I HAVE A 1996 CAT 953C 2ZN Had a local hydraulic shop pull the engine for rebuild which included removing the cab, disconnecting wire harnesses, sent the engine off for complete rebuild, sleeved, new injectors, turbo, exhaust manifold etc. Reinstalled and engine sounds great. Now for the problem. Went to pick it up and at full RPM Loader moves forward very fast at first and then slowly decelerates to a stop after 50-60 ft, both forward and reverse. Changed 2 hydro filters under right side of cab with NAPA 1730 and 1759 filters. Ran it again, added more hydro fluid and noticed quite a bit of air in the sight glass, guessing do to the filter change. Ran it again, no significant difference. Lowered the throttle rpm by a 200 RPM and comes out of it and acts similar to the way it did before the engine rebuild. Full throttle acts up again. Lower throttle seems better. Disconnected all power to the machine hoping to reset any codes or computer related issues. Called Cat dealer and the field tech has never heard of such a thing. Just signed up for this forum today after reading the below post from 2010 with a gentleman that had the exact same issue, but I dont see that he posted a resolution. I would like to know the fix if possible. Any help will be greatly appreciated. Ran fine, pulled engine, disconnected wiring, sits for 30 days, reassembled and now there are problems. Only 1 voltage light appears at low RPM which was not present before the rebuild. Is this a grounding issue? I didnt do the work but are these possible issues. Grounding issues with wiring, wiring issues, computer reset, Engine RPM too high since rebuild and tranny going into bypass mode do to high pressure or rpm? Below is the post I found from 2010. Any help will be greatly. Thanks 953C Problem posted by flametamer Posting for a friend: We have a 1999 Cat 953C track loader with an attitude. The history is: The engine was just rebuilt, which entails cab-off. After rebuild, the head shop which did the heads botched the job and the cab and engine came out again. The problem is: Now...the engine runs sweet. It's all hydrostatic and ECM controlled. At full throttle it takes off and then slows to a crawl in 30 ft. Engine still at full rpm. Bring the trans into neutral and it will again take off and slow down slowly to a crawl. Now, if you keep the rpm 200 below the recommended operating setting (full rpm)....it works just fine, but lacks the governor response of the full throttle setting. Cat has put their computer on the ECM and downloaded the data. Also two occurrences of low voltage, which was the battery going dead after sitting a while, which they said are not important. One weak track sensor was found and replaced. No difference. It has been operated for hours with the ECM on wireless and the laptop recording all data. Nothing shows up as the errors occur. At this point they have given up on it. Cat has a unique form of doublespeak which really means "We are stumped, but give us all your money and we'll try to figure something out." (So BP-ish) Has anyone dealt with or heard of a similar problem in any Cat hydrostatic drive systems?
There's a couple of things to start off with; Check the engine speed sensor hasn't been damaged. It screws into the bellhousing. Check what your engine RPM is at full throttle and moving at full speed. It should be >2200rpm. It's possible the throttle linkage hasn't been adjusted properly.
I have a Cat Field Tech coming over next week. I will have him check the RPM and Engine Speed Sensor on the Bell Housing as well. Also going to check voltage on the on the charging system. The Cab assembly is mounted on rubber bushings to isolate it from the main frame. The computer and all wiring is attached to the Cab assembly. I need to check the ground strap going from the main frame to the Cab assembly to make sure there isnt any grounding issues with the wiring causing the computer to get false signals from the sensors. The only wierd thing I see as far as guages is the voltage light is on at idle during initial start up. Rev it up and the light goes out. Thanks Anyone know where the main ground strap is supposed to be mounted when this machine was built?
I've seen where the voltage light will stay on for almost 30 seconds or more at start up. I'm not sure why they do this. We had a D5M that did it as well. One other thing that happened to me while running a 53C 2ZN , the temperature sending unit went bad. The gauge on the dash would creep up to hot and the unit would default to stop. It did this several times at that time I had a book that had all the codes in it. It pointed toward the sender. I picked one up and it remedied the problem. The bad sender was telling the controller the engine was hot and it went into a limp mode.
Today I did some trouble shooting on it. All ground connections checked out ok. Voltage good as well. The throttle is designed to be in the WOT position. If you backed down on the throttle and didnt lock it in WOT it worked fine. So basically at 7/8 throttle fine, wide open problems arise. Inside the throttle control housing inside the cab there is a switch that activates only at the WOT position. With engine off you can hear it click on and off. 7/8 throttle doesnt activate, full throttle switch activates. I disarmed the switch so that it does not activate at full throttle. Machine now seems to run fine, like it did before the engine change. So what does this switch do? And what does this switch control? I am sure it sends a signal to the computer. Thanks
The microswitch turns on the ECU underspeed strategy. That's why I suggested you check your engine RPM. The ECU thinks the engine is losing speed.
Sounds reasonable. Thanks for your input. I will have the Sensor checked and also the RPM's of the engine. Thanks
Problem solved. Buy a DIGITAL LASER TACHOMETER and set the RPM 2200-2350. Fixed instantly.
Was the engine running over speed or under? What are they supposed to run high idle no load? Its funny how these things can be fixed simply by little adjustments. Don't these machines require to run a certain amount of rpm before they will move anyway? Cmark is pretty sharp on these things. I just post off past experiences I've had.