1992 Fleetwood Bounder 460 7.5l loss of fuel pressure

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Weber1429

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Jun 24, 2017
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4
Hi all,

I have been a guest viewing information here and other sites for about a year now.  I purchased a used 92 fleetwood Bounder a year ago and still have yet to be able to use it.  It will idle fine and drive for about 45 minutes before it will lose fuel pressure and not be able to accelerate.  This will be a long post because I am going to outline everything that has already been done.  First of all I had the transmission rebuilt because it ran in safety mode for quite some time due to some connections not being hooked up properly.  It would overheat and spew transfer fluid everywhere.  That competed it seemed all was ok.  First test drive went about an hour before the engine began to sputter and lose power.  At idle it will have 30 psi of fuel pressure.  Once hot though when the gas pedal is pressed, the pressure will drop to about 10 psi.  Her eis the laundry list of what has been done: fuel tank dropped and cleaned, new fuel pump, a secondary pump placed inline, fuel filter replaced, new temperature sensors, new map sensor, new throttle position sensor, new injectors, new batteries, new fuel regulator.  It will still idle fine all day, but after about an hour it will lose fuel pressure when pressing the accelerator.  Myself and my mechanic are at a loss.  Any help would be greatly appreciated.
 
First off I would get rid of the secondary fuel pump. Not needed. If the primary fuel pump is working correctly and there are no restrictions in the fuel line, you should have about 32# of pressure at idle and about 40# of pressure at wide open throttle, while under load. I run a stroker 460/528 in my 95 Bounder with only factory fuel pump. Could it be that there is a high resistance connection some where, and the in tank fuel pump is not receiving the proper voltage? Could it be the replacement in tank fuel pump is a Asian knock off? The second generation OEM Ford in tank fuel pump is a good product. Maybe checking the fuel lines with air pressures would point out a problem. It really can't be that difficult.

Richard
 
Thanks for the reply Richard.

The in tank fuel pump is one of the OEM Ford Motorcrafts and is actually a second one tried.  The voltage is good at idle.  Planning on checking it at WOT as well as a full inspection of the fuel line end to end.  My mechanic supposedly did that already, but you just never know.  The fuel rail itself looks extremely rusty in spots, but does not appear to be leaking.  At idle I barely reach 30 psi.  It does rise to about 38 psi at WOT when engine is cold.  If I remove the vacuum off the regulator it goes up to about 38 psi. 

Dan
 
You might consider insulating your fuel line as that can be a source of vapor lock.

Just my two cents.  Those engines were known for having fuel starvation problems.
 
They only had fuel starvation problems with the geo rotor fuel pumps and he's past that. I second the " get rid of the secondary pump". At least bypass it and check fuel pressure.
 
Obviously the 2nd fuel pump didn't solve the problem and is unnecessary, but I see no harm in leaving it in place. The problem seems to occur after driving and the engine heats up. Unless that 2nd pump is the heat sensitive component, what harm is it?

Agree with HueyPilot's notion - it sounds a lot like a fuel line vapor lock condition due to external heat. Insulating fuel lines in the vicinity of exhaust pipes and the engine isn't difficult or expensive and might just turn the trick. Seems worth a try, anyway.
 
Vapor lock is pretty much a thing of the past, with pressurized fuel lines. The higher the pressure the higher the boiling point. At 30# of fuel pressure it's a non issue. Also the fuel in your lines is constantly being recirculated. EFI fuel pressure regulators return the excess fuel back to the tank. This recirculation keeps the lines cool along with the fuel. Not like the "good old days" when fuel was being sucked from the tank, and allowed to lay stagnant in the lines.
The more I think about your problem, the more I'm inclined to think you have a high resistance circuit, in the fuel pump feed, that offers more resistance over time. Here's a quick and easy try. In front of the fire wall is a Ford OEM fuse box. In that box is the fuel pump relay, Swap it with one of the other relays. Look on inside of cover for device print. Or maybe the crash/kill switch on the left side of the steering column mount is offering high resistance. It has a set of contacts that can fail.
Also, on IRV2 is a guy called "subford". He is the most knowledgeable person around, when it comes to old style 460/E40d F53s. He has wiring prints, that he shares and his advice is golden.

Richard

 
Thanks again Richard for your ideas.  I have done so many things that I forgot to mention I had already tried a new pump relay with the same results.  I have read a lot of "subfords" posts on IRV2 I guess I need to signup there too and get his thoughts on my problem.

In my search for the Kill/shutoff switch,which I can't seem to find, I noticed something else.  It seems the previous owner had a ton of dielectric grease he wanted to get rid of.  I say this because i found all of my multipin connectors under the dash are covered in it, inside and out.  I think I will be spending some time cleaning them all. 

Dan
 
What happens if you leave the fuel cap loose?  If there's a problem in the tank vent system you could be pulling a vacuum in the tank after it's driven for a while, which will reduce fuel flow.
 
