1986 Cummins Diesel

rfazio

Member
I have a 1986 Cummins Diesel in my Allis backhoe. All of a sudden she won't run right. She will start and run for 30 seconds then dies and won't restart. Wait a day and she will start again. Got some suggestions here and checked the tank vent. checked for bacteria in the tank, all good. I pulled the fuel line to the engine drivin pump and fuel flows like crazy. Then after the pump and pumped with the manual handle and fuel flows great. Just before the injector pump there are bleeders. I pulled them and turned the engine over, fuel flows great. I disconnected the injector lines and get drops of fuel, hardly any. You are probably going to tell me the injector pump is bad? But all of a sudden like that? Usually from my experience they go slowly. Get worse and worse. this was from working great to nothing in one run? I did maybe let it get low on fuel and try starting it. Then filled an bled it. She ran after that ok. Could that have caused my problems?
 
Is there a procedure to get the air out? I figured once it was running it would eventually clear out. But it seemed to get worse and worse. Now I can't keep it running.
 
Probably not the problem. I have a caseih 5250. Mechanical lift pump. Has a small plastic screen inside fuel pump can't see it can't access it without destroying pump. Mine would run but high idle would go from nothing to full throttle and back to almost dead. Always seemed to have fuel when checking. Finally drilled bolt where fuel comes from pump to filters and pipe threaded pressure gauge in so I could watch it, pressure fluctuated wildly. Maybe could take 1/8 rod and bend to get into hole and puncture filter have had not needed yet. Screen was about size of little finger in diameter and as long from second knuckle to end of finger. HTH Tom
 
Hello rfazio,

Crack each line and compare fuel flow-pressure. Once a line is craked, it should spit pretty hard. It may need a good bleed on all cylinders. Check the pump screen to make sure you are getting fuel to the pump,

Guido.
 
Air in lines usually makes them spit and sputter and rough idle if it starts at all. If it doesn't start then usually you have to bleed the lines or keep cranking a long time, meaning simply letting them sit usually does not cure the air problem, in fact in most cases it would make the problem worse.

How does it run before it dies, does it start running rough or does it simply die like you shut it off? When it restarts, does it start right away or does it crank awhile, and when it starts doe it run smooth? It might help to know what kind or brand of injection pump is on this engine, does it shut off electrically or mechanically? Does the lift pump have a filter/screen on it or just one big fuel filter?
 
It starts normally. Runs perfect for 30 seconds or so then just slows down and dies. Not all of a sudden, like shutting the key. Once I got it
running after trying for a while and it wouldn't take the throttle. If I pressed too hard it would die. If I went easy it would go. It has two fuel filters,
one with a water drain and a second smaller one. I changed both. And like i said fuel really flows from the tank. Before the fuel filters it goes to
an engine drivin pump. Looks like a typical gas engine fuel pump. It has a pump lever on it, and when I pump it with the bleeders open it
pushes out a ton of fuel. The bleeders are before the injector pump, looks like too me.
 
Have not worked on that engine much. So I am going on what I have learned over the years. Have you checked the return line system. If it is stopped up. It will slow down after starting and come to a stop. Because with a clogged line pressure will back up causing the pump to quit working.
 
It could be drawing in some air anywhere on the suction side of the fuel pump until it gets too much air in the system and sputters and quits. My 6BT in my Dodge truck would start and run fine for 30 minutes, then start to lose power, then quit. If it sat for an hour, it would start again and repeat the cycle. In that case there was an air leak in the connector hoses at the fuel tank. Try replacing the return line downstream from the injectors with a piece of clear tubing. Air bubbles in the return indicates a leak somewhere on the suction side of the fuel pump. Not a pro diesel mechanic, but I hope this may help.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top