1982 911 sc Targa Fuel Pump

[jmtaylor75]

When I first turn my key to on, should I hear the fuel pump running? I don't hear it when I first turn the key and on cold starts it starts for a few seconds then stumbles and dies. I have to repeat this several times before it stays cranked. Today while driving the engine shut off completely as if it ran out of gas. It took several attempts to get it restarted. Any help would be greatly appreciated. Also, I have read in different articles referring to a second pump.

[Discseven]

JM... when fuel pump runs it makes an audible hum/buzzing sound. Forgot exactly what position key is in when it fuel pump runs but yes... when key is turned, it should run before starter runs. When is last time you changed fuel filter?

[GothingNC]

Fuel pump should not run until the starter is engaged. You can pull the red FP relay and use a jumper wire to see if the pump works.

[theiceman]

sorry but the above information is incorrect unless it has been modified. edit . john beat me to it .. the information above the above information


The pump with only run in the "start" position , not in the run position on initial starting until the relay is set . This is intentional. Some cars get modified but lets leave that alone for now.

it is possible you have a dying fuel pump however.

Just for your info turn on the ignition go around back and remove your air filter and cover. lift the small air plate underneath, you should here the pump run very distinctly. ( only do this for a second as you are running fuel through your injectors. )
do not confuse the buzzing of the pump for the cdi ignition module out back.

before swapping any parts i would suggest getting a set of fuel guages and hooking them up to check system pressures an control pressure etc.

it is also possible you have a bad WUR so some troubleshooting is in order. the fact it starts stumbles and dies tells me you dont have a starting isue , but maybe more of a cold running issue.

[simsalabim]

Jim,

In addition to the solid advice above, check if your pop-up valve (assuming you have one) under the air filter is fully closed and sealed. Sometimes a random backfire (too lean a mixture ?) will open them and they will not close fully. Also, make sure the o-ring is in place and lubed.

Good luck

[timmy2]

If not mentioned above check the fuel pump red relay is fully seated in the front fuse area.
They have been known to wiggle loose.
You can do a quick check by swapping in another relay should it die again while driving.

[Bob Kontak]

Originally Posted by jmtaylor75

I have read in different articles referring to a second pump.

930's have two pumps. Not the SC.

Red relay timmy2 talks of makes some sense. Although, when mine used to wiggle out I could never get it restarted without re-seating it. For grins, pull it out and put a thin blade in the male plugs and open them a wee bit. Something like a fishing knife or a box cutter blade.

You should have a backup relay in your glove box as they can fail. They are $30 or so. Given there are electromagnets in them, once they die and cool a little, circuit can be restored - roughly related to your symptoms.

[jmtaylor75]

Thanks for the info. I'll post my results after I have a chance to work on it again.

[psalt]

and on cold starts it starts for a few seconds then stumbles and dies.

jm

This is a common problem with 81-83 911SC's and has nothing to do with the fuel pump. After you verify that the FP is OK, try searching for cold start stumble and stall. Usually it is a combination of vacuum leaks at the injector sleeves, the vacuum retard, mixture adjustment and the wrong spark plugs. The FP on an 82 SC should not run with the key in the "ON" position unless the engine is running and lifting the airflow plate. The engine should fire immediately on the first crank and settle to a 1500 rpm fast idle without touching the pedal.