Hello and thanks in advance for any help. I have an 85 E350 with 460 (Jayco MH) that was given to me. The motor home has all kinds of ‘band aids’ and duck tape type of fixes…put another way, one of the previous owners probably had stock in JB Weld.
It ran fine last year but, after stupidly letting a friend borrow it for a trip, it is having issues. I drove it and it seemed normal at first, on flat back roads. I got it on the highway and at 40 MPH, it would loose all power. Let off the gas, apply it and it would give me some power, then cut out. It did the same thing on a hill but at 5-10MPH. If I tried to give it open throttle it would bog out immediately, 1/3 - 1/2 throttle and it would manage. It would do this regardless of which tank I selected (it has dual tanks).
I rebuilt the carb and connected all the vacuum lines appropriately, took it for a drive and same thing. My buddy drove it and he thinks the bowls are not getting enough fuel because it can only stay wide open for so long before bogging out (both the primary and secondary do this).
So I decided to look at the fuel system, but my Haynes manual does not go into hardly any detail regarding my fuel system (chasing the lines and reading earlier posts, I have the dual electric in-tank pumps with hot return).
What should the fuel pressure be and where do I check it? I checked it at the generator (there is a 't' after the selector on the supply line that feeds the generator) while running, and my gauge did not register anything (it is a 0-200psi gauge, I am going out to get a lower gauge), although there was definitely flow and pressure there...I would guess around 5psi.
The other question I have is regarding the vapor separator, if that is indeed what I am looking at. It is a brass 't' looking fitting, just before the carb and has the supply and return lines coming into it as well. How does it function?
Basically, if you have any thoughts regarding my situation, any help would be much appreciated. Am I even on the right track?
Thanks again.

 

> I would guess around 5psi.

5-7 is normal for a carb.

The first thing to do is check the vacuum at idle (18 hg) and WOT ( near 0). Then while driving.

What I did for a boat with two motors that had a lag problem, I had the owner drive at various speeds while I watched the vac. gauge, rpms, and throttle. By adjusting the carb and dist. I was able to get anothr 4mph out of the motors.

Everyone (like his previous "mechanic") always assumes the carb is bad or has a fuel pump issue. On a carb. motor you should always start with the vac. gauge (imho) before you start messing around with anything else.

Now, on your setup if the vac. is decent, I would look at the spark module and then make sure I have good voltage under load. RVs have a ton of toys and the battery can get weak, under WOT you might not have enough juice for a good spark.

 

To start with you can not check the fuel pressure at the generator, the generator has its own electric fuel pump and its fuel source only goes 2/3 the way down in the fuel tank.

The vapor separator (AKA hot fuel bypass) work with a small hole sending fuel to the supplying tank. They come with three different size holes depending on the need.

Try changing your fuel filter.

Your fuel system:

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Try changing the ignition module. A friend suggested this to me after I went through the same problems you describe. I thought the modules either worked or not. I had changed to an Edelbrock 750 and thought I had the problem solved. Wrong! The ignition module got me again. My problem was that the motohome never quit, it just acted like the thing was starving for fuel. Anyway, the module is cheap enough to experiment with it. My motorhome was a 1987 E350 460 carb. Hope this helps. After that module change no problems for years, till it caught fire underhood. But that's a whole different tale.

 

I notice this is an old thread but I have a similar issue I think. I lent my motor home to my sister and they called me broke down and I had to tow it home. Anyway, Its an 86 country squire with a 460. Before i lent it out it had chugged a couple times while on the road I thought nothing much of it because it came right back and we were able to finish our trip without any problems I just thought it was a slug of air or something because it was low on that tank. ANYWAY, after I towed it home I was checking the fuel tank selector valve and the relay, it has electric pumps in both tanks, I ended up pulling all the lines off the selector and splicing them direct and also jumping the relay direct just to get it moved. NOW.... I cannot find the correct replacement selector valve and I have no ideas what else to do. I seen another post that said that that had nothing to do with the fuel but i thought that is what actually controlled the pumps. PLEASE HELP!!! any suggestions.

P>S> now I cant get it running even with the jumped relay.

 

Its a motorized fuel tank selector valve and it also switches the fuel gauge on the dash to the tank the switch on the dash is set to.

You did not say but I am guessing it is not getting fuel to the Carburetor now.
Do the pumps run?
Try bypassing the oil switch and turning on the key. The selected fuel pump should run and you should be able to here it if under the tank or have your ear to the fuel filler tube.





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9 times out of 10 the problem you're describing with a motorhome is junk in the fuel tank and fuel lines from sitting for extended periods of time. More than likely it ran until the fuel filter became so clogged it quit.