Will not start when hot

[GTL253]

Hi there
I am a new member here and I have a 1978 Pontiac trans am that will not start when it get hot. When I turn the key there is nothing ,so I got a relay put in, Now it will wind over but still not start when hot. Next thing I did was put the starter out & get check out, There wasn't too much wrong with the starter so I put it back in, test it still same problem. Depending on how hot it is I have to wait 2,3 or 4 hours and it will start fine no problem at all .When I first notice this issue I was stuck out on the side of the road it was dead so I got a jump start to try anything and it started straight away so I kept driving until I got to my sister place .Came back about 4 hours later I started it up and drove home 125km away . I petty sure it a electrical issue but it could be something simple like a sensor. Had anybody got any idea ? Thank

 

[EaOutlaw]

does your TA have the Pontiac 400?

It sounds to me like you may have the distributor set too far advanced.

check the timing with a timing light with the vacuum advance disconnected.
Verify the vacuum advance works and the centrifugal weights and and springs etc in the distributor are working freely and make sure the bushings are not worn out.

You may have a stretched timing chain that caused someone to advance the timing to make up for the lack of power.

the same thing goes for a non functioning vacuum advance and or weights in the distributor.

When checking the timing with the vacuum advance disconnected you will want to see a steady mark on the harmonic balancer , if it is jumping around you most likely have a worn timing chain set.

Let us know how setting and or just checking the timing goes, and we can further advise you.

Also check the battery and charging system along with the battery connections.

Check your oil level and coolant. if the engine is overheating it will prove hard to crank over.

Pontiacs seem to respond better having a ported vacuum source for the vacuum advance, make sure the vacuum line either goes directly the vacuum advance or to a known working and tested thermal vacuum switch.

If none of this makes sense just follow the emissions label under the hood or found in a service manual.

 

[melsg5]

When it wont start, have you tried removing a spark plug wire from the plug, inserting a screwdriver with a plastic handle and holding the metal part of the screwdriver near something on the engine, while someone cranks the engine, see if a spark jumps from the screwdriver to the engine to determine if you have spark at the plug? If you have no spark I would suspect a failing HEI module.