Jinma 254 starting problem

[Raw Bone]

Hello Everybody,

I'm new this website and I am having a problem starting my Jinma 254 after it has been sitting for about 4 months. It has been stored inside and when I went to start it, it started after just a couples of revulsions. However it starting gaining rpm's without giving it any throttle and I pulled the kill button/plunger to stop the fuel feed and it died. When I attempted to start it again it will crank just fine but won't fire. Normally when I crank it to start I'll get a small cloud of black smoke prior to it starting, but after the runaway start I just get a very little light gray smoke that dissipates as soon as I stop cranking it. It seems as if I'm not getting any fuel. The tank is full and the glass sediment bowl just below the tank is full and clean. If I have lost the prime, how do I get this problem cured? Any suggestions would be greatly appreciated.

Thank You,

Raw Bone

 

[RonMar]

You might get more answers with this in the chinese section, but don't repost it there(multiple posts are very annoying). Send a message to admin and ask them to move this one there. Down in the lower left below where your name and avitar go is a little red triangle to report the post to admin. Click on that and there wll be an area to write them a note to tell them where you want it moved.

To help try and solve your problem, when you pulled the kill knob, it works a lever on the injector pump. When you release the kill knob and it goes all the way back into it's run position, does the lever on the injector pump also go all the way back into the run position? IF the lever didn't go all the way back, this could explain why it won't start now. How much throttle are you giving it for startup? I usually give it about 1/3, or about the position that gives me about 1200RPM when running. and as soon as it fires, I pull the throttle back to the idle position and let it warm up at it's 900RPM idle. How is your cranking RPM. A little slower RPm can make a big difference in how well it will start.

If you had lost pump prime, the engine probably wouldn't have started in the first place. How warm or cold is the engine. Did you try glowplugs during that first start? Could anything possibly have nested in the air intake pipe during the past 4 months?

Just a couple of things to look at...

 

[psj12]

From the initial runaway situation it may be possible that the rack is binding or stuck. The govenor flyweight/spring pressure couldn't move the rack to a reduced fuel position but you did manually. Now the govenor cannot overcome the no fuel position on the rack. When did you last change or add lube oil to the pump sump? Sometimes the rack can be freed by lubing it and manually moving it back and forth.

 

[Diamondpilot]

I think its a stuck rack or something else in the pump. Have you checked the injector pump oil for clues? Is it possible all the pump oil ran out during storage?

Chris

 

[greg_g]

Yup, Chris has likely identified your problem. I too am betting one or more piston (inside the injection pump) stuck during those four months sitting idle. When a piston sticks, the governor is fooled into thinking it has to cope with a full throttle situation. Usual reason is that new owners don't realize that the pump assembly has it's own oil sump that must be checked regularly. Less common -but still possible - is an actual pump casualty.

It's possible to partially disassemble the pump and free a stuck piston. If no associated damage has occurred, a little local lube followed by draining/refilling the pump sump (with engine oil) should free it up. After that, check periodically to see if any diesel fuel has seeped through into the sump. I try to drain/refill mine on a semi-annual schedule (spring/fall).

//greg//

 

[Raw Bone]

Hello Again,

Do you have anymore info about how to free these stuck injector pump pistons that you're refering too? If you have any photos of this fix could you post me a reply with them? I'm going to remove my injector pump to gain access to the governor located at the back of the pump. I noticed that ears for the mounting bolts are slotted and I'm pretty sure that this is for adjustment / timing of some sort, for the pump. I'm going to match-mark it's present location before removal so I can reinstall it in the same position. I would like to know what the adjustment is for exactly. Any information in regard to this will be appreciated.

Thank You
Raw Bone

 

[greg_g]

Well, I've never had the problem with any of my pumps. But I'm almost certain (most of) those who've described "unsticking" pistons did so without removing the pump from the tractor. I can't recall where I saw the photos now, but the pump was partially disassembled - but still on the engine. Not all pumps are the same of course. But for mine, I'd just start by removing the hard lines -and see where that takes me.

//greg//

 

[Rich Waugh]

Those slots are, I believe, how you adjust the injector timing, which is similar in function to th espark timing on a gas engine. I would definitely look to do whatever I could to free up the pistons without removing the pump if at all possible. Drain both the pump and the governor ( you should get about 20 oz. of oil, I believe) and then refill with white kerosene and run it through a few minutes and drain out. If the engine won't start at all, just pull the compression release and crank the engine for a minute or so, in bursts of ten seconds or less so as not to overheat the starter. After draining the flush out, refill with the proper lube, giving it time to run from one side to the other to be sure both sides are properly filled. After that, you can try using the hand pump to re-prime it if you think it is out of fuel.

I trust you have actually pulled the fuel line where it enters the pump to make sure fluel is actually flowing. There are hidden filters/strainers in the tank that can get clogged with dirt, debris and bugs and the sediment bowl and external filter look full bu tno fuel is flowing to the pump.

Let us know how this works out and we'll see what else we can come up with if that doesn't work for you.

Rich

 

[biggerten]

Drain both the pump and the governor ( you should get about 20 oz. of oil, I believe)

Considerably less, just a few ounces.

 

[Red55]

When I change my injector pump oil I get considerably less too (about 12oz) Yes I do pull both drain plugs. Kinda leary of running with kerosene in the pump might be better with diesel either way I wouldnot let the engine run without the proper oil. Don't know if it would help but what about AT fluid? Hear stories all the time on how it will flush out a dirty engine and then blow it up when the oil pump pick-up screen gets clogged Good Luck -Ed

 

[greg_g]

I'm pretty sure that kero has better lubricating properties than does diesel fuel. And anyway, there's likely already some diesel fuel mixed with your pump oil. That's why I try to drain/refill my pumps twice a year - to get rid of the diesel that's gotten past the rings.

Kero should need less than a minute of the engine running to flush that little pump. No guarantee it will actually free a stuck piston though, you should actually try to do that first - then drain/flush and refill with clean lube oil

//greg//

 

[Affordable]

The stuck piston is below where the hard lines attach to the top of the pump,you can remove all the hard fuel lines,carefully take the head off,under it are 3-springs and disc's one for each cylinder,the disc are what stick most of the time or have debris in them,it also could be a stuck fuel rod.You do not have to remove the pump to do this,

Tommy
Affordable Tractor Sales
Home of compact Jinma, Foton, and Koyker Tractors and Parts, Wood Chippers, Backhoes - Affordable Tractor Sales Company

 

[psj12]

Kerosene does not have the lubrication quality of diesel. In fact jet fuel, which is kerosene, has to have lubricity additives put in it to make it compatable with the army's diesels. The army and all the services now use JP8 in ground equipment and aircraft. We experimented with the older diesels prior to the army adopting this standard and found it did shorten injector and pump life even with the additives. The difference was not signifigant enough to stop its' adoption. Newer military diesels are more compatable. Also kerosene produces on average about 11% less power per volume than diesel. In the older style pumps found on Chinese tractors it is all about volume.

 

[greg_g]

Fair enough - but this is about cleaning (flushing) the pump, not the engine. Perhaps you assume the pump shares engine oil - it doesn't. The vast majority of injection pumps on these Chinese utility tractors have their own little sump. Filling the injection pump sump temporarily with kero flushes the pump only - and has nothing to do with the engine.

//greg//

 

[psj12]

The oil sump in the pump lubrecates the cam and followers for the pump and the govenor assembly. The pump piston itself is lubrecated by fuel only.

 

[Ranch_Hand_Supp]

Kerosene does not have the lubrication quality of diesel.

.

I agree.
Doing a un-educated test by rubbing Diesel fuel then Kerosene between your fingers will allow you to feel the difference.


Ronald
Ranch Hand Supply

 

[greg_g]

I stand corrected. I drew my own unscientific conclusion after obtaining exactly the opposite of Ronald's uneducated test. Yet the 2-1 margin pushed me to actually look it up. Kerosene and #1 diesel fuel do in fact contribute less lubricity than does #2 diesel fuel.

