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News: Suspected Vapor Lock Problem FINALLY SOLVED

FactoryC3

Active member
Joined
Oct 14, 2014
Messages
44
Location
USA
Corvette
1981 Black Coupe Red Interior
Vapor lock came back...Adding electric fuel pump and return line regulator...Dealer analyzed.
See this link for reliable info on vapor lock.
Ask Away with Jeff Smith: Understanding Vapor Lock--and How You Can Fix It! - OnAllCylinders

:happyanim:
Another success story. Well, Not So Much

I had posted for fix ideas pertaining to a suspected vapor lock situation with my factory stock 1981 Vette. I was running into problems after driving, parking for a bit, and restarting. The engine would start fine but die after going about 100 feet or so. The reason we suspected vapor lock was because there was no fuel flowing when looking down the carb when working throttle linkage.. After waiting a bit and cranking, it would finally start and stay running. I followed all suggested leads, from plugged fuel lines to vacuum problems. Looked at bowl leak-down and insulated fuel line to carb. I put a fuel pressure gauge in the cockpit to monitor fuel pressure. Felt that was kind of a long shot since the engine ran strong and no normal fuel pump problem signs were evident. Then, we were out in late November ’17 and the choke out happened at 45 degrees outside temp. I noted that the gauge was reading 4psi when I started the car. (Factory Service Manual said it should be in the 7-9 psi range). The pressure had been noted jumping up and down at times…irregular. I decided to change out the fuel pump and put in a GM Restoration pump. Hooked it all back up and fired it off. PERFECT. No long cranking start when cold. Awsome throttle response and a solid 8.5-9 psi at all rpm’s.

I believe that when I got the start and choke out problem, the pump was not putting out enough fuel to keep the bowl full. Enough cranking got the bowl full...finally, and we got a restart. Kind of came and went. Fuel output was enough at higher rpm to run well. Who'da Thunk???
:hb
:beerAgain, thanks to all who assisted by sending ideas and suggestions.
 
Last edited:

Tom Bryant

Well-known member
Administrator
Joined
Nov 9, 2000
Messages
7,322
Location
Edgerton, Ohio, United States
Corvette
1959 black 270hp (9/2/69) 1981 Beige L81(10/20/80)
I'm glad that you got it figured out. Back to worry free cruising again.

Tom
 

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