83'SC starts but won't run for more than 58 seconds

[fast911ray]

OK guys/girls, here's the scenario. I pulled the motor about a year ago to deal with a leaking head gasket. Assembly went with no glitches, and after doing 5 cam timing rechecks put the timing cover on, installed the motor then tried to start. Prior to removal it never failed to start, always without hesitation or drama. Now it fires and runs, but for just a few seconds. If I manually move the sensor plate for a couple of seconds the motor fires, but again dies after a few seconds. Now here's the wierdness...if the sensor plate is held slightly open the engine continues to run..a bit ragged, but running. The moment it closes, engine dies. Thinking it might be a fuel pump wiring problem, I even tried jumping fp relay #30 to #87a..still the same..starts and dies. I'm at wits end..anyone have any idea about what I'm overlooking?

[Justin@Athens]

Pelican Technical Article: Tuning and Adjusting CIS Fuel Injection - 911 (1974-83) - 930 Turbo (1975-89)

If I had to guess I'd say the car was probably tuned to manage vacuum leaks pre engine service, now that leaks are corrected it is running too rich. Not enough air to fuel.

[blpetry]

With the engine off and ignition in the run position, do you hear the FV buzz when you push up (briefly, don't want to flood it) on the sensor plate? Should be a distinct sound over and above the injector squeal. If not, check the multi-pin connector up by the driver's side shock tower. My car did the same thing upon reinstall and fiddling with that connector straigtened it out...

[boyt911sc]

Originally Posted by blpetry

With the engine off and ignition in the run position, do you hear the FV buzz when you push up (briefly, don't want to flood it) on the sensor plate? Should be a distinct sound over and above the injector squeal. If not, check the multi-pin connector up by the driver's side shock tower. My car did the same thing upon reinstall and fiddling with that connector straigtened it out...

bipetry,

The above suggestion will not work unless the car is wired incorrectly. First, the FV would need power coming both from fuse #18 and terminal #30 (FP relay) at the same time and a good working FV relay.

Tony

[blpetry]

Originally Posted by boyt911sc

bipetry,

The above suggestion will not work unless the car is wired incorrectly. First, the FV would need power coming both from fuse #18 and terminal #30 (FP relay) at the same time and a good working FV relay.

Tony

You sure about that? Just went out and pushed up on my 82 SC's sensor plate (with ignition on) and it started buzzing like a champ... I recall doing the same thing when I first encountered this issue.

In any case, you can also jumper pins 30 + both 87's on the Lambda relay socket under the passenger seat to achieve the same thing (also with the ignition on).

From what you're describing it really sounds like that is the issue, given the recent engine install.

[boyt911sc]

Originally Posted by blpetry

You sure about that? Just went out and pushed up on my 82 SC's sensor plate (with ignition on) and it started buzzing like a champ... I recall doing the same thing when I first encountered this issue.

In any case, you can also jumper pins 30 + both 87's on the Lambda relay socket under the passenger seat to achieve the same thing (also with the ignition on).

From what you're describing it really sounds like that is the issue, given the recent engine install.

Bipetry,

You are indeed correct. I misread you post by missing 'push up' thing. What registered in my mind was having the ignition @ ON only. My mistake.

Tony

[fast911ray]

Thanks for all the input guys. OK, moving the sensor plate does indeed trigger the frequency valve..in fact that's the only way I can get it to fire up after the first try or two. I'll check the connecter you suggested Blpedtry. Incidentally, I replaced all injectors as a matter of precaution thinking they might have become corroded from sitting. Oh, and with key on there is no 'Injector squeal', but I can feel the pump working through the soft fuel lines when I do the 30-87a bypass. Could that be an indication of something ?

[ossiblue]

Originally Posted by fast911ray

Thanks for all the input guys. OK, moving the sensor plate does indeed trigger the frequency valve..in fact that's the only way I can get it to fire up after the first try or two. I'll check the connecter you suggested Blpedtry. Incidentally, I replaced all injectors as a matter of precaution thinking they might have become corroded from sitting. Oh, and with key on there is no 'Injector squeal', but I can feel the pump working through the soft fuel lines when I do the 30-87a bypass. Could that be an indication of something ?

All you describe is proper. With the key on, there should be no injector "squeal" and no fuel pump running. Jumping the relay would cause the pump to run, but the injectors should not "squeal" unless the plunger inside the intake is raised. Your system seems to be working correctly.

[fast911ray]

It appears so Ossiblue..all except for not running for more than 5-8 seconds unless I lift the sensor plate manually!

[boyt911sc]

Originally Posted by fast911ray

It appears so Ossiblue..all except for not running for more than 5-8 seconds unless I lift the sensor plate manually!

fast91ray,

Please correct/edit the title of your post. It leads to confusion when it says 58 seconds when you meant was 5 - 8 seconds. Check your fuel pressures (control, system, and residual) and source/s of air leak/s. Pressure gauge kit is a mandatory tool for troubleshooting any fuel injection system. Keep us posted.

Tony