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D3C fuel transfer pump (3204)

Jaybuild

Well-Known Member
Joined
Sep 29, 2007
Messages
48
Location
Connecicut
Had a fuel delivery problem and decided to pull the pump to clean the screen, and put in new o-rings and those silver valves. I noticed what appears is a piston within a piston. The small inner one seems to slide fine, but the larger one appears frozen. Is this normal? Or is it supposed to slide? If it does not slide, what is the purpose of the large spring on the cover side? Any information on how this pump operates and any tricks or procedures to be aware of before I assemble and install the pump would be much appreciated. The knowledge on this board is a great asset to the small owner-operator and has saved me much wasted time.
 

DigDug

Senior Member
Joined
Dec 11, 2005
Messages
577
Location
Maine
Hello, I just had one apart on a 3204 in a Cat skidder. The part I think your calling a piston moved freely in my transfer pump. I could fax you some dissasembly or assyembly instructions that I got from the dealer if you need? Mine had 3 check valves in it that were bad. Good luck, doug
 

LonestarCobra

Well-Known Member
Joined
Sep 4, 2008
Messages
228
Location
WV
There is a sleeve that goes into the aluminum housing sealed with o-rings that does not move. The piston inside of that, has to move freely to move fuel. The operating rod that protrudes into the injection pump must move freely also. Usually the most common problems with those transfer pumps is trash in the little dime size check valves.
 

Jaybuild

Well-Known Member
Joined
Sep 29, 2007
Messages
48
Location
Connecicut
I got the pump in and and started it up. My problem persists. I ran it at high idle and it ran fine for about 1000 ft. or so and it started to starve for fuel. I hit the decelerate pedal to bring it to low idle, barely stays running and after a couple of minutes it seems to "catch" and I can go another 100 ft. or so. The pump is assembled correctly (I went to the dealer service dept. and they brought me to the fuel lab where they had one that he quickly disassembled to make sure I did it right), the filter is new and there is fuel in the tank. Any suggestions on what to check next?
 

willie59

Administrator
Joined
Dec 21, 2008
Messages
13,363
Location
Knoxville TN
Occupation
Service Manager
You said in your first post you pulled the pump to clean the screen. Which screen are you referring to? Some Cat pumps have a screen inside the banjo bolt fitting feeding fuel to the lift pump. Is this the one you checked? Is there a filter prior to lift pump? If so, I suppose you changed that. If you've done all this, I'd blow compressed air back through the fuel line to the tank to remove any obstuctions. I just removed a fuel obstruction on the 90 degree fitting on top of a JLG 80HX fuel tank today, it happens quite frequently with equipment of all types. If it still doesn't work properly, you need to check or replace your fuel line from tank to filter or lift pump. You could have a hole rubbed in the line from vibration causing air to enter into fuel line, has the same affect. ;)
 

Tex3406

Active Member
Joined
Sep 27, 2008
Messages
42
Location
South Australia
We have a D3C dozer with 3204 engine.

It often blocks up the outlet tap right back on the bottom of the fuel tank with muck.

You have to blow back through the line to clear it, and then it is right to go. I have never had the filter block up, but the tank outlet tap has blocked heaps of times.

In my opinion it is too small for the job and therefore blocks before the filter does.

This may or may not help, but good luck anyway.
 

Kgmz

Senior Member
Joined
Mar 21, 2007
Messages
308
Location
Portland, OR & Eatonville, WA
Occupation
General Contractor
Been there done that also.

Our D3C LGP has the same problem with crap blocking the fuel outlet pipe at the bottom of the tank. Just unhook the hose running to the pump at the pump. Blow in some air and it is good for awhile.

If you unhook the hose from the tank at the pump does fuel run out fast, if it just trickles or not at all then the pipe into the tank is clogged.

We bought this D3C used quite a few years ago. And someone before us cut a hole in the top of the tank and made a plate to cover the hole. Probably had this same problem and tried to clean it or something.

