Fuel pressure regulator

[Doulou]

Morning all

I have had a situation for some time now where by when the engine is cold the engine cranks over for around 10 seconds before firing, once fired everything runs fine. My question is, , is there an O ring fitted to the fuel rail other than the one inside the fuel pressure regulator itself? I am thinking that my fuel pressure isn’t high enough and may be leaking from somewhere on the fuel rail or pressure regulator, causing the excessive cranks.

also thought it’s worth mentioning that the fuel pump is new.

I may be well of the mark so any help appreciated.

thanks Paul

[sailorbob]

I would expect that if you have a fuel leak sufficient to cause cranking issues then you would also be having issues during higher fuel demand. Put a fuel pressure gauge on the fuel rail and see what pressure you are getting during KOEO and how quickly it drops after the fuel pump stops priming. Then see what happens to the pressure during cranking.

[Doulou]

Thanks Bob

i will order a fuel pressure testing kit

would you happen to know the name

of the adaptor on the FPRV when ordering the kit  I want to make sure I get the correct one

thanks again 

Paul

 

[sailorbob]

It's a Schrader valve, I think it may be SAE 7/16-20 sized.

[Doulou]

Perfect thank you

[Doulou]

Sorry one more question what should the pressure be?

[sailorbob]

I just measured a spare FPR and the test port diameter is 11.09 mm with 20 threads per inch so the SAE 7/16-20 size looks to be correct.

The Delco fuel pressure regulator is nominally rated at 3 bar but the specs in the Lotus Service Notes and GM workshop manuals and are a bit 'loose' with a range of about 3.5 psi either side being quoted as being acceptable.

[Doulou]

Thanks Derek, the kit should arrive on Saturday so I will let you know what the numbers are.

Paul

[ragingfool35]

the fuel pressure does bleed away after sitting for a while.  There is a 2 (or 3) second fuel pump activate each time the ignition switch is turned to the ON position for this reason.  wait for the fuel pump to finish before cranking, see if that helps

[Doulou]

Morning all

so I have just measured the fuel pressure, on ignition while fuel pump is priming I get a little over 3 bar, but once the pump stops it rapidly drops to around 1 bar. Can I crank / start the car with the pressure gauge attached?
 

thanks

[sailorbob]

Yes, you can start the engine with the gauge attached as it is only tee'd into the fuel rail.

The rapid bleed down of pressure could be due to a fault in the pulsation damper fitted to the fuel pump. There's a post from Vulcan Grey giving details on this problem 

If you do need to replace the damper use SAE J30R10 hose.

[Doulou]

Thanks Derek

what is the pulsation damper? I cannot find it in the parts diagrams 

[sailorbob]

Lotus only supply it as part of the pump assembly.

[Doulou]

Yes I just found the section you referred fromTravis however I don’t have any running problems no fuel starvation or lack of boost. Also there is no smell of fuel anywhere

would it be useful to take a pressure reading while cranking and with engine running?

thanks

And thinking about it we replaced the fuel pump in the hope of curing this problem but it never did

[sailorbob]

It does not take much of a leak to drop the fuel pressure when the pump isn't running. Also, you can be running lean and not notice a drop in performance but exhaust temperatures can soon rise. I had a fuel pressure regulator go faulty on my MR2 turbo and it boosted fine but the turbo soon ran extremely hot and went bright red.

[Doulou]

Is there any way of checking if it’s running lean? Would a free scan tell anything?

[sailorbob]

An exhaust gas analyzer or wideband lambda sensor is the definitive way. You can possibly use the BLM values but it's not guaranteed as the learning only occurs during closed loop fuelling and you may only be going lean during times of higher fuel demand such as when in open loop fuelling.

[Doulou]

Ok thanks Derek,

I may well be wrong, but I think we’re heading in the wrong direction with this. I am still leaning towards the FPRV, but I have no way of checking because I cannot buy one.

thanks for your help, and should I find the problem I will let you know what it was.

 

[ragingfool35]

wow they are no longer available....Tom Mieczkoski probably has some used ones.  i think i gave him 2 from me.  I made this in 2014 to utilize an aftermarket regulator on mine.

fuel rail adapter.PDF

[Doulou]

Yes absolutely none available and I am not skilled enough to fabricate one. I will put a plea out there to see if anyone has one sitting around

thanks

[sailorbob]

They can still be found as 'new old stock' and pattern part equivalents, there's several of the latter currently on eBay.

[Doulou]

Hi Derek, I must be missing something I have search everywhere but cannot find, can you send a link?
 

[sailorbob]

Go to ebay.com and search for 'pr103 fuel' in eBay motors (there's even a Herko branded one for under a fiver).

[Doulou]

Wow just shows if you know what your looking for!!
thanks Derek, I will make a point of letting you know how I get on

Paul

[Chillidoggy]

I have a good used spare FPR on the shelf if required. Strangely, I’ve just had a message from Sparky asking the same question. Odd!