Perkins 4-108 Injectors

[NAILS]

New to diesel engines. I've gone through all the suggestions without a solution to a hard-start. Now looking at the engine's injectors.

Seeking guidance on their (injectors) removal, whether or not it's better to repair or replace and who makes replacements.

Thanks in advance. Yes, I did search this forum but did not see answers to my questions.

Nails

[roberttigar]

Removal is pretty strait foreward.
Shut off the fuel line at tank
Remove return lines
Loosen fuel lines at injectors and slack at pump to give some flex to clear injectors
Loosen and remove 2 bolts on each injector
Wiggle them out-them side to side and they are supposed to pull straight out.
That's were it becomes difficult. If the injectors have been in a while they could be frozen in the head. A socket wrench on the cap helps move to loosen the seat. I got 2 out easily. The other 2-I put the bolts on-not tight and turned the engine over with the starter-using the compression to un-seat the frozen injectors.

If your engine is running well, it may not be the injectors. Possibly a deteriorating fuel hose or loose connector or time to rebuild the pump. Probably alot of other reasons as well. Bob

[Lepke]

If the engine does eventually start and run, I doubt it's the injectors, all 4 don't go bad at once. 4108 injectors are just a spring loaded valve with a nozzle. The valve opens with high pressure and closes before ignition so combustion gasses and debris doesn't foul the valve.

To start a diesel - compression has to be good enough to raise the air temp above diesel ignition temperature (about 500°F). As air compresses it get hotter. Air leaking past rings and worn valves can defeat starting. A cold engine in cold air can need heat either in heated air or block/pan heaters. Even a hair drier held by the intake can help start a diesel without glow plugs. So a cold engine with poor compression can still be started with heat because you start at a higher temp before compression.
Fuel is usually the problem in an engine with good compression. Air in the system will compress in the injector lines enough to cause the valve to remain closed or only partially open. Improper bleeding, sagging fuel lines or loops with air pockets, leaky fittings all contribute to the air in the fuel problem.
And then if the starter turns too slowly, it allows time for air to escape the cylinder before ignition.
Using too much ether, running an engine on ether because of fuel problems, will create extremely high pressures, usually cracking the rings. That's why it's said if you use ether, you'll eventually use it all the time. Ether has its place, but needs to be used at the smallest rate possible.
If the valves are bad in the lift pump, allowing fuel to bleed back to the tank, the engine has to crank a long time to bring fuel back. Usually the engine half way fires and then requires cranking.

[oldcal46skipper]

I hope to help

Originally Posted by NAILS

New to diesel engines. I've gone through all the suggestions without a solution to a hard-start. Now looking at the engine's injectors.



How I do it...



Perkins 4.108's and many others:
AAAAAAAAAAAA

*** System check: 1-Check battery voltage. It should be 12.8 Volts DC if fully charged. Check voltage at the starter while someone attempts starting. Look at voltage. Could be faulty wiring, corroded fasteners, worn solenoid. If electrical is ok, fuel is next
2-Is your fuel old? If so, have it polished or replaced. Naturally vented fuel tanks on boats expel air in the tank during the warm day, then inhale moisture laden air at night, thus drawing moisture into the tank which condenses and settles to the bottom of the tank eventually rising to the level of the pickup tube. Then you are sucking water instead of diesel fuel.
"Fuel polishers" should pump all the fuel/water mix out, clean the tank and replace with clean, DRY fuel. There are several good fuel tank cleaner liquids on the market.
3-Assure all of the fuel filters are new, then bleed them properly starting at the tank pick up.. Carefully replace filters, "O" rings and gaskets. I use a touch of lube oil on my finger tips and smear on the gasket or O ring. Carefully tighten the filter canister to manufacturers torque rating.

4- Assure all of the fuel line connectors, "crush washers", bases and "banjo" nuts are clean and not damaged. Face them if indicated.
5-For a test run, I often use a known clean, plastic outboard fuel tank with a pump bulb and assure all AIR is expelled from the feed lines by loosening the bleed nuts, first on the filters, then the high pressure pump, (If in doubt, get the Engine Mfg's SHOP MANUAL)
6-Loosen the high pressure line to each injector, (AKA "Atomizer" in some parts of the world), as you turn the engine over with the starter at full throttle. One at a time starting at the shortest line from the high pressure pump until all air is expelled and you are seeing only fuel expelled. NOTE: Have some means of capturing the excess fuel as it is flammable over 138 degrees F. I use 3M oil diapers, then discard them properly.
7-Now she is running! Allow a few minutes warm up while observing oil pressure, cooling water flow, looking for leaks an/or smoke. After about 5 to 10 minutes running at high idle speed, (depends on the engine), at a set RPM, say 700, loosen the high pressure line at each injector - one at a time- and observe engine speed reduction. It should be about the same for each cylinder, if not, you have an injector that needs repair, cleaning or calibration.

Find a reputable shop and have them test, clean and calibrate the injector. Often the nozzle must be replaced and/or internal shims.


If you are near Bayou Chico, FL, call me, bring them to my shop and I will test your injectors while you watch. No charge if no parts or adjustments are indicated. I have rebuilt, calibrated and tested fuel injectors for Perkins 4.108's for $85USD exchange.


Seeking guidance on their (injectors) removal
,***
Removal of rusted, stuck fuel injectors can be a difficult job. Kits for various brands injectors are available from several sources.


whether or not it's better to repair or replace and who makes

replacements.
***I have original injectors in my 1987 Perkins 4.236 with 3,600 hours, but I remove, test and calibrate each 1,000 hours as Mr. Perkins suggests.


Hope this helps.
Tom


Thanks in advance. Yes, I did search this forum but did not see answers to my questions.

Nails