1991 Bobcat 753 losing power

[Bassfisher89]

I bought a 1991 Bobcat 753 about a year ago. My cousin has had it for years. He recently had the motor rebuilt and the injector pump. Before that he was having issues with it seeming to bog down or lose power and sometimes stall out. He made me a deal i couldn't really turn down especially because if figured it was something simple. I am pretty mechanically inclined and also have a shop manual for it. I will list below what i have done and also what it seems to do.

Issue: When turning hard or trying to go full speed in forward/reverse, using two bucket functions at the same time, it will bog down as soon as you let off of the handles or pedals it idles right back up most of the time like it never happened. Also loses power going up a grade when you try to go full speed but downhill it does fine. When it bogs down you can't influence it with the throttle control at all doesn't matter if you push it all the way forward or all the way down makes no difference.
One thing i have noticed is at times when i first turn the key on the Fuel Shutoff solenoid doesn't always lock in, i can turn the switch on and off a few times then it will usually lock in but sometimes i have to do it manually then it holds.
I have it running better than he did but it still can't be used like it should be. I can grade dig etc with it at a fairly good speed with no issues but obviously you want a machine to run correctly at any speed. It doesn't die when it bogs down now. I don't think its hydraulic related because they are strong no issues picking up a heavy bucket, pulling stumps etc. doesn't seem to bother it. My right side is slower than my left when it comes to tramming. The left will outrun it if i let it. Curious about that as well.

What I have replaced:
All fuel lines, pickup filter in the tank, lift pump, fuel filter, hydraulic filter. Made sure all bleed valves are closed all the way etc. Primer bulb is good. I have ran it off a separate jug of fuel and had the same issue. I haven't had a chance to replace the following but i have them on hand fuel shutoff solenoid, drive belt, tensioner pulley. Mostly because I'm pulling my hair out trying to figure it out haha. I appreciate any help or advice glad to find this forum!
I attached a few videos to see if it helps. The first one from the rear if you want to speed up to around 38 seconds that was after i cranked it waiting on it to warm up runs rough then takes off. The second video is where if you likely dead head the hydraulics how it idles down and the third video is doing a tight turn.

 

[fortworth-cowboy]

Check your belt tension from your drive belt

 

[Bassfisher89]

Sorry for the delay havent had time to mess with it until today. I actually installed a new tensioner and set it to the proper tension between 1 and 3. It didn’t make a difference still bogging down full speed and tight turns. Thanks a bunch for replying though! Any other suggestions?

 

[fortworth-cowboy]

You said something about a hand fuel shutoff solenoid, what do you mean with that? Is your fuel shut off solenoid damaged?

 

[Bassfisher89]

It’s the normal fuel shutoff solenoid but sometimes it locks right in when the key is turned sometimes it takes turning the key a few times and sometimes I have to turn the key to the on position and push the lever manually to make it lock it.

 

[fortworth-cowboy]

It's the normal fuel shutoff solenoid but sometimes it locks right in when the key is turned sometimes it takes turning the key a few times and sometimes I have to turn the key to the on position and push the lever manually to make it lock it.

Well, I think you found your problem. The Fuel shut off solenoid is restricting the fuel going to the pump, so when it it half way only open that is when you notice that your engine is bogging down.

 

[KyMadMan]

It's the normal fuel shutoff solenoid but sometimes it locks right in when the key is turned sometimes it takes turning the key a few times and sometimes I have to turn the key to the on position and push the lever manually to make it lock it.

Check your electrical connections to the fuel shut-off. Lots of dust back there. Had a similar issue, purchased a new shut-off BEFORE I checked and cleaned the contacts. DOH!

 

[Dave the Ozzie]

If you’re having issues with the stop/solenoid then replace it as could be restricting the governor from opening up the rack when called upon under load. Also replace the starter relay as it could also be a problem which is mounted just under the top door hinge on my 763.
The way these relays and solenoids work is that there are two circuits; one is the strong pull circuit which then times out after a second or so by the relay and switches over to the hold circuit while ever the key is on. If the pull circuit were to stay on for an extended time the solenoid would overheat and burn out.

 

[Bassfisher89]

Alright sorry it took me so long to report back! I replaced the shutoff solenoid. Haven't replaced the Starter relay yet but i will. Even the new solenoid it took a minute for it to pull it in like a delay as it did with the old one. The loader ran the exact same way as before. Bogs down when going full bore etc. All that said i can work it fine as far as moving dirt etc. but not at the speed you should be able to. Any other suggestions besides the relay? Thanks for all the help i really appreciate it. I will try to update quicker next time have had some family health issues that obviously take priority.

 

[DirtRodeo]

After a quick scan of the post, I don’t believe anyone mentioned cleaning your grounding points. It becomes a routine maintenance item with old machinery. Good luck!

 

[oiu789]

Was the governor look at to make sure it is operating as it should? But sounds more like electrical, Check voltage to them.check latching and hold in voltage if the fuel solenoid. If it has 3 wires it uses a latching circuit and a hold in circuit,Check the grounds from neg on battery to them should be 0 resistance

 

[Equipment_Tech]

Did you resolve this issue ?

 

[Bassfisher89]

Not yet. I hope to work on it this week and i will report back with results.

 

[Bassfisher89]

I finally checked everything mentioned above cleaned up my grounding points etc. I ran across another post where someone was having almost the exact same issues that i was having. Someone there told them to adjust their governor screw/fuel delivery a half a turn to see if it helped. I turned my screw a half a turn counter clockwise and my bobcat now runs like a new machine no more bogging dragging etc. For you guys that are pretty experienced on these things does this sound like something that should have worked or should i look into other things that may have caused this? I don't know if my cousin or whoever worked on it had messed with the governor screw but i do know the cap where the springs etc are has been removed recently before i got it. Appreciate all the suggestions and help everyone on the thread has provided!

 

[[email protected]]

I think you should try it now and let it show you if the results good. Then also you may want to cover that spot over the Gov. again somehow. Good Luck!

 

[Bassfisher89]

Running good so far. The governor was still covered i just noticed where it had sealant around it that it had been taken off and put back on recently.