Diesel Engine "Surging" or "loping"

[sandybeach]

My diesel engine has developed a problem with "surging" or "loping." The engine speed changes dramatically repeatedly below 2200 RPM It will jump from 800 to 1500 down to 1200 up to 1800 and so on. Sometimes it will drop below idle speed and shut off the engine.

This speeding up-slowing down is constant. The only way to stop the cycle is bring engine speed up to operating RPM=2200. Even then the speed varies a little bit, in the 2000-2200 range.

This started the last time I used it (2 days ago). Engine has less than 100 hours.

Ideas of why - and how to fix it?

 

[TORQUIN]

First, I think trash or dirt in fuel system. But, if that's all clean, how old is it? I wonder if it's governor springs getting weak, but the governor springs are extended a little at 2200 RPM so they have more even tension there and hold the RPM better. Yes, I read the engine has less than 100 hours, but I don't know if that means new or rebuilt, and if rebuilt, that doesn't necessarily mean the governor was rebuilt.

Chris

 

[Tx Jim]

How long since fuel filter was changed? Have you checked for good fuel flow from tank to inj pump? Is fuel tank venting?

 

[DLTTrekkers]

Make and model will help a lot !

 

[DLTTrekkers]

Mereringvalve sticky deu to dirty fuel

 

[sandybeach]

Nothing like surgery to take you off-line at the tractor and the internet

(Original question was about engine surging on a Branson 3510H (year=2010). Engine rebuilt and injector pump replaced 200 hours ago (under warranty)

I changed the fuel filter - it didn't have a lot of crud. Also changed air filter, since it was quite dirty.

After changing the fuel filter I primed the system - or thought I did. I opened each nut (flared pipe), one at a time.I cranked it until bubbles stopped, and tightened the nut. The difference in how the engine ran was insignificant.

Ignoring Einstein's advice, I tried the same thing again hoping for a different outcome.

The next time I opened each nut more - one at a time - and cranked. I got a feeble spray squirting out if each fuel line. I was expecting a flow of diesel.

QUESTION: is this the right way to bleed it?

When I started the engine, it started easily (all things considered). It runs without surging. Too soon to celebrate! Moving throttle handle 1/2" either "faster" or "slower" made the speed move instantly to 500 or 2100. Not slowly, instantly: before I could count "one thousand-one" either way (faster or slower), the speed flips between minimum and maximum.

Sorry Einstein, but I did it again. Now it runs mostly smoothly (very slow and small fluctuations) but has very little power.

By the way, I'm sure the dealer drained the fuel: the fuel gauge has been wrong all the time, ever since.

1. I idled it several minutes and then ran it at 2100 for several minutes. It runs runs smoothly, but it has "no" power. At 2100 lifting the bucket slowly almost kills the engine.
2. I backed the tractor up a small incline and ... it kills the engine.

Since bleeding makes a difference - but not enough difference, I assume that there is some blockage or remaining air bubbles.

What should i try next?

 

[Tx Jim]

Engine attaining 2100 rpm's but lacking full power indicates engine possibly isn't firing on all 3 cylinders. I agree with you I think fuel system still has air in it somewhere from tank to injectors. Is tank venting?

 

[sandybeach]

Engine attaining 2100 rpm's but lacking full power indicates engine possibly isn't firing on all 3 cylinders. I agree with you I think fuel system still has air in it somewhere from tank to injectors. Is tank venting?

Hmmmm. To vent it, for purposes of diagnosis, I could just remove the cap on the filler. I'll get back to you.

Dealer said look for a bleed screw on the fuel bowl assembly. Bleed there before bleeding at the injectors.

Also: a good fuel additive. I asked "Sea Foam?" She (yes she) said it's as good as any and can't hurt.

Because of our cool, damp climate (Washington coast). there might be algae on the inside of the tank when the inner surface of the tank is exposed to cool, damp air when the tank isn't topped off (which is 99% of the time). Clumps of algae could block the the fuel line opening. Sea Foam might break up the clumps so they can clog my fuel filter instead.

