B7100 Won’t Start

[jrclark32]

I know there are several threads on this, but I haven’t had any luck with the advice on those.

My B7100 just cranks and cranks... it doesn’t even seem like it’s trying to fire. I changed the fuel filter, and bled the air out of the system. It’s getting fuel to all 3 injectors, so I’m not sure what else to try.

Here’s a video of trying: https://youtu.be/kNDTPioq8nQ

I’d appreciate any suggestions

 

[Dave_eng]

I know there are several threads on this, but I haven’t had any luck with the advice on those.

My B7100 just cranks and cranks... it doesn’t even seem like it’s trying to fire. I changed the fuel filter, and bled the air out of the system. It’s getting fuel to all 3 injectors, so I’m not sure what else to try.

Here’s a video of trying: https://youtu.be/kNDTPioq8nQ

I’d appreciate any suggestions

It would help if you provided more history on this tractor and your ownership of it.
How long you owned it?
Has it been starting and running OK?
Did it run out of fuel?

Do you have a workshop manual for it? If not go to Kubotabooks.com and download a free one.

http://kubotabooks.com/AutoIndex/in...s/&AutoIndex=ed9ab2466a6a197902ba648d1f6c82d3

Section 3.1 explains in detail how to "Vent" the fuel system. Vent being just another term for bleeding out any air. It is important to follow the manual procedure with no shortcuts!

Depending upon your answers to the history of your tractor, some other ideas are possible concerning the glow plug operation.

You need a cheap multi meter like this one for less than $10 to check if the glow plugs are good.

Remove the wiring from each glow plug and then measure the resistance from each glow plug terminal to the engine block. They should all be the same number. the actual value from memory if around 1 ohm.

Has any wiring been changed? A key switch changed? The glow plugs are to be on while the engine is cranking which is controlled by the key switch.

Dave

 

[Lil Foot]

It spins like there is no load, no compression. Does it have a compression release?
(maybe stuck open?)

 

[jrclark32]

Thanks Dave. I haven’t owned the tractor for very long... I bought a piece of property and it was left behind by the previous owner. He said that it had a bad head gasket and the engine was seized. I’m not sure how or why he came to the head gasket diagnosis, but it turned out to be hydrolocked, and after I took care of that it fired right up. I haven’t messed with it since it ran that time, but it’s just been parked indoors.

I do have a workshop manual, and that’s the procedure I followed to “vent” the fuel system after I changed the filter. Nothing electrical has been changed since it ran last.

I’ll check the glow plugs with my meter when I’m down there tomorrow and report back.

-John

 

[jrclark32]

It spins like there is no load, no compression. Does it have a compression release?
(maybe stuck open?)

It does have a decompression knob, but it was disconnected at some point. Do you know what it was supposed to connect to, or how to check if it got engaged somehow?

 

[Lil Foot]

The knob connects to a cable that operates a shaft inside the rocker cover. When the knob is pulled, the decomp shaft rotates & pushes down on the exhaust valves, opening them slightly. If yours isn't hooked up, maybe the shaft got bumped or moved enough to open the valves.
The pic below shows the assembly. If you think that might be the cause, you can pull the rocker cover, & the decomp assembly comes off with it. Then you can try starting it.
If your glow plugs are heating, that might be the next thing to check.

 

[thepumpguysc]

Def. check the GP's.. & the decomp. lever..
U didn't say how long it sat.. fuel goes bad..
& for hevens sake, don't "add" fresh fuel to stale fuel.. u just end up w/ a tank full of bad fuel..
U said u had fuel to all 3 injectors..??
Do u have fuel COMING OUT of all 3 injectors.??
Unscrew them & hang'm outside the engine.. to SEE if they are squirting..
U can look at the exhaust too.. white-black smoke out of exhaust will mean your getting fuel into the cylinders, its just not burning..
IF u have a manual.. theres all sorts of warnings about fuel injectors & hands.. heed the warnings..
U DONT wanna be anywhere near the squirting injectors outside the engine..

 

[D2Cat]

On your compression release, if you had the knob to use it you would push the knob in to close the valves. So instead of removing the valve cover you could simply rotate the small shaft at the front of the valve cover clockwise (as you're setting on the tractor) to get them in the shut position.

How did you discover it was hydrolocked? Have you had the head off?

 

[North Idaho Wolfman]

It ran, then now it won't run, and you haven't changed anything, what position is the throttle lever in?

