Workhorse 8.1 and Stalling...dealing with a real problem

[benge1]

after reading several post about heat is getting to the fuel line I remembered that the several times that has happened to me was always in the afternoon after driving all morning.

[Arch Hoagland]

Originally Posted by ktoutoor

About the temperature. when I was troubles shooting mine I attached a remote thermometer to my fuel line where it runs next to the muffler and i was getting 145 degrees on flat ground. But after i insulated it i had no more trouble.

What was the temperature AFTER you insulated it?

[ktoutoor]

On a hot day around 120

[Full.Monte]

Originally Posted by ktoutoor

On a hot day around 120

From 145 degrees down to 120 degrees on the fuel line temperature is significant. Good work!

[Full.Monte]

In this thread, we have discussed, among other things, the purpose of the fuel canister. We conjectured that the original designers might have dumped the return line fuel into the canister to cool the fuel pump. I just stumbled on a data sheet from Delphi that suggests that the "large fuel reservoir maintains sufficient fuel in low fuel situations and vehicle cornering".

More Information for DELPHI FG0061

This is something we haven't discussed, but it makes sense. With a tank the "size of a Mini Cooper" (according to a previous poster), and a vehicle going up and down hills and around corners, the gasoline can move around in the tank and possibly allow the fuel pickup to suck air. So, I am concluding that drilling "ventilation holes" in the pump canister could facilitate fuel pump cavitation. But people who have drilled such holes have universally claimed that the vapor lock situation improved. And since most of us don't drive our RVs like sports cars, maybe the cavitation problem is a lot less likely than the possibility of vapor lock due to overheated fuel.

[M&EM]

FM,
Very possible!
Ascending a long steep grade with a low enough level of gas, a dry canister might occur. Vapor may get pumped into the fuel rail as pressure falls with resultant misfires until the vapors are displaced with liquid fuel and flushed thru the return line. The pump will move about 1/2 to 2/3 gallon per minute, so it wouldn't take long to empty a canister with drain holes low on the sides and return fuel diverted else where in the tank.

Regarding cavitation /vapor lock, I believe these may be one and the same in a high pressure in tank pump system. It would occur at the suction end of the pump as cavitation.

Vapors that do get into the high side of the system would probably re condense at the 60 psi level unless temperatures got extremely high aka vapor lock.

[Firebug5]

Originally Posted by M&EM

FM,
Very possible!
Ascending a long steep grade with a low enough level of gas, a dry canister might occur. Vapor may get pumped into the fuel rail as pressure falls with resultant misfires until the vapors are displaced with liquid fuel and flushed thru the return line. The pump will move about 1/2 to 2/3 gallon per minute, so it wouldn't take long to empty a canister with drain holes low on the sides and return fuel diverted else where in the tank.

Regarding cavitation /vapor lock, I believe these may be one and the same in a high pressure in tank pump system. It would occur at the suction end of the pump as cavitation.

Vapors that do get into the high side of the system would probably re condense at the 60 psi level unless temperatures got extremely high aka vapor lock.

OK, bear with me guys! We have talked a little about the gas cap myth, yet both times my Dolphin stalled, I was going up a steep grade at the end of the travel day, so fuel tank was between 1/3-1/2. Outside temps were in the 90's, high barometric pressure, you know the drill. After barely making it to the shoulder, shut her down, remove the locking gas cap to a huge "whooooosh" that blew my hair! After a few minutes, start her up, and away we went. Both times this happened as we were near the top of the pass, so no problems going downhill and into camp. Did the locking gas cap have anything to do with building up the pressure just mentioned by M&EM? Thanks again for your patience with my myth.

Bruce

[M&EM]

Bruce, I was alluding to the thread above regarding certain modifications made to the pump canister and return line to the tank.

In any event I believe the inside of the tank should be at slightly negative pressure if the cap and vapor recovery system is functioning properly.

[Firebug5]

Originally Posted by M&EM

Bruce, I was alluding to the thread above regarding certain modifications made to the pump canister and return line to the tank.

In any event I believe the inside of the tank should be at slightly negative pressure if the cap and vapor recovery system is functioning properly.

.

So the release of pressure when I remove the "newer" locking gas cap is not what you want, correct? I should preface this by saying I used to have the original non-locking gas cap, but replaced it with a locking one once they became available. I have read info that the new locking caps do not allow air to enter the tank, like the non-locking caps did. Kinda makes sense now, I just wish I could find the non-locking cap. . .

I do agree with Full Monte that we are looking at several causes.

Bruce

[Full.Monte]

The fuel tank is designed to operate at a vacuum. At first, I thought the Whoosh sound was pressure, but it was vacuum. I also tried three different gas caps, and the vapor lock problem happened with any cap and with the cap off.

[Basegasket]

This is something we haven't discussed, but it makes sense. With a tank the "size of a Mini Cooper" (according to a previous poster), and a vehicle going up and down hills and around corners, the gasoline can move around in the tank and possibly allow the fuel pickup to suck air. So, I am concluding that drilling "ventilation holes" in the pump canister could facilitate fuel pump cavitation. But people who have drilled such holes have universally claimed that the vapor lock situation improved. And since most of us don't drive our RVs like sports cars, maybe the cavitation problem is a lot less likely than the possibility of vapor lock due to overheated fuel.[/QUOTE]

Very good point. I never thought about that. I should never let it get low on fuel, because what you have pointed out could be a real problem!

[Full.Monte]

I just bumped into this interesting video on this forum. If you want to know what's going on with your fuel system, this seems like a really good solution.

http://www.irv2.com/forums/f22/dash-...ec-226095.html

[Full.Monte]

Just to let you guys know, since I made the modifications described in this thread, we have had not one single incident of the RV stalling like was happening before. To recap: my theory was that the stalling was due to vapor lock. Also, I assumed that the fuel return was dumping unused gasoline that was heated by the engine into the fuel pump sump bucket. This caused the pump to pick up hot gasoline, creating a possible vapor lock situation. By re-routing the return line to dump the heated gasoline into the gas tank rather than the fuel pump sump, the gasoline was cooled before it reached the fuel pump again. The results seem to validate my theory. Not. One. Single. Stalling incident. Since then. None. If you are having this problem, your life is in danger and if you don't fix it, you are also endangering the lives of other people. I had a couple close calls before I figured this out. Be safe out there!

[Arch Hoagland]

Full.Monte...thanks for the update, glad to hear it's fixed.

You'll know for sure if you come to central California in July.