I seem to have a wierd fuel pressure regulator? For the last few weeks I’ve had the regulator set to 3 bar, I’ve now filled the tank whilst programming my fuel gauge and the regulator is now reading just under 4 bar and won’t adjust back down to 3.

It’s not a cheapo china made one but it isn’t an expensive one.

1: Has anyone else had the same issue,
2: does it sound like a faulty regulator.
3: if my tank is full + the filler neck the return would be under the fuel level, would this cause a pressure increase through the regulator.

I know Dale at Bailey Performance removes adjustable regulaters when he maps cars,as he says you waste loads of time fiddling with them and getting unrealiable readings!

He recommended a 1:1 rising rate Bosch reg for mine

Yes but not that much. 1/2 a psi per foot of additional head pressure is the rule of thumb for water and about 0.7 of that for gasoline

The car now won’t start. I can hear the fuel in the return pipe at the regulator, it sounds airy.

There is fuel flowing to the TB’s (took the line off and ran the pump into a can). Should the gauge still read a pressure? Before at 3 bar the pressure gauge held at 3 bar for a while after the engine stopped, It now drops to 0 straight away.

Sounds like broken check valve - when you turn the ignition before starting, it should run the pumps for a moment to pressurise the line and then the check valve holds the pressure. Usually this valve is built into the pump, but the simplest solution is to buy one and put it between the fuel pump and the regulator.

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Originally posted by rodgling
Sounds like broken check valve - when you turn the ignition before starting, it should run the pumps for a moment to pressurise the line and then the check valve holds the pressure. Usually this valve is built into the pump, but the simplest solution is to buy one and put it between the fuel pump and the regulator.

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The car should still run without a check valve, it migyt take a few more seconds to start but it will still work fine. My car doesnt have one and runs perfectly, fuel pressure drops to 0 as soon as the pump stops.

Can you try a standard pressure regulator with the gauge still attached to see if it holds a steady pressure?

It’s holding at 3.7bar dropping to 0 when the pumps off. No vac line attached, doesn’t seem to be leaking fuel anywhere, just unable to adjust the pressure down and won’t run. All was fine on Tuesday just a little rich and showing 3 bar. now nothing and high pressure. The only thing I’ve done is fill the tank.

Is the tank vented properly? Where does the return line go to - is it low in the tank i.e. now that it's full it's "more difficult" for the returned fuel to go back in? I'm clutching at straws here - doesn't seem to make any sense!

The check valve won't affect your excess pressure issue, that sounds like the regulator. I think you have two issues here, a broken check valve and a broken regulator.

FYI my car won't start (maybe one time out of ten it will) without a check valve, so if yours used to hold pressure and now it doesn't, and it used to start and now it doesn't... this is probably the issue.

The return is in the top of the tank next to the filler neck, if the tank is full up the neck then the vent will be under the fuel level... the vent is an inline one with the vent pipe looped down and out underneath the car. I haven’t checked yet to see if thats blocked.

Did it run out of fuel? I'm just wondering if the FP gauge has air in it and giving a dodgy reading - I would have expected it to read zero though with air in it.

It got low on fuel but it didn't run out, I’ve had the TB connection off and ran the pump so there shouldn’t be any air in it? I’m going to remove the tank vent tonight and check its the right way round. All i can think of other than a faulty regulator is if the tanks not venting and pressurising the return line????

So I’ve just been to check over wverything again.

Tank vent is ok.
Drained 5 ltrs to lower the level.
Tried adjusting the regulator , now about 3.6 on the gauge. (doesn’t mean its right)
Removed and checked the plugs, (a little black and wet).
Reloaded a different map and it tried to fire but then died.

plugged in the laptop and all sensor seem to be reding ok and the ecu seeing crank signal.
The only thing i’ve noticed with the laptop plugged in is the coolant temp is highlighted red. Reading the manual it says theres a fault with the sensor?
So not only do i seem to have a faulty regulator my coolant sensor seems to be fubar as well.

Don't get too fed up, I could have built a second car out of the bits that were faulty, wrong or mispurchased! Whathe TBA set up are you using?

Check all the terminals are pushed into the sensor connectors before putting a new coolant temp sensor in, I had a faulty crank sensor that turned out to be a pen pushed out of the plug - that was with an emerald supplied loom 8 d9nt know if yours was?

Hayabusa TB, I’ve checked the pins are all ok, taking the coolant sendor out of the housing it reads <-30 on thr live adjustments red 80 with it in. never done that before. I loaded your IVA map on tuesday and it purred along better than it ever has before. it is the original coolant sensor so its 17 years old, add the regulator issues to it and all of a sudden its 2 days of hair pulling.