Fuel pump operation questions
10-04-13, 03:47 PM
#1
2stroke1971 (Neil)
Thread Starter
Join Date: Oct 2012
Location: east coast
Posts: 121
Likes: 0
Received 0 Likes
on
0 Posts
Fuel pump operation questions
ITs a 1985 Rx7, 5 speed with the 12A, Nikki 4 barrel.
I know it has a fuel pump relay under the dash.
I know the fuel pump runs at relatively low pressure.
What controls the relay normally? When running and driving, should the pump EVER cut off? If the pump runs constantly, it wont overload the carb, when the floats cut off flow, the gas just recycles right?
(Im troubleshooting a fuel problem. Very intermittant cutting out due to lack of fuel...mostly during long highway runs--Ive read the list of usual suspects, crap in the tank, filter, pump etc....just trying to understand what that relay does here.)
If I bypass the relay, (hot wire the fuel pump, and maybe add a cutout switch on the dash for those times when the ignition is on but the car is not running, would that work or what...it would eliminate a sketchy relay in any case as my cause.....
I know it has a fuel pump relay under the dash.
I know the fuel pump runs at relatively low pressure.
What controls the relay normally? When running and driving, should the pump EVER cut off? If the pump runs constantly, it wont overload the carb, when the floats cut off flow, the gas just recycles right?
(Im troubleshooting a fuel problem. Very intermittant cutting out due to lack of fuel...mostly during long highway runs--Ive read the list of usual suspects, crap in the tank, filter, pump etc....just trying to understand what that relay does here.)
If I bypass the relay, (hot wire the fuel pump, and maybe add a cutout switch on the dash for those times when the ignition is on but the car is not running, would that work or what...it would eliminate a sketchy relay in any case as my cause.....
10-04-13, 04:07 PM
#2
I thought about adding an indicator light to the dash and run the wire to power it from as close to the pump as possible. I'm having issues with the pump not running unless I jumper the reply connector. At least this would tell weather the pump has powder or not.
The funny thing with mine is that I've tried several relays and get the same no pump running issue. New pump, filter, and clean tank.
The funny thing with mine is that I've tried several relays and get the same no pump running issue. New pump, filter, and clean tank.
10-04-13, 05:50 PM
#3
Moderator
iTrader: (3)
Join Date: Mar 2001
Location: https://www2.mazda.com/en/100th/
Posts: 30,835
Received 2,604 Likes
on
1,847 Posts
the emissions control unit gets an RPM signal from the trailing ignitor and then turns the relay on for the fuel pump. so as long as the engine is spinning the fuel pump should be on.
way back when, i did have one Rx7 where the emissions control unit went bad, and it would run the pump with the key on, but shut it off with RPM, which was a ***** to find because with a carb the float bowls have enough fuel to run the engine for a minute or so.
i ended up bypassing the relay, so it worked with the ignition key, like the 83 and earlier cars
way back when, i did have one Rx7 where the emissions control unit went bad, and it would run the pump with the key on, but shut it off with RPM, which was a ***** to find because with a carb the float bowls have enough fuel to run the engine for a minute or so.
i ended up bypassing the relay, so it worked with the ignition key, like the 83 and earlier cars
Thread
Thread Starter
Forum
Replies
Last Post
trickster
2nd Generation Specific (1986-1992)
25
07-01-23 04:40 PM