Last resort, drain tank. Sounds weird, but she gets paid to service tractors. I pay for the privilege of driving one. I'll bet on her solutions.

Come to think of it, I pay for the privilege of paying for one. :thumbsup:

 

[sandybeach]

Engine surges frequently.

I bled the air out at the bleeder screws on the fuel filter assembly - good flow of fuel coming out at the screws, so fuel flow into the fuel filter and out to the injector pump is good. But fuel flow out to the injectors seems weak - it sprays instead of flows. I'm probably wrong, but I thought the spraying should be at the injectors inside the head, not at the nut at the end of the fuel line that delivers fuel to the injectors.

Sometimes I can get the engine to idle for several minutes at 650 RPM and at 2100 RPM, and most speeds in between. However, RPMs still sometimes go up up and down without my help.

The throttle lever and cable seem to work fine when the engine is off: full throw on the lever and full movement where the cable connects to the throttle (which I assume is inside the injector pump). But when the engine is running, a tiny movement of the throttle lever - less than a half inch either up or down - can cause big movement in RPMs.

Worse, it has low power at any RPMs. At 2100-2500 raising the bucket drops the RPMs rapidly - as in kills the engine - if I don't give it more throttle (to keep from stalling). Same for driving up a very slight incline - it wants to stall unless I futz with the throttle lever.

I'm already planing for the worst case: R & R the $600 injector pump. That project looks nasty. There's fuel lines (running from the pump to the injectors) sitting behind other stuff. Who designed that?

Any ideas here?

 

[Tx Jim]

It's possible something in the governor has failed. What type inj pump does Branson have piston or rotary?

 

[Jerry/MT]

Nothing like surgery to take you off-line at the tractor and the internet

(Original question was about engine surging on a Branson 3510H (year=2010). Engine rebuilt and injector pump replaced 200 hours ago (under warranty)

I changed the fuel filter - it didn't have a lot of crud. Also changed air filter, since it was quite dirty.

After changing the fuel filter I primed the system - or thought I did. I opened each nut (flared pipe), one at a time.I cranked it until bubbles stopped, and tightened the nut. The difference in how the engine ran was insignificant.

Ignoring Einstein's advice, I tried the same thing again hoping for a different outcome.

The next time I opened each nut more - one at a time - and cranked. I got a feeble spray squirting out if each fuel line. I was expecting a flow of diesel.

QUESTION: is this the right way to bleed it?

When I started the engine, it started easily (all things considered). It runs without surging. Too soon to celebrate! Moving throttle handle 1/2" either "faster" or "slower" made the speed move instantly to 500 or 2100. Not slowly, instantly: before I could count "one thousand-one" either way (faster or slower), the speed flips between minimum and maximum.

Sorry Einstein, but I did it again. Now it runs mostly smoothly (very slow and small fluctuations) but has very little power.

By the way, I'm sure the dealer drained the fuel: the fuel gauge has been wrong all the time, ever since.

1. I idled it several minutes and then ran it at 2100 for several minutes. It runs runs smoothly, but it has "no" power. At 2100 lifting the bucket slowly almost kills the engine.
2. I backed the tractor up a small incline and ... it kills the engine.

Since bleeding makes a difference - but not enough difference, I assume that there is some blockage or remaining air bubbles.

What should i try next?

The fact that it idles throughout the rpm range but won't run under load implies a fuel delivery issue. Most commonly this is cause by a blockage at the tank strainer, the fuel filter head, or the fuel filter itself. You changed out the fuel filter so that isn't the problem. Remove the fuel cap, open the line at the tank out let and use compressed air to blow back through the tank strainer. If you get a temporary reprieve from the symptoms then you've found the problem. Bacterial sludge can form in the tank due to water in the fuel. Water can get in there from normal condensation and you'll need a biocide to kill the bacteria. Sea Foam won't do it. If there is a clog, you have to drain and flush the crud out of the tank or it will be a recurring problem. Keeping the tank as full as possible can help reduce water accumulation. If treatment with compressed air does not work, check the fuel passage in the filter head to make sure it is not clogged.

