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I asked a specific question about my Jinma injection problem and have not found a solution (Posted about 6 posts below this one on June 4th and titled 'Jinma 284 fuel injection problem'). I would like to ask a couple of more general questions to try to get pointed to the source of the problem.
I have a new injector pump and am trying to determine if the problem is with a defective injector pump/governor or if it can be caused by the timing being incorrect. I have changed the timing a little at a time over a wide range and the problem stays about the same. The engine can pull fine as long as you want it to, but as soon as it idles down it acts like it is starving for fuel and is unresponsive to any change in throttle position. Once this happens it has to be turned off for a good while, after which it is back to normal. It is not a problem of lack of fuel from the lift pump or with filters or lines. It appears it may have to do with excessive fuel accumulating in the cyliners from being injected out of time because it puts out more smoke as it struggles to keep running. I have a timing gear with centrifugal advance and have wondered if it may not be working properly. I can start the engine and let it idle util it starts starving out after about 5 minutes with no action from the centrifugal advance, so I don't think that is the problem. My question is, is it possible for timing to cause this problem and still have the problem remain unchanged over a wide range of timing changes? Does anyone know any technique to narrow down the source of this problem or to eliminate possibilities? I've got the timing in the right area based on the timing mark on the front pulley and spill test.
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There is no obstruction on the return line. When I pump the manual lift pump it pumps freely and I can hear the fuel splashing into the tank. Pumping the manual lift pump has no affect on how the engine is running when it is running normally or when it is acting like it is starving. The engine keeps running normally at working speed, but once it idles down it starves fairly quickly.
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When I start the engine and leave it at idle, never revving it up, the centrifugal advance does not advance. I can verify this by watching it, but the engine will still starve after about 5 minutes of idling. I can also see it smoothly advance and retard when I rev and slow down the engine. One test I have not done, but can, would be to rev the engine while watching the centrifugal advance then, after running a few minutes at higher RPM, let it slow to an idle while watching the centrifugal advance. Since all other indications are that this is not the problem I'm not expecting any surprises with this test.
The smoke is black, but not heavily so. I still haven't thought of a definitive way to figure out if the engine has gotten flooded with excess fuel at this point or if it is starving for fuel. It does seem more like it is flooded. If I crack an injector line in this state it seems like the amount of diesel squirting out is about the same as it is when running normally, but maybe it doesn't have enough pressure behind it to force it through the injector. Is there some guage I could put on an injector line that would solve this mystery?
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The only way to see if an injector is performing correctly is to pop test it on a bench tester, that way you can see if the atomization spray pattern is correct, see if it is dribbling, has a crisp “chirp” sound, and witness the pop pressure.
Black smoke is caused by two different scenarios. 1) Not enough air to burn a specific amount of fuel as determined by the governor. 2) Too much fuel for a given amount of air as determined by engine speed.
If I understand correctly then, you start the engine (no hand throttle movement) and it will idle fine (smokeless) for about five minutes, then it will seem to lug (bog down) and begin to smoke, and eventually stop. Is that correct?
Account deleted.
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The injectors are working fine. The engine starts well enough, although it usually needs a little ether unless it has been running recently enough to be warm (It doesn't start as well as it used to, so the timing is probably at least a little off.). It runs, responds to throttle and pulls well until the RPM are allowed to drop.
Your understanding is correct, but I've always started with the hand throttle open. If left idling it takes about 5 minutes before it starts to sound different. It is sublte at first, but within another minute or two it is barely able to run and has no response to throttle position (or very little and delayed). If pulling it will pull well as long as it is not allowed to idle down. If it idles down it starves. I test run it in my driveway, which is uphill. I pull up the hill and wherever I stop and disengage the engine the engine starts to starve. I put it in reverse and the hill allows me to pick up RPM on the engine and it seems like it is pulling normally going downhill, but when I stop at the bottom of the hill it can barely move the tractor in low gear at full throttle.
The engine was running fine, but I had a mishap with a seized injector pump that broke the key in the timing gear. I replaced the injector pump and have tried many, many, many timing positions. The only possibilities I can think of are:
1) The centrifugal advance mechanism was damaged when the pump seized. If this is the problem I will get another timing gear that does not have a centrifugal advance.
2) The new injector pump is defective, but why would it work fine until it idles? Might there be something in the governor that does this? There is an injector shop about 75 miles away, but when I talked to them on the phone they said it is very unlikely that they would be able to test this injection pump. If it is a problem with the pump, it is probably a problem of starving for fuel.
3) The timing is wrong. This seems the most likely problem, but I've changed the timing and the start position of the centrifugal advance so many times and have not seen any clear pattern to help me zero in on the correct timing. This engine was, I believe, the first “EPA” engine with centrifugal advance. I think they changed the timing gear advance from the one I have, but I believe all the timing gears and the one injector pump used with them are interchangeable. I suspect the timing mark on the front pulley was not changed to accommodate the centrifugal advance timing gear, but I would guess that the spill test timing would be the same with or without centrifugal advance. I have bent the injector lines so many times to make major changes that I'm reluctant to bend them much more. If I don't find out some test for the injection pump my next move will probably to get a new timing gear without the centrifugal advance. One big advantage of that will be that I can make timing changes without rotating the injector pump.So, to sumarize, I think I have either
1) a timing problem resulting in too much fuel collecting in the cylinders due to it being injected out of time, requiring over throttle to run normally until it is so “wet”, or flooded, that it can't ignite properly at lower RPM. If this is even possible it seems like it would be experienced commonly by others when engines aren't timed quite right.
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2) A defective injection pump. If this is the problem it would no doubt be a starvation problem (no smoke?). -
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Jim,
This is very interesting. I'm not aware of any adjustments or how they are made. I'm told it is a Bosch injector pump, but don't know where I can find out about any possible adjustments.
Did yours run OK at higher RPM until it was allowed to idle down? I suppose it's possible that a limiter would not kick in and limit until the RPM drops or the fuel delivery rate drops. I would very much like to learn more about this. It is an EPA engine.
/Jon
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Jon,
Your symptoms sound very similar to mine. Very poor low end power/throttle response but pretty much fine above 1400-1600 rpm.
Check out this post:
http://www.ctoa.net/forum/trac…..when-cold/
Mine was a bit worse cold. It would start right up but if you tried to throttle up it would smoke like mad then possibly stall. If you slowly ramped up the speed it would then run fine.
No governor response at all at low speeds . After the adjustment it just runs super, you can drop it back to 800 rpm and ease the clutch out in 2nd and high range and take right off. Before now way at all that it would do that.
Hope that your problem is related to this.
Jim
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