perkins 4-108 stalls at idle

[CoCoKnots]

I have a 1975 Perkins 4-108. This is my first Diesel engine... Please excuse me as this is unfamiliar territory. I had the injectors & alternator rebuilt 3 years ago. Replaced the starter a couple of months ago, which probably has nothing to do with my stalling issue... It starts fine & runs under load. It just stalls when I return to idle to change gears.
I have replaced the Racor filters, but the problem still persist. It's been a couple of years since I've changed the primary fuel filter on the engine. I do use fuel additive. I haven't used the boat very much at all during that time.

Could the primary filter be the cause of the stalling problem?... Or is this an indicator of a more involved problem.

I hate changing the primary filter. A mechanic told me of a screw-on upgrade available to replace the sandwich type currently located on the block. Does anyone have feedback or experience with the aftermarket filter bracket?

[onestepcsy37]

yes, the primary is a pain in the butt, butt it has to be done. go thou and do it..

[CoCoKnots]

Thanks OneStepCSY37
Are you (or anyone) familiar with the screw on mount modification ?

[capttman]

Us your idle low

[CoCoKnots]

Yes it is Capttman,
But the throttle lags all the way as I advance. After the engine dies in neutral I must start it again in gear with the throttle a little engaged to keep her running.

[afmstm]

Check your injection pump - it typically has a screw (called the anti-stall device) that you need to adjust. If your engine dies when you reduce the RPM to idle, this is a likely suspect. Check your 4-108 manual for instructions on how to adjust the anti-stall device and the idle speed. As a test, you should be able to run your engine at rated continuous RPM (which is 3000 for the 4-108) and then drop it to idle over two seconds, and the engine should settle down at the idle speed correctly.

Van
s/v Rainshadow

[SkiprJohn]

I think something is interfering with your throttle control. You need to track it down starting at the engine and investigate every inch of the way and determine if your gear shifting lever and throttle lever are a drag on each other. Have a friend go through the shifting action and throttle action while you are down below looking at the fuel injection pump. Do it while the engine is not running just to see what's happening. Then, do it with the engine running and all your fingers and toes are out of the way of any moving parts, belts, pulleys, etc..

Your engine should idle around 800-850 rpm when you throttle back to shift. Any lower than that and it might die when you engage it in gear. Watch your tachometer or get an electronic tachometer so you can judge the idle speed. Idle speed is adjustable.

[CoCoKnots]

Thanks Van & John,
Tomorrow's project.
I didn't think about the injection pump.

[brutb]

CocoKnots, I am on Merritt Island and have a 4-108 service manual if you need one and if you do not have a helper, pm me and I will try to assist.
SV Magic
SV Iron Jack

[Dynamo1181]

I will be in Melbourne for 5 mos starting 11/1. Would be glad to help. I have been intimate with my 4-108 for more than 20 yrs. PM if you need a hand.
A

[donradcliffe]

Its most likely the injector pump--if adjusting the anti-stall to factory specs doesn't solve the problem, you probably need to take the injection pump off and have it rebuilt--tell the rebuilder your symptoms so he double-checks the governor.

[River Cruiser]

Is there any other problem other than the stalling at idle rpm, if you bring the throttle slowly to the idle will it still die? If you have no other symptoms out of the ordinary it may be the low idle adjustment isn't set correctly. The low rpm & the high rpm are adjustable, you'll need a photo tach to adjust it.

[SailOnEverAfter]

I have a 1975 Perkins 4-108I can't seem to bleed the system completely
The engine looses prime when reved up and has caused me major problems. I have keep the engine running fairly well by running it around 1400 RPM and it has been running and starting right up. Today I started it and it reved up after being in idle and lost prime and wouldn't start. I have gone through every line and it SEEMS to be getting air in between the pump and the main filter. I suspect that the fuel pump isn't keeping up and needs to be rebuit? I took it off and cleaned it and put it back in and got the engine to start but the idle is all over the place. Maybe starving for fuel, then getting it?
I'm in Beaufort NC trying to head south and just spent all my cruising $ on getting ready to go. I'm so frustrated. Any ideas and how hard would it be to rebuild the fuel pump? That diaphragm looks a little tricky and I inspected it and put it back together just cleaning what I could.

[SkiprJohn]

After you bleed your engine or replace fuel lines those little copper washers become flatter and sometimes allow air to get into your system. Replace a few at a time and trace your fuel system from one fuel line connection to the next. Eliminate each area by bypassing using a can of clean fuel with a fuel line into it. If you find where it loses prime, i.e. fuel filter, replace o rings and washers and top it off and start again. Any little crack in a line or loose fitting or even your fuel tank pickup tube can cause what you experience.

[paldrich]

I have exactly the same problem and have been unable to trace the source. I have adjusted the idle higher and worked with the anti-stall device without success. I note one post that suggests having the high pressure pump overhauled, but would like to know if anyone has had success without going to that amount of work pulling things apart.