Generally bleeding the system consists of bleeding at the filter head , bleeding the pump, and then bleeding the injector lines ( not the injectors themselves). You owners manual should tell you how to do this for your specific model.. If you don't have access to one, I can give you some general instructions.

 

[artfull dodger]

I agree on a fuel delivery system problem. Had one tractor have a crack in the line inside the tank, would stuck little bubbles of air into the line when the fuel was below the crack. Bacteria crud blocking the pickup screen will do it to. I also recommend Power Services (white bottle) in the fuel, helps with cold weather gelling, raises the Cetane number a bit and helps with other stuff. I also keep thier orange Diesel911 in my tool box just in case(its for fuel already gelled up). Does the tractor have a lift or pusher pump that feeds the injector(high pressure) pump? A failed or weak lift pump will starve the injector pump for fuel at higher rpms, but run fine many times at low rpms, just lack power when it needs to. Many times the injector pump can pull its own fuel, but not enough to run well or even keep the injector pump safe ie the Dodge 24valve with the VP44, a failed lift pump quickly kills the expensive VP44 main injector pump. Good luck. Mike

 

[Soundguy]

Ditto on fuel obstruction.

These things are just fuel powered air pumps..

 

[artfull dodger]

suck squeeze bang blow

 

[Soundguy]

....go diesel go

 

[Chlawson]

Mine was doing something similar but was a little low on power. The actual fuel lines were clogged. I had to take the inline filter out and blow the lines out with an air hose.

 

[PJ The Kid]

Its is possible algae problem, we have had that issue at work and now have to add algicide (sp.) to out 10k underground tanks. If that is the issue, you will need to thoroughly clean the tank and ALL lines. I don't think it is a governor issue as it is fluctuating, most gov. issues will just let it die without trying to catch themselves. Possibly pump timing or (depending on pump design, not familiar with this machine) an advance issue, Is the pump loose on the bracket at all? If you are getting small improvements every time you bleed the system, I would look there or look for somewhere the system is sucking air.

 

[THennessy]

I am no diesel expert, my deceased brother maybe was, but I know common issue on gas/ diesel generators on RVs/ stationary equipment is the electric fuel pump. On gas, intermittent/ failing operation of pump causes surging, dying and hard start/ no start/ no restart until cooled. All this in gas engine as symptom of float bowl level being low. I know in diesel that electric "Lift pump" often feed the high pressure mechanical pump that feeds injectors. If tractor gravity feeds fuel to high pressure pump, ignore this/ but if electric pump used, consider electric pump and rubber low pressure fuel lines as possible culprits. I know every engine requires free flow of fuel to the metering device/s vs restricted. I also know most/ all diesels have water separator/ filter. Have you drained and checked that? and if electronic controls in engine, does it give error codes thru flashing light. If so, get the book/ chart to read the codes?

 

[THennessy]

Its is possible algae problem, we have had that issue at work and now have to add algicide (sp.) to out 10k underground tanks. If that is the issue, you will need to thoroughly clean the tank and ALL lines. I don't think it is a governor issue as it is fluctuating, most gov. issues will just let it die without trying to catch themselves. Possibly pump timing or (depending on pump design, not familiar with this machine) an advance issue, Is the pump loose on the bracket at all? If you are getting small improvements every time you bleed the system, I would look there or look for somewhere the system is sucking air.

One issue about algae in fuel is that it only grows in the water that is in the bottom of the fuel tank/ fuel bowl, but once grown, fuel movement can cause it to break loose and move in the fuel itself and clog filters, jets, nozzles. Algae can also lock down moving parts like needle/ seat, or solenoids/ plungers.

 

[THennessy]

I do now see this post is 9+ years old, but OP did not post final resolution? HERE IS ONE youtube that may help some/ others, and there are several other videos on diesel engine surging: