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 > Ford 460 fuel pump

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Old Rockwood

Montana

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Posted: 09/14/10 08:58pm Link  |  Print  |  Notify Moderator

I have read in other forums about the Ford use of an oil pressure switch to energize the electric fuel pump. I believe there is also an engine driven fuel pump. This week we took a "shakedown" trip with our "new" '83 Rockwood. 5 miles from destination the engine started starving. It would restart but only run about a minute before starving out gain. Fuel filter was fine. Ended up the hot wire to the pump was breaking or shorting. Couldn't trace the line in the dark after it runs into a large bundle but assume it runs to the pressure switch. Never know on this one. There are disconnected vacuum lines and an aftermarket carburetor (I discovered). We temporarily ran a new line directly from a keyed output at the fusebox to the pump and got to camp and home again. Any others with similar issue and insight?

T18skyguy

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Posted: 09/14/10 09:41pm Link  |  Print  |  Notify Moderator

Rock your probably going to be wrenching a lot more on an 83. When they get that old the insulation on the wiring gets brittle and starts breaking and flaking off. Make sure there are no vacuum leaks into the engine. Probably a few of the disconnected lines are smog stuff but are there any other problems that are vacuum related? I don't know about the pressure switch but there must be somebody on the forum with a model like yours. Put up a post like " Anybody have an 83..." and you'll find some good help. Good luck


Retired Anesthetist. Pilot with mechanic/inspection ratings.1996 Jayco C 22 foot with 460/Banks Powerpak/Bilsteins.Wife and daughter. Two cats which control my life. 1975 Ford F-250, 84 Coupe Deville, Thorp T18, tons of tools and tons of junk.

j-d

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Posted: 09/15/10 09:29am Link  |  Print  |  Notify Moderator

If your 83 coach is actually on an 83 Ford E350 chassis with 460 engine and two gas tanks, we had one. It was under an 84 coach which is why I ask about chassis year. You can get that by VIN or Ford sticker in the door frame.
On ours:
1. No engine-mounted mechanical pump
2. One electric pump in each tank
3. A calibrated "Y" right near the carb that fed back to a return line
4. Six-port tank electric select valve on chassis rail near driver's door
5. Ports were 2 fuel and 2 returns from/to the two tanks, and 1 fuel and 1 return leading to the engine
6. Wiring inside driver side fender leads to a bracket with two relays that control fuel pump action
7. Starter solenoid in passenger side fender has a terminal that powers whichever pump is selected at the dash switch while the engine is cranking. This bypasses the oil pressure safety switch on the rear of the engine.
8. If an in-tank pump turns out to be bad, you can leave it in place and install and inline aftermarket pump. It'll pull fuel through the dead pump. This does NOT work with later EFI systems!
9. Many aftermarket carbs aren't rated for motorhome use. Check this out on the Holley site
10. An OP here posted the fuel pump wiring diagram. I'll try to find it and post it here.
11. I found a resistance wire in the harness I mentioned in (6.) above, when it burned out and the engine quit. I bypassed all that and ran the fuel pumps from by powering the lead at the solenoid from the fuel pump fuse in the panel by the steering column inside. It worked but probably wasn't a good idea since the safety switch was bypassed and the pumps always ran at full voltage instead of the lower voltage provided through the resistance wire.
12. BE CAREFUL!!! A friend flooded his engine with gas trying to rig this exact system. Badly burned on both arms from resulting engine compartment fire that also damaged most of the in-dash components. Would've been worse if his daughter hadn't run out with an extinguisher after seeing him rolling on the ground.


If God's Your Co-Pilot Move Over, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100 218" WB

j-d

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Posted: 09/15/10 09:39am Link  |  Print  |  Notify Moderator

Fuel Problem Thread

Look all this over. I think the diagram will come up on Page 8 and the link should open to Page 8. But right click that diagram and "save as" so you can store it for future reference. All I had till subford posted the diagram was a Haynes Ford Van manual. It was good in general, but did not go into the pump wiring in this detail.

Old Rockwood

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Posted: 09/16/10 01:53pm Link  |  Print  |  Notify Moderator

Thanks j-d. I think I already read your thread and printed out some parts. I didn't see a diagram but will look again. On our RV there is only one tank I know of unless it is a single fill double. I have used more than 20 gallons at one time so don't think I have a problem there. The only pump I know of is the chassis mounted one. It may even be aftermnarket. I'll be working on it today.

Old Rockwood

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Posted: 09/16/10 10:07pm Link  |  Print  |  Notify Moderator

j-d
I read thru the whole thread again and picked up a few things but could use some clarification.
You guys did an awesome job of guiding James.
I need to run a more proper hot lead to the pump. I have the Hanes book and it has a pretty good diagram for the '81-'84 7,5L engines. It seems to resemble mine. It shows leads for single or double tanks so apparently either was an option. In the diagram the hot lead runs from somewhere hot through a fusable link to the inertia switch to fuel relay to pump. The pump relay is energized by a circuit from the fuse box thru the oil pressure switch. Somehow the throttle position solenoid is also involved in this circuit. Pretty simple. Except I don't know where the inertia switch or pump relay are or what they look like. I found the oil press. sw. I would like to run the new wire up to the output of the pump relay where it belongs. It is now obvious that the fuel pump is an aftermarket install. The hot lead was just "T"d off a wire running aft from who knows where. I'd better check fuses per the other thread also.
Also, in the other thread, it sounds like James' starter battery is on the passenger side. Mine appears to be on the drivers side. I found one small square "element" next to the drivers side battery that has a wire running from it to a fusable link and the same color wire as described in the wire diagram but haven't been able to trace it out. Lots of taped bundles.
Don S.
I have accounted for most vacuum lines and have no vacuum issues. I expect some are emmissions related or are for the Holly carburetor. Mine has an aftermarket Edelbrock installed. The air pump and who knows what elso have been removed

j-d

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Posted: 09/16/10 10:51pm Link  |  Print  |  Notify Moderator

