Community Forums

SLC83 · 07-30-2020, 11:57 PM

I'll do my best to keep this short but i'm very confused with this fuel system. I've searched other threads and i'm not finding the answers i'm looking for, so...

I just bought myself this motorhome in hopes of getting it running. The friend I bought it from said it had been running but it had issues getting fuel to the carburetor. He had someone work on it at one point but could never get it running.

I'm having a hard time understanding how this fuel delivery system works. Whoever worked on it previously cut corners and it's a mess. The way it sat when I got it was a newer looking electric fuel pump mounted to the frame that was hooked up to the (about 20 gallon)rear gas tank. The center gas tank was unhooked and the hose crimped so it wasn't even being used. I read that many ford e350's have an in tank electric fuel pump so I dropped the rear tank and it just has a basic fuel sending unit. The large center tank doesn't appear to have the in tank fuel pump either because the fuel runs out of that tank from a line on the bottom corner of the tank (That is the fuel line that is crimped off) There are no fuel lines running to the top of that center tank like there were on the back tank. That center tank is very large, i'd say about 40 gallons. There also is not a mechanical fuel pump on the motor.

I am a pretty novice mechanic so i've had a friend helping me. He determined the electric fuel pump on it now doesn't work so I know i'll need a new one. I have many questions and a lot of work to do but i need to start somewhere. So my first question is:

Can I run the fuel system with one electric frame mounted fuel pump?

I know i'll have more work to do with a tank selector, switches, relays etc. Any advice would be greatly appreciated! Thanks

Waiter21 · 07-31-2020, 07:16 AM

Quote:

Can I run the fuel system with one electric frame mounted fuel pump?

Welcome to the forum.

Yes, two items I'll mention.

1) It MUST be a low pressure pump designed for a carb. I believe these are in the 6psi range.

2) mount the pump as low as safely possible. Ideally, if its lower than the tank this is very good. This allows the pump to gravity prime rather than sucking fuel out of the tank. If the pump needs to suck out of the tank, this increases the risk of vapor lock during hot weather.

If able, you may want to drop the center tank to inspect it.. Someone disabled it, why?? holes, rust, etc, etc,

Sundancer268 · 07-31-2020, 05:00 PM

As stated, I would remove the center tank and inspect it for damage and to see if it has a return fitting on it. If there is a generator, it will probably draw from the center tank so there might be a fitting on the top for that service. I say on the top as the generator normally runs out of fuel when the main tank is drawn down to 1/4 tank so there is fuel left for the main engine so you can get to a gas station to refill. I don't ever recall any carburated engines having a return line to the fuel tanks so a simple selector solenoid placed between the fuel tanks and the pump would work fine. In the 70's, I had fuel problems with carburators and found that installing a fuel pressure regulator at the carb set for 3-4 psi helped prevent flooding when fuel expanded from the high under hood temperatures.

SLC83 · 08-01-2020, 12:52 PM

Ok thanks for the help! My rear tank draws fuel from the top so I’m wondering if I should install an in tank fuel pump like I see on many econoline vans. I’ll post here when I get some work done on it and have some results

SLC83 · 08-01-2020, 12:53 PM

I will make sure to put on a fuel regulator. Also would it make sense to install a mechanical fuel pump on the motor even though this didn’t originally come with one?

Sundancer268 · 08-01-2020, 01:02 PM

If you are only going to use the one tank, you probably could do that, but look at it this way, when the in-tank pump fails, you have to drop the tank to replace it. With an external pump, just pinch off the hose and it is right out in the open. My luck has been for the pump to fail shortly after I have filled up the tank. Also you have to make sure the in tank pump is for a carb engine and not fuel injected. My John Deere tractor with fuel injected Kawasaki engine has a 27 PSI fuel pressure and automobiles run in the 50+ pressure range. If you intend to use the big tank, you will have to install another fuel pump and check valves to prevent the fuel from pumping to the off line tank.

Jim_HiTek · 08-01-2020, 01:04 PM

Quote:

Originally Posted by SLC83

Ok thanks for the help! My rear tank draws fuel from the top so I’m wondering if I should install an in tank fuel pump like I see on many econoline vans. I’ll post here when I get some work done on it and have some results

Not recommended. External pumps are much easier to install. If they are good enough for 10's of thousands of race cars under the harshest of conditions, they'll be good enough for your RV. And they are cheaper. Plus with the external pump you never need to drop the tank. Which is not fun, or inexpensive.

Quote:

Originally Posted by SLC83

I will make sure to put on a fuel regulator. Also would it make sense to install a mechanical fuel pump on the motor even though this didn’t originally come with one?

Err, no, don't think so. Retrofitting an engine with a mechanical pump? Not recommended as they aren't very reliable and your engine had to have been made for one to begin with AFAIK. If you've done this before, how is it done?

SLC83 · 08-06-2020, 10:59 PM

This 460 motor has a spot to mount a mechanical fuel pump. In some applications they used mechanical fuel pumps but because this came with the electric pump they didn’t add a mechanical, just bolted a plate to the block where it could mount. I can’t even imagine what it would be like to try and retrofit a mechanical fuel pump�� I picked up the electric pump now just need to drop the middle gas tank to see what kind of condition it’s in. Hopefully I can do that tomorrow.

Sundancer268 · 08-07-2020, 05:12 AM

Quote:

Originally Posted by SLC83

This 460 motor has a spot to mount a mechanical fuel pump. In some applications they used mechanical fuel pumps but because this came with the electric pump they didn’t add a mechanical, just bolted a plate to the block where it could mount. I can’t even imagine what it would be like to try and retrofit a mechanical fuel pump�� I picked up the electric pump now just need to drop the middle gas tank to see what kind of condition it’s in. Hopefully I can do that tomorrow.

Not sure about the 460, but some engines drove the Mechanical Fuel Pump from an eccentric bolted on the front of the Cam Shaft so if the engine didn't come with the Mechanical Fuel Pump from the factory, they probably didn't install the eccentric to save a few cents on that engine build. To install the eccentric, you would have to remove the Timing Chain Front Cover to access the front of the Cam Shaft. My bet is if the Mechanical Fuel Pump mounting boss is on the front of the engine, the eccentric was required and might not be there.

Sundancer268 · 08-07-2020, 05:23 AM

Quote:

Originally Posted by SLC83

I picked up the electric pump now just need to drop the middle gas tank to see what kind of condition it’s in. Hopefully I can do that tomorrow.

There is a company called Gas Tank Renu

https://www.gastankrenu.com/

that I used to repair the Gas Tank on my small Cabin Cruiser many years ago and it is holding up beautifully. You might have to ship it out for repair, but this would save the tank which might no longer be available. i know my boat tank was no longer available from SeaRay and the original manufacturer of the tank had gone out of business.

leadman · 08-12-2020, 06:51 PM

Don't know for sure about your rig but if it came with an electric pump from the factory it also probably has an oil pressure safety switch so if the engine stalls the pump will shut off. It would be easy to wire in a system like this if your rig doesn't have one.

ZBHRImperial · 08-23-2020, 08:58 AM

Quote:

Originally Posted by SLC83

I'll do my best to keep this short but i'm very confused with this fuel system. I've searched other threads and i'm not finding the answers i'm looking for, so...

I just bought myself this motorhome in hopes of getting it running. The friend I bought it from said it had been running but it had issues getting fuel to the carburetor. He had someone work on it at one point but could never get it running.

I'm having a hard time understanding how this fuel delivery system works. Whoever worked on it previously cut corners and it's a mess. The way it sat when I got it was a newer looking electric fuel pump mounted to the frame that was hooked up to the (about 20 gallon)rear gas tank. The center gas tank was unhooked and the hose crimped so it wasn't even being used. I read that many ford e350's have an in tank electric fuel pump so I dropped the rear tank and it just has a basic fuel sending unit. The large center tank doesn't appear to have the in tank fuel pump either because the fuel runs out of that tank from a line on the bottom corner of the tank (That is the fuel line that is crimped off) There are no fuel lines running to the top of that center tank like there were on the back tank. That center tank is very large, i'd say about 40 gallons. There also is not a mechanical fuel pump on the motor.

I am a pretty novice mechanic so i've had a friend helping me. He determined the electric fuel pump on it now doesn't work so I know i'll need a new one. I have many questions and a lot of work to do but i need to start somewhere. So my first question is:

Can I run the fuel system with one electric frame mounted fuel pump?

I know i'll have more work to do with a tank selector, switches, relays etc. Any advice would be greatly appreciated! Thanks

Fuel filters and change your hoses. That fuel gums up. Also try cleaning your carb with compressed air and carb cleaner. I had a similar issue.