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Old 08-12-2008, 02:45 PM   #11
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OK, here's an update. I now have the vehicle back from my mechanic, and they couldn't definitively find the problem.

But, here's another issue that could be related... On the same day that I was having engine stumbling & dying issues driving up steep upgrades, I found that (when stopping for lunch on a flat area) gas was quickly dripping out of the rear of the vehicle! I guessed this was the evaporative canister, and that it had somehow gotten smashed by underbrush -- so I disconnected the fuel line going in and plugged it.




My mechanic thinks the evap canister isn't damaged, but that fuel was coming out because I was driving up such a steep hill. That is, instead of just gas fumes, actual liquid gasoline was flowing back from my Transfer Flow gas tank into the evap canister. (It seems that Sportsmobile had repositioned the evap canister from the stock Ford location to the front-outside of the rear under-floor storage compartment.)

Furthermore, my mechanic thinks that the engine stumbling and dying are caused by this fuel being returned to the engine via the air intake, causing an extreme-rich running condition.

This is an interesting theory, but I'm not entirely convinced:
  • - Why did the engine continue to stumble & die on the next big uphill after I plugged the evap canister input? (But perhaps there still was gas in the line.)

    - Why did this never happen to me before? (But perhaps something was done incorrectly when my fuel pump was replaced this winter.)

    - Why does this fuel flow from the evap canister (in the rear of the vehicle) to the engine (in the front!) when going *UP* steep hills?
-- Geoff
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Old 08-12-2008, 02:48 PM   #12
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Thanks for the fuel filter tip. It was changed 4000 miles ago.

For this issue, my mechanic said he checked that, but I didn't realize there could be vehicle-angle issues with the filter.

-- Geoff
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Old 08-12-2008, 03:12 PM   #13
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It all sounds plausible. You mentioned that when the engine did start after prolonged cranking there was lots of black smoke ie, unburned gas (white smoke if you are diesel). Fuel injected engines usually don't "flood" with fuel so maybe the fuel from the evap canister was somehow being drawn back to the engine. Way too complicated for my brain! Can you try those hills again?
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Old 08-12-2008, 03:40 PM   #14
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The hills in question are a couple hours' drive from home, but when I get some time I'll look around here at home to see if there are any road steep enough to trigger this.

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Old 02-03-2016, 01:34 PM   #15
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I know this is ancient history, but I'm still dealing with this issue. Having the engine stumble when driving up steep 4x4 inclines isn't fun.

Here is a fix I'm considering:

Rather than drop the tank yet again and properly install fuel limit valves in the top of the tank to prevent liquid gas coming out when the van is angled, I'm thinking of splicing into the vent tube from the tank to the evap unit, and running a loop of hose significantly up higher than the tank, and back down again.

This is somewhat like how dishwashers are installed under the sink, where a loop of dishwasher drain pipe should run up higher than the sink basin level (and back down) so dirty water can't flow from the sink drain back into the dishwasher, contaminating the clean dishes.

The obvious place on my van that allows me altitude access higher than the fan floor is the fuel filler hole, so I'm thinking of running my loop of hose up in there.





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Old 02-03-2016, 02:23 PM   #16
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Yeah definitely sounds like fuel sucking into the evap canister.

I don't think the elevated loop will work. The system is under periodic vacuum, so it will simply draw the fuel uphill. Adding a vacuum breaker will trigger a check engine light, since it measures vacuum in the system.

My suggestion, add a normally-open solenoid inline between the tank and evap canister. Simply activate the solenoid when driving off-road. It' possible it may trigger a check engine light when active (because it will draw down vacuum faster than expected), but if you have a scangauge or similar, that's an easy instant fix.

1/2'' 110V AC Normally Open Electric Solenoid Valve 110-Volts

You could even add an angle-sensing switch to activate the solenoid automatically:
http://www.amazon.com/3-3-12V-Angula.../dp/B00HR5C0NQ
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Old 02-03-2016, 09:45 PM   #17
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Yeah, I'm far from certain that the elevated loop would work. I'm hoping that most of the pressure would have been sucked out of the tank before the first steep hill climb, so the pressure wouldn't change enough after that to suck the fuel all the way up and over my loop. And I'm hoping that when I return to level ground the fuel would drain back down into the tank (if I have no large dips in the line).

But I want to keep it simple. I'm leery of adding a solenoid, etc.

If it doesn't work, at least I'll have lots of tubing easily accessible to pinch off when I go offroading -- hopefully just by kinking it tight and holding it in place with a rubber band.

I do have a Scangauge, so I can clear the the codes this would throw later.
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Old 02-03-2016, 10:46 PM   #18
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Quote:
Originally Posted by geoffff View Post
Yeah, I'm far from certain that the elevated loop would work. I'm hoping that most of the pressure would have been sucked out of the tank before the first steep hill climb, so the pressure wouldn't change enough after that to suck the fuel all the way up and over my loop. And I'm hoping that when I return to level ground the fuel would drain back down into the tank (if I have no large dips in the line).
Got it. How about adding a small catch-can / reservoir at the top of your loop? Should make it even more likely to work as you intend. Even using an inline fuel filter (like the OE E350 version) should give plenty of extra volume to do what you intend, plus the filter itself might add enough extra resistance to liquid fuel to keep it from getting drawn up.
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Old 02-07-2016, 08:24 AM   #19
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Just experienced this problem for the first time yesterday at the King of the Hammers. I have driven the same steep hill several times years past with no issues.

Midway up the hill it would stop but not actually stall. All of the gauges starting bouncing all over the place and it would not move forward at all. I backed down the hill and tried it several times in a row with the same result in the same place each time. All at low range.

Why all of the sudden?

Did you get that fix to work Geoff?

Another thing of interest was on the way home yesterday on the freeway the AC would rotate from the top vents to the floor while going up hills. When the I reached a flat it would cycle back up the top vents.

Both happened for the first time on the same day. Are they related somehow?
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Old 02-07-2016, 10:46 AM   #20
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Quote:
Originally Posted by haywoodphotomaccom View Post
Just experienced this problem for the first time yesterday at the King of the Hammers. I have driven the same steep hill several times years past with no issues.

Midway up the hill it would stop but not actually stall. All of the gauges starting bouncing all over the place and it would not move forward at all. I backed down the hill and tried it several times in a row with the same result in the same place each time. All at low range.

Why all of the sudden?

Did you get that fix to work Geoff?

Another thing of interest was on the way home yesterday on the freeway the AC would rotate from the top vents to the floor while going up hills. When the I reached a flat it would cycle back up the top vents.

Both happened for the first time on the same day. Are they related somehow?
Brent you may have had trouble this time simply because you were carrying more fuel. Or possibly you hit the vacuum draw-down sequence at the same time (it only turns on the vacuum solenoid for the fuel canister intermittently).

Your floor vent problem is most definitely a vacuum leak, and it could be related if the fuel that was sucked up damaged the vacuum line going to the canister.
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