Hi everyone I just got a new toy D47J3952 I'm having fuel pressure problems any help would be much appreciated. I have blown air/cleaned everything I can think of dealing with the flow of fuel to the injector pumps. I put new fuel filters in I have decent flow of fuel on bottom and top bleeder but only about 5psi. It will not get enough pressure to flow fuel to the pumps, so I decided to pressurize the fuel tank, I throttled the valve to get 15psi after that I started to get fuel to the injector pumps and she fired right up. My question is are the gears themselves going bad or the housing wore, or is there seals inside the transfer pump that are going bad?

Could be all of your suggestions, might also be the most common cause, there is a one way valve about 1/2" across in the transfer pump secured by a spring, it's very common for crud to get stuck under the valve, or the spring to rot out, or simply lose tension..

Remove the fuel line from the tank, and inside that small housing you will find the valve and spring, remove them and report back, most folks simply stretch the spring out to gain more tension. The spring and small valve are available new if needed. I'm working on my D4 7J fuel transfer pump right now.

Hi Mike I have already replaced the spring and valve in the bottom of the pump, from everything that I'm reading about it almost has to be something going on with the transfer pump. Thank you

It only takes a few minutes to open up the transfer pump, remove the outer cover and you will see straight away what your internals are like, post photo's up of what you find.

I don’t think seals are an issue unless you have a restriction of the supply line between tank and pump inlet so it pulls a vacuum. Of course if you get into the pump to replace gears etc, you’ll probably want to start out with new seals.

The problem with the original design if all old CAT equipment I’ve ever seen was the lack of a strainer/sediment trap ahead of the gear pump. So anything that comes out of the tank goes through the gears causing wear. In addition, excess flow recirculates back UNFILTERED (I think) into the pump inlet through the bypass valve and causes more wear. The warning “BUY CLEAN FUEL AND KEEP IT CLEAN” is very appropriate!

Models after around 1960 have a fine mesh strainer and trap between tank and lift pump. There have been several retrofit spin on furnace type filter setups shown here to prevent that kind of wear.

I think either the gears and housing could be worn or the check valve isn't holding. I'm going to plug where the check valve is and see if that creates more pressure if that doesn't do anything then I will put grease in the housing to see if that increases pressure. It will be a few days before I can try either of these out and get pictures. I would like to thank everyone that has responded on here and this is a great site of knowledge Clayton.

Hi clayton,
check the transfer pump end/cover plate for gear gouging wear--can face up to tighten clearance between the gears and the plate--spec. is usually 0.001" to 0.0022" with a max. of 0.0035"
NOTE--that there is no gasket between the end cover and housing--relies on a lap fit--facing the faces on fine wet/dry with oil kero mix working in a figure of eight motion to a polished finish, then sealed with Prematex Aviation gasket cement or its current equivalent---
The cover plate can be draw filed with a fine file and faced to a polished finish as described above--done many in the field.

www.permatex.com/products/gasketing/gask...no-3-sealant-liquid/

Check for wear to the inside bore of the idler gear, where it runs on the stub shaft--can look not worn when assembled but the shaft usually does not protrude the end of the idler gear and so fools one into thinking it is not worn--if worn excessively then the main housing gear bore and the idler gear tooth side faces will be worn too--new gear and stub shaft should suffice a repair.
The stub shaft is cast iron and so is easy to drill and tap for 1/4" NPT so a puller bolt or slide hammer can pull the stub shaft out of the main housing--install a new stub shaft just so it is below the top face of the pump body so it does not interfere with the seating of the cover plate.
This can be done without dismantling the drive/seal end of the pump.
Cheers,
Eddie B.
Cheers

Clayton, edb (eddie) gave me some great advice a few years ago
(1) Try the easy fixes first
(2) If that doesn't work, always return a machine to original specification before attempting new types of fixes

You have replaced the spring and valve, how was the seat, often they are rusted and will not allow the new valve to seat properly, how was your valve seat, it's not unusual that it might need machining a new face?

I'm working on my D4 7J fuel transfer pump right now, for the second time, you will see in another thread how the camshaft gear in my 7J decided to strip teeth, so I pulled the transfer pump initially because I wasn't getting fuel pressure at the tower, the same problem you have. I took a heap of photo's of the internals this afternoon for your benefit, it will allow edb, who is a pump expert, to better guide you, he generously helped me rebuild my pump a few years ago, and made me some special tools that are necessary if you intend working on yours.

