Hi hi,
Setup: kgrail secondary rail, 1680cc inj. oem primary rail, 550cc inj. sard fpr. bosch 044 fuel pump.
(see vid for quicker explanation)
I\'ve replaced the secondary fuel rail on my fc with an aftermarket one. There was a vac line going into the oem secondary rail (think coming from the block?) which i have blocked off as the kgrail does not need vac line plugged in.
The fuel pump primes and holds 1.1kg/cm^3 but when cranking the engine over, after a couple of seconds the fuel pressure drops to zero until i stop cranking which it returns to 1.1kg/cm^3.
Would this have something to do with the blocked off vac line? Should that be plugged into the fpr?
There is already a vac line from frp to the block.
http://youtu.be/RPHjSmreiGw
(sorry forgot how to embed the video)
Thanks in advance guru\'s :cheers
Any photos of how the FPR is plumbed up ?
Shaun
Hey Shaun,
No pics as car is not with me, at garage and i paid her a visit earlier to try start her.
Using pic as ref:
A - vac line to uim (off the top of my head)
B - to secondary rail
C - fuel return?
Was working before i changed the secondary rail. B was connected to secondary rail which i replaced. C i didn\'t touch. A i didn\'t touch.
The only thing that\'s different now is the vac line going to the secondary rail (from uim? or block) is blocked off.
Hope this helps more.
(http://i121.photobucket.com/albums/o231/Vindi06/DSC_0959-1.jpg)
Video just looks odd. The pressure on mine (aeromotive FPR) bleeds off slowly when the car is switched off (when pump stops) so I wouldn\'t expect there to be a problem with the pump. Just wondered if it was plumbed back to front.
Looking at the workshop manual there is a Pressure regulator solenoid control valve (pg 4A-5) not sure if its the EFI one though.
Shaun
I only took one pipe off when i changed the secondary rail and plumbed back in.
Was working fine before so only thing i can think of points to the vac line i blanked off that came off the oem secondary rail :(
Any change of a pic of that page shaun?
The vac line in the oem fuel rail operates the in-built fpr but as i have external one then that vac line is not required?
Unless i need to split it so it plugs into the fpr? (though im sure the vac line in the fpr is plugged into the block so same source?)
Image attached. pm me your email and I\'ll send you the original document.
Shaun
Remove the vac line going to the frp and block off the feed pipe, and try and start.
During vacuum condition the pressure line to the frp lowers the fuel pressure from whatever you set it at.
From the vid the pressure gauge is showing a very large decrease in pressure (more than vacuum would cause), so suspect that either your frp needs adjusting/faulty or there is an issue with your fuel pump coming on long enough to clear any air locks.
I\'m not familar with the FC wiring system, on the FD the pump primes for 5 seconds and then shuts off until the engine starts. If you have switch rails then you most likely have drained all the lines and could have an air lock in the rails. If you can jump the pump so that it is continuously running and allow it to run for a few mins to help clear any vapour locks then try and start the car with it running.
Cheers shaun, email: rex7parts (at) googlemail com
re7boy: the fuel pump is wired so it is constantly on and relayed via the battery so there is a good power to the pump.
the line pressurises so seems its gotten rid of air in the line.
FPR is new and only covered 1000 miles (ish). Will try leave pump on for a min or two just to get any more air out.
From the diagram i think maybe try swapping the blocked off vac line and plugging that into the frp. not sure what to do with the current line in the frp.
after some googling, it seems not all vac lines are the same off the block (noobie error)
seems the fpr needs to be plumbed into the Pressure reg solinoid valve.
so the vac line that was goinging into the om secondary rail needs to specifically be plumbed into the fpr.
Just need to find out where the current fpr vac line is plumbed into and either block it off or do something else with it.
Anyone know where the 4 solinoid valves are located? I hone have car with me to check it out.
(http://www.rx7club.com/attachments/2nd-generation-specific-1986-1992-17/317308d1224499169-vacuum-hose-diagram-1987-mazda-rx-7-turbo-ii-coloredtwo-jpg)
Its probably worth hot-wiring the fuel pump and let it get rid of all the air.
Plus 1.1kg/3 doesn\'t sound like a lot of pressure, is the FPR a rising rate one or fixed ?
Shaun
Got the email, thanks Shaun :cheers
Its a Fixed 1:1 FPR.
Any ideas what fuel press should be at ON position? idle?
I think its the vac line thats causing the issue, will have a play tomorrow and see if its any better.
Should say somewhere in the manual. If you haven\'t changed it I would adjust it to be honest. I\'m going off FD knowledge and it runs on a rising rate regulator.
Shaun
F should be running 34psi from memory. Though I have mine set to about 38psi running a smiler set up.
Bosch 1680 secondaries in a KGParts Rail
With standard primaries.
Aeromotive A1000 FPR
I used the stock FPR vac feed that did not go through a Solanoid.
Mine is running an Aeromotive Stealth 340 in tank and an Apexi PFC. All solanoide haberdashery been removed.
Have attached a guide taken from FC3s Pro on plumbing an FPR I know its aeromovive they refer to but it should be similar. I did plum mr rails in series though (not parallel) to simplify the piping
Thanks guys.
Same setup as you Aston. The VAC line is plumbed into lim where OEM VAC line is and running in series.
I\'ve adjusted the for to 34psi and tried cranking it over. Same thing happens. It primes to 34psi, then when you crank engine, the fuel press drops to 0. Then if you stop cracking it returns to 34 psi.
Can\'t think of any reason why, VAC leak should show even before cranking?
You tried cranking with the vac line on the top of the regulator removed and. There is no reason I can think of why if you\'ll be dropping. Unless your fuel pump is not getting enough current while cranking.
If you have a second battery maybe try wiring the pump to that then crank it.
The risk you have is continually cranking and failing to start you could flood the motor
woo.. found the problem. though was very mysterious. the fuel pump relay, switched the wires around a bit and works without fuel drop.
Very mysterious as was working fine before.
The joys of modified motors lol
Thanks for the input guys :)
Glad your sorted.
Enjoy the car.
Good to hear you found it :D
Shaun
Could be that if you \'rewired\' the fuel pump - you may have taken a positive feed to the fuel relay from a positive that\'s switched out during cranking.
Normally in the fuel pump rewire, you keep the existing fuel pump wiring but use it to only drive the relay coil, and then use a beefy fused positive straight from the battery to the fuel pump (or to the fuel pump resistor relay block if you are keeping the 2 speed fuel setup), maybe you took a positive feed that\'s not on with all three key positions other than off?
Its a weird one prof as the fuel pump wiring was done before and worked ok. then randomly decided not to work.
I think there\'s a gremlin in my car continuously causing me grief :(
You may have a faulty ignition switch, perhaps one of the 12v feeds is dropping when you crank? you could test this by disconnecting the 12v to the starter motor temporarily, and measuring the 12v feed to your fuel pump relay when your ignition switch is in cranking position. I used to have intermittent issue with wipers and roof motors not working and a gentle tickle on the ignition switch would have them working again...
If you are getting a solid 12v with the above test, then it could just be that the voltage drops so low during cranking that the relay drops out, could be a sign of a flat or dying battery.
ok thanks prof, will check it out once i get the car back :)