A throttle lever stuck in off position, will keep it from starting.

 

[les.smith99]

I had the same problem with my B7800, turned out to be a 10+ year old battery. It would not crank it robustly enough to introduce fuel.


Sent from my iPad using Tapatalk

 

[Dave_eng]

I had the same problem with my B7800, turned out to be a 10+ year old battery. It would not crank it robustly enough to introduce fuel.


Sent from my iPad using Tapatalk

In his video there are heavy booster cables attached.

Dave

 

[jrclark32]

I checked the glow plugs, and they’re all showing about 1 ohm on the meter. The decompression lever on the valve cover was up a bit, so I was hopeful there, but I tried to start her after I pushed it all the way down and nothing seems to have changed.

I didn’t pull the injectors all the way out, but I cracked the lines and they’re all getting fuel to that point.

The battery seems good, and I was also jumping from my truck battery to make sure that there’s enough juice to turn over strongly, so I don’t think that’s an issue.

The last time I had it running was about a year ago. Someone suggested that it was hydrolocked, so I pulled the injectors and it shot a plume of water 10’ in the air when I turned it over. It started up after I put the injectors back in and bled the fuel system. That diesel was fresh when I put it in then. I know the gasoline they’re selling us is garbage.. is it likely that diesel would go bad in a year?

 

[North Idaho Wolfman]

Do a compression test!

 

[KEO316]

I know there are several threads on this, but I haven’t had any luck with the advice on those.

My B7100 just cranks and cranks... it doesn’t even seem like it’s trying to fire. I changed the fuel filter, and bled the air out of the system. It’s getting fuel to all 3 injectors, so I’m not sure what else to try.

Here’s a video of trying:

I’d appreciate any suggestions

Did you ever get this problem fixed? I'm going through the same thing. Mine is a 1996 B7100 HST, no compression release. 2100 hrs. It ran good when I parked it in shed. When I went to start it two weeks later it wouldn't fire a lick. I've put in new glow plugs ( and they get hot), Injectors are squirting, it's getting fuel.
I checked everything I could, and found my compression was only 100-180 before doing any work. So I bought a new head complete with new valves and installed. New gaskets, and new fuel injectors. Tried to start it and it still won't fire a lick. rechecked compression and find I have no compress at all on one cylinder and only 80 on the other and 50 on the other. Worse than it was before. I'm totally in the dark. I have a friend who is a retired diesel mechanic and he has no idea either. I find that my valve lifters aren't pumping up. a couple will pump up when I try to start it, then the next time two others will pump up, but never all of them. Checked oil pressure and it's 50 lbs with just the starter turning it over. The compression issue looks like the problem. After doing the 'oil in the cylinder trick' I'm sure the piston rings are not the problem. It started and ran good one day and not at all the next. Then the compression was around 100-150, it shouldn't even have started before the trouble. I don't know where to start.

 

[Dave_eng]

Did you ever get this problem fixed? I'm going through the same thing. Mine is a 1996 B7100 HST, no compression release. 2100 hrs. It ran good when I parked it in shed. When I went to start it two weeks later it wouldn't fire a lick. I've put in new glow plugs ( and they get hot), Injectors are squirting, it's getting fuel.
I checked everything I could, and found my compression was only 100-180 before doing any work. So I bought a new head complete with new valves and installed. New gaskets, and new fuel injectors. Tried to start it and it still won't fire a lick. rechecked compression and find I have no compress at all on one cylinder and only 80 on the other and 50 on the other. Worse than it was before. I'm totally in the dark. I have a friend who is a retired diesel mechanic and he has no idea either. I find that my valve lifters aren't pumping up. a couple will pump up when I try to start it, then the next time two others will pump up, but never all of them. Checked oil pressure and it's 50 lbs with just the starter turning it over. The compression issue looks like the problem. After doing the 'oil in the cylinder trick' I'm sure the piston rings are not the problem. It started and ran good one day and not at all the next. Then the compression was around 100-150, it shouldn't even have started before the trouble. I don't know where to start.

I do not understand what you mean:
I find that my valve lifters aren't pumping up. a couple will pump up when I try to start it, then the next time two others will pump up, but never all of them

Are you talking about bleeding the fuel injectors?

With low compression it will not start. Are the valve clearances set properly?

Dave

 

[KEO316]

I do not understand what you mean:
I find that my valve lifters aren't pumping up. a couple will pump up when I try to start it, then the next time two others will pump up, but never all of them

Are you talking about bleeding the fuel injectors?

