Bosch Fuel Pressure Regulator AN Adapter

[nick_968]

I currently have issues with my Fuel Lab adjustable fuel pressure regulator as it bleeds off pressure quite fast and this is causing me hot start problems i.e. vapour lock.

I would like to go back to the factory style Bosch pressure regulator but as I am now running AN fuel lines I need something that can house the regulator and allow the AN lines to connect. Either that or a fuel pressure regulator that is known to hold pressure well that takes AN lines.

From speaking to Fuel Lab it seems their FPR's lose pressure by design so there is nothing they make that will solve the problem and as such no point in buying a new one the same. As most of the others seem to be similar design, not sure if there is any point in trying those either. I would have thought this is a common problem but not managed to find a solution other than going back to the factory setup.

I have seen products from international sellers that seem to house the Bosch unit with AN ports but wondered if there is anything similar available here in the UK or if anyone has any better ideas?

[Steve_D]

Are you saying you have issues with it losing pressure after the pump has turned off?

If so then I'm failing to see why that would be a problem as the pressure will come up again within seconds of the engine start or even before if the ECU has a prime setting.

Steve

[nick_968]

Its a hot start issue. No issues when cold. The pressure is dropping fast enough that it makes hot starts a pain compared to running the same setup with a factory regulator which has virtually zero pressure drop. If you have pressure drop, you get fuel vapour issues when hot.

I don't really need any help on the diagnostic side as it is an issue I have done to death, its a full standalone system and I can get it going with more fuel but it is still not ideal and hence looking to go back to a factory regulator as they don't lose pressure, just stuck with the AN lines due to running a billet fuel rail hence the question.

[eliot]

My rail drops to zero on key off and I've never had a problem. (bosch 044 with missing one way valve)

[nick_968]

No doubt yours is fine, but mine is not....even cars with the factory setup, it is listed in the manuals if the factory regulator loses pressure you will get hot start issues.

The question is does anyone know of a way to fit a factory style Bosch regulator but using AN fittings?

[stevieturbo]

Never had any starting issues on any car where the FPR or pumps allowed pressure to drop.

You know the pump primes on key on....there will always be pressure available to start the engine unless something else is badly wrong with the system

[nick_968]

It is not a problem with priming, the system primes fine. The problem is not there on an identical setup without the pressure drop and it is a known issue on these cars (944 turbo) that if you have a weak FPR you will be likely to get hot start issues.

[stevieturbo]

Post a picture of exactly what your after then, it may help.

But if the system is primed and there is pressure in the lines.....there is zero problem really.

[eliot]

You can of course prove your theory by removing the fuel pump relay and connecting a piece of wire in place of the relay contacts(pins 30 &87) to run the pump continuously as a test.

[nick_968]

Clearly no one on this thread has experienced fuel evaporation on a hot engine. Re jumping the fuel pump relay I am not sure what that would achieve? I already have a fuel pressure gauge that shows clearly that the pump is priming.

[nick_968]

stevieturbo said:

Post a picture of exactly what your after then, it may help.

But if the system is primed and there is pressure in the lines.....there is zero problem really.

https://www.efihardware.com/products/2336/EFI-Hardware-Fuel-Pressure-Regulator-Housing

Above is the kind of thing I am looking for but not very common in the UK. Re - zero problem, interesting that everyone is quick to point out that I don't have a problem. This is a long standing issue and almost certainly due to pressure bleeding off which as I have tried to point out will cause an issue on this setup, as recognised by the factory. All I am trying do do is eliminate the most likely source of the pressure drop so I can rule it out or not. Happy to be proven wrong but nothing in this thread is making me think otherwise so far.

[Steve_D]

Is your fuel rail 'dead head' or is the pressure regulator after the rail?

If the regulator is after the rail I fail to see why a prime will not clear any vapour prior to start.
If the regulator is before the rail then I can see that a vapour lock could cause an issue.

Steve

[nick_968]

The regulator is effectively on the return end of the rail but it then feeds back into the tank down the return line.

[eliot]

nick_968 said:

Clearly no one on this thread has experienced fuel evaporation on a hot engine. Re jumping the fuel pump relay I am not sure what that would achieve? I already have a fuel pressure gauge that shows clearly that the pump is priming.

