Strange running issue, Fuel tank vent? |
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Strange running issue, Fuel tank vent? |
sdoolin |
May 1 2018, 07:50 AM
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#1
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Member Group: Members Posts: 359 Joined: 1-May 14 From: LouKY Member No.: 17,299 Region Association: None |
73 2.0L, built to 2056 running dual Dellortos. I have just over 3k miles on the engine since the rebuild, and it has been running strong, and I have been loving it. Went to pick up my wife from the airport last week and about 30 miles into the trip, the car started running poorly. Really poorly. Had been all freeway miles, and I was running at 80+ MPH. Car had been running fAntAstic!
Felt like it was running on 3 cylinders, and running out of gas. No strange/unusual mechanical noises before poor running, or during poor running. Completed the next 5(ish) miles to the airport and strangely, once I slowed (exited the freeway) the engine picked back up and began to run normally again. Made the 40(ish) mile trip home, running poorly the entire way. Pulled into the garage, shut the car off and heard the STRANGEST noise from in front of me. Sounded like the gas was boiling in the tank. Quickly opened the frunk and removed the gas cap. Large sucking sound on gas cap removal. So, I am thinking that my tank was not venting properly, not allowing proper fuel to get to the carbs? I have put another 300 miles on the car since this event - no more issues. I am running a 3 PSI pump, with a return line from the carbs. Anyone else ever experience this (or similar)? |
jvmarino |
May 1 2018, 10:03 AM
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#2
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Member Group: Members Posts: 80 Joined: 22-March 09 From: Baltimore Member No.: 10,188 Region Association: None |
Sounds like exact thing that happened to me a long time ago. After a long run on the highway, there was a large vacuum on the gas tank because I had no vacuum relief on the tank. I had assumed the gas cap had this feature, but I think it only has pressure relief. Since I am running carbs, the vent and return lines were plugged off.
After my experience, I added a vent check valve on the vent line at the firewall under the engine. Have not had the problem since. I think local driving doesn't cause the problem and maybe even a higher fuel level in the tank helps the issue, but once you open the vent line back up, there should be no problem. Jim |
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