CAT 420D Fuel System Tests and Pictures

[JCinNC]

Just some tests and information I thought I'd share to help anyone or get any input on as I chase my fuel/performance issue.

There will be many pictures. Hope that's ok.

Thanks,

J.C.

 

[JCinNC]

This work, like the title says, is on a Caterpillar 420D. Your model may or may not be different.

First, I consider myself amateur compared to many other great mechanics. I do not have any manuals with this....yet. So this is just based off my experience and proceed at your own risk with anything show or recommended. PLEASE correct me on anything that I post that is not correct so we can have the right information for anyone to keep their equipment running. Thanks.

With that:
I first removed these clamp bolts that hold a wiring harness, the oil filler hose, and the dipstick. I did this 'cause that oil filler hose is right in the way and this gives flexibility left and right as you work around checking and removing or replacing things.



I then loosely put the bolts & washers back in holding the dipstick and wiring harness so as not to lose the bolts & keep those things in place. They have not been in the way so far staying in place.

 

[JCinNC]

Then following the "typical" arrangement on injection pumps I've encountered, I find the return line at the pump here.


I follow the lines off the screw clamp elbow around and they come to a Tee here. This is the drivers side of the engine with the panel removed. Near the cab and lower frame.
My thumb is on the line coming from the screw clamp elbow and my index finger is on the line coming from the filter housing. These two lines have flow going towards the brass tee.

This is the line on the same Tee that exits back to the tank.

 

[JCinNC]

I disconnected the line at the Tee return above to confirm flow at this point. That little hose was on there tight even after removing the screw clamp. Lots of prying, twisting and pulling. I then hooked ups some 3/8" ID tubing I had to the Tee with the screw clamp. (Estimated size of tubing. Not sure exactly.)
Then cranked the tractor and confirmed decent flow on return to this poing. Didn't measure the exact GPM or anything though.


I then shut the tractor down and connected a standard gauge to the return line rig I had set up, cranked the tractor, and observed return pressure of 21 psi.

 

[JCinNC]

Next, I removed the input to injection pump coming from the tank pump that's mounted on the filter near the drivers side frame rail.
Shown here by my index finger after the quick connect elbow is removed. Didn't get a picture of the elbow. Sorry. It, or mine, has two blue squeeze clips on it. One visible and one directly behind the visible one. You squeeze them and lift off the injection pump mount.
There is a screw clamp on the other end of the elbow coming from the little pump on top of the fuel filter.

I then set up another hose coming from the little lift pump on top of the fuel filter to check flow. I bumped the engine to make the pump run and got good flow. However, it registered zero pressure if that matters.


Showing flow with lift pump pumping. Did not measure GPM.

 

[JCinNC]

The little pump on top of the fuel filter/water separator housing is located here on the drivers side frame rail. Side cover removed, near the cab. Again, earlier Caterpillar 420D.

 

[JCinNC]

If you want to remove the pump to check or replace, you'll need to lay underneath at the drivers side and look up near the fuel/water separator filter. There is a wiring harness zip tied together shown here. (On mine at least.) You disconnect the lighter grey wiring connector. Pretty easy to trace back if needed or if they changed the color of the connector.


Then I disconnected this hose at the return line Tee. Kind of goes over the top of the pump and is just in the way of work and getting the pump out.


In this photo, I'm pushing the return line hose out of the way with my index finger and pointing to the black plastic mounting nut you have to remove to remove the pump.
I've rotated the pump a little bit clockwise for a better view and to get something on that nut. Doesn't hurt anything. Just a compression connection with an o-ring underneath.


I then took a long screwdriver and bumped the nut counterclockwise to get it loose. I can't think of and/or don't have another tool to do it a better way. Open to suggestions though. Note it is a threaded connection. Not a "turn to lock" connection.

 

[JCinNC]

After loosening the plastic nut on the pump. You should be able to remove it. Might have to do a little moving & weaving with the hoses and wiring harness. Then you can look in the top of the mount like this.

 

[JCinNC]

This is the removed pump number if needed. (I already started taking some things apart as you can see.)


This is what it looked like at first removal. If you want to take it apart farther, you start by removing the four screws in the white-yellowish piece facing here. I did it with a Torx bit. Not sure the size.


Then that piece and the black screw ring that holds it on the fuel filter housing come off and it will look like this.


Next there are 6 screws, 3 on one side, 3 on the other, that you remove to split the case. Can't remember if they are Torx or Phillips.

 

[JCinNC]

I only got one side of the case off. Other may be pressed or epoxied in? Scared to muscle it or the filter screen much though. Anyway, this is what it will look like.

Inspect and clean parts. I found this o-ring not seated correctly.

 

[JCinNC]

All for now. More tests possibly to come or will perform any suggested tests by ya'll.
Hope this isn't an annoying thread or way of posting. (Pretty new to forum.)

Thought it might help someone else in some way as I have not been able to find something similar.

Thanks,

J.C.