It's not rocket science, but it is easy to screw up I found, plus those transfer pumps changed design during the D4 evolution from RD4 through D4 7J to 2T/5T to 6U/7U, so what the parts book, or even Cat Inc tell you parts that should fit, is often wrong. The key thing is to try and avoid dismantling the inner seal section of the pump if possible, UNLESS you are sure the seals have failed, so DO NOT remove the rear drive gear at this stage.

edb will confirm this, but my gut feeling is if the seals are bad, the engine oil level in the diesel motor will increase as fuel leaks past the seals in the pump into the fuel tower housing, from there into the sump, so if you are not making engine oil, then for now assume your seals are OK, that will make this job much easier for you. I'm pretty certain the later D4 pump has a shorter drive shaft than the 7J, and I've seen pumps where the drive gear is completely different, so it's not a simple matter of switching in a new pump, the D4 7J pump is a bit of a orphan.

As ccjersey said, those transfer pumps move unfiltered fuel, so any trash in the tank goes through the pump gears, also, because the pump is the lowest point in the fuel system, it's where all your water will find itself, and sit, so tractors that aren't driven for years may have badly rusted transfer pump gears, and drive shaft, you will see that in my photo's. The pump is very simple, but the running surfaces must be good, as edb mentioned, hand lapping on a piece of glass can often save parts, but if the gears are badly rusted, or worn, it's best just to buy replacements.

You will see in the photo's a simple clamp that edb made for me, if you do have to fully dismantle the pump, you will need to make one of them, because until you get the drive gear secured safely on the shaft, there is the very real risk the springs inside pump, holding tension on the seals, will force the pump apart again. You will see the old original gasket from my pump in the photo's, it's busted a small piece out, please overlook that and imagine the bottom section is still in place. That is how the transfer pump came from the factory originally, with a one piece mounting gasket 4B5098, later Cat went to a 2 piece idea, with a small circular gasket to sit under the "Seat" 3B4749, and a different, larger mounting gasket that surrounded it, you will see that in my photo's too.

If your pump is like mine, you will need to decide what gasket system you use to refit the pump, if your original mounting gasket get's damaged when you pull the pump, but be aware you will need to at least make the larger gasket, as it's not available from Cat. You will see in my photo's the one piece mounting gasket I made this afternoon, I'm sure edb will comment on this, if you do not fully dismantle the pump, you will need to get creative and cut your new gasket to fit over the "Seat", then glue the gasket back together.

One thing to watch when making new gaskets at home for any spot on a Cat, is to duplicate the original thickness, because gaskets are often used as a spacer as well as a sealer. My old original gasket 4B5098 measures around 0.027" thick, interesting the new gasket Cat sell for this job, but won't fit my pump, is thicker, it measures around 0.035", not sure why the difference, maybe my original gasket just got crushed over the years, or Cat changed the specification. I had a roll of 0.027" thick gasket paper, so that is what I used to create the new gasket.

They say a pictures worth a thousand words, so hopefully you get some help from my photo's, I have spares of these pump parts, so don't think the photo's are from just one pump.

Cat Inc changed the design of the shaft seals, which makes them far more challenging to fit than the old original seals, if you need to go down that path, the new seals will unravel very easily if you are not careful, and it is easy to damage the internal bores cutting them on the keyway for the drive gear. You will see in my pics the 2 special tools edb kindly made for me for fitting new seals, one with the dished face for firmly seating the new seals into the "Seat", the other smaller pencil shaped tool for protecting the inner bores of the new seals.

I'm no Mechanic, just a dopey farmer, so I found it very challenging getting the transfer pump sorted, and was very appreciative of the help I got from edb.

Special tools I mentioned, and the pump shaft seals, the last photo shows the old style seal in one piece sitting on Eddies special tool, and the newer Cat seal that loves to unravel if you look at it wrong, and easily pulls the center bore out, they are nasty.

Mounting gaskets, the original gasket is in photo's #1 and #2, it was accidently busted when I pulled the pump years ago, it is not available from Cat anymore, their replacement you will see in the photo, will not fit the 7J pump, so you will need to make one. Note how I cut my new gasket to allow it to slip over the "Seat", I have glued that zigzag cut back together, and will use Permatex Aviation Gasket Sealer on both faces of my home made gasket.

Hopefully it all works OK, I'm the first to admit I'm not the sharpest knife in the drawer.