Fuel Pressure Problems
03-14-07, 12:21 PM
#1
Senior Member
Thread Starter
Join Date: Nov 2001
Location: Malaysia
Posts: 567
Likes: 0
Received 0 Likes
on
0 Posts
Fuel Pressure Problems
Hi All,
I've been trying to figure this one out for a while now with no luck. Perhaps someone here can point me in the right direction.
I've set my static FP at 32psi and even after i turn on the engine it stays at 32 psi. When i WOT fuel pressure never exceeds 40psi. DOes this sound right?
I've wired the fuel pump to the battery via a relay. Any insight or ideas are most welcomed.TIA.
Regards,
Dave
I've been trying to figure this one out for a while now with no luck. Perhaps someone here can point me in the right direction.
I've set my static FP at 32psi and even after i turn on the engine it stays at 32 psi. When i WOT fuel pressure never exceeds 40psi. DOes this sound right?
I've wired the fuel pump to the battery via a relay. Any insight or ideas are most welcomed.TIA.
Regards,
Dave
03-14-07, 01:29 PM
#3
Recovering Miataholic
Here is a paragraph by me from an earlier thread:
The 1994 factory manual states on page TD-4 that the FPR specs are 35.6 - 37.0 psi output pressure. (The fuel pump itself should provide 71.1 - 106.7 psi.)
Fuel pressure was tested with engine not running (obviously), F/P jumpered to ground, MityVac directly connected to FPR control line, gauge teed into input fuel hose. Results: Fuel pressure at 20" Hg vacuum = 34 psi. At atmospheric pressure = 43 psi. At 10 psi simulated boost = 51 psi. Pressure held up well, I thought. After killing ignition at 34 psi, it stayed above 30 psi for 5-6 minutes, down to 20 psi in about 30 minutes, and down to zero in about 2 hours.
Last edited by wstrohm; 03-14-07 at 01:35 PM.
03-14-07, 05:18 PM
#5
Senior Member
Join Date: Jun 2002
Location: Cincinnati
Posts: 415
Likes: 0
Received 0 Likes
on
0 Posts
Are you testing the fuel pressure with the car running?
There are 2 relays for the fuel pump, the standard fuel pump relay and then fuel pump relay (speed) which bypasses the resistor and increases the voltage to the pump. Make sure you didn't take this out of the loop when you wired it up.
edit : I see that you did your own wiring and took the resistor out of the equation. Have you tested the voltage at the pump? It sounds like either you're not getting enough voltage (bad relay or wires), pump on its way out, or maybe you have a clog somewhere in the line prior to where you're checking the pressure.
charlie
There are 2 relays for the fuel pump, the standard fuel pump relay and then fuel pump relay (speed) which bypasses the resistor and increases the voltage to the pump. Make sure you didn't take this out of the loop when you wired it up.
edit : I see that you did your own wiring and took the resistor out of the equation. Have you tested the voltage at the pump? It sounds like either you're not getting enough voltage (bad relay or wires), pump on its way out, or maybe you have a clog somewhere in the line prior to where you're checking the pressure.
charlie
03-14-07, 11:19 PM
#6
Senior Member
Thread Starter
Join Date: Nov 2001
Location: Malaysia
Posts: 567
Likes: 0
Received 0 Likes
on
0 Posts
Thanks for the feedback guys. I pretty much worked on the back of the car. Splicing 12V power supply wire to pump and running it directly to battery via relay.
What sort of fuel pressure are you guys seeing in the following rpms:
Idle -
0psi-
Boost-
What sort of fuel pressure are you guys seeing in the following rpms:
Idle -
0psi-
Boost-
Thread
Thread Starter
Forum
Replies
Last Post
trickster
2nd Generation Specific (1986-1992)
25
07-01-23 04:40 PM