My engine is a 5.7 twin turbo with the turbo's mounted high up next to the rocker covers and it gets very hot after a shutdown yet always starts despite zero rail pressure.
The idea of running the pump is so the rail pressure doesn't drop to zero which would prove the theory - just trying to help.....

Anyway i'll ask an mate who own's and spanners on porsche to drop in to see if he can assist...
calling Ant..

[LarJammer]

Ant here...
Before going any further Id like to dispute the fuel vapourization myth on porsche 944's. It seems to be an internet invention. Ive tested loads of them and as yet havent been able to blame poor hot starting problems on vapour. I am also ready to be proven wrong.

op how are you testing fuel pressure?

Anyway, the early 944t uses a 2.5bar regulator with a metric fitting on one end, the other end is a push fit into the stock fuel rail. all later regs and the 3bar versions use push fittings so neither will suit an aftermarket rail. but since you are using an aftermarket ecu (the stock ecu only enables the fuel pump whilst in crank / run) cant you simply prime the pump for a few secs with ign on?
Ill have a think about it...

[stevieturbo]

nick_968 said:

https://www.efihardware.com/products/2336/EFI-Hard...

Above is the kind of thing I am looking for but not very common in the UK. Re - zero problem, interesting that everyone is quick to point out that I don't have a problem. This is a long standing issue and almost certainly due to pressure bleeding off which as I have tried to point out will cause an issue on this setup, as recognised by the factory. All I am trying do do is eliminate the most likely source of the pressure drop so I can rule it out or not. Happy to be proven wrong but nothing in this thread is making me think otherwise so far.

If you believe that will fix your problem...why not just buy it ?

Or what is the problem with the OEM rails and regulator that you cannot connect whatever hose type you're using to it ?

Exactly what hose and sizes are you using ?

Googling seems to bring up images showing a regular barb on the FPR so unless you're actually using teflon hose and on the return line, it should be a doddle to hook up to it.

[eliot]

Does your fuel pump have a one-way valve fitted - as that's more likely to keep your rail pressure up rather than the FPR.
Again - you can test your theory of a leaky FPR by simply putting the return hose into a container and look for a dribble after key-off
Are you sure your pump is running during cranking?

[eliot]

nick_968 said:

its a full standalone system and I can get it going with more fuel but it is still not ideal and hence looking to go back to a factory regulator as they don't lose pressure, just stuck with the AN lines due to running a billet fuel rail hence the question.

You sure your Air temp sensor isn't heat-soaking? If it's a MAP based system, a heat soaked AIT will make it go lean on restart.

What system is it? Datalogs?

[nick_968]

LarJammer said:

Ant here...
Before going any further Id like to dispute the fuel vapourization myth on porsche 944's. It seems to be an internet invention. Ive tested loads of them and as yet havent been able to blame poor hot starting problems on vapour. I am also ready to be proven wrong.

op how are you testing fuel pressure?

Anyway, the early 944t uses a 2.5bar regulator with a metric fitting on one end, the other end is a push fit into the stock fuel rail. all later regs and the 3bar versions use push fittings so neither will suit an aftermarket rail. but since you are using an aftermarket ecu (the stock ecu only enables the fuel pump whilst in crank / run) cant you simply prime the pump for a few secs with ign on?
Ill have a think about it...

Hi Ant - As mentioned above the system primes fine for 5 secs as I have set it to do in the Motec software. Fuel pressure gauge is mounted to the FPR.

[nick_968]

eliot said:

Does your fuel pump have a one-way valve fitted - as that's more likely to keep your rail pressure up rather than the FPR.
Again - you can test your theory of a leaky FPR by simply putting the return hose into a container and look for a dribble after key-off
Are you sure your pump is running during cranking?

Yes to a one way valve on the feed and I added another one further up near the engine to be sure in case the one on the pump was faulty.

Yes the pump is priming and the pressure comes up fine on the gauge, re cranking it is hard to hear but it primes as soon as the ignition comes on and I can turn the key on again while it primes a second time and crank it just to be sure and still no different.

Re the leaky regulator all of the adjustable regulators like Fuelab, aeromotive etc bleed off pressure by design when they are not running so it is not faulty per se.