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Old 05-21-2017, 01:21 PM   #1
Al
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Injector pump and over propping

Greetings.
Within the last couple of days an interesting issue regarding the discussion of ‘Over Propping’, WOT, and such became relevant.
The subject has several threads in history, yet this I believe, is a different approach to the subject as a whole with a specific point.

A couple of weeks ago while diagnosing a different issue, [Why did the tachometer not register with the engine running] for a future subject, the young mechanic noticed that my fuel injector pump housing was damp with leaking fuel. Not bad or dangerous, but noticeable. I then stated that within the last couple of outings, the throttle idle had dropped from the normal 550 down to 200 or less. Everything ran well, there was not concern with the range of throttle while underway, that the idle had dropped without any adjustment was nagging.
The mechanic indicated that there were springs within the pump and that the drop without any physical involvement happened and the pump was showing leakage perhaps a re-build of the pump was in order.
With the time frames involved with removing, shipping, re-building, shipping back and reinstalling, I decided to search out a rebuilt pump or new depending on cost. In my search I found a source offering brand new injector pumps at the normal rebuild cost plus free shipping [To Alaska that is a item as many lower 48 states consider us a foreign land!!]
I purchased this pump. The arrival was four days from the East coast and the mechanic installed. Now here is the interesting discovery.
On start up all was well 550 RPM out of the box. Following warm up the maximum throttle RPM in neutral was 1900 RPM. The old pump allowed near 2800 RPM in neutral. It has been believed that was the accepted normal WOT RPM even knowing that in some applications the engine is rated at 3000 RPM WOT. I had never given the thought to the difference and how that was obtained.
As we pondered this shortage of RPM at WOT, the mechanic adjusted the full throttle setting to the max. We obtained 2500 RPM with his forcing the pump to the furthers point. Still thinking on it, the mechanic then had a ‘Eureka’ moment. He sought out the replaced pump and read the plate on that pump. It ended with the numbers “2750” He read the numbers on the replacement pump which were “2200”.
As I do not exceed 1600 RPM while in operation as that is ‘Hull Speed’ max. I normally set the throttle between 1450-1550 RPM. With this setting the pump delivery is still far more than the demand will ever be.
The point of this post is in discussion of over propping always includes the ‘'”Recommended wheel based on the manufactures RPM rating” So in the case of our engine as applied to marine use, the two RPM ratings, 2800 and 3000 are in play depending. The assumption being in any discussion is that the engine in question is achieving that RPM, There is not a proviso “If”. Here now is a “If” situation. Were I to sell the boat the new owner not being able to achieve 2800 RPM would inquire to a source such as this forum and receive multiple responses as to why he is not able to obtain WOT setting of 2800. The more probably response would relate to “Over Propped”.
In this case it may be a factor, however that the fuel injector pump is ‘Rated at 2200 RPM’ if that is the case with the relationship of these numbers given, then the engine will not exceed for lack of fuel, RPM over the 2200.
I am submitting this to the forum for digestion and comments. As everything related to this pump and our boat operation reflecting a smooth operation, it would not be an intention to make any changes, yet it would not be unheard of to have other or future readers come in contact with a similar or same issue.
Regards,
Al-Ketchikan
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Old 05-21-2017, 01:50 PM   #2
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Basically, you put the wrong pump on. If you sell the boat and get an engine survey, the low high idle rpm and low full power rpm will be noted. You can explain it the surveyor, but it remains the wrong pump. What other things are different internally?? Who knows.

Probably no harm in running it as you are, provided engine runs well, does not sound louder and does not smoke.

You stated the original pump would drop from idle rpm of 550 down to 200rpm?? Engine will probably not run at 200 and if it did would be shaking like crazy. Are you sure it was not just a flaky tach indicating 200?
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Old 05-21-2017, 08:34 PM   #3
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Originally Posted by Ski in NC View Post

You stated the original pump would drop from idle rpm of 550 down to 200rpm?? Engine will probably not run at 200 and if it did would be shaking like crazy. Are you sure it was not just a flaky tach indicating 200?
Hi Ski, Sorry, should have caught your discovery. Yes, the engine reacted as you stated. it loped to the point of dying if the throttle was not jiggled upward quickly. The tach issue is related to the alternator and the on board shore charging system. The batteries are being maintained at 100+percent with the shore charger making the demand for the alternator to "Start charging" mute.
There need be a drain on the battery system to wake up the alternator. Not normal for sure, yet. no alternator seller/repair source can come up with a different fact with this alternator, yes, had it completely tore down an checked. regulator, stater, brushes, all, everything checks out. Put my 50 amp alternator in line and the tach works fine. No big deal, I just activate my inverter on boarding,disconnect the shore power, hit the toaster for a cycle and the battery drain is enough that upon starting the tach works and continues. Having a moment, but I believe that until I again am on shore power, there is no issue.

