Intermittent No Start when Warm (2 miles) or Hot (12 miles).
Dealing with this issue for at least a year -- vehicle driven infrequently (once every week or two).
Same whether 32 degrees or 100 degrees outside.
1984 Mercury Cougar 3.8L
Engine rebuilt about 4000 miles ago. Had problem prior to this so it persists.
What I've done.
Get OBDI (EEC-IV) codes of 13 and 14.
Plugs look like they been running rich.
When running manifold vacuum at 19 1/2 steady as a rock.
Fuel Pressure 39 - 39 1/2
Spark is good.
CAT (Catalytic Convertor) OK.
Idles great when running.
Replaced both O2 sensor recently, but problem existed prior to this.
New Cap and Rotor.
1) Swapped out distributor and TFI when down - still no start and vehicle had cooled quite a bit (about 6 hours).
2) Did find that by removing the fuel "return" line vehicle started for some reason.
Putting the fuel return line back on, no start.
Taking fuel return off again, vehicle started.
3) Pulled fuel filter and dumped gas contents from inlet port. No trash came out.
High pressure pump on rail was replaced couple years back and found a lot of what I would call gray graphite in the fuel filter at that time. Low pressure in-tank pump has NOT been replaced.
Vehicle has nylon fuel lines except for short run to Throttle body on top engine.
4) Put spoon under Injectors after cold start shutdown. No leakage.
Don't see this as a vapor lock because of failing after only 2 mile run.
Also don't see this as a fuel relay going bad -- located in trunk -- can hear hi pressure pump working while attempting to start.
In-tank pump possible (???) but don't understand why disconnecting return line would affect starting??