81 911 warm start issue
06-07-2020, 03:53 AM
#1
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81 911 warm start issue
I have an 81 sc that I rarely drive. For nearly 25 years, I connect the battery and the car fires right up, smokes a bit, then clears and runs strong. It's first warm start issue, which it has had for years, is that once the engine is warm, and then having been shut down, it doesn't wan to crank. It almost sounds like a suddenly weak battery that can't turn the engine or an engine that is getting stuck on a compression stroke. After maybe an hour or so of cool-down the car cranks fine and fires up.
Newest warm start problem has been even after having let the car cool for an hour or so the car cranks fine as it always has after cooling, but now doesn't want to fire up. Oddly I can crank it numerous times, and each time it seems that just before the battery is about to die the engine fires up. I had read a bit and thought maybe this last issue was the fuel accumulator valve, which I changed out, but doesn't seem to have been the issue. If I leave teh car sit overnight, all problems go away as I can turn the key the next day and the car fires up and runs fine.
Any thoughts would be greatly appreciated. Thx, Jack
Newest warm start problem has been even after having let the car cool for an hour or so the car cranks fine as it always has after cooling, but now doesn't want to fire up. Oddly I can crank it numerous times, and each time it seems that just before the battery is about to die the engine fires up. I had read a bit and thought maybe this last issue was the fuel accumulator valve, which I changed out, but doesn't seem to have been the issue. If I leave teh car sit overnight, all problems go away as I can turn the key the next day and the car fires up and runs fine.
Any thoughts would be greatly appreciated. Thx, Jack
06-07-2020, 11:12 PM
#2
My guess is either the speed or reference sensor aren't working any more.
Had similar issue, finally degraded to a no-start condition.
Replaced both sensors and it fired right up.
As long as you are in there, replace them both.
The cable insulation on mine just crumbled due to age.
Had similar issue, finally degraded to a no-start condition.
Replaced both sensors and it fired right up.
As long as you are in there, replace them both.
The cable insulation on mine just crumbled due to age.
06-08-2020, 12:12 PM
#3
Team Owner
ummm... good luck finding speed and reference sensors on an SC since they dont exist.
im confused about your issues... if it wont " crank" or " turn over" which means the starter motor has trouble turning it over after it warms up i would suspect you are having heat soak problems with your starter and you need a new high torque starter.. ( after you have verified battery and connections. )
if it will crank and turn over but will not "fire" after shutting down warm ( just cranks and cranks" ) i would suspect your residual fuel pressure is low. This should really be checked with a set of CIS gauges. But common culprits as mentioned is fuel pump check valve and accumulator.
im confused about your issues... if it wont " crank" or " turn over" which means the starter motor has trouble turning it over after it warms up i would suspect you are having heat soak problems with your starter and you need a new high torque starter.. ( after you have verified battery and connections. )
if it will crank and turn over but will not "fire" after shutting down warm ( just cranks and cranks" ) i would suspect your residual fuel pressure is low. This should really be checked with a set of CIS gauges. But common culprits as mentioned is fuel pump check valve and accumulator.
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