Perkins 4.108 Fuel Injector Pump Question

[Alan B]

Hi Everyone,
I have a Perkins 4.108 and tried starting the engine which I have rebuilt but it won't start so I took the injector pump off to check it.
I had previuosly dismantled fuel injector pump myself and replaced with some kit parts-filters, "o" rings ect before I put it back on the engine.
When I had the pump in the vice with all the fuel injectors attached I bled the system and turned the pump using an electric drill.
I am getting fuel out of all of the injector nozzles but I am not getting any fuel coming out of the return section of the injectors which I just left open. Should I have fuel coming out the injector returns? I think I should have.
I am wondering if anyone can tell me if I have enough pressure coming out of the pump and the injectors?
I would assume that the injectors won't open at all if theres not enough pressure coming out of the pump. The book says the atomizers(injectors) open at about 135-150 atmosphers.

Has anyone got any information that they can share with me please?

Thanks in advance

Cheers

Alan B

[btrayfors]

While 4-108's are very tough and there's a lot you can do yourself on them, fuel injectors are one thing you don't want to fool with. Proper rebuilding and adjustment is an art, and doing it right requires a very expensive machine (well over $10K).

I'd suggest you find a shop which can test your pump, and be sure it's to spec.

Bill

[ulpilot45]

Alan while testing with a drill let's you know the pump is capable of opening nozzles its not calibrated to specs the fuel from the return of the nozzle is leakage and builds up as the engine runs to cool nozzle you should have the pump checked to make sure it built right and calibrated. - I own a fuel injection shop

[Chief Engineer]

That's the part of the manual that says "refer to qualified technicians"

Why some people do this stuff......just keeps me in business.

[Alan B]

Hi All,
Well after fooling around a bit with the pump I found that I had put the roller saddles in back to front.
For those that don't know, if they are in the wrong wrong way it will only pump about half the amount of fuel.
These rollers run on the inside of a cam for pumping the fuel.
I found the pump easy to overhaul myself in the garage. I'm an auto electician by trade. I just bought a basic repair kit from Peter Slater in the UK their website is www.pslaterfie.co.uk. I think it cost me about $30 AUS and was well worth it.
So, for those who have any basic mechanical knowledge do the pump yourself. It will probably only take about 3-4 hours to do it.
If the engine used to run ok just make sure that you don't adjust the plate screws that deterimes how much fuel is pumped out by the pump.
This plate will determine how far the rollers move in the outward position.
I can't see the value in paying someone $500 to whatever it costs for something that's so easy to do yourself.
Just make sure the saddles that hold the roller bearings are in the right way to begin with.
I just washed all the parts in petrol in a small container and reassembled it with new "o" rings, seals, rotor viens and gaskets.

Too easy

Happy motoring

Alan B

[Dynamo1181]

Alan / Others
Is there a simple O ring repair that will stop throttle shaft leakage...short of a pump rebuild on the 4108?
A

[Tellie]

No offense Alan, but Btrayfors and Chief are right. Injection pumps are an area the vast majority of boaters especially DIYers should avoid.

[Alan B]

Hi Dynamo,
If your pump has a hydraulic governer like mine you can take that part of the pump off by undoing the two screws that hold it onto the injector pump.
Mine did not leak so I didn't replace the seal.
On my pump you have to take the metering valve out before you slide out the shaft.
Also, I noticed on my pump that you might need a very small socket or tool to unscrew the nut that keeps the regulating valve in the body.
It unscrews from the top once you remove the large nut that has the bleeder valve on the top of the body.
There should be a seal inside.
Measure the distance of the metering valve position before you start to undo the small nut. You want to put it back to where it was to begin with.
If you don't buy the kit you should be able to just pick up the "O" ring by itself.
You can buy them here in Sydney from bearing suppliers.

Cheers

Alan B

[Dynamo1181]

i do have the hydraulic governer. Thx much for the info.
Alan W

[beneteau-500]

and you can still get all the tools for these perkins engine for setting up the pump and timing for a tool company in Peterborough uk

[lituya1617]

There are those who say an injection pump and injectors must be done by a professional shop and there are those who are mechanic enough to do it themselves. It is a time-consuming job when done without the fancy balancing setup a shop has. Now, it often costs over $800 to get a pump and injectors overhauled in a shop. I can do a lot of work for $800. I believe a sailor should be able to repair anything on his boat - if it can be repaired. To me, it is a safety issue. Now injectors and pumps are very closely machined and you must be extremely clean when you work on them. A little dirt will ruin an injector or pump. If you have the overhaul manual, the proper tools, and you take your time, you can do your own overhaul. It is a bit of a pain to measure flow and adjust each injector, but the pump is straightforward. Just follow the manual. If you are not sure, take it to a shop. It is expensive but so is boating.