My car never starts on its own unless I push start it. It's a fresh rebuild with good compression numbers. I'm wondering if I have sensor problems or a major vacuum leak or something else.

When I searched I only found numbers for vacuum test with people's engines running.

I have a bouncing -6 psi with the throttle plate closed, and steady -6psi with WOT.

Thanks.

 

Fresh rebuilds don't pull a lot of vacuum until the seals wear in. Low compression and hard starts is a common problem too. Your profile states an 86 FC, doesn't help much. Before starting, pour 2-5 capfulls of motor oil down the carb. This will help bring compression back up and make starting easier until the seals set.

Crap, hit the wrong button and came to the 2nd gen section instead of the 1st. Advice is the same except for the carb part.

 

You said good compression.

The only sensor I know of that could cause a difficult start is the water thermo sensor. If the plug is left off, then the mixture during cold starts would be too lean making difficult starts.

That said, after the engine fully warmed up the starts would be normal.

IF the sensors wire is left off, the ECU defaults to 176 degrees approx, even if the real engine temp is 36 degrees. That's just FYI.

The START cycle of the RX is as is shown in the attached jpg. As you can see, more fuel for colder temps and less fuel for higher temps.

 

Thanks for the info on the coolant sensor. I'll check this tonight.

I'm still wondering if anyone knows how much vacuum at cranking speeds. We'll push start the car tomorrow, but it's still hard to keep it idling with out cracking the throttle a little.

I started this thread BTW.