76LQ9TA

iTrader: (1)

What controls the length of time that the fuel pump runs when the ignition switch is first turned to the run position? My car is cycling the relay on and off very quickly and doesn't stop until the key is off. I have checked the wiring on the four pins of the relay and swapped out the relay. I am thinking that I have a bad pcm. Everything was working two weeks ago. Is there anything that I can check before I send out the pcm?

jay_lt4

iTrader: (4)

check your supply voltage at the relay, low voltage can cause relays to pulse on and off

76LQ9TA

iTrader: (1)

The voltage is good. I thought about that. The car was also hooked up to the battery charger.

Carshopinc.com

iTrader: (5)

Is the battery good? The pcm may be acting funny if the voltage is low...

76LQ9TA

iTrader: (1)

I found the problem last night. One of the ground wires was loose. The bolt bottomed out and left the terminal a little loose.

pushrod36

I want to resurrect this thread because I am having a similar problem. My fuel pump relay is cycling very quickly, but I do not believe that it is because of a bad ground (grounded to the same location as the negative battery terminal). I also know that I have 12 volts coming from the ECU.

Just like 76LQ9TA said, the relay chatters and does not stop until the key is off. I have the added complication, though, of the engine won't start with the relay connected. If I build fuel pressure, and then disconnect, it fires right up. This makes me think there is short through it (short would still provide the 12v that I see).

Any thoughts?

Pop N Wood

iTrader: (1)

Could be a bad relay. Could also be wired wrong. Has the harness been modified?

pushrod36

More information...

If I unhook either the lead from the battery, or the wire to the fuel pump the relay behaves exactly as it should. I am thinking that this means a bad ground at the fuel pump. I'll let you know how that pans out for me.