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Old 17-05-2016, 11:28   #1
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Is the throttle range adjustable on the injector pump for a Perkins 4.108?

I was getting fuel in the oil on my Perkins 4.108, so I switched out my injector pump over the weekend for a spare the PO had left on my boat (already ruled out the lift pump). With the new injector pump, there's a shorter range of motion with the Morse throttle control, and where the old pump throttled up from a minimum of 800 rpm to over 3000 rpm, the new pump stalls at the bottom and throttles up to a maximum of 1100 rpm at the top. Is there an external adjustment I can make or does the pump need to go in to the shop? There are adjustable stops but I've read dire warnings about messing with those.

Thanks!
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Old 17-05-2016, 12:15   #2
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Re: Is the throttle range adjustable on the injector pump for a Perkins 4.108?

You probably saw the other holes in the throttle arm at the pump,( further out more travel.) There were also 2 stops on the fuel pump at the throttle arm that limit travel in both directions. There is also an adjustment on the top of the fuel pump to control de-acceleration to idle.
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Old 17-05-2016, 20:26   #3
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Re: Is the throttle range adjustable on the injector pump for a Perkins 4.108?

Yup I see all that. Is it a terrible thing to adjust the stops?
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Old 17-05-2016, 20:30   #4
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Re: Is the throttle range adjustable on the injector pump for a Perkins 4.108?

How about the lift pump? I seem to remember being told that a bad diaphragm can result in diesel in the motor oil.
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Old 28-05-2016, 16:52   #5
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Re: Is the throttle range adjustable on the injector pump for a Perkins 4.108?

Quote:
Originally Posted by sv lark View Post
Yup I see all that. Is it a terrible thing to adjust the stops?
depends, how about disconnecting the cable and operating the arm by hand? The low stop is adjusted all the time, never messed with the high stop. My engine goes way up there in neutral, not sure how high, maybe 4000.
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Old 28-05-2016, 19:25   #6
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Re: Is the throttle range adjustable on the injector pump for a Perkins 4.108?

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Originally Posted by Guy View Post
depends, how about disconnecting the cable and operating the arm by hand? The low stop is adjusted all the time, never messed with the high stop. My engine goes way up there in neutral, not sure how high, maybe 4000.
It should go to 4000 in neutral and while running in gear if propped right.
(Except if tied to a dock then 90% of rated RPM is the magic number)

As for the new high pressure pump not delivering the RPM..?
Is it overhauled, clean, etc?
Did you check temp on each cylinder? (Not a blocked fuel line and a dead cylinder or two?)
The Perkins manual should explain adjustments. Sold my boat with the 4-108 3 years ago and the shop manual went with it, otherwise I'd look it up.
Curious to what the problem turns out to be.
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Old 28-05-2016, 19:51   #7
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Re: Is the throttle range adjustable on the injector pump for a Perkins 4.108?

Hmmm, I just had our pressure pump rebuilt and reinstalled due to the same problem of leaking diesel into oil. Engine now purrs (as much as an old Perkins ever purrs), but I notice it is hard to reach high RPMs.

The revs seem to lag behind throttle. It increases nicely to about 1500, but then seems to respond slowly to more throttle (fuel). I can get the tack up to 2500+, but it seems to lag behind the throttle.

Same issue?
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