I'd never seen an 83-84 or so that wasn't two tanks, so I figured the single tank was some of the vans, not the dually cutaway E350. But Grillmeister's RV has one filler to two 44-gal tanks connected by a 1" pipe. So his tanks serve as one 88-gal tank.
Our 83 chassis had the battery passenger side, right next to to the starter relay/solenoid. There were two fuel-related relays inside the driver fender. I used to pull the blue wire off the relay/solenoid and touch it to the positive battery terminal bolt to run a fuel pump and prime the carburetor. I could hear both pump and fuel flow.
Anyhow, looking at subford's diagram, it seems a single-tanked vehicle would have the Fuel Pump Cutoff Relay, but not the Tank Select Switch, Relay, or Valve.
Sorry to say, but I never found the Inertia Switch. I know it wasn't in the common location in the passenger side kick panel, and I think I also pulled the driver side kick panel looking for it too. Maybe somebody'll jump in with the location.
It seems to me that what you need is the priming circuit shown on the stater solenoid/relay, but applying battery 12V in RUN, through a fuse or breaker, using a momentary contact switch. I'm not sure what the diode did, perhaps Ford wanted to be sure that the engine going to RUN couldn't engergize the solenoid.
Then it seems you need at least a fuel pump relay, energized through the oil pressure switch (and inertia switch if you can find it...) sending 12V to the pump, again protected by fuse or breaker. If you disconnect the prime circuit by unplugging from the starter solenoid/relay, and pull the fuel pump fuse, I think all the OEM system will be dead. You could plug your wiring into the hot side of the fuel pump fuse cavity and go from there with fuses or breakers to your own prime switch and pump relay circuits.
You could get tricky and use a double-pole momentary switch. It would bypass the oil pressure switch when it powered the pump relay in prime mode. When you released the switch, the power would flow through the oil pressure switch. At least I can picture that. I'd have to try and draw it out to see if I'm missing something. The benefit would be that the ignition switch never carries the fuel pump load, whether in prime or run. Radio Shack offers a relay that'll do the job

I can only speculate that the OEM electric fuel pump was designed to run on less than the 14V or so that the electrical system runs at, and the resistance wire accomplished that drop. But since the starter pulls voltage way down, Ford tried to apply all available voltage to the pump in start mode.
If you're running an aftermarket pump, it may be intended to run at operating voltage without a resistor drop. In that case you don't need the resistor.
If I'm right about the diode (I never found that in ours either...) being there to avoid backfeeding the starter solenoid, you don't need that also, since you're no longer connecting to that terminal.
If you want to run all your own wiring, I'll pass two comments:
1. From a friend in the auto electric business - Study the diagrams, understand the functions, then run the wires you need to accomplish the results. Bypass the OEM wiring, don't try to decipher it.
2. From an uncle retired from the auto electric business - Many electrical problems result from non-OEM wiring because it isn't as well protected, gets rubbed, pinched, snagged, etc.
So, seems you can do it, but be thorough and careful.

* This post was edited 09/16/10 11:01pm by j-d *

Old Rockwood

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Posted: 09/17/10 04:04pm Link  |  Print  |  Notify Moderator

Thanks John. Right now I think I just need to find the fuel pump relay. Is that the solenoid on the fender by the battery? I'll just connect the pump to that just as in the Hanes wire diagram. I'll work on mods later.

My generator starter is also connected to the battery on the driver side. I assumed that it was the same as the engine start battery but maybe the gen starts from the house battery. If so I think I have the fuel pump relay found. maybe I'll just disconnect a blue wire and tery it!

j-d

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Posted: 09/17/10 04:28pm Link  |  Print  |  Notify Moderator

In our case, chassis battery and starter solenoid were passenger side. Driver side had a large open space and it was easy to see a bracket with two relays on it. Since you have one tank, you wouldn't have a tank select relay, only a fuel pump relay. Logically, you'd see one relay where I saw two, inside driver side fender. Our house battery cranked the generator but it was in the driver side of the house body, behind the driver's compartment.

Old Rockwood

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Posted: 09/18/10 02:54pm Link  |  Print  |  Notify Moderator

Got it!! I think. Following the Hanes diagram and other info from here I actually found the inertia switch on the passenger kick panel and followed wires to the solenoid on the driver front fender. All wires made sense by the diagram. I found the keyed terminal of the solenoid which, wonder-of-wonders, had a wire terminal still connected to it where the wire had been cut. The temporary wire we had run directly to the fuse box almost reached to this location. I added a little and connected. Starts great. I'll take a test drive in a bit. I have not had the hard start problem so may hold off onb the low pressure bypass switch. Haven't had the test of a hot summer day yet.

Only curiosity now is that the pump runs in start position AND in the acc. position. Now if I want to play the radio I get the fuel pump hammering in the background. With the way this thing has been modified its probably a switch wiring problem. The owners manual says the acc. position turns on all electrical systems but the ignition. A lesser problem for sure.

BTW I can try to scan the wire diagram if anyone needs it. Hanes says it is only for the '81 to '84 7.5L.

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