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Old 11-10-2013, 18:02   #1
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Perkins 4-108 Anti-Stall Adjustment

I mistakenly unscrewed the Anti-Stall screw while bleeding my Perkins 4-108! The manual says to adjust the Anti-Stall screw while the engine is running, but the engine won't start. Could someone tell me more details on how that adjustment screw works? (i.e. screw it in too far and the engine gets too much fuel, preventing a successful start? <--- Total guess on my part, hehe)

Here are more details:

1) My engine has been running great since I bought my 1978 Cal 39 MKII Tall Rig 6 months ago.

2) The engine recently had a slower time starting. It always started first try with a half-second push of the starter. Then, over a period of 3 weeks it gradually took longer to start until it took 5 seconds to start. It still started first try, just took a bit longer.

3) I decided it may be a dirty filter, so I replaced the Racor 500 filter, ran the engine without an issue for about 4 or 5 sails, but still started with a 5 second crank.

4) I changed the primary filter on the engine (it's the sandwich type) and bled the system per the manual's instructions.

5) Unfortunately, when cracking the screw on the top of the Hydraulically Governed Fuel Pump it also rotated the whole column, including the lock nut and Anti-Stall screw. I'm not sure how far I rotated it, so it could be as much a 1.5 turns off.

6) I tried to put it back as close as possible, but the engine wouldn't start after completing the bleed process.

7) I tried re-bleeding from the scratch, bubble-free fuel comes out as I bleed, then I crank the engine with the starter and bleed the high-pressure inlets to the injectors with no luck. I tried 7 times, waiting for the starter to cool between tries.

8) I decided I either have a leak in the system or the adjustment screw is off. But the engine ran perfectly fine before I changed the primary filter. I tried re-seating the primary filter and re-bleeding, even. I bought an electric pump to tie inline from the fuel tank to the Racor filter in case the lift pump was bad. Nothing going.

Any suggestions? Seems like if it ran before changing the filter, all the other connections would still be solid.

Thanks for the help!
(Oooh, this perfectly describes my frustration right now: )



Update: Ok, after letting the starter cool, I tried again.
Electric pump on and pushing bubble free fuel through clear lines into the first filter (Racor)
Opened the bleed screws in order until fuel came out bubble-free and closed them.
Cranked the engine for 30 seconds while opening the high pressure injector lines until fuel came out and then closed them.
As the last fuel line was tightened, the engine started!
It ran for 10 seconds at 1/4 throttle then quit completely. From hero to zero, just like that.
Air in the system still? Argh!
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Old 27-11-2013, 08:43   #2
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Re: Perkins 4-108 Anti-Stall Adjustment

Found the problem:

The primary fuel filter has an automatic bleed feature. It works by directing extra fuel from the injectors into the top of the primary fuel filter. So after changing the filter (It's the type where you have to sandwich the filter by screwing a "cap" on from the bottom. There's no way to fill the filter before replacing it) the resulting bubble is removed automatically by filling it with the return fuel.

Anyway, the check-valve at the fuel filter where the return fuel comes from was busted. So that valve wasn't doing its job thus preventing the bleeding process to work.

Talk about a gotcha! Had to remove and replace each fuel hose in turn, bleeding between each to finally find the problem. I never did replace the check valve but was able to bleed the system by removed the return line, plugging it with my thumb and bleeding normally. I then replaced the hose and she started right up.

(I'll wait to replace that bugger for the next fuel filter change!)
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Old 27-11-2013, 08:49   #3
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Re: Perkins 4-108 Anti-Stall Adjustment

As a side note the experts at TAD (transatlantic diesel) told me never use a inline booster pump. They said these engines were not designed for it.
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Old 27-11-2013, 09:30   #4
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Re: Perkins 4-108 Anti-Stall Adjustment

Glad you found the problem with the new primary filter fitting.

However, if I'm reading this correctly it still doesn't explain the original problem, i.e., why the engine now takes 5 seconds of cranking to start.