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Old 05-21-2017, 08:38 PM   #4
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Buy the correct pump!
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Old 05-21-2017, 08:47 PM   #5
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Buy the correct pump!
The pump that came off will be rebuilt at the mechanic's leisure.

As to 'Correct' if you would, on what basis other than that described in the original post?
Were it a gear ratio issue or a item that required machine work to make it work, I have no known reason to purchase another new pump. Open to stated reasons for sure.

Thanks- Al
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Old 05-21-2017, 09:07 PM   #6
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Once the mechanic has rebuilt your old pump, install it and determine if you can get somewhere near 3000 rpm, both high idle and under load. Assuming that is the case you could run either pump for your own use, subject to the new pump\'s performance. If/when you sell the boat, install the original (rebuilt) pump.

The other issue is whether your new (wrong) pump will let you get 2200 rpm under load. If not, then you would be overpropped and would need to either change props, or return the pump and get the correct one.
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Old 05-21-2017, 10:12 PM   #7
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Al, you don't say what brand engine/pump you are talking about, so I'm not sure that what I have to offer is going to be of any assistance in the matter.
This is what I learned when rebuilding the pump on a 6BT Cummins rated at 180 hp. 2500 rpm.
The governor spring has multiple setting options for different engine ratings.
It is possible to increase high idle by moving the spring to the next setting, as the same pump and injectors are utilised on the 210 hp version of this motor.
Hope this helps!
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Old 05-21-2017, 10:42 PM   #8
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Once the mechanic has rebuilt your old pump, install it and determine if you can get somewhere near 3000 rpm, both high idle and under load. Assuming that is the case you could run either pump for your own use, subject to the new pump\'s performance. If/when you sell the boat, install the original (rebuilt) pump.

The other issue is whether your new (wrong) pump will let you get 2200 rpm under load. If not, then you would be overpropped and would need to either change props, or return the pump and get the correct one.

The old pump came in at 2800 plus/minus light and 2400 under load. Yes and I am purposely aware of being over propped. As I do not exceed 1600 RPM (Hull Speed )6.7-7 knots. the need to push the throttle is mute with either puimp.
Yes, the old pump after rebuild, will become part of the inventory for a future owner or need.

By the way, the engine is a Perkins 4-236. it is a 2011 engine and as Lucas went out of business some years ago, I am not sure the make of the pump removed. The one purchased is from:New Perkins Fuel Injection Pump A4.236 | eBay

My error was not relating to the difference the injector pump setting held, it was not a thought, only that a pump is a pump mentality. As it works due to the application, we will not fret about it.

Thanks for the comeback[s] All comments were and are welcome in the context offered.

Al
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Old 05-22-2017, 01:09 AM   #9
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Didn't you write "He sought out the replaced pump and read the plate on that pump. It ended with the numbers “2750” He read the numbers on the replacement pump which were “2200”?

Doesn't that mean you bought the wrong pump???
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Old 05-22-2017, 05:01 AM   #10
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Right pump, wrong pump , the question is does it work for your vessel.

If the unit holds your current cruse speed when heading into waves that would slow or almost stop the boat , look astern.

If there is no black smoke (over fueled) or your EGT stays normal your pump is working fine.

The ability to spin a prop to Ski Boat speeds (with a 5 min limit) is never going to happen on a well propped cruising boat.

Regardless of what a survey reads from a truck speck sheet.

Enjoy the correct cruise prop advantages . lower noise, lower fuel burn and longer engine life .

Seldom can a "mechanic" overhaul a mechanical HP fuel pump and gov like a Bosch style.

Too few tools , too few spare parts , and no test bench to check it.
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Old 05-22-2017, 07:53 AM   #11
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"The pump that came off will be rebuilt at the mechanic's leisure.
As to 'Correct' if you would, on what basis other than that described in the original post?
Were it a gear ratio issue or a item that required machine work to make it work, I have no known reason to purchase another new pump. Open to stated reasons for sure."


Per your question above....
It is certainly not the same pump that came out - what would then lead you to believe that the fuel mapping on the new pump is therefore accurate for your engine?
Now you may be overpropped and also have a pump that can deliver fuel at rpm's that the engine was not designed for.
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Old 05-22-2017, 08:11 AM   #12
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Al

Why not contact the vendor and tell them they sent the wrong pump and do an exchange for the right one. What does the order say was requested. With engine serial number in hand the right pump can be found if the current vendor doesn't have it. Gallery Marine in Seattle can find a matching OEM pump I betcha.

