I'm having a problem with my 1993 850 GLT. On extremely hot days, the car may start and run for awhile, but will start slowly loosing power and revs drop off. Eventually it will die until it can cool off. The temp gauge stays normal, there is no Check Engine light therefore the OBD I shows no codes, and I don't hear any unusual noises. One thing I notice is that I never hear the radiator fan kick on unless the A/C is on. This problem only happens when it is very hot outside (upper 90s or especially over 100 degrees). Any ideas?

 

Tune up. How old are the wires?

 

And ck the fuel pressure (should be around 42 psi at idle); fuel pump relays have been known to die in the heat.

 

Wires are original (53,000 mi). Just replaced plugs.

 

I don't have a gauge, how much do they cost?

Is there an easy way to check the relay? Where is it located on the 1993?

 

I'm wondering...if the relay failed, the pump would then fail. If that is the case, wouldn't the fuel cut off completely? Will some fuel gravity feed? This doesn't appear to be a total fuel loss. Maybe a considerable loss in pressure. I'm not sure if the pump provides fuel flow or supplements fuel flow. Maybe you can help clear that up for me.

 

What I can tell you is that if the relay cuts out, the pump will not run, and when the pump is not running, your fuel pressure will drop like a stone, your car will die, and will not start and run properly until it has the correct fuel pressure. So, yes, the fuel pump's operation is entirely necessary for the car to run.

The idea with the fuel pump relay is that its operation can get a bit flaky if the relay is old and intermittently failing, usually exacerbated by high heat. This is why the car will die and then start up again later, after a cool down period.

I'm not definitively saying this is your car's problem, but the symptoms you are describing definitely point to the relay being a possible trouble spot. Certainly, there could be other things causing your stalling issue, but the relay/fuel pressure is easy to test and is a good place to start looking for issues.

Good Luck!

1995Volvo850