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Discussion Starter #1 (Edited)
Problem:
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
Throttle body
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.

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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.

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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??

Any ideas?
 

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I believe that car has either crank and or cam position sensors - If I were going to "suspect" something that'd be a thought. Other than that I'd try combing sites specific to your years range (this is primarily 67-73 stuff here) good luck...
 

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Discussion Starter #3
I believe that car has either crank and or cam position sensors
Not on this, but later Mercury's -- started around 87, I believe.

try combing sites specific to your years range (this is primarily 67-73 stuff here)
Done web search and no-start / stall seems to be a big issue with Fords.
Most cases issue never resolved even after replacing lot parts including in-tank pump.
Saw one solution to clean radiator fins. Person was from Minnesota so could see where mud / salt might cause problems but in Arizona (where I'm at) just little dust and my radiator rodded and cleaned few years back.

Appreciate anyone elses thoughts if they care to respond.
Thanks
 

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My mom had an 83 Tempo that did exactly that now that I recall!! Your right, we changed fuel pump twice, various sensors, and finally gave up on the thing. Never could get a solid answer out of anybody. That reminds me, I still have a PRE ODBII code reader for Fords if anybody is interested in it? (Didn't help us!! LOL) I don't plan to ever need it but ya never know.

Good luck on this one, that friggin car left me stranded on my way to a good job interview and I never got there in time. Hated that thing!! Traded it for a different car and let the dealer have the headache.
 

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Just a guess, even for newer cars, is to make sure you have a well grounded starter. Also, you mentioned that if you remove the fuel return rail, that seemed to help.
Can you insulate it with hi-temp 'header wrap' or similar?
 
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