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Hot Weather Blues

B_to_C

B_to_C

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This problem has been occuring for the past 3 years (summers). It only happens when the outdoor temperature is above ~80*F.

The problem is: After about 1-2 hours of constant driving (can be either city or highway driving... i'm not usually driving in the city for 1-2 hours straight...but it does happen) the engine loses power and shuts off within 30 seconds of the first "symptom"

-The engine is a 1990 TBI 350

-A complete cooldown of the vehicle solves the problem.
-If I let it cool down for 5 mintues I can get it to start again and run for another ~10 minutes before it will die again. I usually use that ten minutes after the first "involuntary shut-down" to get to a safe place to let the truck cool down.

Steps I have taken to try and fix the problem:

-New spark plugs / wires
-New ignition module
-New TPS Sensor / O2 sensor
-Coolant flush / fill

Notes:
-Engine temperature is never above normal when this happens
-Again, I could drive for 3 days straight in 60* ambient temperature and this would not happen, but when the temperature is above 80* (roughly) I can COUNT on this happening.
-The new TPS sensor made the biggest difference. I drove from Boulder, CO to Albuquerque, NM last year, and this happened about 20 times on the way down....I replaced the TPS in ABQ, and the problem only occured once on the drive back.
-But now it's back! :(

Any ideas are welcome! :deal:

My last "clutching at straws" guess is that it may be connected with my TBI spacer (gasket issues), because the problem did not start until after I installed the spacer....In the same category, the problems did not start until I moved to high elevation.

I'm planning on a road trip to Alaska as soon as I get a huge bonus, so this needs to get fixed before another three years go by :rotfl:
 
Outside chance, you've confirmed the ECM is seeing the same temp that the gauge says the engine is?
 
Yes, I ran WINALDL all the way down to ABQ to get data while the truck was having issues. And the gauge and ALDL printout match up.

(that's when you diagnosed that my TPS was having issues :D )
 
Time to start driving around all the time with laptop and ALDL cable. :dunno:
 
Do you have spark when the engine dies? Are the injectors firing when you try to restart it right away?
 
B_to_C said:
That doesn't accomplish much...just shows the truck losing RPM's and then shutting off
Click to expand...
Just thinking you might see some other anomaly right before it happens. Like maybe some sensor reading cutting out or something. :dunno:
 
B_to_C said:
That doesn't accomplish much...just shows the truck losing RPM's and then shutting off
Click to expand...

Can you post a log that shows it dying?

Might be something to glean from that...IAC steps going weird, distributor reference pulse disappearing, SOMETHING...
 
I just looked through my logs... must have "cleaned them up" after I replaced the TPS....thinking I had solved the problem :doah:. The 5 logs I have left don't show it dying, I guess I will have to drive aorund with the laptop again...however dangerous trying to log / drive / handle a stalled vehicle on the highway may be :eek1:
 
HarryH3 said:
Do you have spark when the engine dies? Are the injectors firing when you try to restart it right away?
Click to expand...
It's a little hazy because I haven't had to deal with this all winter, but I think I checked those things...:doah:guess i'm going to have to try again and report back to this thread...maybe after a summer of constantly adding data to here we'll have it figured out :dunno:
 
Even that ten minute post-stall period might answer some questions, which sounds like it would be a bit safer. :)

Have you by chance checked to see if it's tied into fuel level? IE, you've got fuel pump prime/fuel when cranking when it acts up? Gas tank isn't building pressure, etc.

Does it ever get to a point where it simply won't restart unless it sits for a given amount of time? Something like fuel delivery issues or lack of spark is likely to be obvious if so.
 
I know for sure it has happened at every fuel level. I have tried taking the gas cap off during that initial ten minute cool-off period, and it didn't help.

When I go to start it again, I find myself pumping the gas....but I don't know if that actually helps get it started. I feel like it does, but who knows.

When I was going down to ABQ, I had no choice but to get it started as soon as possible and get on the road again (had to get there on a tight deadline). So yes....by the time I reached ABQ city limits it seemed as thoguh all was lost. It died and I was stuck in an intersection (right off the off ramp) for about 1/2 hour....blowing fuses left and right (cranking too long) and almost getting killed several times. As soon as I was about to give up hope the truck started and I took off through the intersection and raced to my destination as fast as possible before the truck died again...talk about stressful!
 
Well Im not sure about your exhaust setup but my dual exhaust on my 77 is to close to the fuel line causing my engine to hydro lock, the fuel boils in the line. Same exact symptoms as you, I let it cool and it fires right back up.
 
Yeah sounds kind of the way my Furd taurus would be. When it would get really warm and I would take a longer trip it would basically vapor lock the fuel. On those the temp sensor was mounted to close to the exhaust and would read that the engine was really hot, so the computer would lower the pressure of the fuel. Never made much sense, but cooling it down for a few would allow it to start and run for a short period of time. Your issue sounds like it is the same thing, the pump tries to prime, but the fuel is boiling in the lines. Just a suggestion, but see if the fuel lines run close to the exhaust and try shrouding any place where the fuel line might get hot with a little aluminum foil. It is a cheap way to test the theory.
 
EFI vehicles *should* be immune to this. The pumps always move fuel, and what isn't used is recycled to the tank, essentially providing cool fuel through the lines at all time. This isn't the case with some of the carbed setups.

The important question is, when it won't start and/or when it is dying, is it losing spark or fuel. Fuel pressure gauge would be handy.

Blowing fuses from cranking is abnormal.
 
dyeager535 said:
EFI vehicles *should* be immune to this. The pumps always move fuel, and what isn't used is recycled to the tank, essentially providing cool fuel through the lines at all time. This isn't the case with some of the carbed setups.

The important question is, when it won't start and/or when it is dying, is it losing spark or fuel. Fuel pressure gauge would be handy.

Blowing fuses from cranking is abnormal.
Click to expand...
My taurus was EFI so that is not the case. They can still boil fuel in the lines, the local highway patrol around here can confirm this. This can happen with EFI or carb vehicles.
 
Not saying it can't happen, but that is the SOLE reason GM added a fuel return line to the carbed applications.

I know nothing of the Taurus, but if the Patrol Cars are new, it's probably happening because the new fuel systems are "returnless".

Vapor lock happens because a pump can't move air. Problem with a carb, not stock GM EFI that these trucks have...a pump that is submerged in fluid can't vaporlock, as it's not trying to move vapor. Even if fluid was boiling in the lines (pretty hard to do, since it is moving at all times) the pump would still be pushing fluid through the system.

1-2 hours is a long time to wait for a heat soak problem, especially since the problem is occurring on a moving vehicle, which not only cools better, but pushes even more fluid through the lines, which lessens time, and thus heat absorbed by the fuel.

I'm addressing this particular problem, not others. Not to be snooty, but based on the symptoms, it doesn't fit the vaporlock idea well IMO.
 
Well this was a 94 taurus and it definately had the return line. I have seen them vapor lock that was the only reason I recommended it.
 
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