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Topic: Fuel transfer pump?? (Read 621 times) previous topic - next topic

Fuel transfer pump??

Started engine, all normal, began driving, engine began to not respond to accelerator, became rough and quit. Replaced both fuel filters as per Cummins instructions, primed using primer button , engine starts idles 5 minutes or so, dies...engine will continue to run if primer button is continuously pressed...possibly the transfer pump?
1994 U280 Unihome Grand Villa aka "Lazy Dayzz"                                              Cummins 300hp
    Allison 6 speed

Previous coaches:
1984 Revcon Duke 29 aka: "The General"
1984 VW Westfalia
1976 VW Westfalia

Re: Fuel transfer pump??

Reply #1 –
Fuel line is pulling air is my first guess. Does your engine have the troublesome lift pump?
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Fuel transfer pump??

Reply #2 –
Small mechanical pump with built it primer button, yes
1994 U280 Unihome Grand Villa aka "Lazy Dayzz"                                              Cummins 300hp
    Allison 6 speed

Previous coaches:
1984 Revcon Duke 29 aka: "The General"
1984 VW Westfalia
1976 VW Westfalia

Re: Fuel transfer pump??

Reply #3 –
The lift pump I was referring to is electric. Do a search with your engine model number and fuel problem.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Fuel transfer pump??

Reply #4 –
All points to the transfer pump, was just posting to see if anybody else had experienced same symptoms same engine
1994 U280 Unihome Grand Villa aka "Lazy Dayzz"                                              Cummins 300hp
    Allison 6 speed

Previous coaches:
1984 Revcon Duke 29 aka: "The General"
1984 VW Westfalia
1976 VW Westfalia

Re: Fuel transfer pump??

Reply #5 –
What Chuck (craneman) was trying to determine is what kind of transfer pump do you have on your engine.

My engine (C8.3) has a mechanical transfer pump mounted on the passenger side of the engine block.  It does have a manual priming button but I can't imagine keeping the engine running by "keeping the primer button continuously pressed".  It is very difficult to physically reach the pump and hard to push the button repeatedly.  Wouldn't want to be doing it while the engine was running.

It sounds more like you are talking about pressing a electric button (switch).  Do you have a electric transfer pump or a mechanical transfer pump?

The mechanical transfer pumps are pretty reliable.  The original lift pump on my coach was still working OK after 160,000 miles when I changed it out purely for preventative maintenance.  I agree with Chuck that your symptoms sound more like air being sucked into the fuel line.

Photo below of my old and new lift pumps:

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Fuel transfer pump??

Reply #6 –
That's the one, and no electric button, repeated pressing kept the engine running just long enough for trouble shooting, it wasn't pleasant underneath anyway new pump on the way, local Cummins nil stock
1994 U280 Unihome Grand Villa aka "Lazy Dayzz"                                              Cummins 300hp
    Allison 6 speed

Previous coaches:
1984 Revcon Duke 29 aka: "The General"
1984 VW Westfalia
1976 VW Westfalia

Re: Fuel transfer pump??

Reply #7 –
I think if I were sucking air somewhere it would be unlikely the primer would become hard to press after the air is bled out through the bleeder, in any event pump will be changed, watch this space...
1994 U280 Unihome Grand Villa aka "Lazy Dayzz"                                              Cummins 300hp
    Allison 6 speed

Previous coaches:
1984 Revcon Duke 29 aka: "The General"
1984 VW Westfalia
1976 VW Westfalia

Re: Fuel transfer pump??

Reply #8 –
If you wish to optimize the fuel system on your mechanical C8.3 a fresh lift pump is a good start.  To ease the installation I recommend you install studs.  Makes positioning the pump much easier.  It is possible your engine may already have studs - some do and some don't.  If not:

LarryB's EASY Stud Mounting Kit for Lift Transfer pump for 12 valve Cu

Another potential weak link in the fuel system is the overflow valve.  If the spring is broken, or the valve seat is partially fouled with garbage, then fuel pressure seen by the fuel injection pump may be incorrect.  Without a fuel pressure gauge you can't know the fuel pressure at the injection pump inlet.  Adding a gauge between the lift pump and the injection pump is recommended.  Using a pressure gauge adapter/snubber makes the installation fairly simple.

Cummins 14MM Pressure Guage Adapter Snubber CBS010

If you determine the fuel pressure on your engine is not up to specs, the solution is a new overflow valve.  I recommend the Tork Tek OFV020.  It allows you to fine tune the fuel pressure for optimum injection pump performance.

Overflow Valve to Adust your Bosch P7100 Injection Pump

I contributed to a long thread 6 years ago where we discussed these modifications.  If you are interested:

Fuel System Science Project
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Fuel transfer pump??

Reply #9 –
Thanks a lot...will let u know
1994 U280 Unihome Grand Villa aka "Lazy Dayzz"                                              Cummins 300hp
    Allison 6 speed

Previous coaches:
1984 Revcon Duke 29 aka: "The General"
1984 VW Westfalia
1976 VW Westfalia