But I'm skeptical about diesel fuel lubricating the pump piston. A rotary pump maybe, but these are inline pumps. As such, I thought that the piston rings (or discs) drew oil up from the sump to lube the cylinder wall. It's always been my understanding that the lubricity characteristic of (sulphur in) diesel fuel was for the benefit of the seals, valves, injectors, etc. So I'm still thinking that temporarily replacing the pump's lube oil with diesel or kero will wash the cylinder walls, against which a ring (or disc) may be stuck.

But I was wrong about diesel versus kero lubricity, so please educate me if the above is incorrect or inaccurate as well.

//greg//

 

[psj12]

Diesel high pressure fuel pump pistons do not have piston rings. They are precisely lap fitted to bore of the pump cylinder. The clearance in the pump piston and cylinder are measured in hundred thousandths and even millionths of an inch. This gap would not allow lube oil to work. The upper end of the piston gallery is sealed from the lower end of the pump assembly to prevent oil sump contamination. The clearances are so small that when handling the pistons you should never touch them with your dry fingers. Always wet your fingers in fuel or light oil first. The dry spot caused by touching them could cause them to sieze. Pistons are permanently mated to the bore they are in. A very small amount of fuel that gets by the piston is returned in a return line. The small clearances are the reason pump pistons sometimes freeze in their bores due to contamination. Water and solids being the worst. The only thing that returns the piston from an up stroke is the spring on the lower end of the piston.

Sometimes a piston can be manually freed and will continue working. Sometimes it becomes siezed in place permanantly. When this happens if the pump has individually removeable pumps then that one has to be replaced and the pump calibrated. If it has integral pumps than the entire pump assembly must be replaced.

The piston has a helix cut in it that opens a small port on the side of the piston bore that allows fuel to flow into the bore of the pump. The rotation of the piston determines the position of the helix in relation to the port thus changing the amount of time the port is open during the down stroke thus how much fuel enters the bore. The rotation of the piston is controlled by the rack which is moved by the govenor.

When you press on the throttle all you are doing is putting more pressure on the govenor speeder spring that has to be overcome by the flyweights. So the flyweights have to spin faster to overcome the spring pressure before returning your fuel rack to a lower fuel position.

 

[greg_g]

Diesel high pressure fuel pump pistons do not have piston rings. They are precisely lap fitted to bore of the pump cylinder. The clearance in the pump piston and cylinder are measured in hundred thousandths and even millionths of an inch. This gap would not allow lube oil to work.

Bear with me, it's clear that I'm still climbing the learning curve here. I admittedly have zero design knowledge of these Chinese tractor pumps. But that said, methinks you may be attributing tolerances to them that may not typically exist. Elsewise, how is it that fuel-contaminated pump oil is reported so often in these Chinese tractor forums? Can't blame one specific pump either, cuz both my current tractors use different pumps - and I still find myself draining fuel-contaminated oil from both about twice a year. And I say we collectively - since this specific issue has been reported here across the manufacturer and model spectrum.

Or am I also incorrect in assuming that compression pressures force fuel down the cylinder walls and into the sump? Is it leaking in from somewhere else? Yet - if there isn't even molecular tolerance between the piston and the cylinder wall - what makes a formerly reciprocating piston stick after sitting idle for a while? I thought it was from wet fuel. And if the tolerances are as tight as you state, how does diesel fuel "lubricate" the cylinder walls in the first place? Matter of fact, why then do they have lube oil sumps beneath the cylinders in the first place?

Again, I'm not challenging your knowledge - you obviously know more about injection pumps than do I. And your descriptions are very clear. Unfortunately - for me - they have created more questions than answers.

//greg//

 

[Bob Rooks]

If I may interject here, psj12 is correct on all counts.
What may cause plunger/barrel sticking after sitting idle for some time is moisture in the fuel causing oxidation or bugs. Bugs live in the water/oil interface layer and can completely ruin entire fuel systems, hence the necessity to keep fuel clean, very clean.