Onan 15 MDJF-3CR fuel pump help

The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.

tobyyost

Veteran Member
Joined
Jun 2, 2016
Messages
38
Location
USA
Hi all, My fuel pump is leaking on my Onan 15.0 MDJF-3CR/2268AA generator. rebuild kit part number seems to be 149-1703. But Cummins says that it is obsolete and cannot get it. I have seen some other posts about replacing with an electric fuel pump, but cannot believe that nobody makes these parts any longer. Any thoughts or comments are appreciated, if the electric pump is the way to go, can anyone give me some recommendations on pump model numbers etc... that they have used.

Thanks for all your help
 
I put in a Walbro pump for $140 and it works great. Cummin's can be a pita sometimes.
 
A Facet 5psi is often available at auto parts stores. Cut an aluminum plate to cover hole where lift pump went.

Also, if it is the kind with screws holding the pump together, try snugging the screws. cured many a leak on those that way.
 
Thanks for the input. If I do end up replacing with electric pump can someone put me in the ballpark of where the best sot would be to tie into the 12 v power so that the pump turns on and off at the proper times?

Thanks all
 
Connect to fuel solenoid lead. It will run any time the engine is running. If you want to prime, disconnect pump and jump to starter lead. Also make sure you get right voltage, those old gens could be 12,24 or 32v on the control system.
 
You need a pump that meets or exceeds the stock pump. Diesel fuel pumps supply excessive fuel to cool the injector pump before being returned to the tank. Also the fuel passes thru the filters several times so debris or organisms are caught soon after being introduced.
The electric pump will help bleeding, too. Pumps like the one pictured are available on ebay for about $16 and pump up to 35 gallons/hour. Cheap enough to buy 2. I have them on my Detroit mains as backup and for filling new primary filters. They are powerful enough to supply fuel if the engine driven pump fails.
 

Attachments

  • fuel pump.jpg
    fuel pump.jpg
    153.8 KB · Views: 96
Hi, I found this thread from 2016 since I have the same problem with my 12kw MDJF.
I am a layman (read: have no idea what to do, or-better-: completely new to this matter) and read about an electric pump replacing the old one. Is any one from you readers able to explain to me what to do (pls step by step) the moment I have purchased a set like @lepke mentioned in this thread? Or is there a vdo on YT I should watch to see this process?
 
Hi, I found this thread from 2016 since I have the same problem with my 12kw MDJF.
I am a layman (read: have no idea what to do, or-better-: completely new to this matter) and read about an electric pump replacing the old one. Is any one from you readers able to explain to me what to do (pls step by step) the moment I have purchased a set like @lepke mentioned in this thread? Or is there a vdo on YT I should watch to see this process?

If I remember correctly, on those units you have a lifter pump assembly that has a fuel bowl on the left (as you look right at it from the side of the motor) and the lifter on the right. On the left side, before the bowl is where the supply /hose/ comes in. More toward the right, closer to the fuel pump proper and the pump lever is another line that runs to the fuel filters. That one may be a hard line, but I remember it also as a hose.

The easiest thing to do may be to splice the electric fuel pump into the hose close to where it enters the fuel pump assembly by that bowl. It is okay to add more hose if you need to do that to get a couple or small few more feet to be able to secure the pump well.

The basic idea is that you want it close to the motor so you can do the electircal wiring and so that it is pulling more than pushing, and you want tyo splice it into the supply line. so that it is pulling fuel from the tank and pushing it into the old pump and filters, etc.

...but, please let others chime in, in case I have details wrong. Memory is fallible.

You could also remove the existing pump and plate over it. And, that is the right way of doing it. But, it can get more involved. I've seen plenty of people leave them unless and until they cause a problem, and I get defer removal until then.

...you may want to standby for other opinions on this. Others may feel leaving the old pump in is the wrong thing to do.

Others have already discussed the wiring.

What I want to add about the pump is to make sure you get one rated for /continuous/ vs /intermittent/ use (and, of course, rated for diesel). A lot of pumps that look like they'd be right, but are way less expensive than they should be, if you look, are only rated for intermittent use, e.g. for transferring while stored, or priming, etc, vs continuous use, e.g. to supply as long as the unit needs to run, indefinitely.
 
So here is what I did, may not look the prettiest, but it's been working for years now with no issues. I will try to post pics, but I tend to have issues when trying to do that.
  1. I am using a very cheap Mr. Gasket diesel fuel pump that you can buy at any auto parts store, you do not need any kind of high volume pump.
  2. Disconnect hose from incoming side of existing fuel pump and I adapted that through a few adapters that I am sure I was probably able to get at Lowes or home depot into a barb that I could slide fuel line onto and clamp down with hose clamps. This end goes into the new fuel pump
  3. Disconnect hose from the outgoing side of the existing fuel pump that goes into the fuel filters. Now I don't remember why, but for some reason I replaced that with a piece of brake line, so I have metal brake line going into the fuel filter, then the other end of the brake line is adapted to a barb just like the incoming line above. Again just slide the outoing fuel line from the fuel filter onto the barb and tighten with a hose clamp
  4. Find somewhere to mount the fuel pump, I just zip tied it to a water line that was in the area
  5. For the wiring, find the solenoid that shuts off the fuel to kill the engine. If you are not sure, try to start the engine and keep an eye out for a solenoid that is moving a lever up and down when you crank the engine and then let off. the top of this solenoid should have one wire coming out of it. This will be the wire that you want to tap the positive side of the fuel pump into. for the negative side of the fuel pump, just put it under any bolt that is in the area. I put it under one of the bolts that holds the solenoid in place.
  6. the only issue I ever had was getting the pump primed. I had to take the outgoing hose off and supply power to the pump manually for a bit to get fuel flowing through the pump. then I connected it back up and all was good.
  7. I did have a small fuel leak at the one filter which caused me to lose the prime on the fuel pump. I fixed that leak, primed the pump again and have not touched it since and we have spent many nights out on the hook with the genny running.
  8. It's been on my list to pick up a spare fuel pump in case this one ever gives out on me, but still haven't gotten around to it.
good luck, I will try to put some pics into another post
 
I think I got the pics to work.
First pic is the incoming line adapter to a barb
Second pic is the outgoing line adapter to a barb and going into that short piece of brake line into the fuel filters
Third pic is the pump zip tied to water line
Fourth pic is the wiring tapped into the solenoid and the ground attached to the solenoid bolt.
Again, not pretty, but it's been working great.
 
Also, I did not remove my old pump. did not see a reason to yet as it is not causing any issues. I do get a bit of an oil drip from it, but not enough yet for me to worry about it and make a block off plate.
 
Wow Thank you so much for these messages. Man I am a happy sailor!!!:thumb:
 
ONAN Fuel Pump 149-1703

I have a ONAN Fuel Pump 149-1703 new one in the box(NIB) if anyone is still looking


Also have a NIB raw water pump
 

Attachments

  • IMG_4138.jpg
    IMG_4138.jpg
    168 KB · Views: 13
First Boomer, Do you still have the ONAN fuel pump 149-1703. If you do, by any chance, I would like to buy it from you. Thank you
 
Back
Top Bottom