I have a cat d5g sn 5XK37095 that will not consistently start. The parking brake light on dash goes on and off (with the switch)so I don’t believe that is the issue. Batteries are new and charged and when I jump the start relay? (12v directly to starter solenoid wire By the circuit breakers) it will start right up. The prelude system is working and building oil pressure just no 12v to the starter solenoid to crank. I know it’s a loose wire or bad relay or solenoid but having a hard time following the wiring. Does anyone have a wiring schematic for this thing? Thanks in advance!
That’s the engine number. The machine number will be on the line above it on the data plate.
What Prelude system are you talking about? According to the electrical diagram for your tractor's serial number, the Prelube system (pre-start engine oil priming) is not present.
Sorry about that, serial number is CAT00D5GPFDH01718
Sorry about that, serial number is CAT00D5GPFDH01718
As @Deimos pointed out there is no prelub system listed for that machine, either as an option or not. Do you have any photos of what's installed.? Is the prelub pump part of the starter motor or separate.?
I believe it is separate and mounted towards the front right of the engine. I will get some pics and update the post.
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Pic View attachment IMG_3737.jpeg
It could be an add on after the factory. We bought the machine used and unsure what previous owner had done to it.
I would say it is, because the electrical schematic doesn’t show it. Let me take a look around for anything that may mention it. It kind of looks professional but I’m not convinced that it is factory. BTW your second photo shows a fair bit of butchery to the electrical system by the flywheel housing.
That looks aftermarket. Can't sat i ever saw a prelube system on that small of a tractor
Just thinking is that a quick oil change set up I think I would trace the hoses off the pump
Well I think I can figure it out if I have the wiring diagram (even if it doesn’t include the prelube). Yes there is a lot of butchery on the wiring harness, I am just trying to figure out at what point it is losing the starter signal. It looks like an aftermarket solenoid has been added above and to the left of the starter, but I am not an expert on these things.
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Appears yours got a new crank case in there some one was/ is trying to prevent it from kicking a rod out. Tge 3 or 4 of those engines ive dissassebled tgat where blown up all had the rod nuts unscrewed laying in the pan.
Picture 3737 states that when you turn the key to start the pump will activate until sufficient pressure is reached and THEN the starter will go. Tells me there has to be some kind of oil pressure switch that has to close when pressure is reached, that may then energize a solenoid or relay that then powers up the starter "S" Terminal. If I was installing a system like that it would have something like that for control of starter S Terminal. Check for a oil pressure switch with some non-oem wiring attached to it. Something controls that pump. Simon C
The engine has been basically replaced… we had an incident where I believe it was overfilled with oil and the block cracked (out the side) and ended up getting replaced. Supposedly with all cat parts. It has had a lot of work done to it, just trying to figure out the starting problem.
The thing is, when it works correctly (1 out of 10 times), the oil pressure will get to about 20psi and fire up no problem. Other times it will run until the oil psi gets to 30+ and keeps building pressure without starting … I think the prelude is working, it’s just that the starter isn’t getting the signal to fire…
Sounds like bad oil pressure switch The s terminal wire on starter is probably going to your extra solenoid and a wire one the same post goes to a two terminal oil pressure switch then to s terminal on starter to engage starter after ail pressure is reached sounds like you need a oil pressure switch that closes at 20 psi
That is where in lies the problem if the starter solenoid needs 20 amps to go, it is very short life for the oil pressure switch. Should check with an old pair of vice grips attached to the oil pump motor cable connection and try a large booster cable onto the vice grips to see if the motor turns over, cause if it doesn't or is drawing too many amps for the surplus solenoid something will burn out fast. Those systems run best with 2 solenoids installed so that the oil pressure switch is only powering up the switching terminal of a solenoid and won't burn out. The output big cable of a second solenoid powers up the "S" Terminal of the starter. Hard to explain but could draw it out if nothing else works. Simon C
Check your message inbox for a machine electrical schematic. Cat used systems manufactured by this same "Prelub" outfit on larger tractors and on off-highway trucks. In some cases (large tractors) the prelube pump was actually part of the starter motor. In others (trucks) it was a separate electrically-driven pump like yours mounted on the RH frame rail ahead of the front suspension mounting. If this system works like the ones I have seen before then it either runs until a certain oil pressure has been reached, or until a certain amount of time has passed. In the case of the latter a timer cuts the power to the prelube pump and sends it to the starter just like it would if the specified oil pressure had been attained. If your system has this timer installed then that could be what's not functioning correctly, or you just may have a bad electrical connection somewhere. See attached.
So studied that schematic some and it only feeds enough oil to lube the main oil gallery, mains , rods and maybe the cammshaft bearings as the cut out switch is cutting off the ground at 4-7 psi which is more than enough for rollover protection prelube. On his system I see the picture of the relay so bet the installer opted for an oil pressure switch as it is way cheaper than a cat timer with all the wiring aaasociated with the timer. Most Forget to Remember that those kinds of pumps can only be used with oil pressure switches that are set very low unless you use 0W40 oil only. Why, because even in Texas if you were using a thick oil on a 30-40 Degree F winter morning the electric motor will draw way more amps than the Small solenoid can handle. They burn out very fast from the arc when the solenoid contacts release. If he follows the hose feeding the Oil gallery most likely, he will find a Tee with the pressure switch on the tee being fed the oil from the pump. Would be good to see another picture. Simon C
The size of the oil lines on the pump plus the gray wire wire tied to the hose is why I said about quick oil change I seem to remember that gray wire going to a plate with a switch and a quick connector that was part of some prelube systems Like he said I'd like to see pictures of hoses
You could be correct about a quick change oil pump instead of it prelubing. Need more pictures. Hard to see through the crystal ball. Simon C
I will get more pics in a little while when I am at the machine. I appreciate all the help and info!
