Help with diesel tractor engine miss

[Red Rex]

1968 Massey Ferguson 135 with AD3.152 Perkins 3 cylinder diesel.

Engine miss at all RPM.
Will make redline rpm of 2000. There is a lag on acceleration. N
Rpm when held steady @ 1000 rpm will fluctuate up 50 rpm down 50 rpm for a 100 total swing on a 3 second cycle.
Starts on 2.5 rotations of the crank shaft.
No fuel leaks anywhere.
Rebuilt injector pump.
Rebuilt injectors.
Clean fuel tank and lines all the way to the pump.
No oil in radiator no water in oil.
I do not have a compression guage but the motor does turn over with no fluctuations in speed when cracking with fuel shut off.

The rpm fluctuation reminds me of a vacuum leak in a gasser. Is it possible for a fuel line to suck air and not leak fuel?


I am stumped. Anyone have suggestions?

Thanks, Andy

 

[Midnightmoon]

Did it have the same issue before the rebuilt injection pump?

 

[Bextreme04]

1968 Massey Ferguson 135 with AD3.152 Perkins 3 cylinder diesel.

Engine miss at all RPM.
Will make redline rpm of 2000. There is a lag on acceleration. N
Rpm when held steady @ 1000 rpm will fluctuate up 50 rpm down 50 rpm for a 100 total swing on a 3 second cycle.
Starts on 2.5 rotations of the crank shaft.
No fuel leaks anywhere.
Rebuilt injector pump.
Rebuilt injectors.
Clean fuel tank and lines all the way to the pump.
No oil in radiator no water in oil.
I do not have a compression guage but the motor does turn over with no fluctuations in speed when cracking with fuel shut off.

The rpm fluctuation reminds me of a vacuum leak in a gasser. Is it possible for a fuel line to suck air and not leak fuel?


I am stumped. Anyone have suggestions?

Thanks, Andy

Diesels are pretty simple. Most likely you have an air leak in a fuel line. The only other option is a clog/contamination or low compression. Next step for me would be running a compression test. After that, if you dont find any compression issues, I would look at the individual fuel lines.

 

[80BrownK10]

Yea crack that line at the injector and see if it makes any difference after awhile. Can you pull the injector and check it's spray pattern while you crank it? As you know it's not getting fuel or compression....we are pretty sure it's getting air since the other two are fireing.haha

 

[Red Rex]

Diesels are pretty simple. Most likely you have an air leak in a fuel line. The only other option is a clog/contamination or low compression. Next step for me would be running a compression test. After that, if you dont find any compression issues, I would look at the individual fuel lines.

If it leaks air in would it not leak fuel out when not pressurized?

 

[Red Rex]

Yea crack that line at the injector and see if it makes any difference after awhile. Can you pull the injector and check it's spray pattern while you crank it? As you know it's not getting fuel or compression....we are pretty sure it's getting air since the other two are fireing.haha

Injectors were just rebuilt by the injector pump shop.

I cannot find a compression tester that will work on my engine short of loading and towing 70 miles one way and waiting for them to get around to it

 

[Bextreme04]

If it leaks air in would it not leak fuel out when not pressurized?

Its actually more likely to be an air bubble in the line than it sucking air. Crack each line after you get it running and let some diesel run out to make sure it has been properly bled. I have absolutely seen them have an air leak and not leak fuel though. That is usually on the suction side though and makes it not run at all. A fuel issue that is causing it to run rough and not have pep is usually from not being fully bled of air on the pressure side.

 

[Itali83]

Run the motor, crack the injector lines one at a time while it’s running to isolate which cylinder is skipping. You can now at least double check valve adjustment to rule that out. If nothing obvious, take that injector out and swap it with another cylinder. See if the skip follows. Report back.

Ben

 

[Red Rex]

Run the motor, crack the injector lines one at a time while it’s running to isolate which cylinder is skipping. You can now at least double check valve adjustment to rule that out. If nothing obvious, take that injector out and swap it with another cylinder. See if the skip follows. Report back.

Ben

I adjusted the valves when I pulled the injectors to be rebuilt

 

[Red Rex]

Run the motor, crack the injector lines one at a time while it’s running to isolate which cylinder is skipping. You can now at least double check valve adjustment to rule that out. If nothing obvious, take that injector out and swap it with another cylinder. See if the skip follows. Report back.

Ben

I will loosen at the injector to

Its actually more likely to be an air bubble in the line than it sucking air. Crack each line after you get it running and let some diesel run out to make sure it has been properly bled. I have absolutely seen them have an air leak and not leak fuel though. That is usually on the suction side though and makes it not run at all. A fuel issue that is causing it to run rough and not have pep is usually from not being fully bled of air on the pressure side.
i will do that injector line thing. On the pump inlet line I will try some ether while running to see if it is sucking air around the steel line

 

[Blue Ox]

Crack the injector lines one at a time and see if it's an actual miss. There are symptoms called irregular exhaust beat that just sound like a miss, but aren't an actual misfire. Also there's a synchronizing thing with the transfer pump rotors on three cylinder pumps that can cause issues. As @Midnightmoon said, history. When did this issue start?

