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No Fuel To Engine

May 21, 2019, 03:11:48 pm

My 1986 Grand Villa engine turns over but won't fire up.  I have removed the fuel filter and turned the engine over but no fuel comes out of the hose.  I suspect the fuel pump to be faulty but before I undertake the hassle of removing the fuel tank I would like to eliminate anything else.  It has a Ford 460 with carburetor and only one (electric) fuel pump in the fuel tank.  My Oshkosh wiring diagram only shows the the electrical circuit which supplies the fuel pump once the engine has started and the oil pressure switch has closed.  That circuit runs from a relay, through the oil pressure switch, through a fuse or circuit breaker (as the 12 volt supply), through the inertia switch, back to the relay and then to the fuel pump.  With the ignition switch in the RUN position, I am getting 12 volts on one side of the oil pressure switch but when I jump the wires the fuel pump does not run.

My understanding is that there is another circuit that powers the fuel pump more directly when the ignition switch is in the START position.

I have found the inertia switch under the dashboard and that has not tripped.  I think the circuit breaker is next to it as one wire runs from the inertia switch to it.  That wire has 12 volts with the ignition switch in RUN.

My questions are:
1.  How is power supplied to the fuel pump when the ignition switch is in START?  There appears to be an extra wire (not shown in the Oshkosh diagram) attached to the starter slave solenoid.  Could that be it?

2.  Where is the relay (also called the fuel cut-off switch, I believe)?

Any help will be greatly appreciated.

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Reply #1 – May 21, 2019, 03:25:12 pm

Well Marty, You have a unique setup and there may not be much experience around on it.  I have known of similar setups on cars/trucks, and you may just forget the in tank fuel pump and install a pump between the tank and the engine.  You just need to make sure that the pump you install is compatible (pressure wise) with your carburetor.  Check with Ford for the spec's.  Have a great day  ----  Fritz

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Reply #2 – May 21, 2019, 03:40:00 pm

 
 Does the fuel level gauge work?  If not , it may be grounded  at the same point as the pump. Pretty sure that no ground shows full fuel all of the time.

Jump the inertia switch .
  If that does not power up the fuel pump, go back to the tank/pump area and check for chassis ground,
 Then check power in to the pump. If you can reach the pump, check the harness leading to it . If it has only 2 wires , it may only be the Fuel sender wires, If it has 3 or more wires, one should power the pump.

 If the pump has power ,  but fails to run  and is in tank mounted, there is a frame rail mounted pump that may work and suck fuel through the intank pump .
 Carbed is low pressure 
 https://www.oreillyauto.com/detail/b/mr--gasket-4367/performance-16477/fuel-system-16571/fuel-pumps---electric---universal-17799/6816540a63e4/mr-gasket-35-gph-fuel-pump/12s/4513658/1993/ford/f-150?q=Fuel+Pumps+-+Electric+-+Universal&pos=0

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Reply #3 – May 21, 2019, 06:35:35 pm

Carb pressure is usually 4-7 psi. Higher end at idle, lower number at full load.

P

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Reply #4 – May 22, 2019, 02:12:49 pm

Thanks to all for the responses.

The fuel gauge does work.  So far, I have been unable to get a good view of the top of the fuel tank and access appears to be impossible.  I shall try to find the wire(s) going to the pump and see if I can trace their route and check their integrity.  I really need to find the origin of the power source when the ignition switch is in START. (I think the Apollo landers had less wires running around them!!)  I also need to find the relay/cut-off switch.

I have read elsewhere about installing a substitute pump in the fuel-line but wondered if that would be able to draw fuel through the original pump if, for example. the original pump was stuck.  (My generator pump stuck once.  It hummed but didn't pump until I released the piston with slight finger pressure.)

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Reply #5 – May 22, 2019, 02:32:24 pm

If indeed there are 2 separate circuits (one with the ignition switch in START and another in RUN) and if the only common denominator is the pump then the pump itself is probably deceased - subject to good grounding.  I wish I could find a relevant wiring diagram!

