I'm getting 5-0 volts to the fuel pump(new), what is most likely to go the fuel pump relay, ignition switch, or opti (one month old)ac delco.

Before the car stalled it had a rough idle and while driving on occasion it would almost die but get started again. When I checked the fuel pressure, it would fluctuate from one day to the other, ie. one day it would get 42psi and another 10psi. From these symptoms I would say probably a low resolution from the opti but not sure since I thought the pump would at least prime at start up, and there is spark. Also no codes where thrown.
Any suggestions would be greatly appreciated

Is there a company sell optical sensors?

 

5volts.... thats it??? your supposed to get at least 12volts to the pump, may have a fuel pump relay, the opti has nothing to do with the fact that your fuel pressure fluctuates, if you have spark that its all good sounds like a fuel problem

 

The opti pulse train has nothing to do with fuel pressure. So, I'm betting your new opti is still good. Check the voltage before and after the fuel pump relay and see what you have.

No you cannot get optical sensors for the opti.

 

There is voltage before but only 5v after, I went ahead and changed the fuel pump relay anyways and still stayed the same. I guess its time to start looking for the ignition switch. Also the gauges stopped working

 

what gauges stoped working, be more specific, all of them? did you check all the fuses? how do you have proper voltage before the relay but after the relay you have 5v even with a new one? is ignition in on position? loose ground somewhere?

 

Sorry for being vague, oil, fuel, batt., gauge were not working even as I cranked the engine over. The 'check all gauges' light was on. I have been checking for a short but have not found one yet. All fuses are good. Ignition was in the on position when checking voltage. sometime tomorrow I will retrace all the wires leading to the fuel pump to make sure there are no frayed wires.

 

What is the battery voltage when the fuel pump circuit is only supplying 5V?

 

The first time I checked it the battery was ~12v, fuel pump circuit after relay 5v. Tomorrow I will also re-check the ground were the fuel pump assembly is at.

 

Check the relay incase the wires wore their "jackets" out. Since the wires plug in like in a wall outlet, mine just increased in size over time and had me think that the pump was out. Maybe it isn't making a good connection with the relay.

 

Finally went back to check the car yesterday and got it started. Red 95 was right I was loosing ground, for some reason the stock location for ground in the fuel pump assembly area was no longer getting ground so I changed the ground location to a terminal next to the fuel gauge and the pump started immediately when the ignition was turned on. It took me a long time b/c the car was at my work place and I could only check it when I was able to get a ride over there.
Thanks to everyone who responded, greatly appreciated.

 

glad we were able to help out and happy you told us the solution as many dont report back when there problems are fixed

bad grounds can do some wierd things in a electical system