Caterpillar D398 Questions

[Dan690D]

Hey All,
I bought a generator- a 500KW Cat D398 that was converted to Natural Gas. Because of the absurdly low price, I bought it without knowing if it ran. It's now time to test it. I have two questions:

1: I need to figure out what batteries I need to turn this sucker over. I haven't been able to find any information on what voltage and cranking amps I need for this motor. It has two rather large starters, and i haven't found info plates on them. Anyone know the volts/amps I need? As best I can tell, it's a 48.3L twin turbo V12 with 10.0:1 compression. CAT/Holt was unable to find any info on the batteries for me.

2: The generator head has had all of the control circuitry removed. There are three large bars coming from the head (480V 3Phase head), connected to the windings, but nothing else. The voltage regulator was removed, and I'm wondering if it's safe to start in this condition? My concern is that it will arc or otherwise damage itself without the regulator. Anyone know if it's safe to start as is?

Thanks,
Dan

 

[ol'stonebreaker]

It's been almost 20 yrs since I've worked around one which was diesel. IIRC the starters are 24 volt but don't quote me on that. As for the gen controls they are quite complex and I'd start a search for a complete one. Ours had an electronic governor which received it's signals from the gen controls and it was quite sensitive to even small load changes. I'd check w/ Cat for the gen control panel first. If your's has the electronic governor I'm not sure what it will do on startup w/ no signal, so be ready to manually control the arm on the governor that goes to the rack. If it's hydraulic type that runs off engine oil pressure it should work fine. Ours had a relay setup so when you turned the switch to "crank" it activated an engine oil precharge pump and when oil pressure was sensed then it would start cranking. Remove the back panel on the gen and remove the field brushes from their holders. No field current= no output. Not much help but that's all I can tell you. I hope someone on here has an operation and repair manual for it that can make a copy for you. If not you can maybe find one somewhere on the web.
Good luck,
Mike

 

[Birken Vogt]

Where is this thing? I am in Grass Valley and I work on generators for a living. I might like to look at it complimentary to give you some ideas at least, if it is not too far in the boondocks.

 

[Dan690D]

IIRC the starters are 24 volt but don't quote me on that ... Remove the back panel on the gen and remove the field brushes from their holders. No field current= no output. Not much help but that's all I can tell you.
Good luck,
Mike

Thanks Mike. I figured it was 24V, they usually step up to that to keep amps and heat down. Maybe I can look at the impedance to figure out the current requirements.

As for the field brushes, that's what I was thinking I might have to do. I'll pop the back cover and see if that's feasible.

Where is this thing? I am in Grass Valley and I work on generators for a living. I might like to look at it complimentary to give you some ideas at least, if it is not too far in the boondocks.

That would be great. It's in town, I'll PM you my phone number, and we'll work out a time for you to take a look at it. I'll need someone to put it all together. I've called two local generator guys, but they both only knew what they were doing up to about 10KW and were apprehensive to the idea of something this big.

 

[Dan690D]

OK Birken Vogt, I can't PM you because I haven't posted enough I think, but I found your number on Google. I'll call you tomorrow. Thanks again.

 

[lantraxco]

At least a pair of 8D batteries, maybe a pair for each starter.

I worked on a pair of D399's (V16) in a tug, but they were air start.

 

[Nige]

An engine that big is almost certainly going to be 24V electrics. As a guide our 3516 gen sets had 4 x 8D 1200AH batteries wired in 2 pairs to produce 24V and that was for a single electric starter, not two......

Maybe a good first step would be to get hold of an Operation & Maintenance Manual. Plug the Serial Number into https://servicemanualpro.com/ and see what comes up. It ought to be about $35 for a CD version.

 

[Dan690D]

An engine that big is almost certainly going to be 24V electrics. As a guide our 3516 gen sets had 4 x 8D 1200AH batteries wired in 2 pairs to produce 24V and that was for a single electric starter, not two......

Maybe a good first step would be to get hold of an Operation & Maintenance Manual. Plug the Serial Number into https://servicemanualpro.com/ and see what comes up. It ought to be about $35 for a CD version.

I'll check Service manual Pro, thanks. I haven't found the plate for the serial number yet either.

The 3516 is bigger than the D398. sounds like 4 4d's or similar should do the trick.

 

[Nige]

Don't skimp on battery power is something I learned a long time ago....... I would suggest that if you decide to go for a 4D frame size then go for 1400AH batteries.

 

[Dan690D]

Don't skimp on battery power is something I learned a long time ago....... I would suggest that if you decide to go for a 4D frame size then go for 1400AH batteries.

Yep, I agree Nige. I learned that one the hard way with my pickup.

 

[kshansen]

Well the D398 gensets we used to have were set up with 32 volt starting systems. It was a pain at times finding big enough 8 volt batteries to hook up to get that voltage.

On the other hand we had a D399 genset that was set up as a 36 volt system. Hard to be sure but believe that one was connected to six 8D's. Two sets of three in series to get the 36 volts then paralleled for the cranking amps.

Did some digging and find that they list spec's for three different 50MT starters for the D(G)398-399 engines. They are 24 volt, 32 volt and 64 volt. Surprised that they do not list the 36 volt I remember our D399 had, unless they just used the 32 volt starters and upper the output of the alternator to get the 36 volts. I doubt running a 32 volt starter on 36 volts would do any harm. Heck I've been running my old Farmall BN with a 6 volt starter on 12 volts for about 30 years!