With low compression it will not start. Are the valve clearances set properly?

Dave

I'm sorry, I was sort of rambling.
I assume a B7100 HST has hydraulic lifters. After installing the new head which came with new valves/springs installed, the engine will not start or fire. The cylinders check for 0-50 psi for compression. After cranking it trying to start it, most of the rocker arms have up to 1/8" gap (I didn't check or reset the tappet gap after installing new head). After cranking, a couple of the 6 rocker arms are tight but the others are loose. If I let it set a few minutes then try to start it, a different couple rocker arms are tight but the others loose. I'm figuring that the hydraulic lifters are not pumping up (maybe I'm wrong). By the way, the oil pressure checks at 50 PSI while the engine is cranking.
The cylinders are getting fuel. We bled the fuel lines properly and the injectors are getting fuel. And there is a whitish mist coming out the exhaust when cranking it. But all the time the compression continues to check 0-50 psi. I was afraid to reset the gaps on all the rockers afraid I would be pushing the valves down onto the pistons. Is it common to have to adjust the rockers 1/8" after installing a new head? I am praying someone will tell me I should have recapped the rockers and they are the cause of the no compression.

 

[Dave_eng]

I'm sorry, I was sort of rambling.
I assume a B7100 HST has hydraulic lifters. After installing the new head which came with new valves/springs installed, the engine will not start or fire. The cylinders check for 0-50 psi for compression. After cranking it trying to start it, most of the rocker arms have up to 1/8" gap (I didn't check or reset the tappet gap after installing new head). After cranking, a couple of the 6 rocker arms are tight but the others are loose. If I let it set a few minutes then try to start it, a different couple rocker arms are tight but the others loose. I'm figuring that the hydraulic lifters are not pumping up (maybe I'm wrong). By the way, the oil pressure checks at 50 PSI while the engine is cranking.
The cylinders are getting fuel. We bled the fuel lines properly and the injectors are getting fuel. And there is a whitish mist coming out the exhaust when cranking it. But all the time the compression continues to check 0-50 psi. I was afraid to reset the gaps on all the rockers afraid I would be pushing the valves down onto the pistons. Is it common to have to adjust the rockers 1/8" after installing a new head? I am praying someone will tell me I should have recapped the rockers and they are the cause of the no compression.

I do not know how you came to think a B7100 would have hydraulic lifters. It does NOT.

Are you working from a workshop manual. You need to!.

If you follow the proper valve setting procedure you wont have valves hitting pistons. If you do not follow the procedure you will bend the valves and damage pistons.

Kubotabooks.com has free manuals for the B7100.

Dave

 

[KEO316]

I do not know how you came to think a B7100 would have hydraulic lifters. It does NOT.

Are you working from a workshop manual. You need to!.

If you follow the proper valve setting procedure you wont have valves hitting pistons. If you do not follow the procedure you will bend the valves and damage pistons.

Kubotabooks.com has free manuals for the B7100.

Dave

Thank you so much. The lifter revelation sheds a whole new light on the situation.

 

[KEO316]

Thank you so much. The lifter revelation sheds a whole new light on the situation.

Well, I Adjusted the valves. All seem to be working fine. I still have zero compression on the cylinders.
I'm stumped. Basically the problem is that it went from starting and running fine. Parked it for two weeks, then it wouldn't fire a lick. The compression is now zero. Installed new head/valves/springs/injectors. Zero compression..........total mystery.

 

[Daferris]

Well, I Adjusted the valves. All seem to be working fine. I still have zero compression on the cylinders.
I'm stumped. Basically the problem is that it went from starting and running fine. Parked it for two weeks, then it wouldn't fire a lick. The compression is now zero. Installed new head/valves/springs/injectors. Zero compression..........total mystery.

Go back to the basics...
If the valves are now opening then check to see if you have air moving into the intake and out the exhaust. An engine works like an air compressor If the valves are opening Turn the motor by hand and make sure the intake is opening on a down stroke and the exhaust is on an upstroke ( can pull a injector and or a glow plug to check that). Are you getting bubbles in the radiator? Is the head gasket leaking? I am going to assume that when you had the head off the cylinders looked good that there were not any gouges or deep scratches going up-down that could indicate a problem with the rings.
Another thing you can do squirt a small amount of motor oil in the cylinder then hook up the compression gauge to see if that changes the reading. If it does you have bad rings.