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Message |
    
ssnoc
New member
Username: ssnoc
Post Number: 1
Registered: 09-2010
| | Posted on Sunday, September 12, 2010 - 03:45 pm: | 
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How much pressure should come from the injection pump on my YSB8? I had the pump rebuilt and it squirts out fuel from the high pressure line with the injector off, should that be a super strong stream? I can put my finger over it and hold it back. When I connect the high pressure line to the injector and leave it outside the combustion chamber to check the spray - There is NO spray, nothing comes out of the injection nozel.
There is NO air in any lines I bled them all a million times. I need to be clear on how the injection process works. Does the little sqirts build up pressure in the injector and then it finally mists? Or should the injector start to mist as soon as it gets the squirts from the injection pump? Its got me very confused because the injection shop siad the injector was good, yet it never mists out any fuel.. The high pressure pump is a very simple pump - a needle valve controls fuel level and the cam shaft pushes the plunger. It sends out a "sqirt" with each crank, but no mist from the injector.
How much force should should be in those "sqirts" from the injector pump? And can you please explain to me where this pressure comes from to open the injector and make the mist?
I've been trying to fix this thing for two months and NO one seems to know any of these answers.. Does anyone know?
Thanks! Rob on Long Island. |
ernie
Senior Member
Username: ernie
Post Number: 1263
Registered: 01-2002
| | Posted on Monday, September 13, 2010 - 11:51 am: |
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Rob,
Make sure the needle valve is finger tight closed when you adjust the throttle linkage. If it isn't fully closed the pump appears to work but it will NOT make enough pressure to open the injector.
Closed is full throttle and the engine should always be started at full throttle. Once it starts adjust the RPM as needed with the throttle
There may be a line on the top of the needle valve shaft that usually is in line with the split in the throttle arm that attaches to it most of the time.
If you want post a pic of the pump or e-mail it to me for clairity to make sure we are talking aobut the same style pump.
Also NEVER put any part of your body where the injection system might spray you. When properly operating it can and will penetrate your skin causing a serious medical problem. As in Diesel Fuel under your skin!
Hope this helps
Ernie |
ssnoc
Member
Username: ssnoc
Post Number: 4
Registered: 09-2010
| | Posted on Monday, September 13, 2010 - 05:08 pm: |
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Ernie thank you so much for your very useful information, however even after I turned down the spindle hand tight, no mist from the injector. I took off the injection pump looking to see how it works and it is very simple. The cam shaft turns pushes the spring loaded plunger and it squirts. I suppose the spindle acts as a vacume as you turn it down restricting the fuel? Anyway, I took of the injector and cranked it over and as usual I see some squirts from the high pressure tube, how powerful should those squirt's be? There is no way they are powerful enough to counteract the spring in the injector to force it open and create a mist, which makes me think it is still the injection pump ??
Is there an adjustment under the triangle shaped cam cover that may be incorrect which allows for more "push" from the cam into the plunger spring? If so how do I set that? I have more diesel than the Valdeze on my driveway!  I took the engine out of the boat to work on it in my garage.
Should I be holding the Linkage (Governor?) open or closed when the needle valve is hand tight? As you can see, its driving me crazy! Thanks I appreciate your help |
ernie
Senior Member
Username: ernie
Post Number: 1264
Registered: 01-2002
| | Posted on Monday, September 13, 2010 - 05:54 pm: |
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Rob,
Hold the needle valve closed. (clockwise viewed from above) It is a very finely calibrated bleed off. You may have to disconnect the linkage to verify that the needle valve is fully closed. At low RPM (cranking) if it is open at all it won't make enough pressure to (pop) the injector. Most of these injectors pop between 1600 and 2000 PSI.
Can you get a pic of the pump and linkage so I can make sure I am giving you the proper info?
Do NOT try to start the engine with the linkage disconnected. A diesel without the govenor connected will self destruct in seconds. |
ssnoc
Member
Username: ssnoc
Post Number: 5
Registered: 09-2010
| | Posted on Tuesday, September 14, 2010 - 03:04 pm: |
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I am working on the photos to show you today, will upload later. I am going to reconnect the linkage, make certain the valve is turned closed and see what happens. Just to keep it clear, I have left the injector outside the combustion chamber so I can see it spary when I turn over the engine (hopefully).