Okay, might have a way to tell the voltage of the starters. Need to check the pull-in winding OHMS on the solenoids. Here is the spec's from SIS:



As for the size of batteries I find this from Delco:



Over to the right it lists the max CCA for a 24 Volt 50 MT as 1800 CCA. They claim too many CCA's can hurt a starter. From my experience the same is true or more so for too little CCA's. One other question I have is if you have two 50MT starters would one need to double the total CCA's?

Guess that might require a phone call to Customer Service, number at this page:

http://www.delcoremy.com/Support

 

[lantraxco]

I had heard of 36 volt systems on the tugs, but not 64... hate to cross that with a wrench, be like the 4th of July!

 

[kshansen]

I actually remembered something after I went to bed last night! The voltage is almost always marked on the solenoid between two of the mounting bolts along with the Delco part number.

 

[Dan690D]

Did some digging and find that they list spec's for three different 50MT starters for the D(G)398-399 engines. They are 24 volt, 32 volt and 64 volt.

Over to the right it lists the max CCA for a 24 Volt 50 MT as 1800 CCA. They claim too many CCA's can hurt a starter. From my experience the same is true or more so for too little CCA's. One other question I have is if you have two 50MT starters would one need to double the total CCA's?

Guess that might require a phone call to Customer Service, number at this page:

http://www.delcoremy.com/Support

Thanks for the info.

I found a rebuild tag on one of the starters. it had been painted over, which is why I hadn't found it yet. I called the company that rebuilt it, and gave them the number, and they said it was a 24V "50 frame" starter, which seems to match what you're saying.

They were fairly certain it only needed 300 amps to turn the engine over. That seems really low to me.

Considering the amperage should simply be the voltage/resistance, I have a hard time believing that too much battery would be a problem.

Birken came out and verified that I still have a voltage regulator, so next step is to start this beast. I'll post a video when I try.

Thanks for everyone's help!
Dan

 

[kshansen]

Thanks for the info.

I found a rebuild tag on one of the starters. it had been painted over, which is why I hadn't found it yet. I called the company that rebuilt it, and gave them the number, and they said it was a 24V "50 frame" starter, which seems to match what you're saying.

They were fairly certain it only needed 300 amps to turn the engine over. That seems really low to me.

Dan

I agree that is way low. In a no load test with the starter setting on the bench the spec's are for 90 to 120 amps at 20 volts. Cranking over that 12 cylinder Cat would seem to take many more amps than that! A Cat 769C with a comparatively tiny 3408 uses two 8D batteries. My opinion would be that you will need at minimum of four 8D batteries. Connected with good 4/0 cables one pair to each starter and keep cables as short as possible to reduce voltage drop.

I'm not familiar with the Natural Gas engines, just guessing they may run a lower compression ratio so they might crank easier than a Diesel but just the mass of the moving parts on a 398 will take some power to get turning. Does this engine have a pre-lube pump of some kind? The ones we had used a hand powered pump that we would work till the pressure gauge started to move then we would crank the engine over maybe 1/2 a turn with the starters then pump the oil pressure up again before even trying to start all while using the glow plugs to warm up the pre-chambers!

 

[Dan690D]

Connected with good 4/0 cables one pair to each starter and keep cables as short as possible to reduce voltage drop.

I'm not familiar with the Natural Gas engines, just guessing they may run a lower compression ratio so they might crank easier than a Diesel but just the mass of the moving parts on a 398 will take some power to get turning. Does this engine have a pre-lube pump of some kind? The ones we had used a hand powered pump that we would work till the pressure gauge started to move then we would crank the engine over maybe 1/2 a turn with the starters then pump the oil pressure up again before even trying to start all while using the glow plugs to warm up the pre-chambers!

See, it has 1/0 wires running to each starter, and they're well used, so I'm thinking they're a reasonable size for the job. gives a little credit to the idea that this won't be a extremely high amperage job.

Yes, the three differences between the diesel and the natural gas versions are the fuel delivery (direct injected vs mixer on the manifold), ignition (compression vs spark), and the compression (17 something vs 10.0)

I don't have the slightest clue on the pre-lube pump. this is definitely something I want to know about to protect my engine if it has one, though. Where are these typically found?

 

[lantraxco]

10:1, yeah that won't need much to spin her over.

 

[Scrub Puller]

Yair . . .

I know nothing of this engine but with large units like this in a powerhouse it was a requirement to bar them over at least a full revolution before attempting a start.

If there is no provision for baring It would be prudent I believe to at least bump it over on the starters with no fuel to ensure no hydraulicing . . . maybe not so important on gas but on diesel one of those big injectors gone bad could put a lot of fuel into a cylinder which I found on several occasions. Water in a cylinder from a cracked head or injector sleeve could be catastrophic.

kshansen makes a very valid point about pre-lube. The English Electrics, Mirrlees and Blackstones had electric pumps to charge the galleries, turbo and rocker gear.

Such pumps, hand or electric are typically plumbed into an oil gallery external to the engine and often positioned adjacent the engine control/start panel so the operator can monitor pressure as it builds.

Cheers.

 

[kshansen]

10:1, yeah that won't need much to spin her over.

Well maybe I'm way off in left field thinking this would need big cables. Makes me wonder if it even need two 50mt starters? To my mind 1/0 cables would be borderline for stating a 855 Cummins on a cold morning, but then I'm thinking of an engine with real compression!

Only chart I could find quick said a 1/0 cable would be good for 170 amps so if the total amp draw on the system was 300 amps and it was split between two starters there would be a little extra capacity.

 

[ol'stonebreaker]

Did they mean 300 amps for each starter?
Mike