Cummins 4BT fuel problems

Hyundai R130 LC3, with a cummins 4bt engine. I bought to do projects around the house so its not used much. Couple years ago i had fuel issues where i needed to purge the injectors before starting and after some time, the engine would stall. I ended up cleaning a couple inches of crud out of the fuel tank and seemed to solve the problem. Or so i thought.
Still same problem, I need to prime the engine and it will run great. Eventually rpms will drop and sometimes stall. Restart would require priming. Fuel lines to filter and lift pump were cracked. Replaced those and seemed to work, but no. After some reading, i replaced the lift pump. Same thing, seemed to work but next time i ran it i had the same problems. At this point I cant even operate it. I can prime and start. Engine rpms will go to 2000-2200 but after a couple min, any load on the engine and the rpms drop
The first two injectors have always been wet at the top of the engine. those need to be addressed but its always run well. Not sure if all the previous fixes have just pushed the problem to the next issue.
Also, while replacing the lift pump, i noticed that three of the fuel line fittings at the injector pump were black. I tried tightening them but they seemed tight. Id post pictures but i cant seem to link my phone to my computer.
Not sure where to go. I dont want to keep replacing stuff if its not the problem. if its obvious that its the injectors, please kick me in the arse and tell me to replace them.

Check your vent on your fuel tank it could be stopped up, it could be a breather assembly in tank or in the cap. Check fuel flow from tank to lift pump, and if it has an inline filter check to make sure it's good, and your fitting where fuel line connects to tank.

fuel tank vent, could i just leave the cap off to check? There are two water filters, one between the tank and pump. Now that i think about it, there is a fuel filter and water filter at the top of the engine, not sure where those feed lines are.
i replaced the lines from the tank, to the first filter and then to the lift pump. They were cracked, thought that was my problem but nope.

heres the fuel pump picture

When you say you have to prime to get going, after it falls flat, what exactly are you doing. Refilling filters and purging lines or what.

Ok The pic I see a hose clamp on a hose is that supply to primer pump ?
Somewhere you have a leak is not dripping fuel its sucking air and you have to prime system I would start with hoses and use a crimped hose not hose clamps
Wet injector line still pushes fuel out and return gets air in system ...damn its been a few years since I worked on a 4bt but I think its a banjo fitting on injector pump that has a screen on it I may be wrong ..but if any banjo fitting on fuel system replace all copper seals ,,they cant be reused

Yes, I purge by opening the injector feed at top of engine and turn over with starter. I think tonight I will check the filters.
Hose clamp is new feed line from water filter to lift pump. Originals were cracked at the fittings.

The only thing that holds pressure in the lines is the LIFT pump..
So if thats new.. u must be sucking air or creating a vacuum..
YES, u can run it w/o the cap..
OR.. run it for a minute & when it starts to bog down, loosen the cap & listen for a suction..

Another thing u can do is pressurize the fuel tank a smidge & look for any leaking hoses or connections..
If u use baby powder before u start on any suspect lines or fittings, it should show up pretty quick.

The scenario given sounds a lot like bacteria growing in the tank. Look for some slime in the filters, strainers and water separators. You mention a fuel filter and I think I might have seen an in line filter in the photos. If so did you get it from an auto parts store?

Slim, interesting. I did have to clean the fuel tank out a couple years ago. The sludge was about 2 inches thick. For filters, there is a water separator between the tank and the lift pump. Then i have the fuel filter and second water separator on the engine block. couple more pictures

Completely off the subject, in the upperpicture it looks like you have an ether injection fitting with no hose on the intake manifold. You need to get a tube there or plug that up.

Vetech63, I've been looking for the ether injector forever. My manual says I have one but could never find a bottle or anything. I guess at least I found the input...Thanks.

ktm250rider said:

Vetech63, I've been looking for the ether injector forever. My manual says I have one but could never find a bottle or anything. I guess at least I found the input...Thanks.

Click to expand...

The rest of the system may have been removed. There is normally a bracket within 2 feet of that fitting for the injection bottle. Usually the bracket is on the engine firewall.

I wonder if that was the bracket I removed from the injector pump that wasnt doing anything and was in the way of tightening the injector lines.
Dumb question. In the same picture, the fuel comes out of the lift pump to the fitting above the filters. Then through the filters and out the fitting to the upper left of the first. Then to the injector pump. Is this correct?

Correct. The upper fitting has the bleed screw in it. When you change the filters, you will loosen that bleed screw and pump your supply primer until you have fuel with no air....then tighten the bleed screw. That gets your system air free to that point.

Found a union in the fuel line that inputs into the injection pump. That union was loose. Knock on wood, ran for an hour with no problems. Not sure why there is a union there.

Unions mean there was a hole rubbed in the tube line and the union was how it was repaired

Some of the early 4390 engines had a two piece supply line from filter to pump inlet.

IDK why they did that either.. its like a 4 pc. line.. w/ rubber "olives" inside each connection..

Yup, looking at the manual i have, that line has a union in the middle...not sure why, but i hope that was my problem. Ill find out sat, next time im running.