Bill
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Old 29-11-2013, 07:56   #5
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Re: Perkins 4-108 Anti-Stall Adjustment

I was thinking about lowering my diesel tank and putting it further back in the motorboat to balance out the water tank in the front. Then put a 12 volt pump inline to help with bleeding as it is a problem to to pump by hand on one side of the 4108 lowline while trying to bleed the CAV pomp on the other side.
What type of 12vlt? pump are you using and is it just for bleeding or on all the time?
Did TAD give a full reason why not? and anyone else out there using one that can help me decide which way to go.

I am about to redo the Orings on the throttle shaft that are leaking, so am also interested in the antistall adjustment. I was planning to just measure height and mark the nut and body parts to put it back as it was after taking the shaft out , replacing O rings and replacing the throttle shaft. My motor was also running fine until we replaced the Valve seals and then it started to take longer to start and wont start easily after 2 days left idle, then I found the leak in the throttle shaft, but am not sure if this is where the air leak is coming from or from the fuel or return lines. Will be replacing all the lines to make sure, hence the need for the 12vlt pump to help with bleeding which I have to do a lot of lately.
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Old 29-11-2013, 08:37   #6
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Re: Perkins 4-108 Anti-Stall Adjustment

glad you found the problem. i had a 'no start' problem with my 4-108 ten years ago when i first bought my boat. i changed both the racor and engine mounted fuel filters.

engine would not start. cranked wonderfully but no fuel reached the injectors. no amount of bleeding would help. finally called a mechanic. he asked me if i had changed the engine fuel filter. i said yes.

he went for that first. took the filter out and put it back in. engine started and has run well for the last ten years.

seems the rubber o-ring that fits nicely inside the rim at the top of the can doesn't belong there. if you put it there - and to a beginner it seems to be the place to put it - no fuel will pass the filter. the o-ring actually fits up inside a groove under the top mounting plate.

and it only cost me $300 to find this out....
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Old 06-12-2013, 03:52   #7
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Re: Perkins 4-108 Anti-Stall Adjustment

The original problem was old fuel filters. Not enough fuel was getting through quick enough. That was the whole purpose of changing the filters in the first place. Should have been an easy fix if it weren't for that pesky check-valve. Starts so quick now I hardly have to breathe on that start button!

I only put the fuel pump in the system to make priming faster. I primed that mother at least 20 times during initial testing before adding the pump. Saved tons of time while changing out the hoses and testing connections, bleeding and test starting between each hose change.

The pump came with the boat, so not sure what it is or how much. It's a cylindrical brass pump about the size of both of my fists put together. Alligator clips allow me to connect to positive and negative wherever handy.

I've been meaning to take the electric fuel pump out now that it's fixed, but haven't got around to it. The mechanical lift pump seems to pump the fuel through the inoperative electric pump just fine so I've been tossing around the idea of just leaving it there for my next priming adventure. If it ain't broke and actually makes life easier, why fix it?
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Old 06-12-2013, 04:24   #8
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Re: Perkins 4-108 Anti-Stall Adjustment

Quote:
Originally Posted by beebopbogo View Post
The original problem was old fuel filters. Not enough fuel was getting through quick enough. That was the whole purpose of changing the filters in the first place. Should have been an easy fix if it weren't for that pesky check-valve. Starts so quick now I hardly have to breathe on that start button!

I only put the fuel pump in the system to make priming faster. I primed that mother at least 20 times during initial testing before adding the pump. Saved tons of time while changing out the hoses and testing connections, bleeding and test starting between each hose change.

The pump came with the boat, so not sure what it is or how much. It's a cylindrical brass pump about the size of both of my fists put together. Alligator clips allow me to connect to positive and negative wherever handy.

I've been meaning to take the electric fuel pump out now that it's fixed, but haven't got around to it. The mechanical lift pump seems to pump the fuel through the inoperative electric pump just fine so I've been tossing around the idea of just leaving it there for my next priming adventure. If it ain't broke and actually makes life easier, why fix it?
So the inline pump is between the lift pump and the primary filter on the motor?
foto of the whole setup?
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Old 06-12-2013, 04:39   #9
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Re: Perkins 4-108 Anti-Stall Adjustment

Definitely leave the electric pump in the system for the purpose you described but never ever, ever crank the starter for 30seconds. The heat buildup in the starter is scary.
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