Perkins 4108 Hydraulic Fuel Pump Leak: Auto Advance Device?

[ZFG]

I have noticed a pretty bad fuel leak from my 4108 (the engine starts and runs totally fine, only noticed it on the drip pan soaking in the mat under the engine), and I believe I have traced the source to what I guess is the "auto advance device". The 4108 work shop manual doesen't list any thing specific about this section of the fuel pump, or how its assembled. But this other source I found online looks pretty close. See attached pictures of diagram and my leaking "piston spring cap"

Has anyone taken this apart? Is it doable with the pump still on the motor (ill likley have to take the oil filter off to get any sort of tool on it) or will I have to take the pump off to re seal this? Is there actually just an o ring back there that can be replaced? Anything else back there that will shoot out and fall into the bilge?

[Lepke]

I haven't taken on apart, but it doesn't look like a problem. If you're near a port city, call an injector pump rebuilder.
If you have the make and model number, you might find a manual online.

[Mickeyrouse]

That series of Perkins engines uses a Lucas fuel injection system. Injector pumps are pretty precise devices. Any city that has service for 18 wheelers and construction equipment likely has a diesel injection service. Tell them what you have to be sure it doesn’t scare them. It shouldn’t.

[ZFG]

Ive got the yard mechanic coming out today (hopefully) to take a look and see if he knows any specifics about this. I emailed parts4engines about this and despite selling a rebuild kit, and offering a rebuild service, their support person said "we dont know how those pumps work, we just sell the kit, i cant help you because we dont know how to repair them"...so if the yard mechanic doesent know then ill call some injection shops

[ZFG]

my fuel issues continue to manifest in weird ways...

I went to start the engine and it would crank and crank but not turn over. I noticed the boot on the fuel stop solenoid look ripped (honestly dont remember if it was like that before of if this is new) so i pressed the stop solenoid back to the retracted "stop" position while somone cranked the engine, and noticed if i held the stop solenoid back in the right place the engine would start.

i could then let go of the stop solenoid and lever would return forward and the engine would run fine.

when stopping the engine, i would push the stop button, the solenoid retracted the arm, and the engine would stop.

so, what could be going on with the fuel pump that it only wants to start when the shut off arm is retracted back to a roughly specific position, but runs fine when let back in the forward positon.

note: this is the first time this has happened. engine has ran fine and fired right up for the last 3 months, then i noticed the fuel issue, i havent actually touched or adjust anything yet trying to fix it...then just yesturday this weird issue sprang up. I was able to repeat it this morning as well, so i know its not a fluke.

[skipperpete]

That’s very strange with the stop solenoid, does your injector pump have a mechanical governor or Hydraulic? DPA pumps are very touchy regarding case pressure and metering pressure, a restricted or pressurised return or line can cause case leaks and the metering pressure that pushes the two little plungers apart in the hydraulic head is so precise and minute that its nothing short of magical that the DPA works at all. NO, do not try and re seal the advance mechanism in situ, remove the pump and take it to a fuel injection tech and either tell him you ONLY want a re seal done (relatively inexpensive) or let him strip the pump and do whatever needs to be done, this often means a new vane pump and ring or a new hydraulic head so thats about $1000 dollars here in Australia.

[ZFG]

Originally Posted by skipperpete

That’s very strange with the stop solenoid, does your injector pump have a mechanical governor or Hydraulic? DPA pumps are very touchy regarding case pressure and metering pressure, a restricted or pressurised return or line can cause case leaks and the metering pressure that pushes the two little plungers apart in the hydraulic head is so precise and minute that its nothing short of magical that the DPA works at all. NO, do not try and re seal the advance mechanism in situ, remove the pump and take it to a fuel injection tech and either tell him you ONLY want a re seal done (relatively inexpensive) or let him strip the pump and do whatever needs to be done, this often means a new vane pump and ring or a new hydraulic head so thats about $1000 dollars here in Australia.

its the hydraulic one. If im taking it off, which seems to be the only answer here, its just going to get fully rebuilt.

im new to marine diesels...so im trying to rationalize what might be causing all of this. If I had a restricted line, either in flow or return...i would expect that to effect performance while running in some way...but it doesen't seem to. It just leaks fuel, then out of nowhere had this weird starting issue.

