubishis heat the glow plugs. Slow cranking can definitely be a starting issue and past reading on the subject suggests you usually need to turn 200/+ RPM to start most diesels easily. At 70-80 degrees, it should start right up...especially using ether ( which generally isn't good on the small diesels but I don't think cautious/limited use on your 45-50 HP model would be an issue). frankly, my tractors tach wont even read/hardly moves the cranking RPMs when I start it and at 70 degrees starts almost immediately. If you are showing 500/1200 RPMs cranking/idle, I wonder if your tach is accurate? If you have access to a hand held tach that you can use off the crank pulley to verify starter's cranking speed ( about $32 w/ 20% off coupon at Harbor Freight). that may take some of the questions out of that issue. Is it possible there is a fuel issue ( clogged filter etc.) that is limiting fuel supply after the tractor has sat idle for awhile? Also, I had a recently issue with fuel that was 18 months old and it caused hard starting........just throwing some things out there to start wih.

stonny9 · May 23, 2013

OK thanks for the info. Will probably be 5 months before it is started again. It was filled with fresh fuel after it shut off on me from possible low fuel and then I had to put it away as drain hose was leaking. Kinda hard to see under the hood but there didn't appear to be any heaters. I will look again and try the key trick next time. The rpm reading might be at the bottom of the gauge which is hard to read so I might try to polish the lenses to read it.There isn't a fuel filter but the low pressure pump works fine. Gonna add a filter inline next time I try to start it.

I will update the thread after I try it next time.

Ilikeurtractor · May 24, 2013

There's got to be some sort of starting aid and most likely it's glow plugs. I'd spend some time focusing on this area during your next visit and if it uses glow plugs have some handy to replace the existing ones as necessary. I've never seen a diesel that doesn't have some sort of pre-heat device. I suppose if the manufacturer only intended it to be used in Death Valley in July and August it might not have been equipped with a starting aid but anything beyond that usually is. Incidentally most glow plugs are active when the starter is engaged, and not just when one manually "pre-heats" so those that think their diesels start well w/o glow plugs are usually mistaken. Once you have the starting aid fixed you should be able to start it even if it doesn't turn over quickly as you might expect with the starter. Certainly the faster the better as you have experienced though.

stonny9 · Feb 7, 2014

Final update. 3 weeks ago I was able to work on this tractor again. After removing the air filter canister I was able to find the glow plugs and traced the wiring. Glow Plugs only came on when starting and the key switch was only putting out 10.5v both starting and key on only. I bought a heavy duty push start button and wired the glow plugs to it. It now starts up just fine. I cut about 5 hrs with it and am planning on cutting 80 acres in the next few weeks.

Thanks for your input.

stonny9 · Jun 7, 2014

As an update to this tractor incase anyone runs across another. We used it with a 5 ft brush cutter/bush hog to cut 60ish acres of 3'-4' grass/weeds. It didnt burn a drop of oil or leak anything. Only thing I dont like is the pto engagement. It is a very sudden/harsh/sharp engagement even at idle speed that torques the whole brush deck. Didnt see any adjustment for it. The shear bolts started to break from the engagement so I had to put a clutch on the pto shaft. 3 speed pto but something internal seems to slip when trying 3rd gear. It didnt start to spin after a couple seconds so I abandoned trying it so as to not cause internal damage somewhere. Low 1 gear is probably less than 1/10 mph. Has the set and forget throttle by the steering wheel and and spring loaded foot throttle. Need to get a cable for the foot so you can set the base throttle for working and use the foot to supplement for when it gets thicker so you dont have to stop and go to a lower gear.