I have removed the plate and cleaned the tank, but there really wasn't much in there and what was there is very fine particles. I suppose it is rust falling down or getting washed off of the top of the tank.

But I have been meaning to try something. If you know what a snowmobile tank filter looks like then that is what I am going to try. Snowmobiles have a filter about 2 or so inches in diameter and about 3 inches tall with a fitting on one of the end caps centered, which is attached to a short hose and then to the outlet fitting in the tank and just lays at the bottom of the tank. I am thinking of using a very short hose and clamping it to the fitting at the bottom of the tank and then to the filter. I am thinking this should stop the clogging, but may not be able to use all the fuel at the bottom of the tank. Which would be all right since I usually don't let the fuel in the tank run that far down.
 

Tex3406

Active Member
Joined
Sep 27, 2008
Messages
42
Location
South Australia
The only problem I can see with that idea is that when this new filter you have put inside the tank blocks up, it will be pretty hard to get at to clean, especially if the tank is full at the time.
 

Kgmz

Senior Member
Joined
Mar 21, 2007
Messages
308
Location
Portland, OR & Eatonville, WA
Occupation
General Contractor
I figure it will take a long time to block the filter with that much surface area.

But if I have to empty the tank I pull the pump off of my transfer tank in the back of my truck, open the cover on top of the tank insert the drop tube of the pump and pump it out. Thats what I used when I cleaned the tank.
 

Jaybuild

Well-Known Member
Joined
Sep 29, 2007
Messages
48
Location
Connecicut
Hey Guys, thanks for the help and sorry I haven't been back to update. I blew back through the fuel line and problem solved. Once again, thanks.
 

Jaybuild

Well-Known Member
Joined
Sep 29, 2007
Messages
48
Location
Connecicut
Any tips on cleaning the tank?

I was wondering if anyone had a good procedure on cleaning the fuel tank. I drained it and removed the fittings on the bottom of the tank. I put in a gallon of brake clean and as it came out the bottom I strained it through a paint filter. The filter would clog with particles, then I would blow it clean. I strained it through another paint filter and put it back in the tank. After about 15 times it was coming through relatively clean. I put it together and it ran about 15 minutes before it clogged. What do you think about putting the nozzle of a pressure washer in there and blasting away. Then running a couple of gallons of alcohol to dry it out? Does anyone have any suggestions? The tank would be a bear to remove and that would be my very last option.
 

k.key

Well-Known Member
Joined
Jun 30, 2009
Messages
54
Location
Indiana
Occupation
Mechanic Self Employed
There is really no good way to clean out those tanks, I've heard of a few guys making there own access hole in the side of it and then plating it up, they are not easy to remove at all. Good Luck
 

Jaybuild

Well-Known Member
Joined
Sep 29, 2007
Messages
48
Location
Connecicut
Another question, I am still having fuel problems with this machine. If the lift pump is removed and the fuel supply is attached, you can push the plunger rod with your finger and get a good shot of fuel. When it is installed and you turn over the engine, the fuel hardly dribbles out. The plunger appears to be intact, and the drive cam appears to be in good shape. A rough measurement in the field (limited tools) indicates about 7/16" stroke. Any ideas?
 

rare ss

Senior Member
Joined
Apr 1, 2011
Messages
460
Location
Western Australia
the stroke sounds ok to me, i'd be checking the lift pump pressure when its running, if the pressure is fine then you can eliminate that part of the system and look towards the fuel pump itself,
have you replaced the check valves on the lift pump?... has it got a return line back to the tank with a orifice fitting leaveing the fuel pump?.. some people change these without realising that its an orifice to give you your lift pump pressure (on 3304 & 3306 engines)
 

Cmark

Senior Member
Joined
Jan 2, 2009
Messages
3,176
Location
Australia
Another question, I am still having fuel problems with this machine. If the lift pump is removed and the fuel supply is attached, you can push the plunger rod with your finger and get a good shot of fuel. When it is installed and you turn over the engine, the fuel hardly dribbles out. The plunger appears to be intact, and the drive cam appears to be in good shape. A rough measurement in the field (limited tools) indicates about 7/16" stroke. Any ideas?