I would just love to know what mechanism/passages are happening in that pump that suddenly out of nowhere, i have to hold the shut off lever BACK to get it to run, then i can let it go forward and it runs fine.

[Marathon1150]

We have a Perkins 4.108 and it has been incredibly reliable except for the high pressure fuel pump which has been the source of all kinds of problems and much cash flying out the hatch. Sadly, I can't provide any advice other than try to get someone who knows that pump as has been suggested by others. Its also good if they are familiar with Perkins engines.

The pump problems started with a major leak about 15 years ago. The pump was rebuilt and the leak was resolved, but the mechanic who took it out and put it back was a disaster. I had to find another mechanic to fix some of the problems created by the first one. The pump has been out and back in a couple of times since then and for the past 4 years or so, all seems ok.

The only problem we have had with the solenoid control on the engine stop device was the cable got sticky. A bunch of WD40 solved that problem.

Good luck all around.

[ZFG]

well the mechanic came by (who was a perkins dealer for 30 years so i think he knows perkins engines) and it seems like the leak was mostly the return line copper washers on top of the injectors? I replaced those and he came back to observe so that leak might mostly be fixed...

I also replaced the plunger/boot on the stop solenoid with a spare, but the stop arm ended up in the same place in the "rest" position before and after replacing the boot so i dont think the boot was actually doing anything?

The engine fired right up immedietely the second time (2 hours after the first time that morning when I had to pull the stop arm back to get it to fire) after replacing the washers and the stop plunger. The mechanic said the start issue was the injectors leaking fuel back into the engine, effectively flooding it while it sat for a few days, which is why it wouldnt start after sitting. So if i let it sit for a few days, and i still have to pull the stop plunger back to start the engine, i will need to get the injectors rebuilt (mechanic's condlusion)

Has anyone else experienced this thing happening? injectors letting fuel back in and haivng to effectively "cut fuel" initially to get it to start? I guess it makes sense...it was just way off from what I initially suspected the issue to be.

[skipperpete]

Originally Posted by ZFG

well the mechanic came by (who was a perkins dealer for 30 years so i think he knows perkins engines) and it seems like the leak was mostly the return line copper washers on top of the injectors? I replaced those and he came back to observe so that leak might mostly be fixed...

I also replaced the plunger/boot on the stop solenoid with a spare, but the stop arm ended up in the same place in the "rest" position before and after replacing the boot so i dont think the boot was actually doing anything?

The engine fired right up immedietely the second time (2 hours after the first time that morning when I had to pull the stop arm back to get it to fire) after replacing the washers and the stop plunger. The mechanic said the start issue was the injectors leaking fuel back into the engine, effectively flooding it while it sat for a few days, which is why it wouldnt start after sitting. So if i let it sit for a few days, and i still have to pull the stop plunger back to start the engine, i will need to get the injectors rebuilt (mechanic's condlusion)

Has anyone else experienced this thing happening? injectors letting fuel back in and haivng to effectively "cut fuel" initially to get it to start? I guess it makes sense...it was just way off from what I initially suspected the issue to be.

Thanks for the update and I’m happy to know that the fuel leak wasn’t from the autoadvance. I know of no circumstance where a Perkins 4-108 injector can “flood” a cylinder with fuel....... there might be one but just not in my experience ....given the nature of the high pressure fuel system it’s beyond unlikely if you think it through. For the leakoff line to be able to let fuel into the cylinder, the injector needle would need to be damaged very badly and the return from the leakoff to the tank would have to be pressurised. The engine would either not run at all or run very badly. IF the mechanic is correct and the engine is flooding with fuel the likely culprit is the perkins coldstart leaking into the intake manifold and that might be somehow related to the suspiscious leaking washers on the injectors, there should be bugger all pressure in the return system unless you have an overhead day tank. Some engines CAN leak fuel into the cylinders, Cummins PT injectors and some Cat engines do it but its rare and usually ( but not always) caused by a blocked return line.

