Car won’t start when hot

[Che001]

Hi all,
I have just got my VB 5.0 back from an extended stay at the mechanics… had a sniper EFI system fitted… seems that every time I drive the car, it won’t start unless the motor has cooled right down. Refuses to start when it’s hot, and if it does start, won’t hold the Revs and ends up stalling… I’ve been told it’s due to the extractors being too close to the starter motor…. But I’m unsure.. any ideas??

 

[Immortality]

That is certainly a possibility (headers). The other big problem with early girl Commodores is that the starter solenoid is fed directly from the ignition switch which can draw a reasonably high current, all newer models cars and Commodores have a starter motor relay. It ensures you get the full voltage to the starter motor solenoid.

On early girl Commodores basically all the power goes via the ignition switch and it's not uncommon for these to burn out over time and for the main feed wire to overheat and damage the main loom plug at the firewall.


How to wire in a relay,

It's been a long time but IIRC, there is a big purple wire going to the starter solenoid, remove this wire and connect to pin 86 and wire pin 85 to ground. Connect pin 30 with a decent size wire to the battery and connect pin 87 to the terminal on the starter motor where you removed the original purple wire from. Now when you hit the key the starter motor will get a good 12 volts and should turn over better.

I'd also make sure all your main cable connections on the engine, starter and battery are clean and tight.

If this doesn't help with your hot starting issues than you may need to look at putting a insulator blanket on the starter.

I'd also do the same mod but with a double pole relay for the headlights on a early Commodore to ensure nice bright lights. I used one of these,

 

[Sabbath']

Two seperate issues, but possibly related by the sounds of it.

Heat soak can affect the starter or solenoid (expansion when hot, Contraction when cold.)

When it's hot, does it slow crank or do you get a single click like the battery is dead?

What type of fuel pump are you using?

 

[UTE042_NZ]

In older cars (like really old, 1930's to 1960's) that was often a sympton of vapour lock, especially very common in Ford's flathead V8s due to their mechanical fuel pump configuration and location. It can be heat causing vapourision of the petrol in the fuel lines (when the engine is turned off) starving the carburettor or injection system and preventing fuel delivery until those fuel lines have cooled enough for the fuel to return to a liquid state.

Holley sniper vapor lock - Google Search

Not an uncommon issue, it seems. Or maybe your mechanic set the fuel pressures incorrectly. Doesn't sound as if it was tested adequately after the work was done. Perhaps you should take it back and politely request that they properly complete the installation. I would.

 

[Che001]

That is certainly a possibility (headers). The other big problem with early girl Commodores is that the starter solenoid is fed directly from the ignition switch which can draw a reasonably high current, all newer models cars and Commodores have a starter motor relay. It ensures you get the full voltage to the starter motor solenoid.

On early girl Commodores basically all the power goes via the ignition switch and it's not uncommon for these to burn out over time and for the main feed wire to overheat and damage the main loom plug at the firewall.


How to wire in a relay,

It's been a long time but IIRC, there is a big purple wire going to the starter solenoid, remove this wire and connect to pin 86 and wire pin 85 to ground. Connect pin 30 with a decent size wire to the battery and connect pin 87 to the terminal on the starter motor where you removed the original purple wire from. Now when you hit the key the starter motor will get a good 12 volts and should turn over better.

I'd also make sure all your main cable connections on the engine, starter and battery are clean and tight.

If this doesn't help with your hot starting issues than you may need to look at putting a insulator blanket on the starter.

I'd also do the same mod but with a double pole relay for the headlights on an early Commodore to ensure nice bright lights. I used one of these,

Thanks so much! I’ll definitely give this a try while I have time off over break! Makes sense… I’ll also give the lights a try as they are super dull when on. Almost pointless using lights. Lol

 

[Che001]

Two seperate issues, but possibly related by the sounds of it.

Heat soak can affect the starter or solenoid (expansion when hot, Contraction when cold.)

When it's hot, does it slow crank or do you get a single click like the battery is dead?

What type of fuel pump are you using?

When it’s hot the crank is really slow. Almost like the battery is dying. But the battery is brand new…. So not sure why that is.
It’s got an aftermarket electronic fuel pump. Pumps heaps of fuel…

 

[Che001]

In older cars (like really old, 1930's to 1960's) that was often a sympton of vapour lock, especially very common in Ford's flathead V8s due to their mechanical fuel pump configuration and location. It can be heat causing vapourision of the petrol in the fuel lines (when the engine is turned off) starving the carburettor or injection system and preventing fuel delivery until those fuel lines have cooled enough for the fuel to return to a liquid state.

http://[URL]https://www.google.com/search?q=Holley+sniper+vapor+lock

[/URL]
Not an uncommon issue, it seems. Or maybe your mechanic set the fuel pressures incorrectly. Doesn't sound as if it was tested adequately after the work was done. Perhaps you should take it back and politely request that they properly complete the installation. I would.

I took the air cleaner off and when ignition is on, the sniper is spraying fuel. So I do think it’s a fuel issue… it was dynoed 3 times to get settings right… but I guess they didn’t try start it after it was warm…
We also replaced the distributor, ignition system leads and plugs- all to suit the Holley Sniper system… driving me crazy! Especially when on the first drive it wouldn’t start !! So embarrassing!!

 

[UTE042_NZ]

Perhaps too much?
Do you have a return line to the tank?
A pressure guage in line before the Holley?
A Holley recommended fuel pump or just some generic "she'll be right" model?
Bother reading any of the infrormation available at the search link I supplied, which includes several Holley forum discussions regarding all these items about various Holley Sniper EFI systems (you haven't actually identified yours yet) and advice with other links to further your understanding?
We can't give you answers without complete data, but we can show you where you might find them and begin to help yourself.
Please don't be lazy.

 

[vc commodore]

Slow crank when hot sounds like starter solenoid getting hot or the main feed from the battery to the solenoid is old or too thin causing it to give the dead battery type symptoms.

I have also found if the ignition timing isn't correct, it can also cause slow cranking issues...

EDIT: If the ignition timing as set with a timing light and you're harmonic balancer is old, I wouldn't trust it is set correctly...Old harmonic balancers on these have a habit of spinning the outer ring...With the timing mark being on the outer ring and it spinning on the inner ring, means the timing won't be set correctly

I very much doubt it isn't a fuel supply issue...Fuel supply has nothing to do with a motor turning over....It has something to do with firing.

Having the main ignition feed from the solenoid, if it is getting hot, this could also cause running issues, due to heat soak...

If you can feel the solenoid when the motor is hot, report back if it is way too hot to touch...This might eliminate or confirm it is a heat soak issue, rather than other issues....