Is the pressure from the high pressure tube supposed to come out with great force? Because when I leave the injector side nipple off and crank, I see squirts of fuel, but with no real great force, its a short stream, is that correct? I assume the needle valve controls the speed of the engine, tight = fast and open is slower? Does the linkage attached have anything to do with the injection pressure, I don't see how it could. Its a camshaft that pushes a plunger in and creates pressure? Where does this pressure come from? Is it made in the actual injector? I wish I understood the theory of how it all worked then I could find the problem.... 1600 pounds of pressure sounds like an awful lot before the injector will pop -- the squirts I see from the tube are no way strong enough for that.... If it slowly builds pressure in the injector, then why do I see fuel pouring from the return as soon as I start cranking? can I just bolt off the return on the injector to see if it then pops maybe showing an injector problem?
Ernie, I wish you lived close by< id by you dinner I really do appreciate your help and sharing your vast knowledge ... I am not giving up!! Thanks Again... |
larry_from_maryland
Senior Member
Username: larry_from_maryland
Post Number: 423
Registered: 07-2003
| | Posted on Wednesday, September 15, 2010 - 12:35 pm: |
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The pump makes small squirts and only builds high preasure when blocked by the popoff valve in the injector.If you are getting lots of return flow out of injector thats not right.Could be thats your problem.If you had it tested the place should have seen a problem like that. |
ssnoc
Member
Username: ssnoc
Post Number: 6
Registered: 09-2010
| | Posted on Wednesday, September 15, 2010 - 11:10 pm: |
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Thanks Larry, I thought about what you said and checked the pump against the parts schematic. I found that in the retainer, which is the part that connects the high pressure tube from the injector pump, there was missing parts.
The delivery valve, which consists of a spring, a small ball bearing and a seat/spacer were all missing. I realized that this delivery assembly must allow for a one-way stream from the injector pump, a sort of "check valve" I figure. As the squirts fill the high pressure tube and injector, this delivery valve must not allow the pressurized fuel to backup into the injector pump. It appears to me that the ball bearing fits snugly onto the spacer/seat causing a seal and only allows for a one way flow of the diesel when it squirts and pushes against the spring forcing diesel into the high pressure tube - a little at a time.
These missing parts must have allowed the pressurized diesel to backflow into the injector pump and feed line all the way back to the fuel filter where the return line from the fuel filter was actually feeding the return from the backward flow.
In theory it all makes sense to me. Without that "check valve" , there is no way to hold the pressure being built, it simply starts to back flow... I have ordered the missing parts at my local Yanmar dealer and can't wait to see if it fixes the problem and the injector finally pops. It is all so very basic and thats why it didn't make sense to me until I looked at the schematic of parts.
I think this is the problem as it is the only logical solution I can come up with. There is no way to stop the pump from pumping because it rides the camshaft, so the only reason the pressure is not building is because of a "leak" of some kind. Everyone is always looking at bleeding the air, but without a proper delivery valve, which is nothing more than a spring, a BB, and a spacer, holding the pressure in the tube, it can't possibly build any pressure. It makes perfect sense. Now all I have to do is test it once the parts arrive.