BTW, online ordering of critical engine parts from an unknown source can be tricky, any Chinese lettering on new pump?
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Old 05-22-2017, 09:53 AM   #13
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Quote:
Originally Posted by Al View Post
Hi Ski, Sorry, should have caught your discovery. Yes, the engine reacted as you stated. it loped to the point of dying if the throttle was not jiggled upward quickly. The tach issue is related to the alternator and the on board shore charging system. The batteries are being maintained at 100+percent with the shore charger making the demand for the alternator to "Start charging" mute.
There need be a drain on the battery system to wake up the alternator. Not normal for sure, yet. no alternator seller/repair source can come up with a different fact with this alternator, yes, had it completely tore down an checked. regulator, stater, brushes, all, everything checks out. Put my 50 amp alternator in line and the tach works fine. No big deal, I just activate my inverter on boarding,disconnect the shore power, hit the toaster for a cycle and the battery drain is enough that upon starting the tach works and continues. Having a moment, but I believe that until I again am on shore power, there is no issue.


Regards, Al
This is the first time I have seen any discussion of the "no tach reading without the full load on the electrical system" problem that I have experienced for years.
I thank you for bringing it up.
I will try your startup regime and if it works for me, report back.
I have a 120 Amp alternator to port and the original 50 to Starboard. As the starboard tach always works, not having a reading to port has not been a handicap. It would add symmetry to my dash to have the port one working.
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Old 05-22-2017, 10:03 AM   #14
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What is the engine's rated rpm at wot in neutral? If you are not getting that your pump is the wrong pump. This has exactly nothing to do with how you are propped. "The question does it work for your vessel?" No, it does not.

Sounds like your mechanic does not have a clue either. Buy the correct pump!
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Old 05-22-2017, 10:49 AM   #15
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200 rpm idle?

Is the tach ok?
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Old 05-22-2017, 11:36 AM   #16
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200 rpm:
Ski hit the nail on the head in post #2....


A 4 cyl inline diesel will not idle at 200 rpm and if by some miracle it did it would shake like heck and likely have little oil pressure.
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Old 05-22-2017, 12:10 PM   #17
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By the way, the engine is a Perkins 4-236. it is a 2011 engine
Al
Taking a step back here, the 4-236 is an NA engine and much older than 2011. It is rated for full HP at 2500 RPM. Maybe there is no problem with the new pump, just a few wrong rating assumptions.
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Old 05-22-2017, 04:43 PM   #18
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Taking a step back here, the 4-236 is an NA engine and much older than 2011. It is rated for full HP at 2500 RPM. Maybe there is no problem with the new pump, just a few wrong rating assumptions.
Now this is an interesting post! On my engine manual which is on the boat, but by recollection there are three ratinging given for 'Light 3000 RPM- Medium-2800 RPM and 2500 RPM-Heavy .


I chose to use the 2500 RPM due to the over propping situation as I was able to obtain 2400 RPM WOT in gear.

As to the age. I used the serial number formula that Perkins provides which indicated 2011 at the manufacture date. Your saying that can not be the case as Perkins quite NA engines before that time?

Misplaced the SN here at the house, but will obtain and foreward to you. perhaps with your knowledge and my asking, could verify or confimr the age of the engine. I'd appreciate that help.

The replacement pump makes 2100 RPM WOT in gear running in the channel and 2500 RPM in neutral.
Perhaps one could explain how the engine performs equally with either pump to that 2100 RPM point. What would be the difference at the normal throttle setting of 1500 RPM? There is no difference in sound, or any other past indicator of smooth operation.

As I had earlier stated, yes, at the 200 RPM status, the engine shook and struggled to remain running and would not had not the throttle been jiggled upward to offset. No doubt it would quit allowed to continue. Item: the oil pressure even at that point was reflecting 40#plus. The engine has always had good oil pressure showing and the low oil/overheating buzzer will be going off at 7# or less which is not a issue or situation.

No question that I have a working incorrect replacement pump and replacing it with another new purchase is an option. It would be more so were the results other than what I have reported here. I will inquire of the seller if that is an option. By the way, the unit is manufactured in Poland, no chinese letters!!

To the poster with the tachometer issue, be all means keep me posted, nice to know there is more than just myself with that issue.

As always, the responses are providing good thoughts, thinking and suggestions. Thanks to all.
Al-Ketchikan
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Old 05-22-2017, 04:46 PM   #19
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200 rpm idle?

Is the tach ok?
Two tachs- Fly Bridge and cabin both in sysinc.
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Old 05-22-2017, 04:51 PM   #20
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Originally Posted by Xsbank View Post
What is the engine's rated rpm at wot in neutral? If you are not getting that your pump is the wrong pump. This has exactly nothing to do with how you are propped. "The question does it work for your vessel?" No, it does not.

Sounds like your mechanic does not have a clue either. Buy the correct pump!
O- he knows and so does my Heavy Duty 35 years construction/power house career heavy duty mechanic Son. We agree, wrong pump but as there will be no need to exceed the 1500 RPM setting nothing is effected in terms of engine life. The over propping would be a better argument for engine failure. In both cases there is a 500 RPM
reserve to WOT in gear.
Again, no argument with your premise, more to you alarm and I can accept that.
Thanks, Al
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