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Reply #6 – May 22, 2019, 03:47:27 pm

Marty, I too have chased that gremlin, has the motor quit running at idle or spit and spudder say coming to a stop?
The fuel pump on the Oshkosh V814 series OREG (460 Ford) must see a minimum of 20-25psi of oil pressure in order for the power 12v to the fuel pump to be turn on, it's a safety system so if you lose oil pressure going down the road, it shuts off the fuel pump. This had gone on for over 2yrs time, shop time, man hours, towing 3 different times, a few couch bucks indeed.
I made up a jumper wire from the oil sending unit and the fuel pump circuit (on the side of the road) and bypassed the fuel pump shut down system and it's worked fine (starting and running) with the oil pressure under 23psi. I don't have my GV as its in storage with my manuals, I can get the wiring diagram this weekend if need be

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Reply #7 – May 22, 2019, 03:48:30 pm

Have you contacted James Triana at Foretravel.  He may have a print.  If not he may recall how it was wired from memory.

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Reply #8 – May 22, 2019, 04:42:26 pm

Thanks, Travelray.  A wiring diagram would be marvellous!!  I live in my coach and have not moved it since December.  I run the engine every two weeks.  The last time it ran, it started perfectly.  The next time it wouldn't fire at all.  If I am right, the oil pressure switch (and the relay and inertia switch) is only involved once the engine has started.  Some 460s have a mechanical fuel pump as well as an electric one.  In that situation, the mechanical pump is used to start the engine then, once the oil pressure has built up, the oil pressure switch closes, the electrical circuit is completed and the electric pump runs.  From what I have gleaned elsewhere, where there isn't a mechanical pump, there is a direct circuit to the electric pump when the ignition switch is in START, bypassing the oil pressure switch, relay and inertia switch.  This gives full voltage to the pump initially.  The voltage is reduced slightly by the relay when the other circuit cuts in.  The direct circuit is disconnected once the ignition switch returns to RUN.  I could be wrong, of course.

Thank you for the tip, Green99.  I have not contacted Foretravel as yet

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Reply #9 – May 22, 2019, 04:57:26 pm

Marty,  when you crank over the engine, does your oil pressure gauge on the dash move up above 25-45psi

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Reply #10 – May 22, 2019, 06:06:21 pm

No, Travelray, it doesn't and I don't think it ever has.  If you are suggesting that low oil pressure is the problem, I have removed the wiring connector from the oil pressure switch and jumped the wires with the ignition switch in RUN (engine not running, of course) and the pump did not run - or to be more correct, no fuel came out of the (disconnected) inlet hose to the fuel filter. I am doing this on my own so could not actually tell if the pump was making a noise or not.

 I am doing my reasoning on the assumption that, as I wrote earlier, there are 2 separate circuits for the fuel pump - one with the ignition switch in START and another with the ignition switch in RUN.  I got this information from the 1986 Ford EVTM (Electrical & Vacuum Troubleshooting Manual) where it shows a direct line to the pump when the ignition switch is in START.  Unfortunately it does not show where this direct line comes from but does show that it is separate from the relay, inertia switch and oil pressure switch circuit.  I shall try contacting Foretravel tomorrow.

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Reply #11 – May 22, 2019, 06:17:13 pm

Marty, I wish I could remember exactly what I had to go thought to realize that all I needed was a short piece of wire 3in long to get mine up and running, I'll grab my wiring diagram this weekend and get back to you

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Reply #12 – May 22, 2019, 06:18:18 pm

Will it start with some gas down the carburetor?

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Reply #13 – May 22, 2019, 10:17:12 pm

If you want to try something that gets autos going when the fuel pump in the tanks quits, leave the ignition on with the oil pressure switch jumped, bang on the bottom of the fuel tank several times. Auto club drivers are told to have the owner turn on the key and immediately bang on the bottom of the tank to try to get them going.

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Reply #14 – May 22, 2019, 11:16:07 pm

I used to keep a fuel pump relay jumper in glovebox when I owned FI VW's, banging on tank can't hurt. Also  jumper could be used for the radiator fan or other stuff. Techs rely on jumpers. Measure input voltage to a component, check ground path, then jumper it.

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Reply #15 – May 29, 2019, 03:25:01 pm

Travelray,  I was wondering if you had managed to obtain your wiring diagram.  I called Foretravel but they said that I had to pay $95 for annual membership to the owners club before I could get any technical assistance.  I would prefer to avoid that if possible although it may turn out to be necessary and beneficial.

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Reply #16 – May 29, 2019, 03:28:49 pm

Craneman.  Thanks for the tank-banging tip.  I haven't tried it yet but will do so.  I assume that is to try to free a pump that is stuck although I suppose that the pump should still make a noise even when stuck.

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Reply #17 – September 03, 2019, 04:45:58 pm

Marty, did you ever figure out the answers to your questions in this thread? I'm having similar issues with my '92 FE 460 and would love to hear how yours resolved. Thanks!

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