Perkins 4/108 Challenge

[John Galt]

While sitting in the yard for 7 months, my 4/108 developed an air lock. Once back in the water I bled out all the air and decided to shear the head off the air vent screw. The screw sits on top of what Perkins calls the 'anti-stall device. Foley quoted me $163 for a new device. Being a cheap ass and having a great machine shop near, I had them drill out the screw and I replaced it. I reassembled everything, hit the starter, and the engine went to wide open throttle. I covered the air intake with my hand stopping it. I've since tried both shorter and longer screws with no luck.
The screw presses down on a small spring which sits atop an even smaller piston. This whole assembly threads into the dome above the fuel pump. The engine ran normally when I initially splashed. It ran for 3-4 minutes until the air lock showed itself. I checked the return line to the tank and its clear This leads me to believe it has something to do with the anti-stall device I messed up. I've found a cheaper price ($92) but
before I order it I thought I'd poll the great minds here.
Thanks in advance for any and all help.
Rick

[John Galt]

Wow, not one person out there with any suggestions?
And I brag to others all the time about this board...

[gjordan]

Even though I have owned a Perkins(4-154) I had never heard of an anti stall device. I am going to suggest that you may be chasing the wrong problem. If the engine started and ran for 3 or 4 minutes, it probably is a small air leak before the injection pump, and not a problem with the pump or lift pump. Why it ran away I have no idea, but I think useing your hand to stop it can be dangerous. You might want to pressure test your lines from the tank to your injection pump for leaks. Sitting over a winter can cause even the smallest leak to kill an engine. Different engines respond in different ways to air bubbles. My Mercedes engine in a boat would run rough and and eventually clear itself out if I left a little air in it from a filter change, but my Perkins would stop stone dead if there was the slightest bit of air in the system. It would require a full bleed to get it running again. You may have buggered up your anti stall device, but I doubt that was the initial problem.___Good Luck._____Grant.

[SkiprJohn]

If you have a runaway again I'd not use my hand over the air intake. Find a rubber soled shoe. You could seriously damage a hand.

I haven't replied because my experience with 4-107 is more than 30 years old. I do remember a screw I should have never touched while bleeding the system but can't remember where exactly it was. It went into the side near the fuel injection pump and I could never get it to quite thread in correctly. A friend sorted it out for me and I never was so happy when the beast started and ran well again.

Good luck in your repair.

kind regards,

[John Galt]

Thanks for the replies! I'm now thinking this screw
(which is shown as an air vent ) in the manual may have been hollow. There's a small spring below the screw that might have too much pressure on it. I've gone ahead and ordered the anti- stall device from TAD for $92. Knowing my luck that won't solve my WOT, but you never know.
Thanks again guys...
Rick

[KDH]

According to the workshop manual for the 4-108 the anti stall device is on the fuel injection pump. The adjustment procedure for the idle speed is in section Q6 and is done using both the idle adjustment screw and the antistall screw. First, I would completely rebleed the system. Then I would follow the procedure in the manual. Typing this on my Kindle so if you don't have the manual and need the procedure I can post it tomorrow if you need it just post here or pm. Sitting on the boat in Portimao, Pt. with no internet.

[cburger]

The anti stall valve is ineed an assembly, spring, valve piston, etc. I had to take mine appart just last year when I rebuilt the govenor. Not only do you have to have the entire correct asembly of all the various little parts all put back in the correct order but in addition that bleed screw has to be screwed back to the initial factory setting or the motor will not run properly. Before I had disassembled mine I uses a pair of calipers to measure the height of the adjustment of the valve body above the body of the govenor so it would be simple to have it back to the original setting.

[cburger]

Here is a picture of my 4.108 anti stall with all the parts in there correct order of assembly, can't help with the adjust.ment, hope it helps

[John Galt]

Is the air vent screw bored out (hollow)?
I've tried a screw that same size without results.

[Lagoon4us]

My 4-108 would die because there is an excess fuel return line from the injectors to the CAV filter, in the top of that housing is a ball bearing that is spring loaded.
This ball seals on a seat and as return builds pressure it releases and squirts the excess into the circuit ie filter body.
Moisture and crap in the fuel make these ball's stick in the seat resulting in a flooded engine.
Remove ball and spring, clean, reinstall and all is good. A period of inactivity fits with these valves sticking.
Cheers Frank

[John Galt]

Well, the new device from TAD worked. On a side note, TAD was a pleasure doing business with!
Thanks for all the help, this forum is invaluable to me!

[cburger]

Originally Posted by John Galt

Well, the new device from TAD worked. On a side note, TAD was a pleasure doing business with!
Thanks for all the help, this forum is invaluable to me!

My business dealings with TAD has also been a pleasure.

[Barnhard_Marine]

TAD,
Is a good source for Perkins but Blue Ridge Diesel in Salem, VA Rocks they can find parts when no one else can.

[lastkahuna]

Originally Posted by Lagoon4us

My 4-108 would die because there is an excess fuel return line from the injectors to the CAV filter, in the top of that housing is a ball bearing that is spring loaded.
This ball seals on a seat and as return builds pressure it releases and squirts the excess into the circuit ie filter body.
Moisture and crap in the fuel make these ball's stick in the seat resulting in a flooded engine.
Remove ball and spring, clean, reinstall and all is good. A period of inactivity fits with these valves sticking.
Cheers Frank

where is this ball bearing? My perkins has excess fuel it will only run with fuel dripping from the anti stall valve being loose?