Lift Pump on 8.3L Cummins ISC

[robar]

My MH does not start after removing and rebuilding the alternator.  Obviously the battery was disconnected while the installation took place, but I am quite sure that the wires were replaced correctly and in fact there is power to all of the fuses and all fuses check out to be good.

The lift pump does not make any noise when the ignition is turned on but I can't get at the wiring to check it without removing the pump.  Sooooo, I have a new pump on order and will replace it when it comes in.

I found an old post on this subject but thought I would start a new thread.  Can someone tell me whether this is a big project or not.  Like many other jobs on this coach you need to be a contortionist to get at it.

Are the electrical connections on the bottom of the pump?  I can't see any wires coming in to it from the way it is installed in my coach.

 

[Gary RV_Wizard]

Before condemning the pump, why not disconnect the fuel line from the outlet side of the pump and see if fuel squirts out? And I would test the power to it as well. There is probably a relay that engages the lift pump when the key comes on, but I think the pump then shuts off again after 20-30 seconds. I don't think it runs continuously, but that may depend on engine model and fuel system type.

 

[robar]

".....why not disconnect the fuel line from the outlet side of the pump...."

Gary - Good thought.  I didn't think to do that because I put a listening device otherwise known as a long screwdriver up against it and couldn't hear anything, so I know it isn't working.  But you are right, that type of failure is usually something electrical, but the wires are inaccessible and I would have it out and in my hand before I could check them.  At that point I might as well replace it since it has 90,000 miles on it.  Would you agree that from a peace of mind standpoint it is worth putting a new one in if you have to go that far?

 

[Gary RV_Wizard]

Depends on the price of the pump.

As I said earlier, are you sure the pump was supposed to be running when you checked? Mine runs about 20 seconds and stops. Once fuel pressure builds up, it shuts off.

 

[Rex]

Gary is correct, the pump runs for only about 20 - 30 seconds.  Have someone turn the ignition on while you listen to the pump. 

You said the coach would not start.  What IS it doing?  Does it turn over?  Are the engine batteries fully charged?

Need more information, but I doubt the lift pump died while you changed out the alternator.

 

[robar]

Yes - I don't know how long it is supposed to run but I assumed it ran for only 20 to 30 seconds so I had someone turn the ignition on when I was ready to listen to the pump.  Batteries are fully charged and the engine cranks over normally but doesn't fire up.

Current status is that the pump is removed and with the plug accessible it is not hot when the ignition is turned on as you suspected.  Furthermore when I put 12 volts to the pump it made noise so it probably works. Now I have the fun job of trying to find out why the fuse is hot and the plug to the pump is not.  I have a call in to Spartan but need to find out if there is a relay or something that gets tripped before power goes to the pump.

I'm putting the new pump in and have a good working spare which I hope I will never need.  The new one was something like $315, but I saved some mechanic the aggravation of having to install it for me.

 

[robar]

Thanks for the responses. The problem is fixed and the engine starts. The issue turned out to be a small in-line fuse that Spartan chose to put in the bowels of the engine compartment. I don't know for sure whether it feeds the ECM or the lift pump itself, but when I found it it was blown.

In the mean time, in order to pull the connector on the pump and get access to the fuse holder I had to pull the lift pump. I had half of my tool box in the bedroom of my coach and have just applied for a job at Circ de Soleil, but the job is finally done and I averted the tow truck to a local truck repair place.

Probably a good thing for any Spartan Chassis owners to know about if it ever fails.  The in-line fuse is similar to the ones in the battery compartment and is located about three or four inches away from the large round connector that in my case is mounted to the lift pump.  It may be under some of the other wire bundles and is a 5 amp spade-type fuse.

 

[Gary RV_Wizard]

Don't ya luv it when they hide stuff like that?  I once lost ALL 12v power in the coach when I accidentally caused an arc while changing the porch light bulb. What the hey? The fuse for the bulb circuit wasn't even blown. It turns out the power for my electronic power distribution panel is also the feed for that one particular light, and the inline fuse for that feeder is smaller than the bulb circuit fuse. And that little inline fuse is hidden in the battery compartment, direct-wired to the battery (cause it operates the battery disconnect relay too).

 

[mdbass]

I had to pay an electrician a ton of money to get the dash fan going. Same deal, an inline fuse buried in the dash.