Fuel pump runs continuously
06-03-2004, 01:45 AM
#1
Track Day
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Join Date: May 2004
Location: League City, Texas
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Fuel pump runs continuously
1974 911s 2.7
I have a question about the fuel pump on the early CIS systems. Is the fuel pump supposed to run continuously when the key is in the run position even if the car is not running? I did several searches and users were discussing the 1978 SC and later vehicles. It was said there was a safty device that provented the fuel pump from running when the car was not actually started.
I had problems getting my fuel pump to run after I pulled an old alarm system off the car. After looking at the wiring diagram I found the wires for the fuel pump on the fuse block and got them connected. The car started up but I was worried about the fuel pump running all the time.
Also, the hose going from the fuel accumilator to the metal line leading down to the fuel pump is leaking really bad. I searched Pelican's online catalog and it was not listed. I'll see if they have it in the morning... does anyone have a suggestion for another parts house that may have it? (close to Houston
)
Thanks!
-Stephen
I have a question about the fuel pump on the early CIS systems. Is the fuel pump supposed to run continuously when the key is in the run position even if the car is not running? I did several searches and users were discussing the 1978 SC and later vehicles. It was said there was a safty device that provented the fuel pump from running when the car was not actually started.
I had problems getting my fuel pump to run after I pulled an old alarm system off the car. After looking at the wiring diagram I found the wires for the fuel pump on the fuse block and got them connected. The car started up but I was worried about the fuel pump running all the time.
Also, the hose going from the fuel accumilator to the metal line leading down to the fuel pump is leaking really bad. I searched Pelican's online catalog and it was not listed. I'll see if they have it in the morning... does anyone have a suggestion for another parts house that may have it? (close to Houston
)Thanks!
-Stephen
06-03-2004, 02:51 AM
#2
Rennlist Member
The pump will run continuously if the wire to the switch on the back (toward front of car) of the air box under the fuel distributor is disconnected. It may have been done on purpose by a previous owner, or maybe at the shop when they were checking pressures, and they forgot to put it back on.
I have mine disconnected so that the car starts better. After replacing the accumulator, cold start valve, and fuel distributor, I was still having a hot start problem. I now suspect that it is the check valve inside the fuel pump, but I am not ready to replace the pump yet, since it is still working fine. What happens is that system pressure slowly goes down below what is needed to fire the injectors. With that safety wire connected, the pump will only run for a second or two unless the switch is activated by the engine running, which isn't enough to get the pressure back up on my car. I turn the key to on, let the pump run for 5-10 seconds to build systen pressure, and it always started immediately, no matter what the weather or engine temperature. Before disconnecting the wire, hot starts were always a problem, sometimes embarassingly so. (Not good to park somewhere for 15 mins or so, and come back out to your sweet looking ride and have it not start easliy....costs major cool points! :-) )
No info on the line....maybe used, from someplace like Parts Heaven?
I have mine disconnected so that the car starts better. After replacing the accumulator, cold start valve, and fuel distributor, I was still having a hot start problem. I now suspect that it is the check valve inside the fuel pump, but I am not ready to replace the pump yet, since it is still working fine. What happens is that system pressure slowly goes down below what is needed to fire the injectors. With that safety wire connected, the pump will only run for a second or two unless the switch is activated by the engine running, which isn't enough to get the pressure back up on my car. I turn the key to on, let the pump run for 5-10 seconds to build systen pressure, and it always started immediately, no matter what the weather or engine temperature. Before disconnecting the wire, hot starts were always a problem, sometimes embarassingly so. (Not good to park somewhere for 15 mins or so, and come back out to your sweet looking ride and have it not start easliy....costs major cool points! :-) )
No info on the line....maybe used, from someplace like Parts Heaven?
