"Blow by" question

[bludev]

Can someone explain to me how to reliably check for "blow by" on a Kubota V1702 ... its in a Bobcat that is getting harder and harder to start when cold. It doesn't seem to be using oil but I have taken the oil filler plug out while it was running and did feel air coming from there in sync with combustion cycles ... there was no smoke or other film noticed with the air being pulsed out of the oil feel plug ....

Thanks for any input

 

[gatractorman]

Dont mean to sound smart at all, but the best and most reliable thing to do would be a compression check. Way many moons ago when the B series Cummins were first coming out they did have an apparatus to hook up to the blow-by tube to measure it, imagine same theory would work on Kubota. It's just telling you what you already know. Compression check figures would be more valuable.

 

[Eagleview]

Can someone explain to me how to reliably check for "blow by" on a Kubota V1702 ... its in a Bobcat that is getting harder and harder to start when cold. It doesn't seem to be using oil but I have taken the oil filler plug out while it was running and did feel air coming from there in sync with combustion cycles ... there was no smoke or other film noticed with the air being pulsed out of the oil feel plug ....

Thanks for any input

More than likely what you are feelling are the pulses cause by the returning pistons into the crankcase if there is no smoke . Does it have glow plugs ? Maybe a couple have given up . Does it have an intake heater ? I seem to find also that winter Diesel takes a bit more effort to fire up .

 

[jgl1962]

You really want to make sure your entire glow plug system is working properly. That engine seems to need more time on the glow plugs at a given temp than say a 2203 and the more hours it has the more it needs it. There's a glow plug/relay solenoid (743?) in the tailgate. And the glow plugs themselves just wear out after a while.

 

[bludev]

Thanks guys ... I think I'll change the glow plugs .... the guy that had it before me said he didn't think it had glow plugs, so I'm sure he never changed them. If that doesn't fix it, then I'll do the compression check ...

thanks all and if anyone has input I'd be glad to hear it

 

[Egon]

It doesn't seem to be using oil

Just for information the Kubota B7100 I had always had significant vapours coming from the crankcase even when new. It was also quite hard to start unless it was warm. The glow plugs were required.

The engine did not use any oil even after 3000 hours of operation which is not much in industrial situations.

 

[skidsteer.ca]

Test or change glow plugs and check for power right at the glow plug when activated. Could be a bad relay not supplying juice, test injectors, test compession.
Consider installing a block heater if the motor is getting tired and needs some help to get the last 500 or so hours out of it.
Ken

 

[john_bud]

Glow plugs, glow plug controller, relay, fuse, wires, key switch.

There does not sound to be blow by. If you had that, it would have a LOT of gases coming out the filler plug hole. Smokey blue fumes.

 

[AlanB]

Is this in a 743?

Before you start changing anything, a little time with a meter, or for that matter a test light will go a long way.

Make sure you are getting full power too the glow plugs first so you know which side to start looking.

The glow plug closest to the back of the machine is a bugger to do.

 

[Blagadan]

Bluedev, Just to add a little more, I have a kubota b7100 which emits a lot of vapour from the crankcase tube. I did quite a lot of internet researching to find that crankcase pressure can result in quite a lot of vapour coming from that tube. In winter the cold weather will make the problem look worse.
I thought I had problems until I did a compression test which proved all of my rings were above average and giving a good seal in the cylinders. I also checked for headgasket problems and other signs of concern but could find none worthy of corrective action. I've learned to live with the vapour. To reduce the visual effect of the "blowby" on my b7100, I fitted a crankcase filter to the tube which dissipates the fumes without restricting the airflow. It also lessens the effect of the fumes jetting out of the end of the tube.

Heres a filter similar to the one I have :-

I dont see the "blowby" as a problem unless as stated above, it is emitting blue smokey fumes.

 

[bludev]

Thanks for all the input guys.

It is a 743b ... I did check the voltage on the wire which goes to the glow plugs ... it was around 6 volts with the key turned to the left (ie heating position) ... does anyone know if that is correct ... the voltage on the battery was right at 12 (the battery is getting weak and I have had to jump start it since the weather has turned cooler combined with the hard starting)

Thanks for all the help

Is this in a 743?

Before you start changing anything, a little time with a meter, or for that matter a test light will go a long way.

Make sure you are getting full power too the glow plugs first so you know which side to start looking.

The glow plug closest to the back of the machine is a bugger to do.

 

[Eagleview]

It should have 12 volts @ the glow plugs , it sounds like your battery is on the way out . Even though it is showing 12 volts with the meter , i think if you put a load tester on it you would find the battery would fall on it's face .

 

[AlanB]

6 Volts is a problem.

Off the cuff guess, bad connection, or bad solenoid.

Start chasing voltage back and see where it is dropping off at.

In my 743 it was the solenoid towards the back of the machine, on the left hand engine compartment side.

There is a skidsteer forum, that is extremely helpful as well, and those guys know the SS inside and out. I don't remember the exact name but something like Skidsteer forum should find it.

 

[Terra Firma Scott]

Not sure of the glow plug set-up on your bobcat but i had an issue with my caterpillar awhile ago....

the shorting bar (Battery voltage)which secures to the top of all four glow plugs had vibrated loose the nuts at the top of 3 plugs!!!

im sure if you checked voltage that you would have seen or felt if it was loose but just a thought.....

 

[skidsteer.ca]

6 Volts is a problem.

There is a skidsteer forum, that is extremely helpful as well, and those guys know the SS inside and out. I don't remember the exact name but something like Skidsteer forum should find it.

www.skidsteerforum.com
Ken

 

[EddieWalker]

Looks like you found your problem with the low voltage on the wire and the battery. Winter is the killer of batteries. If a battery is close to the end of it's life, the cold will make it happen instantly. With just 12 volts, I think you are very close to having to buy a new battery.

For the glow plugs, follow the wire until you find where it changes voltage. It could be just about anything, and the only way to know for sure it to follow it.

Testing compression on a diesel engine requires removing the injectors and a special compression tool. You can't do it with the same thing you test compression on a gas engine. Instead of doing this, look at the air that's coming out of the crankcase. There should be a vent tube someplace, but your dipstick to check the oil will work too. Does any oil come out of these tubes? If you are getting oil to spray out of there, you have too much blowby and need to rebuild the engine. Like mentioned previously, in winter, it might look like allot of blowby because the air is colder and you will see it more then you would in the summer.

Constant black smoke and a loss of engine oil are other signs that the rings are worn.

Did it start good in the summer?

Has it lost power?

Eddie

 

[skidsteer.ca]

The voltage at the plus should be almost the same as the battery. You have a bad conection on the the glow plug circuit somewhere. This cause the voltage drop that is preventing your plugs from glowing properly.

Also common is to have some of the glow plugs burn out. Remove the wire/strap conecting the 4 glow plugs, hook you test light to the pos on the battery and attempt to get a ground through each indevidual glow plug by touching the prob on the wire terminal. If the glow plug is burnt out it will have a open circuit through the element and the test light won't iluminate
Ken