To Mod... LAST Stalling Update

[Chris M 2]

I sure hope (as I'm sure many here do too... ) that this is my last message on the stalling troubles my ST has had.



After replacing several parts, doing nearly all the cleanings and treatments, and going a month with no troubles, stalling began anew a couple of days ago after a fill up. The last four times this has happened, it occurred a few hours or the morning after a fill-up.



I immediately took the truck to my mechanic. After a lengthy discussion, we believe the stalling was related to my rounding up to the next dollar and/or topping off the gas tank. So it appears I was my own worst enemy in this situation. :wacko:



My mechanic explained it thus: When you top off the tank or round up to the next dollar, the extra fuel has nowhere to go except into the vent line and the fuel vapor canister. Thus, airflow to the fuel in the tank is blocked or partially blocked. Imagine opening a can of grape juice and only punching one side of the can. The liquid can come out, but does not flow well because you've not punched a vent hole in the other side. The engine is fuel-starved because the fuel isn't flowing properly. Besides this, you run the risk of damaging/bursting the fuel vapor canister, which lets that material into the fuel system.



This problem didn't occur in older vehicles (like my '92 S-10) due to the design of the fuel system. That's why you could top those vehicles off with little or no problem.



Anyway, my mechanic advised me to NEVER top off or round up, and to keep an eye on the situation. After all the measures we've both taken, we're fairly confident this is the cause. I sure hope that's all it is. In the last two days, the problem has stopped since I've been driving and the fuel level has gone down.



Anyway, I went ahead and put on the Zabteck TB. It's nice. I got a little bit of extra pickup, which I like! Thanks Todd! I'm also doing Dingo's "Touch-the-terminals-together-and-drive-it-like-you-stole-it" Adaptive Learning Program. :lol: Thanks Dingo!

 

[Andy Chase]

I have heard that the topping it off is money down the drain. The gas that you are topping off with evaporates before you can use it, so your money is actually evaporating away instead of down the drain.

 

[scott degroot]

While this can be a problem sometimes it just does not fit with any of your symptons in previous posts. Let me ask you this, when it stalled had you just filled up after every occurance? Did he inspect the vapor canistor to see if it was full of fuel? it would have had to been to cause this problem.

 

[Les]

I believe if topping-off was the problem, I would have experienced it, and there would be cars everywhere stalled out. Also, why wouldn't it stall immediately, instead of several hours later ???

 

[Carey Frennier]

I used to buy gas at Stewarts and my vehicle stalled all the time. I read that they buy "bottom tanker" gas at auctions which is lower quality due to contamination and crap like that. I switched to Sunoco fuels and I've never had an issue since.



Last week I filled up at Stewarts because it was 10cents per gal cheaper and guess what....my new truck started stalling again.



I don't really know if that is the issue but it's seems odd that I'd have the same problem with two different vehicles. Of course I've only ever filled up at one Stewarts station in my city so it could be the gas station itself. /shrug

 

[Chris M 2]

I'm certainly no expert, but from what my mechanic and I have narrowed down, it sure seems like a fuel or fuel-flow problem. I guess you have to try and narrow it down, especially when diagnostics aren't finding anything.



Regardless, we're not 100% sure this is the cause, just fairly sure based on when it keeps happening. The last four times it happened, I noticed it occurred after the truck had sat for a least a few hours (or overnight) after a fill-up. I can't explain all the particulars, all I can do is tell ya what's happening, when it happens, and what I and/or my mechanic believe the trouble is. It could just be bad gas, as psycareyo suggests.



I appreciate everyone's skepticism (especially you I1) and suggestions because it reminds me that the problem isn't over until the symptoms go away for good. It also reminds me that there are other possible causes. So thanks.

 

[hal keiner]

I suggest installing a pressure gauge to see if the fuel line pressure drops below normal when the engine stalls. A pressure gauge test is a good way to positively confirm or eliminate poor fuel flow as a cause of stalling, and under what circumstances.



I once had a vehicle that usually ran fine but would unexpectedly stall at times. I eventually determined that this was caused by a fuel pump that failed only when the outside air temperature was very high, the vehicle was parked on hot asphalt for a while, and I was at a high altitude in the mountains. Apparently the warmer than normal fuel temperature in the tank along with lower air pressure caused the fuel pump to temporarily fail until things cooled off. It took a pressure gauge to troubleshoot and confirm this unusual cause.

 

[scott degroot]

I sure wished you lived in Phoenix...this would have been fixed months ago...keep your chin up you'll find somebody who can get to the root cause

 

[Chris M 2]

Thanks everyone, for the ideas and well-wishes. I'm much more optimistic about this now than I was months ago.