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-   -   Severe power loss in hot weather (https://volvoforums.com/forum/volvo-s80-18/severe-power-loss-hot-weather-21854/)

hoolie 07-30-2008 03:54 AM

Severe power loss in hot weather
 
After a couple of hours running in hot weather >34C/90F my T6 progressively loses power and more or less comes to a standstill particularly on steep hills.

I suspect fuel starvation as the engine only fires very intermittently but I can't smell unburnt fuel from the exhaust. I don't have a service manual so I'm not sure what's in the fuel system. Are there two fuel pumps low/high pressure as on a diesel engine? Is there a diapragm pump to bring fuel from the tank that could be failing at high temperature?

I've already replaced the Turbo control/boost pressure valve to deal with another power surge problem, but this total powerloss is really dangerous on blind bends.

bigern45 07-30-2008 07:02 AM

RE: Severe power loss in hot weather
 
i would check fuel pressure when this happens. there is a small service port on your air filter side of the manifold with a blue or black cap, like on a tire valve stem. its on the fuel rail inbetween the manifold and head. when your car wont start, remove that cap and being very careful depress the schrade valve inside and see if you have fuel pressure. obviously if you do thats not your problem. and fuel starvation would not leave an unburn fuel smell in your exhaust. that would be more of a no spark problem, or even worse, a mechanical issue. try the fuel pressure test and repost what you find.

hoolie 07-30-2008 08:36 AM

RE: Severe power loss in hot weather
 
I'll try testing the pressure as you suggest, but I think limited flow rate is the problem as the car will generally start OK but just won't motor along. It's also a problem that appears after 2 or 3 hours running. It's as if what is causing the problem has to get really hot for it to misbehave. Similarly the effect does not immediately go away when the temperature drops.

bigern45 07-30-2008 05:01 PM

RE: Severe power loss in hot weather
 
yeah, it could be a fuel pump getting hot and wearing out, or it could be another issue. try installing a fuel pressure gauge on the shrade valve end that you could somehow work into your cockpit, that way you can see fuel pressure at all times, including when the problem occurs. sometimes you can find a cheap kit at autozone or advance auto that you could hook up..

hoolie 07-31-2008 09:55 AM

RE: Severe power loss in hot weather
 
I'll give the pressure guage a go - better than speculating on a new fuel pump!

bigern45 08-01-2008 01:03 AM

RE: Severe power loss in hot weather
 
i hooked up a cheap boost gauge and found the problem with mine, so worse case senario you eliminate the pump as being a problem if the fuel pressure stays as it should at all times..


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