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Topic: Fuel pump safeties (Read 648 times) previous topic - next topic

Fuel pump safeties

I had this safety device fail me on the road last week. It was wired into the fuel pump circuit in the engine room. Ford 460 gasser. Anybody know what it's called and where to get a replacement? There's no identifying marks at all on it. Really appreciate any info.

Re: Fuel pump safeties

Reply #1 –
What year is the coach and what is it screwed into? Does it stop the engine from running? With that info I might be able to help you.

Re: Fuel pump safeties

Reply #2 –
Ford, and possibly others, used to install a safety device that shut the fuel off in the event of a rollover, in order to reduce the chance of a fuel fire.

Re: Fuel pump safeties

Reply #3 –
That looks like a "resistance wire" that has burned out due to amp overload.

I believe some Ford 460 RV engines used electric fuel pumps, either as primary or secondary pumps.

The electric pumps received full battery voltage when engine was started, but then voltage to pump was reduced for normal running.  Voltage reduction was done by a calibrated "resistance" wire.  I don't know what they look like - never seen one.

If the electric pump is going bad or is overloaded by trash in the fuel line, it will try to draw too much power and the resistance wire will burn out.  Or so I have heard...

See the diagram linked below.  Shows the resistance wire in the circuit.

https://www.justanswer.com/rv-motorhome/31vfm-hi-i-1987-ford-e350-motorhome-460-v8.html




Re: Fuel pump safeties

Reply #4 –
Thanks.... the link was helpful. Just have to decipher the resistance of the old one and find a replacement.

Re: Fuel pump safeties

Reply #5 –
Take it to a Ford truck dealer parts desk, see if they recognize it.  Or perhaps a NAPA parts house?

Re: Fuel pump safeties

Reply #6 –
It looks like a heater....

Need more info.

Do you have a pic of the assembly the device was attached to?

Re: Fuel pump safeties

Reply #7 –
3 wires may be the pump control like above mentioned. Or it may be a low oil pressure shit off. 
The resistance  leads me to think it is the fuel pump power with a oil pressure step down 
 A single 3-5 psi pump at the tank should run the 460 with no problem.  If it also has an engine mounted pump , it could be removed  . Most of these had a 3/8 line  .

Re: Fuel pump safeties

Reply #9 –
If only 2 then the pump must get power on crank  and then this takes over on run.  All data points to simply an oil pressure switch triggering a fuel pump relay.
Does that other schematic show a resistor in the oil switch ?

Re: Fuel pump safeties

Reply #10 –
In reply #3 it does show a .75 ohm resistor in the run circuit and nothing in the start circuit. See this done with coils but never fuel pumps. Interesting. Is there anything on the metal portion of the resister? Looks like a 1/8 pipe thread for mounting. Oil pressure?

Re: Fuel pump safeties

Reply #11 –
If you just look at the photos, it is pretty obvious that thing cannot be a pressure switch of any kind.  It consists of a white ceramic base that holds a coil of wire (which has broken).  The two ends of the coil of wire are attached to wiring connectors.  The ventilated metal cover that includes the threaded projection is attached to the white ceramic base by three bent-over metal tabs.

IMO, there is nothing on the device that could retain oil or sense oil pressure.

I believe the threaded post is simply a way to mount the device.

I agree it would be nice to see some photos of where and how the mystery device was originally mounted on the engine.

I agree with TGordon that it LOOKS like a small electric resistance heating device...but is that its true purpose?  Or could it possibly generate heat as a side effect of its primary function?



Re: Fuel pump safeties

Reply #12 –
Right you are
Not oil switch. Some sort of heater or voltage drop.  It may connect to the oil switch wire that runs to the relay to reduce the amps to ground .
 You could sub a Chrysler ballast resistor.

Re: Fuel pump safeties

Reply #13 –
It was mounted on a steel plate in the engine room right around the corner from the fuel pump that it was in the circuit of. It was in the positive 12v feed before the pump and only two leads (in and out). I did get ahold of the ends on the longer side of the break with a multimeter and the resistance reading settled at 9.2ohms. I don't know if that helps.

Re: Fuel pump safeties

Reply #14 –
Quote from: Goldhound –
It was mounted on a steel plate in the engine room right around the corner from the fuel pump that it was in the circuit of. It was in the positive 12v feed before the pump and only two leads (in and out). I did get ahold of the ends on the longer side of the break with a multimeter and the resistance reading settled at 9.2ohms. I don't know if that helps.

Can you give more information? What year and model coach? Front or rear engine? The device acts like a ballast resister and reduces voltage.
 

Re: Fuel pump safeties

Reply #15 –
Sure.... it's an 87 Grand Villa 36. Oshkosh frame rear engine Gass ford 460