Thank you Ernie and Larry for the very helpful advice. I will post the results as soon as the parts arrive! You can learn an awful lot from a diesel engine that isn't working |
ssnoc
Member
Username: ssnoc
Post Number: 7
Registered: 09-2010
| | Posted on Monday, September 20, 2010 - 12:29 am: |
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OK - well I installed the new delivery valve and the injector started to puff diesel for the first time. Even as I hand crank, the injector would puff with each crank..... BUT all of a sudden now, when I crank the engine, I get only 2-3 puffs and then the injector fails to fire anymore?? If I wait and loosen the high pressure line from the fuel injector and then reconnect it again, I hand crank and again I only get 2-3 puffs and the injector stops firing ... I checked for air in the lines, bled and re-bled the fuel lines, but I only now get a few puffs and it stops.... I have the return line going into a can for testing purposes and I capped off the return on the fuel filter so there is no back flow to worry about. Why would the injector stop firing after 2-3 cranks and only work again for 2-3 puffs after I disconnect it and re-connect it??? Any Ideas are welcome .... Thanks All. |
johnoxley
Member
Username: johnoxley
Post Number: 9
Registered: 04-2010
| | Posted on Monday, September 20, 2010 - 12:50 am: |
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Following the thread but do not know the engine... BUT - Do not put your finger over an injector when firing - even though the puff of fuel looks harmless, it can penetrate the skin and enter the bloodstream possibly leading to blood poisoning, etc. The forces needed to inject fuel are very high and can enter the bloodstream.
Suggest the injector is fine as it at least works a few times - the problem might be in the delivery valve on the pump, but I do not know if your pump is rack type spill or needle valve spill?? What brand engine? |
ssnoc
Member
Username: ssnoc
Post Number: 8
Registered: 09-2010
| | Posted on Monday, September 20, 2010 - 01:01 am: |
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It is needle valve on a older 77' YSB8 the injector pump was rebuilt a few weeks ago. Its strange that it fires 2-3 times then suddenly stops?? I do not put my hand under it, but thanks for the warning, Could the injector spring be gummed up? If I take off the high pressure tube and crank it spurts out like it should..... |
ernie
Senior Member
Username: ernie
Post Number: 1267
Registered: 01-2002
| | Posted on Monday, September 20, 2010 - 07:47 am: |
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Just put the injector in and see if it starts. You might be suprised |
larry_from_maryland
Senior Member
Username: larry_from_maryland
Post Number: 424
Registered: 07-2003
| | Posted on Monday, September 20, 2010 - 12:04 pm: |
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What you describe is not enough fuel flow to the pump, plugged filters etc. When you stop and wait or do something fuel flows into the pump and it starts working again. |
ernie
Senior Member
Username: ernie
Post Number: 1268
Registered: 01-2002
| | Posted on Monday, September 20, 2010 - 01:10 pm: |
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Or not completly bled which will happen once it starts.
As I am sure you have expierenced hand bleeding a diesel almost always doesn't get all the air. The final tiny amounts of air usually pass through once the engine starts.
I have one of these Yanmars and with the needle valve bleed off injection control there is always some air somewhere.
From what Rob tells us I would try to start it before I got nutty checking flow from the tank or supply since these engines use such a small amount of fuel.
However this all beeing said I am NOT saying it isn't a supply problem. |
ssnoc
Member
Username: ssnoc
Post Number: 9
Registered: 09-2010
| | Posted on Tuesday, September 21, 2010 - 08:03 am: |
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Success! I took your advice Ernie and installed the injector. One of the biggest problems is that my starter motor is failing, so I took it apart and cleaned out the brushes, once replaced it had enough cranking power to turn over the engine which now has lots of compression since I rebuilt pretty much the entire thing. Anyway, it cranked about three times and fired up - a great sound to hear!
What I did was:
1: Had the injection pump cleaned out professionally.
2: Changed Injector with a used cleaner one
3: Ordered and installed missing injection valve nozel
4: Took off the head, cleaned and lapped the Valves
5: Cleaned all the built up rust inside the water jacket (a ton)
6: Gapped the rocker arms to .20mm at D/C
7: Reset fuel injection linkage.
8: 50/50 Mix of Marvel Mystery Oil and Reg. diesel Oil
9: Cleaned out exhaust mixing elbo
10: Cleaned out starter motor - which still needs replacing,
Thanks to everyone for the encouragement and great advice, it was a lot of work, but I now have an excellent running engine that starts within two cranks! |
ernie
Senior Member
Username: ernie
Post Number: 1269
Registered: 01-2002
| | Posted on Tuesday, September 21, 2010 - 10:07 am: |
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Great! glad to hear it is now running
by the way is it in a boat and if so what is it in?
Ernie |