 

[1STLS1]

Just change out any suspect fuel hoses or lines to eliminate the possibility. It's possible to be deteriorated inside causing partial blockage. Rubber hoses can leak air in but not leak fuel externally, this usually causes a no start or long extended crank to bring the fuel back up then would run perfect all day only to fight you the next morning. Physically blow out all the hard lines to verify no blockages. Found a dead fly in a hard line after the filter once, have no idea how it got there but it ran right once removed. Assume nothing. On Diesel engines that are tough to crack injectors to listen for drop, we used a temp heat gun on the exhaust manifold to see if it was firing. I once had a Perkins 4 cylinder "gas" engine that had a weird miss long ago that traced to the valve train, it threw a rocker and IIRR, bent the push rod, it was governed at 2400 rpm so there really was not an apparent reason what cause it. I would double check your valve adjustment. Since you do not have a compression gauge I would try to add air to the cylinder with both valves closed after preventing the engine from turning to see if you hear anything coming out of the intake, exhaust valve or excessive pressure past the rings compared to the other cylinders.
Other thoughts, check the air filter. Had a large Komatsu crawler loader down on a site. First tech had the pump and injectors serviced, could not get it to run, found the air filter plugged solid. While he cranked it , I pulled and finally dislodged the filter to watch it bust off and run, the first time in weeks, assume nothing. A bad filter could cause a surge. When running the engine at 1000 rpm and it surging the 50 rpm, I would try whiffing some WD40 near the air intake to just see what the engine would do, if it clears up the surge you know it's lack of fuel. do not ever use either.
Sorry about the random thoughts, my work experience was a material handling tech for over 20 years, fork lifts and under 100 hp construction equipment, saw numerous small Diesel engines of all types.

 

[Red Rex]

Crack the injector lines one at a time and see if it's an actual miss. There are symptoms called irregular exhaust beat that just sound like a miss, but aren't an actual misfire. Also there's a synchronizing thing with the transfer pump rotors on three cylinder pumps that can cause issues. As @Midnightmoon said, history. When did this issue start?

The engine was running like a sewing machine prior to me pulling the injector pump due to leakage where the head goes into the body. Pump rebuilt. Tractor started the problem after the pump was reinstalled. Pulled injectors and had the pump shop rebuild them. Still no fix. Pulled tank no trash inside. Blew out lines. No obstructions. Tractor gets up to operating temp of 175 and does not over heat. I have run both a tiller and a bush hog so there has been a couple hours run time since doing these things.

How important is it that the vanes in the pump be the exact same material of the original ones? I do not believe that the replacement ones are.

 

[Red Rex]

Just change out any suspect fuel hoses or lines to eliminate the possibility. It's possible to be deteriorated inside causing partial blockage. Rubber hoses can leak air in but not leak fuel externally, this usually causes a no start or long extended crank to bring the fuel back up then would run perfect all day only to fight you the next morning. Physically blow out all the hard lines to verify no blockages. Found a dead fly in a hard line after the filter once, have no idea how it got there but it ran right once removed. Assume nothing. On Diesel engines that are tough to crack injectors to listen for drop, we used a temp heat gun on the exhaust manifold to see if it was firing. I once had a Perkins 4 cylinder "gas" engine that had a weird miss long ago that traced to the valve train, it threw a rocker and IIRR, bent the push rod, it was governed at 2400 rpm so there really was not an apparent reason what cause it. I would double check your valve adjustment. Since you do not have a compression gauge I would try to add air to the cylinder with both valves closed after preventing the engine from turning to see if you hear anything coming out of the intake, exhaust valve or excessive pressure past the rings compared to the other cylinders.
Other thoughts, check the air filter. Had a large Komatsu crawler loader down on a site. First tech had the pump and injectors serviced, could not get it to run, found the air filter plugged solid. While he cranked it , I pulled and finally dislodged the filter to watch it bust off and run, the first time in weeks, assume nothing. A bad filter could cause a surge. When running the engine at 1000 rpm and it surging the 50 rpm, I would try whiffing some WD40 near the air intake to just see what the engine would do, if it clears up the surge you know it's lack of fuel. do not ever use either.
Sorry about the random thoughts, my work experience was a material handling tech for over 20 years, fork lifts and under 100 hp construction equipment, saw numerous small Diesel engines of all types.

No rubber lines anywhere. You have given me much to consider.

I appreciate all the replies!

 

[Midnightmoon]

The engine was running like a sewing machine prior to me pulling the injector pump due to leakage where the head goes into the body. Pump rebuilt. Tractor started the problem after the pump was reinstalled. Pulled injectors and had the pump shop rebuild them. Still no fix. Pulled tank no trash inside. Blew out lines. No obstructions. Tractor gets up to operating temp of 175 and does not over heat. I have run both a tiller and a bush hog so there has been a couple hours run time since doing these things.

How important is it that the vanes in the pump be the exact same material of the original ones? I do not believe that the replacement ones are.

What you have is an injection pump timing issue. I don't know your pump off the top of my head. But you should be able to find the procedure in the Perkins manual for your pump. You may even be able to find a video on YouTube to help.