Lou Schneider said:
What happens if you leave the fuel cap loose?  If there's a problem in the tank vent system you could be pulling a vacuum in the tank after it's driven for a while, which will reduce fuel flow.
Very good idea Lou. I too think you should remove the secondary pump, all it's doing is causing a restriction, much harder to push fuel through it. I would be looking at the regulator, if it's possible to temporarily plug the return line to see how much pressure it maintains that way.

If it were mine I'd start from scratch again. Change the fuel filter. Remove the secondary pump, remove the fuel cap, run a jumper wire directly to the fuel pump to make sure it's getting a full 12 volts. Plug the return line so it don't bleed of too much pressure.  If still having problems check the gpm of the pump, by pulling the fuel line put it in a gallon jug and see just how long it takes to fill the jug. It is possible to have a collapsed fuel line.
 
Understand that the term "vapor lock" doesn't really apply to pressurized lines, but boiling fuel is still a possibility and has been known to happen with some of the older coaches with 460's. RV makers tend to enclose the engine all too well and they don't have the vehicle engineering skills to make sure the airflow over & through the engine is adequate.

Since it is a '92, I'm guessing this is throttle body injection rather than multi-point?
 
Gary RV_Wizard said:
Understand that the term "vapor lock" doesn't really apply to pressurized lines, but boiling fuel is still a possibility and has been known to happen with some of the older coaches with 460's. RV makers tend to enclose the engine all too well and they don't have the vehicle engineering skills to make sure the airflow over & through the engine is adequate.

Since it is a '92, I'm guessing this is throttle body injection rather than multi-point?

Gary,
Just so you know, Ford did not make a throttle body 460. All EFI 460s have been port injection since 1988. Ford was way ahead of Chevy in this department.
I'll buy your next steak dinner is you can document a 460 F53, with proper fuel pressure, that has vapor locked or boiled fuel. It just doesn't happen with recirculating fuel systems at pressure.
And while were on the subject of heat. The OEM radiator is more than adequate. I'm running a 528 stroker with no cooling system mods.


Richard
 
Thank you all for the great ideas.

I have tried removing the gas cap.  No change.

I did a visual inspection of the lines and there is no evidence of a pinched or collapsed line.

What is the easiest way to provide direct 12 volt power to the pump?  Can I just remove the Pump Relay and then run a line from battery to the pump for testing?  Then properly do it with a switch and fuse if it fixes my issue?

I will try removing the secondary pump since it did not fix the issue.

I will also try testing the gpm. 

Dan
 
"What is the easiest way to provide direct 12 volt power to the pump?"

I would probably turn on the tail lights and tap the fuel pump in to the tail lights. Both wiring looms run close to each other on the left frame rail.
Or you could pull a lead from the battery control center, all the way back. Think fuse.  ;)
Is your water pump and Intellitec controller in the rear of your coach? There is a fairly large +  wire connected to the controller. Tap in to it.

So many failures, so little time. I need a nap.  ;D
Richard
 
Gary RV_Wizard said:
Understand that the term "vapor lock" doesn't really apply to pressurized lines, but boiling fuel is still a possibility and has been known to happen with some of the older coaches with 460's. RV makers tend to enclose the engine all too well and they don't have the vehicle engineering skills to make sure the airflow over & through the engine is adequate.

Since it is a '92, I'm guessing this is throttle body injection rather than multi-point?

Gary, Richard's statement is spot on, the EFI 460 had port fuel injection from the get-go in 1988.  It is however a bank fired system, not sequential EFI.
1996-1997 460's have sequential injection in the F series pickups with California or Massachusetts emissions package, but NOT on the F53 chassis

Weber1429 should definitely post on IRV2 and hopefully get Subford to post a solution!  I really believe there is no question regarding the 460/E4OD that he can't diagnose lol
 
Well, I know of one subford missed recently. Fellows E4OD was shifting hard and OD light blinking. Problem would go away on restart, then intermittently return, and remain until key off. Everyone was focused on trannny. I was lurking over there and knew answer to problem. Ignition module. TFI. Went through it with mine. Almost pulled tranny before figuring it out. Started to sign up to forum to help the guy out, but it's like joining the CIA to join that forum.
 
Hi Weber1429. I know this is a year-old discussion... Did you ever determine the cause/fault of this problem? I see exactly the same symptoms on my 1990 class c. Same engine, etc. Seems the significant issue here is the problem only occurring after 30 to 60 minutes or so (after engine is hot, often only at highway speed and temperature). I always can restart the engine, and get full throttle response, after an hour cool-down. Engine never indicates excessive temperature. Of course, 30 to 60 minutes later, here we go again. Iwould love to know what finally resolved your issue... and maybe mine. Thanks.
 
Thanks Old Crow. Yeah, ignition control module was our first suspicion. However, it tested good. Nevertheless, I replaced it since it was so old. Sadly, the problem persists to this day. REALLY frustrating. I find references to this same problem all over the internet, but no one ever seems to tell what finally resolves the problem. Thanks again.
 

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