[ZFG]

Originally Posted by skipperpete

Thanks for the update and I’m happy to know that the fuel leak wasn’t from the autoadvance. I know of no circumstance where a Perkins 4-108 injector can “flood” a cylinder with fuel....... there might be one but just not in my experience ....given the nature of the high pressure fuel system it’s beyond unlikely if you think it through. For the leakoff line to be able to let fuel into the cylinder, the injector needle would need to be damaged very badly and the return from the leakoff to the tank would have to be pressurised. The engine would either not run at all or run very badly. IF the mechanic is correct and the engine is flooding with fuel the likely culprit is the perkins coldstart leaking into the intake manifold and that might be somehow related to the suspiscious leaking washers on the injectors, there should be bugger all pressure in the return system unless you have an overhead day tank. Some engines CAN leak fuel into the cylinders, Cummins PT injectors and some Cat engines do it but its rare and usually ( but not always) caused by a blocked return line.

Thanks for the thoughts! I’m not convinced any leak is solved till I run the engine a while and watch the drip pad for a few days, so I’ll see how that shakes out.

Ya I’m still not totally convinced on the start issue being an injector problem as the mechanic said, and feel like it’s an injector problem still, but I’m out of my pay grade here clearly and that guy is a career mechanic. This has been a Florida boat for the last decade or more, i don’t even think a cold start is hooked up? Are they installed by default? I’m just not convinced the stop solenoid is magically in the right place because I put the rubber boot on, since the forward stop of the arm is back against its own stop point.

I’ll try to start again tomorrow after letting it sit, what else in the hp fuel pump or injectors , could over fuel the engine at rest, requiring the fuel shut off to need to be retracted for it to work? What else does that shut off arm do/operate in the pump?
Because once it started the first time this morning there was a bunch of smoke (from excess fuel) just as the mechanic described would happen, then it ran fine, and started fine the second time.

I’ll probably just end up redoing the injectors and pump by the time this is over, I just want to leave for the cruising season and this is the last thing holding us up…I also want a reliable boat motor so I don’t get ****ed up passing inlets lol

[skipperpete]

There’s a mushroom shaped cover on the air intake, just nearby there’s large hex nut with a spade terminal and a big fat electrical cable. Also there’s a skinny fuel line attached in the centre, it comes either from a little tank or from the fuel filter,…. Thats the cold start. It works by a coil getting red hot and allowing fuel to dribble onto it and catching fire. The fire is then sucked into the manifold as you crank the engine and she starts. Crude but it works.

[ZFG]

Originally Posted by skipperpete

There’s a mushroom shaped cover on the air intake, just nearby there’s large hex nut with a spade terminal and a big fat electrical cable. Also there’s a skinny fuel line attached in the centre, it comes either from a little tank or from the fuel filter,…. Thats the cold start. It works by a coil getting red hot and allowing fuel to dribble onto it and catching fire. The fire is then sucked into the manifold as you crank the engine and she starts. Crude but it works.

oh gotcha. ya that is a wildly crude system haha. So that always injects fuel then? and only ignites when the cold start is turned on? Mine comes right off port #1 on the filter housing. I dont see any fuel coming from it at rest, the air intake that i can see is pretty dry...maybe i should watch it when the engine fires up to see how much fuel is going in?

If thats not just dumping fuel then the next culprit you think is the pump itself some how?

[skipperpete]

The cold start only dribbles fuel onto the heating coil , no injection involved but it can leak into the manifold if the thermal expansion part gets worn or out of adjustment. If the intake is dry, this is not the problem.

[ZFG]

after letting the motor sit for 24 hours, i fired it up this morning. it took about 8-10 seconds cranking, i fiddled with the throttle lever while doing so...but didnt have to move the kill lever to get it to start. I talked to the mechanic again this morning, after i described the issue again with the fuel shut off lever, he thinks it was more of a coincidence that it fired when I was pulling it than that being what got it to start.

my only other rationalle is that the injectors or pump are leaking a bit internally, and the pump needs to build pressure, and cutting fuel to the engine allows it to build that internal pressure quicker than if I just didnt mess with it. second time i fired up the engine, 30 min later (like yesturday) it immedietely turned over.

Either way, the mechanic has about 40 years more experience than me, and after poking around the engine the other day for an hour and a half he didnt see the need or reccomend rebuilding anything immedietely. So i guess im going cruising for 4 months, and i get them rebuilt at the end of the season for piece of mind. Thanks all!