Community Forums

hdtrain1450 · 07-27-2008, 05:37 PM

I own a 1990 ford motorhome which is powered by a 460 / 5.7 gas motor which is a carb motor with a electronic fuel pump. Well i was driving for about 80 miles and then when i came off the exit ramp my motorhome shut off because of lack of fuel.. I checked everything and it seemed ok but i took the air cleaner off and found that i still was not getting any fuel while trying to start. Well i sat there for about 15 mins till it started back up and another time that it happened it took 2 hrs to get started and then i got fuel and then it ran great like it always does it runs like nothing ever happened.. I replaced my fuel filters and fuel cap so they are new. Is my Fuel pump starting to fail? did it vapor lock becuase it was hot out? Is my Ignition module bad? do i need to relpace my wiring? Is a relay shutting me down?These are all questions that i ask myself and truley the iring looks good so i limited that factor out Please help !!
2 days ago - 1 day left to answer.

hdtrain1450 · 07-27-2008, 05:37 PM

I own a 1990 ford motorhome which is powered by a 460 / 5.7 gas motor which is a carb motor with a electronic fuel pump. Well i was driving for about 80 miles and then when i came off the exit ramp my motorhome shut off because of lack of fuel.. I checked everything and it seemed ok but i took the air cleaner off and found that i still was not getting any fuel while trying to start. Well i sat there for about 15 mins till it started back up and another time that it happened it took 2 hrs to get started and then i got fuel and then it ran great like it always does it runs like nothing ever happened.. I replaced my fuel filters and fuel cap so they are new. Is my Fuel pump starting to fail? did it vapor lock becuase it was hot out? Is my Ignition module bad? do i need to relpace my wiring? Is a relay shutting me down?These are all questions that i ask myself and truley the iring looks good so i limited that factor out Please help !!
2 days ago - 1 day left to answer.

LVJ58 · 07-27-2008, 06:40 PM

you must have an unusual setup on your 460 as most I'm familiar with had port fuel injection. If it has an electric in-tank fuel pump, they were notorious for failing in the older Ford products. I would check that first and probably replace it.

NeilV · 07-28-2008, 12:25 AM

Your bowl vent valve should prevent vapour lock if it is opening correctly and that is usually a verified with a visual check. Float valve sticking is another possibility which can many times be cleared up with some Gumout or Seafoam carb cleaner.

If you were taking a hard corner when it happened then it would more than likely be float related and need a good carborator cleaning and possibly a float adjustment.

How long has the rig been in your care? After 18 years it probably has a lot of sludge in the bowl of the carb if it has not seen regular care and has sat idle for a while.

hdtrain1450 · 07-28-2008, 04:33 AM

My setup is the fuel pump is mounted directly outside the fuel tank. This is the way that they are if you have a carb if it were a FI model yes it would be in the tank. I am still trying to figure out what is wrong. Also both days that this happened were 90 degrees plus outside. If my carbs bowl was not working proplerly wouldn't my idel be rough and i wouldn't have no power. It's a 34 ft motorhome which in return i 18500 lbs but with all the stuff my wife has loded in her it probally now 20,000lbs.

Freebie · 07-28-2008, 04:42 AM

it sounds like the fuel filter. Sometimes you can get small bits of dirt in the filter and it will run fine for a while then all that dirt collects on the outlet side and stops the fuel flow. after some time setting it settle back down and starts over. if you have a carb You should have a mechanical fuel pump but it is possible. Usually those are for the Thottlebody units. I am not sure but around 89-91 they started changing from the carbs to the TBI. Typically the in tank pumps have too much pressure for a carb because they shoot out any where from 35-50 psi.

Hope that helps.

LVJ58 · 07-28-2008, 08:53 AM

What brand carb does it have, also if you have an electric fuel pump externally mounted, you shouldn't be getting a vapor lock. Is there anyway you can disconnect the fuel line and check the fuel pressure from the pump? You should be getting 4 to 7lbs pressure.

If everything checks ok, check your wiring connections to the fuel pump.

hdtrain1450 · 07-28-2008, 06:13 PM

I think it is a holley but not 100 %. Yes i have a electric fuel pump mounted just outside the tank. I will check my fuel pressure this weekend. I am also going to replace the pump with a holley just for good measure and go over the hole wiring for corrosion or a knicked wire also. But i am almost certain that the pump has lost it's mo-jo. She only has 36,000 and was very well maintained. I know u had said about the carb but she works smoothly. Thanks

LVJ58 · 07-28-2008, 07:26 PM

Good luck, and let us know the final outcome.

Jim

jrcnlc · 07-29-2008, 02:51 AM

There usally is a filter where fuel line attaches to carb 1 inch nut usally ceramic or paper.there also might be an in line filter between tank an carb.Also on 460 there was a fix for vapor lock that involves cutting fuel line at carb leaving enough line to attach fuel hose then get 10 inches fuel line an make loop between cut line an carb .Use fuel injection type hose an clamp good.I think its 5/16 line.also pay up fire insurance.

Forest Grump · 08-05-2008, 12:20 PM

The 460 is 7.5 liter.

Orvil Hazelton · 08-07-2008, 06:22 AM

I also have a Ford 7.5L 460 engine. I would suggest checking for vapor lock caused by fuel lines routed too closely to the exhaust system. If you find fuel lines routed in this manner, try shielding or moving it fromthe source of heat. By the way, my 460 is naturally asperated with a Holly 4bbl carb in a 1984 model. Hope to have helped, oRV

jmerritt · 08-07-2008, 06:55 AM

If and when you have this problem you can disconnect the fuel line from the carb to see if you are getting fuel to the carb which will narrow things down a bit. If no fuel to the carb then suspect the pump or filters. If gas to the carb then suspect vapor lock or a sticking needle and seat at the float. As was mentioned in another post, if the MH has set without running during the winter and no gas treatment, varnish may be present in the fuel bowl and some of it has come loose and is gumming up the needle and seat. You have a 4180 Holley with an electric pump on the frame next to the tank. I have an 88 MH with the same setup. Curious though that you have a 90 MH with a 87 Ford setup since the 87 was the last year for the carbed version and the intro of the FI. MH builder must have had a few 87 Ford chassis in inventory.

John

hdtrain1450 · 08-08-2008, 06:40 PM

I have fixed the problem it think. I replaced the original fuel pump with a Holley Blue, and also put a holley pressure reg and set it at 7.25 psi. Also went through the relays and put a bosch style setup it it with a 30/40 amp relay. I took it for a 80 mile ride and she ran great. I have always out stabil in my fuel during storage and i start it up every 2 weeks for about 10 mins. My MH is a 90 in my manual there was a option for Fi and this was was the last year for the carb on this motor. My Mh is a Osh /John deere chasis if that helps. Thanks alot