Hose from the top of prelude goes over front of engine and down to oil filter housing.
The grey wire that comes from the other side that is tie wrapped to the same hose ends up here also, right beside the hose coming over the top. View attachment IMG_3745.jpeg
So yall may be correct, it could have been for a quick oil change setup or something… but it does build oil pressure before letting the machine start. I have also located what I think is the oil pressure switch that controls prelube. It is wired into the extra solenoid above and left of the starter. I think with the schematic I was sent I can piece it all together and figure out where it’s losing the signal.
Oil pressure switch
Post number 10 shows the sticker stating it has a prelube system on it. Don't think anyone would even get a sticker like that without installing it. Did you see an oil pressure switch at the end of the hose going into the engine, not the suction end, or elsewhere that has that 2 braid wire that is not OEM attached to it. That pump is controlled by a switch, timer, or a toggle switch of some kind. Did you check if there is any fuses or resettable breakers that feed that solenoid in your picture in post # 10, . Simon C
Okay seen your pressure switch and the terminals are not the cleanest. Try to follow the wires from it to either a relay or the S-Terminal of starter is my guess. Simon C
By the way, if it is starting the pump but not starting the engine , the switch is probably not closing the contacts or they are internally burn't out. Have seen many times. Simon C
Here is a few things for you 1 I'm betting there is a wire coming off batt + on starter to your add on solenoid one of bigger terminals the wire on the other larger terminal goes to prelube motor. 2 when it works is there a pause between the prelube pump running and starter engaging ? If There is there is a controller hiding somewhere 3 the plug by the hose that runs over top of engine is for a remote switch to run lube pump for oil change
i assume the oil pressure switch will short internally when the required pressure is reached? So i should be able to just jumper across it with a short jumper wire for a test. if that works I know its the oil pressure switch. if not, it will remove it from the list of possible issues.
yes, there is a wire from starter to large terminal on extra solenoid (12v hot at all times), other large post goes to prelube motor as power. there is a delay when the key is turned over until starter motor kicks on. the prelube solenoids small posts are connected to oil pressure switch shown in post #31. one side of it or both, I am not sure. I will bypass the oil pressure switch and if machine cranks normally without any delay, I will know its the extra oil pressure switch.
Does the oil pressure switch you are looking at have one or two terminals?
two terminals
And it’s located here…
I don't know if I would want you to jump the wires on the switch the s terminal used to be always white is there a white wire on your add on solenoid ? and what color wire on s terminal on starter
I think you could probably combine the machine schematic that I sent to you with the prelube schematic contained in REHS0439 and you ought to be able to figure it out. As I recall prelube was never standard fitment, therefore the electrical side of it was a "stand alone" wiring installation added on to a basic machine. I hope that your tractor follows this pattern and I believe it will have been installed that way. This may also help. An electrical schematic for a D10R where prelube was an attachment. The prelube timer controls a relay connected direct to the starter.
The override procedure for the prelube just popped into my head. Turn the key to the START position and wait for the prelube motor to start. As soon as it does, turn the key to OFF and then straight back to the START position again. That should bypass the prelube timer. Let us know what happens.
I think this is controlled by an oil pressure switch instead of a timer, but I appreciate the info, will definitely try it!
There is a white wire on the solenoid but it is a small wire and has nothing to do with the starter (I don’t think). There is a white wire connected directly to the starter solenoid that goes to the battery box and is connected to a relay over there. (All info I verified with the wiring diagram). I am in the process of chasing down where 12v is supplied to that relay
If it is like other machines I’ve been around the oil pressure switch is an input signal to the timer module. Take a good look at the D10R schematic that I attached above. This is a “Prelub” brand system that is from what I can see very similar (or maybe identical) to what was installed on larger tractors. If the oil pressure reaches the set value the timer module immediately activates the starter. If the oil pressure fails to reach the set value after X seconds the timer module activates the starter.
Sorry but why would it try to start a engine that had no oil pressure kind of defeats the purpose of prelude and could cause major failure
Might want to check harnesses around the relay in battery box for cat numbers on them
The way it was explained to me at the time was the system was designed to get some oil into the bottom end of the engine before cranking, not to generate significant oil pressure. The pressure switch was set at 4psi IIRC.
If you look at rpm industries it states it will prevent engine for starting with no oil it’s pretty hard to find any thing about the prelude system I remember years ago when we first put them on it was not much more than a box of parts
I worked with a number of marine diesel engines where if the prelube pump didn’t raise the pressure to a certain value the engine would refuse to start. The Prelub brand systems fitted to Cat equipment didn’t work like that, if the oil pressure remained low after starting it depend on the warning system firing off a low oil pressure warning and under certain conditions would shut the engine down.
From what I have read the pump is to just prelube the rods, mains, and maybe cambearings. The engine will turn 10 times per second at idle and the pump will feed everything else. If it can't it will shut down under oil pressure mangement, whether solenoid or computer. Simon C
Correct according to posted info set for 4-7 PSI. Simon C