1980 Corvette intermittent dry carb

[80 Vet]

Hiya all, on Sunday Sandy and I joined the club on the Geroa Fishermans run. The night before I filled up with fuel and the fuel gauge showed full. Left Shellharbour and drove to join the club at Picton road ramp onto freeway. Approx 30km later the car started to miss and stopped running. Managed to pull over safely. Fuel gauge showed 3/4.  Lifted off the air cleaner to check for fuel flow in carby and guess what, there was no flow. Gary c and I dipped the fuel tank and there was still fuel in there. Gary took me to a servo and returned with 9.17 litres of fresh fuel. We poured it into the tank. Cranked the engine over for a short time and she fired into life. Gary c and Jacki waited while I went and filled up the tank which took 26.2 litres. Fuel gauge shows full again. While I was there I topped up the jerry cans again as back up. The fuel tank holds 90 litres, 10 months ago I had the fuel tank out, cleaned and inspected the plastic lining in the tank, all was very new inside. Still the original tank, showed 1/2 of the build cert still stuck to tank. Replaced new sender unit and all new fuel hoses throughout the whole system. I had the Rochester carby completely overhauled by a specialist. New fuel line from pump to carby as the original was twisted. A new fuel filter was inserted into the carby inlet 1 month ago. When we arrived at Geroa I poured the last 9.15 litres of jerry can fuel into tank as I did not want it sitting in a hot car for 2 hours. After arriving home from run I removed the sender from top of tank and it still looked like brand new, strainer was clean, pickup was spotless and float moved freely throughout its whole travel. This is the second time in 3 weeks, last time the fuel gauge showed just under 1/2 tank when it ran out. Thanks heaps Gary and Jacki for staying with us. Please guys, any constructive ideas. At the moment I am driving around with 10 l of fuel as backup and staying in the left lane in case she dies again.     

[Jethro]

Hey Bro forgot to ask you yesterday it's not a air lock is it ? the tank has a vent, either through the fuel cap or alternatively through a breather hose somewhere . Just my 2 cents worth 

Jethro

[bfit]

Mate am I getting this rite
You used about 30 lt of fuel to kangaroo valley

Have you checked the lift pump
It may work with a full head of fuel but not work when the head drop

2ft head will give 1 psi pressure

As I remember  it  350s transfer fuel back to tank I don't remember just how that works
Worth looking into

Bfit

[80 Vet]

Thanks Jethro and Bob, I always run with the fuel cap loose because in the past I was getting vapour lock every time the cap was removed at the servo. I used 35.4 litres for 135km, thirsty bastard hey, but I was having fun. The only component that has NOT been replaced is the fuel pump. I was under the impression that the diaphragm leaked first and then leaked out of the tell tail when the pump was failing!!!

[MY081]

Hi Chris thats about 10 miles per gallon something seriously wrong there my 81 gives about 16 to 17 on a trip like that . Trouble is things like that are hard to pinpoint , the problem with the cap also sounds odd. I hope you have a good mechanic mate .

[bfit]

Mate next time it stops feel the steel supple line as close to the pump as posible on the suction side
If its quit hot there is a possibility you are getting vapor lock
Bfit

[sabre]

Hi Chris, Uncommon but have heard of a valve in the fuel pump falling out. Bfit is right, a full tank would just give you enough pressure to run but would usually stop as soon as you went up hill. A lost or badly leaking valve will give very low pressure. The standard pump should give 2 to 4 psi while running. Have you got a pressure gauge?
Don't know about the apparent poor consumption. I would have thought you'd be seeing black exhaust. I didn't notice it following you. A damaged diaphram would explain excessive usage but you'd normally see the leak at the vent hole under the pump unless it was blocked. In that case you'd expect to see increased oil level as the fuel would go to the sump. I've got a spare pump if you want to try it.
Good luck.

[sabre]

As I remember  it  350s transfer fur back to tank I don't remember just how that works

Tank on late C3 should be sealed with air return through the charcoal canister. Common problem of tank vacuum occurs when the canister is removed and hoses blocked off. Usual fix is drilling a small hole in the cap but I'd prefer to keep the original line with or without the canister.

[toyvet]

If all fails call Steve at SR performance 95974048   

[bfit]

If all efforts fail  swap the engine out for a BB
Bfit

[80 Vet]

Thanks everyone for all your advice and support. Update on the situation. Firstly my consumption figures are wrong. It should have been 35.4 litres for 235 km, which is 15 litres/ 100km. Second, I leave my non venting fuel cap loose because my son has borrowed my locking vented cap for his ute because it is parked outside and mine is not. Third, I have just spent a wonderful 3 hours replacing my fuel pump. It all seemed to point in this direction and it was the only outstanding item that was not replaced during the rebuild. Cannot tell if this has fixed the problem, as my fuel tank is too full at the moment. But one thing is for sure, its sounds different and seems to have more power, especially at the top end. It used to bog down under hard acceleration. Thanks again for all your kind words. I will still carry the jerry cans for the week and stay in the left lane and I will keep you all informed.
On another note, during our time in the club we have been amazed at the help and support and good times on all the runs. It is a wonderful club and now I will go as I am starting too cry. Chris and Sandy


 

[bfit]

Mate I have to agree with those kind words regarding the  club
Some  g8 people and no one is ever left to fend for them self
When things go wrong
Bfit

[80 Vet]

Am down to half a tank and all is well

[80 Vet]

Just a final update guys, have nearly gone through my second tank of 98 octane and all is well. Thanks again for all your advice. Bfit seemed to have hit it on the nose. Its not true what people say about you Bob. See you all on Sunday. It is going to be a warm one so don't forget to slip, slop, slap. Chris

[bfit]

Mate if enought ideas are put foward
All problems will be sorted
Bfit

Ps I have seen some  odd problems when it comes to fuel problems
From Ping pong balls in a petrol tank to a Complete bed spread in a Cat 633 scraper fuel tank