C3 technical question - engine cutting out

[v-spec]

Also posted on CCCUK. Hope eveyone's enjoying the nice weather in their 'vettes!


Out today and my engine died. It's the second time it's done this, both times it was about 5 mins after starting off, but the last time was about a month ago and it has been driven in between.
I thought it might be the choke cutting out too quickly, but the funny thing is that everything dies - no lights, no "brake" warning, nothing. Almost like the battery has been disconnected, but I checked and it is firmly connected at both terminals. When I take the key out and then try again it starts first time, and was fine for the rest of the journey.
When it died today, I was slowing (braking) from about 20mph and the engine just cut out - I watched the revs drop from 1500 rpm (on choke) to 500rpm for a few seconds and then die.

Any ideas? It's a '72 Auto 454.

Oh and while I'm asking - is it normal to get lots of exhaust fumes (steam?) from one exhaust but not the other when the car is cold? Compression test done when I bought the car showed all cylinders ok...

Thanks for reading!

[anonymous-user]

I've no specific C3 knowledge but it sounds like the earth strap to me if it's taking out the lights as well as everything else. Check all earth connections, particularly where the earth strap goes from the battery onto the frame. There can be corrosion that's hard to see so it's worth removing the strap, cleaning connection and frame with wire wool and refitting with some vaseline. (The other possibility is a major short circuit; relatively unlikely but a big fire risk if it happens.)

[seefive]

I had a simmilar problem on a TVR Griffith 500 - except is wasn't too fussy when it kicked in. One of the best was halfway through maggots pretty much flat.... all got a bit tail happy after the HP was suddenly switched off. Anyway, that fault was in the alarm - the immobiliser kept kicking in for no reason. Tell tale was that to get it going again, an alarm/unalarm and all was well - till the next pants filling moment. Changed the alarm and it went away. Hope you find it....

[roscobbc]

Heat stove to carb choke linkage is usually from only one exhaust manifold. This is a spring loaded flap with a bi-metal spring actually inside manifold. When in operation (ie cold start)it will restrict exhaust flow from the respective manifold thus causing exhaust on opposite side to 'steam' more initially.


Out today and my engine died. It's the second time it's done this, both times it was about 5 mins after starting off, but the last time was about a month ago and it has been driven in between.
I thought it might be the choke cutting out too quickly, but the funny thing is that everything dies - no lights, no "brake" warning, nothing. Almost like the battery has been disconnected, but I checked and it is firmly connected at both terminals. When I take the key out and then try again it starts first time, and was fine for the rest of the journey.
When it died today, I was slowing (braking) from about 20mph and the engine just cut out - I watched the revs drop from 1500 rpm (on choke) to 500rpm for a few seconds and then die.

Any ideas? It's a '72 Auto 454.

Oh and while I'm asking - is it normal to get lots of exhaust fumes (steam?) from one exhaust but not the other when the car is cold? Compression test done when I bought the car showed all cylinders ok...

Thanks for reading![/quote]

[v-spec]

roscobbc said:

Heat stove to carb choke linkage is usually from only one exhaust manifold. This is a spring loaded flap with a bi-metal spring actually inside manifold. When in operation (ie cold start)it will restrict exhaust flow from the respective manifold thus causing exhaust on opposite side to 'steam' more initially.

Thanks. Makes sense and matches what I'm seeing.

Regarding the engine cut out, the earth connection seems to be the prime candidate, so as soon as the snow clears I'll be be checking it! Thanks for your help guys.

[roscobbc]

I had a similat thing when I first got my '68. When breaking heavily it would cut-out. Reason why? battery wasn't strapped down and earth terminal kept pulling on and off intermittently.
I replaced the standard battery terminal with an isolating terminal which you can get from rally specialists etc. When you leave the car you can then isolate the power supply. Useful in a Vette when you consider the fire potential.