Is this the dreaded 914 vapor lock?, Asking for your ideas and thoughts |
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Is this the dreaded 914 vapor lock?, Asking for your ideas and thoughts |
Artfrombama |
Jul 14 2024, 05:04 PM
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#1
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Member Group: Members Posts: 156 Joined: 21-January 24 From: Alabama Member No.: 27,870 Region Association: South East States |
Drove my 914 to a PCA function yesterday morning, 93f and humid.
After driving on the interstate at 70-75mph for around 45 miles I exited and the motor died. I had enough momentum and coasted into a gas station/convenience store where I topped off the tank and tried to restart the car, no luck. The car would fire, run a few seconds and die then refused to re-start for another 10-15 minutes then the same scenario again. No tools to diagnose or repair. While waiting on AAA for three hours (another story) I would occasionally try to start the car with the same results. Today, car started normally, runs normally. 1974 L-jet, original three bung fuel pump, original location. 500 miles on new tank, sock, filter, ss lines. |
wonkipop |
Jul 25 2024, 08:45 PM
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#2
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Advanced Member Group: Members Posts: 4,611 Joined: 6-May 20 From: north antarctica Member No.: 24,231 Region Association: NineFourteenerVille |
@ArtfromBama
ah yeah, thats probably right for the cht. given its summer over there isn't it. one of the things that can produce this problem is the harness connecting the AFM and the ECU. i feel the plug to the AFM is particularly vulnerable like all plugs. taking them on and off over the years to service car. removing air filter and replacing etc. on an original wired car with original wired fuel pump if that pump signal doesn't get through it won't run. i think i have mentioned it before on this topic. i've done it, like a dunce, forgotten to replug in the AFM. it will fire (off the squirt it gets from the cold start injector) and then the pump will only continue to run on command from the AFM. another thing to check is the TPS under the throttle body. make sure its working. the tests are in the factory manual. make sure its electrical connection is clean and good. when the throttle is not open, the idle setting on that is sending a command to let the ECU know the car is in idle. The TPS on the L jet is much simpler than the D jet. its basically an idle setting. and a wide open throttle setting. all inbetween is run off the AFM to the ECU. i think mr. perrine is right. its likely to be that harness. its occasionally connecting. sure sounds like its there. |
Artfrombama |
Jul 25 2024, 09:04 PM
Post
#3
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Member Group: Members Posts: 156 Joined: 21-January 24 From: Alabama Member No.: 27,870 Region Association: South East States |
@ArtfromBama ah yeah, thats probably right for the cht. given its summer over there isn't it. one of the things that can produce this problem is the harness connecting the AFM and the ECU. i feel the plug to the AFM is particularly vulnerable like all plugs. taking them on and off over the years to service car. removing air filter and replacing etc. on an original wired car with original wired fuel pump if that pump signal doesn't get through it won't run. i think i have mentioned it before on this topic. i've done it, like a dunce, forgotten to replug in the AFM. it will fire (off the squirt it gets from the cold start injector) and then the pump will only continue to run on command from the AFM. another thing to check is the TPS under the throttle body. make sure its working. the tests are in the factory manual. make sure its electrical connection is clean and good. when the throttle is not open, the idle setting on that is sending a command to let the ECU know the car is in idle. The TPS on the L jet is much simpler than the D jet. its basically an idle setting. and a wide open throttle setting. all inbetween is run off the AFM to the ECU. i think mr. perrine is right. its likely to be that harness. its occasionally connecting. sure sounds like its there. @wonkipop I'll check the TPS tomorrow. I did check the continuity of terminals 6, 7, 8, 9 from the AFM to ECM and near 0 ohms. The air vane in the AFM actuates the fuel pump relay as well as the fuel pump when the engine is cranked |
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