Engine question

[TruChaos]

My Jinma has a miss, not a dead miss but a a miss that can be felt and heard. When using the woodchipper and the engine gets heavily loaded it will blow puffs of blue smoke that smells like oil.

I've checked the compression and all three cylinders register exactly 550 PSI on my gauge. I've checked the valves one was a little tight so I readjusted it. Oil pressure is good, at 65 then 45 psi hot with a mechnical gauge.

Recently, while driving the tractor back to the house, the engine started knocking and the missing got worse. So, I took a ball peen hammer and tapped the injectors and the injection pump and the engine knock went away and it ran smoother.

I tried bleeding all the lines and got nothing with no change in running condition.

I'm about 99 percent sure it's an injector.

Question: How do I locate the bad injector? I've tried slightly cracking the fuel line to each injector and in each case, the engine loads a little and runs smoother. I can't differentiate which injector is the culprit.

Also, what if it's the pump? How can I tell and what fuel pressure should I see with a gauge? Obviously they should all be about the same. I just need to find a high pressure fuel gauge. How high a pressure do I need?

 

[greg_g]

The injectors are comparatively inexpensive, less than a hundred bucks for a set of three. I'm thinking injection pump pressure is something over 3000 psi, and replacement cost is significantly higher than three injectors. So if it was my machine, I think I'd replace the injectors first. All three at the same time. Sorta like changing spark plugs, you don't usually change just one.

//greg//

 

[RonMar]

Your description does sound like an injector problem. You could try a mechanics stethescope(or the screwdriver behind the ear trick) to listen to the injectors to see if one sounds different than the others.

You could de-install all 3 injectors and re-connect them to their fuel lines outside the engine. Bleed out the air and Crank over the engine with the compression release set and observe the fireing spray pattern of the injectors with the throttle at different positions to look for a difference between the three. If you note a difference, swap that injector with one of the others to see if it is the injector or that port on the injector pump. With the injectors disconnected, this would also be a good time to check their fuel inlets for any debris that may have made it past the filters and pump.

You could get a single injector and replace the injectors one at a time till the problem is found.

 

[Affordable]

Sounds like you have a injector problem,Greg is right the injectors for the tractors are not very expensive.Buy one or three,for the time and effort I would just replace all of them.

Tommy
Affordable Tractor Sales

 

[Kobi]

The scientific way to check the injectors would be to put them on a bench tester and check the opening pressure and the spray pattern. Adjustments to the openig pressure can be made via shims or spring replacemnt. If the spray pattern is bad - replace the complete or the lower unit of the injector. This will depend on the design or the manufacturer of the injector.

The tests on the pump side are: volume delivery per line, main pressure, wear on the lobs of the cam and pump timing.
(For a simple mechanical diesel pump stup).

An injector tester basically is a hand pump, fuel reservoir with a gauge that attaches to the injector. You pump several times to get the air out and then you monitor at what pressure the injector opens - while this is happening you check for a nice uniform cone pattern. Angles are usually given in the specs. of the injector or repair manual. You will be fine even if you don't know the correct angles as long as you are getting a nice even uniform cone pattern. You can reference one injector to the other and see what you got......

Having that said - a tester costs money and unless you can make one yourself... or have access to one - it will be a lot cheaper just to go out and buy a set. Once you got a spare set - you can always have them cleaned or rebuilt at a local diesel injection repair shop. 3 Injectors for less than a hundred is a bargain - I have some that are 1K a piece..... they don't come cheap on some of the new Bosch high pressure rail system.

Cheers, Kobi
/forums/images/graemlins/smile.gif

 

[TruChaos]

I bought a new set of injectors. The new units had EPA marked on the boxes. On the tester, they performed differently than the used injectors from the tractor and from an old cleaned set of injectors I had in storage.

Two of the injectors I removed from the tractor seemed to be popping at a lower pressure than the book specifies (1400 PSI). Although one popped consistently at 1600 PSI.

The new injectors don't really pop like the others, they sort of spurt. They emit a much more broad cone and produce a LOT of mist. I had to back away several times to avoid the cloud. The old injectors do not produce mist and have a very narrow cone.

One of the new injectors seems a bit leaky to me. I'm going to retest it today.

Since there seemed to be a considerable difference between the old and new injector performance and one of the new injectors seemed to be leaky, I decided to recalibrate and install the injectors I had in storage. They had been disassembled and cleaned but not calibrated.

I also noticed that the new EPA injectors open at a lower pressure (1700 PSI) than I believe the book specifies. Am I correct that the factory manual specifies about 1900 PSI? I remember it being about 13.2 Mpa.

Does anyone know?

Thanks

 

[JohnS]

Interesting Info. If and when you install the "EPA" injectors, I would be interested in what differences you see in the engine performance.

 

[TruChaos]

I played around with the leaky injector and it seemed to stop. So I installed the entire set of EPA units. The engine has a different sound and there seems to be less diesel smell. Previously, on throttle up and down there was a slight bit of dark visible exhaust. Not really smoke but I suppose that's what it was. When I would start and run the tractor indoors the fumes would build up fast even with 16 foot door open. With the EPA injectors the exhaust does seem to be less.

However, the engine still misses and under heavy load from the chipper, the engine releases a puff of blue smoke.

I'm now thinking its the injection pump. While the engine was running I placed my fingers on the hard metal fuel lines going from the pump to the injectors. On the first two injectors a sharp pulse could be felt. On the third the pulse feels like it has much less amplitude, at least half as strong.

Just for grins, I disconnected the fuel line coming into the pump and the banjo filter was perfectly clean and the fuel flow seemed good.

Additionally, I tested the old injectors and I didn't see any problems with them.

Any suggestions for testing the pump? I don't have a high pressure gauge nor have I seen one on sale.

 

[cowboy40]

Just had a problem like yours 2 days ago on my 05 Jinma 454 with 180hrs. After extensive trouble shooting,found my problem to be in the fuel line between the low pressure pump and the fuel filter. Don't let fuel flow without a load fool you.I don"t like those banjo type fuel lines, they are hard to check to see if they are clear. Found my problem by taking the fuel line off and tried to blow through it. The problem became pretty clear at that point. Then had to cut it in half to try to blow it out with a air compressor. That didnt work. Finnally got small dia. wire through it. What came out appeared to be particals of fuel line. Threw it away and made a fuel line out of a 1 foot hyd. line and 2 adapters. Now pulls a 7 foot mower/ conditioner. Befor, would sputter pulling a 2 rotor hay tedder. Just something to look at.

 

[TruChaos]

Thanks for the suggestion. I'll definately give it a try.

By the way, there is a screw and a nut on the banjo fitting on the return line, what is the screw for? Is it some sort of flow adjustment? If so, what?

Thanks again.