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Faulty Fuel pressure regulator?
MkIndy7 - 26/4/11 at 02:42 PM

Howd'y.. being a skinflint i've gone and bought one of those £35 type Nice and shiney Adjustable fuel pressure regulators from ebay with the guage on.

With the fuel pump running you can set the pressure etc but as soon as the fuel pump stops the guage drops to zero,
Should this not remain at the set pressure?
or is the guage actually in the return leg?

Unfortunately theres no Schrader valve on the rail for me to test its true pressure as its a modified duratec rail.
I have a sneakey feeling this regulator has been opened before and is damaged aswell as being dreadfull quality

I'm having a nightmare trying to start the car for the first time, but suppose I need to be sure of the physical things before I blame it all on the Megasquirt!

[Edited on 26/4/11 by MkIndy7]

MakeEverything - 26/4/11 at 02:48 PM

The pressure will drop, as the regulator only restricts the return flow.

I had nightmares getting megasquirt set up on mine, and it turned out to be my fault (well, not completely, but it wasnt the MS at all).

Dont be too quick to condemn it. The MS systems are very robust and its very hard for it to prevent an engine starting. Check the throttle / idle valve, injectors, earths, etc etc. Then set up MS according to Extra-EFI instructions and give it a go. You should get something from these base settings on www.extraefi.co.uk.

tomgregory2000 - 26/4/11 at 02:49 PM

the pressure gauge should be placed in the feed line.

some fuel pumps hold the pressure in the fuel line when they are turned off but mine (bosch 044) does not hold the pressure with the pump off

ive never trusted those cheap regs, comes under the old saying, ye get what ye pays for

MakeEverything - 26/4/11 at 02:53 PM

quote:
Originally posted by tomgregory2000
the pressure gauge should be placed in the feed line.

some fuel pumps hold the pressure in the fuel line when they are turned off but mine (bosch 044) does not hold the pressure with the pump off

ive never trusted those cheap regs, comes under the old saying, ye get what ye pays for


The gauge on the regulator is on the feed side. The plastic diaphragm inside is pressed against the feed holes to restrict flow to the return.

The pump itself will not prevent a back flow, though some pumps are fitted with a one way valve to stop fuel draining back to the tank and causing problems starting / leaning out at startup.

MkIndy7 - 26/4/11 at 02:59 PM

I wanted to use an OEM style one but not knowing (for definate) what pressure the standard duratec injectors need to be run at we thought we'd better go with an adjustable one.

Have tried quite a few maps but there doesn't seem that many about or have a very good description of them, were running the standard manifold so that might be a disadvantage as most maps are probably for ITB's

Have tried fuel values up and down but the longest i've had it running is about 10sec and random backfires from the induction and exhaust.. so am tempted to wire up and EDIS aswell in limphome mode to control the sparks (I've never been that happy with the sparks side of MS even when running it on the old engine) untill its running just to rule that out.

Was just a little querie before I head off home to a freshly charged battery to try again tonight!

matt_gsxr - 26/4/11 at 03:10 PM

I've got one of these cheapy ones too (Mine was direct from McGillMotorsports).

Seems to work fine. The pressure does drop off by design, but that is a good thing (to my mind), previously I had a dead head system with a gsxr1000 pump (and regulator) and then I used to get sprayed with fuel when I had to swap and injector. Now its much drier. I liked the gsxr1000 set-up but it didn't supply enough fuel for my needs!

Exact pressure shouldn't matter much as long as the pressure is consistent, its all mechanical so I wouldn't expect its performance to drop-off with use. The gauge is a bonus as you can tell what is going on.

BobM - 26/4/11 at 03:22 PM

I've just thrown away the cheapie I got from McGill Motorsports on EBay. I initially set it up correctly then on first test day it was reading nearly 70psi.

At the first race at Mallory the pressure was swinging all over the place and triggering my DigiDash low fuel pressure alarm, dropping below 20psi and making the lambda a bit lean. Fitted a decent FSE one and at Brands last time out pressure was rock solid at 44psi.

matt_gsxr - 26/4/11 at 04:56 PM

Interesting fault. Maybe it got blocked.

It difficult to know what can go wrong with a spring.

I'll keep a closer eye on mine now.

Matt

MakeEverything - 26/4/11 at 05:05 PM

quote:
Originally posted by matt_gsxr
Interesting fault. Maybe it got blocked.

It difficult to know what can go wrong with a spring.

I'll keep a closer eye on mine now.

Matt


Its not just a spring though. It is possible that it could block inside the void of the diaphragm if theres no pre-filter.

With mine, i ditched the adjustment screw (which screwed all the way in with no effect) and replaced it with a bolt and lock nut. Ever since, its settled down to give me a constant 2.5 bar. Im planning to up this which may mean a new regulator.

matt_gsxr - 1/5/11 at 10:10 PM

I have investigated this a bit more.

If I up the pressure to 4atm then it retains the pressure,

Also the pressure was adjusted to 4atm and now (Stoneleigh and back) it has crept to 4.3atm.

I think I am going to invest in one from a well known brand and let McGill know. It just isn't worth the risk.


To Dr Bob: Sorry for doubting the empirical evidence

Matt