Fuel pressure drop and wont start.

L18M · August 23, 2014, 01:03:44 PM

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

shaunwil · August 23, 2014, 01:10:51 PM

Any photos of how the FPR is plumbed up ?

Shaun

L18M · August 23, 2014, 03:36:31 PM

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.

shaunwil · August 23, 2014, 03:55:48 PM

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

L18M · August 23, 2014, 07:05:53 PM

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?)

shaunwil · August 24, 2014, 12:54:19 PM

Image attached. pm me your email and I\'ll send you the original document.

Shaun

rx7boy · August 24, 2014, 01:48:16 PM

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.

L18M · August 24, 2014, 02:31:49 PM

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.

L18M · August 24, 2014, 02:48:34 PM

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.

shaunwil · August 24, 2014, 06:11:26 PM

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

L18M · August 24, 2014, 10:03:27 PM

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.

shaunwil · August 25, 2014, 09:59:21 AM

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

Arnie_O · August 25, 2014, 10:20:02 AM

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

L18M · August 25, 2014, 01:07:42 PM

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?

Arnie_O · August 25, 2014, 01:47:42 PM

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