When you say you can push the plunger in with your finger, do you mean that literally? The return spring is fairly heavy and needs good push with the palm of your hand. If you can compress it with your finger then the spring may be weak/broken/wrong part.

It's the spring that makes the fuel pressure. The cam just compresses the spring.
 

Jaybuild

Well-Known Member
Joined
Sep 29, 2007
Messages
48
Location
Connecicut
I am unaware of any orifice fitting. Is this also true on the 3204 engine? The lift pump has a 3rd check valve before the line to the filter to give it pressure. It appears to be a flared fitting going back to the tank (from the injection pump). The lift pump is new. When operated manually it appears to pump fine. The spring does not appear weak. The tank has been cleaned (again), the fuel lines replaced, the lift pump replaced, new "plunger' pump above the filter, new filter (the old one showed a little grime), fuel in the tank, good gasket on the fuel cap When the engine gets fuel it runs strong. In my opinion, this is a simple and basic fuel system. A number of people have looked at it, and we can't figure it out. Any one have any experience with a problem like this?
 

rare ss

Senior Member
Joined
Apr 1, 2011
Messages
460
Location
Western Australia
give us a good account of how it performs, does it start first go and run fine then stall, or do you have to prime the fuel system then it starts and runs ok.. has the issue just started on its own or has any work taken place to the machine before this problem started or has the issue been there all the time?.. i had a simlar problem on a 966FII with a 3306 it had a hole in the fuel line going to the transfer pump, wasnt leaking due to the tank being below the line but it would let the fuel drain back to the tank over night and not start some mornings if it has been parked for 2-3 days other mornings fine, sometimes it would stall during the day and start after a prime then be fine (when it was low on fuel)
another one i had was a D7HXR it would run fine 99% of the time but if you worked it on load for a good 20mins it would pop & miss and die under load, it has been doing it according to the operator for 3-4 years but wasnt a huge issue as it was only pushing loose stuff most of the time, anyway "everyone" checked this that timming, auto advance gear, fuel filters air filters ect, checked the lift pump pressure and it was 0! but beacause the tank was higher than the engine it feed enough fuel to keep it running most of the time unless you has it on load for awhile, new lift pump, 32psi, ran sweet under load all day
like you metioned its a pretty basic system the fitting you metioned leaving the fuel pump on the return line i suspect that should be an orifice (not a full bottle on a 3204) to restrict fuel flow from the lift pump to give you the transfer/lift pump fuel pressure, sometimes people change these out for a normal fitting and you will never get enough pressure and causes all sorts of issues, check your pressure if its fine and theres still a problem there that will tell you theres another issue somewhere else or if the problem is a fuel supply/pressure issue
 

StreetBob

New Member
Joined
Nov 27, 2011
Messages
3
Location
Sweden
Hi, sorry for hijacking this thread!

Writing you guys from Sweden hoping that someone here can help me. I have a 1986 IT12 with a 3204 engine (total rebuild 2 years agoo). Now to my problem, yesterday i changed the fuelfilter and decided to clean the fuel transfer pump screens. Well it was pitchblack outside and freezing and i managed to somehow mess it up. now the engine starts up fine, but as soon as i push the accellerator it stalls, picks up again quite fast, then stalls as soon as i push the accellerator. Bottom line is i need help. would be great if someone could supply me with an exploded view of the fuel transfer pump valve setup.

http://rpservice.se/it12.jpg link to a pictu what i belive is called "fuel transfer pump"

Hope you understand my Swenglish!
 

StreetBob

New Member
Joined
Nov 27, 2011
Messages
3
Location
Sweden
I´m going to reply to my own question here since the problem is solved. It turned out to be the new fuelfilter that was faulty. Very strange but that was the simple solution to it! Discovered it after changing all serviceparts in the fuel transfer pump.

Oh.. and if anyone wants a schematic picture of the fuel transfer pump with part no list. Send me a msg and i will mail it to you.
 
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