Fuel pump relay (speed)
07-04-08, 05:51 PM
#1
Fuel pump relay (speed)
When you jump the F/P and GND terminals in the diagnostic box should the fuel pump relay activate and provide full voltage to the pump? I would think so because the FSM says to listen for relay operation during "key on".
Mine is not switching on. The relay tests out fine and the 12 V hot source is good. The other end is not grounded and after looking at the wiring diagram it looks like it gets switched to ground by the ECU. This concerns me because I just installed an untested PFC. I haven't run the car with it yet, but it turns on and the commander functions as it should. I don't have a stock ECU to test with.
Any ideas?
Also, I am running dual pumps and they don't produce enough pressure with the resistor. I'm only seeing ~30psi with the feed line plugged after the pressure sender. I'm pretty sure there aren't any leaks because it holds that pressure for a LONG time. With the resistor bypassed the pumps see full battery voltage and produce a healthy 90+ psi.
It looks like I'll need to eliminate the fuel pump relay and bypass the resistor anyway to get enough pressure at idle/low load. Either that or find a different resistor to meet my needs.
I have done a full rewire of the fuel pump circuit as well, including providing a direct positive source to the circuit opening relay from the battery.
Mine is not switching on. The relay tests out fine and the 12 V hot source is good. The other end is not grounded and after looking at the wiring diagram it looks like it gets switched to ground by the ECU. This concerns me because I just installed an untested PFC. I haven't run the car with it yet, but it turns on and the commander functions as it should. I don't have a stock ECU to test with.
Any ideas?
Also, I am running dual pumps and they don't produce enough pressure with the resistor. I'm only seeing ~30psi with the feed line plugged after the pressure sender. I'm pretty sure there aren't any leaks because it holds that pressure for a LONG time. With the resistor bypassed the pumps see full battery voltage and produce a healthy 90+ psi.
It looks like I'll need to eliminate the fuel pump relay and bypass the resistor anyway to get enough pressure at idle/low load. Either that or find a different resistor to meet my needs.
I have done a full rewire of the fuel pump circuit as well, including providing a direct positive source to the circuit opening relay from the battery.
07-06-08, 09:58 AM
#3
Eye In The Sky
iTrader: (2)
Join Date: Feb 2001
Location: In A Disfunctional World
Posts: 7,895
Likes: 0
Received 114 Likes
on
66 Posts
There are two FP relays. The main and speed control. You are only activating the main which supplies the +12V to the system.
You have to manually jump the speed relay to get full voltage to the pump.
You have to manually jump the speed relay to get full voltage to the pump.
07-06-08, 10:37 AM
#4
This is the quote from the FSM that confused me:
The relay does not activate when the ignition is switched to on. Maybe it isn't supposed to and it is just an error in the FSM. That wouldn't surprise me... lol. It should be off during idle and low load anyway.
Right now I have the speed control relay jumped and the car is running OK. I'd like to keep the functionality of the dual speed system, but it appears that might be impossible with dual pumps.
The following users liked this post:
tomatoto (03-15-20)
07-06-08, 02:22 PM
#6
The circuit opening relay is over by the battery. The relay I am concerned about is the fuel pump speed relay by the front of the car.
Thread
Thread Starter
Forum
Replies
Last Post
trickster
2nd Generation Specific (1986-1992)
25
07-01-23 04:40 PM
immanuel__7
2nd Generation Specific (1986-1992)
89
09-05-15 10:23 AM
