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Perkins 4108 problems


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on behalf of a friend down south...

 

has a Jeanneau Gin Fizz (38' cruising fin keel, skeg hung rudder with a fixed 3 blade prop). No idea what size prop off the cuff.

 

Normal start regime is to let it warm up and kick it in the guts to 2400rpm just because. Yesterday will not go beyond 1500rpm (unloaded) after warm up. Motoring from Nelson to Mapua it would not go beyond 1500 rpm. Cruising revs are 1500rpm underway but normally when asked - will push on to higher rpm and dig a bigger hole in the ocean....

 

Got to Mapua, tied up to the wharf for a cup of tea and a sleep, later in day started again but now would not run beyond 1000rpm. 

 

Injector pump rebuilt approx.1 year ago. Nothing else has changed - except the inevitable fouling.

 

Oil pressure seems ok, fuel bowl clear of water, no warning lights, new diesel fill just recently. Boat gets used regularly. 

 

What could the issue be?

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Do I understand correctly that this is 1500RPM and now 1000 RPM in Neutral??
Fuel flow or lack of tends to be the most common for such a symptom. Even if the filter bowl is clear does not mean the filter element itself is not blocked. That would be my first check.
Blocked air filter will cause black smoke which is the tell tale sign of air starvation.
Also check that the throttle cable is connected properly and moving the throttle lever on the inj pump all the way.

Also, NEVER let the engine idle out of gear to warm up. Start engine, give it a minute to bring up Oil pressure and some warmth. I usually use the time of letting a mooring line go or lifting an anchor and then get the thing into gear and start motoring. Don't rev the guts out till you reach a decent engine temp. Usually by the time you motor out of the Marina, she should be sweet to go. If you let a Diesel warm under no load, you will cause it to smoke and go through Oil.

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wheels advice is good. Before I knew better and before I knew of the dangers of carbonised engines, I took my boat to a well known Auckland marine engine company who failed to even look for carbonised engine. They ripped me off too in presenting an invoice which was a huge margin above their quote. Happy to provide details. email me if you're interested.  Take out brackets, spaces etc

{kevin 1] mccready) at[] gmail [[]]com]

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intake air block should be first to check as it's so easy

 

just take off the manifold

 

if still can't rev, next check is fuel flow

 

bleed the system esp. to make sure no air is in the injection lines

 

maybe try and bypass all filters by hanging a cup of clean fuel above engine and gravity line to injection pump input

 

if not air flow OR fuel flow restriction

 

could be no compression on a first 1 cyl and now 2.........  

 

how's the coolant level now, has it been very low recently?

 

has the engine recently overheated?

 

can you get engine compression tested?

 

 

my old 2cyl diesel would run ..........but not rev

 

on only 1 firing cyl 

 

DPO had let a coolant leak overheat engine and spin out a crankshaft bearing 

 

killing compression in that pot

 

https://www.youtube.com/edit?o=U&video_id=7ZO8ftgm6sM

 

importing a new engine and self fitting was cheaper - faster - smarter?

 

than rebuilding the old

 

and helped the sale of the boat when a faster vessel appeared

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Take off the air filter. Test.

Change fuel filters, test.

Then start looking at other more complex issues. This is the order I'd look in

Fuel pump

Injectors

Compression

Intake then exhaust manifolds

Carbon build up ( head off)

Etc etc

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After changing fuel filters and checking the screen in the fuel lift pump there is one further filter to check - the CAV rotary injector pumps generally have a little nylon "sock" filter on their inlet, remove the feedline from the secondary filter(s) and it can be removed for cleaning. Had this issue on my 6.354 Perkins, spent a month chasing my tail until a mechanic told me about the filter.

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Do I understand correctly that this is 1500RPM and now 1000 RPM in Neutral??

Yes Wheels that is what I believe I was told. He was speaking in an Auckland version of South Islandish though, so I could be mistaken.

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Sounds very much like Fuel or a throttle issue. So as already said, check those filters and the one in the lift pump and the rotary pump.
If all checks OK, then as I said earlier, check the throttle cable and connections.
Failing all the above, then something in the injector pump where there is a thing called the Fuel rack. This is what adjusts the amount of Fuel delivered to the injectors. The throttle is connected to the Fuel rack and also the Governor is connected to the Fuel rack. Simply, a Diesel increases/decreases the amount of fuel delivered in each squirt to regulate it's speed. Simple as that. The internals are fairly basic, but MOST CERTAINLY NOT, something any novice should attempt to pull apart.
       All the other scenarios, like compression, Injectors, restricted air etc and so on, all come with tell tale smoke signals. Fuel is the only thing that can cause an issue and maintain a clean Exhaust output at the same time.
 

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