Author Topic: Fuel pressure regulator  (Read 817 times)

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sudsy

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Fuel pressure regulator
« on: November 17, 2019, 11:27:15 PM »
Hi,

Just a quick question regarding the fuel pressure regulator on a 116 twin weber/dellorto

What is the general consensus regarding how essential the fuel pressure is to a twin weber/dellorto carb set up.?

Local brains have somewhat dismissed its importance...however as I am still getting popping back firing, it suggests over fuelling.
Don't get me wrong the car is running very strong, and enjoyable..but it needs me to shake its grumbles out of its system..

Popping, hesitation on initial throttle requests all suggest a flooding..it wants to go but needs massaging to do so..

Once opened up however she takes off like a bullet, again suggesting fuel pressure aligned to demands.

FWIW  ...The car initially had a load of lead shot in the fuel pressure regulator chamber...!!


 
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giulia_veloce

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Re: Fuel pressure regulator
« Reply #1 on: November 18, 2019, 06:50:08 AM »
Well Sudsy

You have your opinion.= Rich

From what you are say,,its over Fueling

From what I know,,its running too lean.

Popping comes from lean mixtures Generally.
Fuel pressure is Very important on Alfa twin cam,twin carbys,,like about 3psi.

Go try and give it 10+ PSI and see what happens
It will either flood,,or still pop.

Can be an easy fix if you know what you are doing.
I fix this problem all the time on customers cars especially Alettas.

Consult a reputable Alfa old school mechanic.

If we knew where you were Located,,many Local to you Alfa Romeo specialists would be recommended.
Its not a hard fix,,but knowledge is the key.

Sudsy,,im not being vague or keeping secrets.
Just lots of things to check .

Lets start,,

Show us a picture of your spark plug colour.
Compression test.
Fuel pressure + volume..
Point gap
ignition timing
Possible camshaft timing
Carby internal leakage.
Dist leeds
Coil
Condensor
ign advance
Etc Etc Etc

I don't usually check the above first,, but you need to verify the above is all in great working condition,before we continue


Keep us posted.

bonno

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Re: Fuel pressure regulator
« Reply #2 on: November 18, 2019, 09:18:08 PM »
Have one question, does it idle fine @  900- 1000RPM???. As guilia_veloce has indicated it could be a multitude of reasons that's causing your problem. I would start by checking for blocked idle jet/s which is a usual symptom for snapping and popping you describe.
« Last Edit: November 18, 2019, 09:26:38 PM by bonno »
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Colin Edwards

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Re: Fuel pressure regulator
« Reply #3 on: November 19, 2019, 10:19:16 AM »
Hi Sudsy,
If your running Delorto's there should be a very fine mesh filter housed in the DHLA Banjo.  These can clog, reduce fuel flow and impact fuel levels in the bowl under transient conditions.  These fillters often get tossed out when they age as they require regular inspection and cleaning.  Worth a look if you're running Delortos.

The height of the fuel level in the bowl of any carby has an impact on mixture strength.  If for any reason the level of fuel in the bowel is lower than it should be, the carby will run lean.  A 1<2 mm reduction in fuel level is similar to running one size leaner jets. 

The setting and operation of the fuel pressure regulator will have a huge impact on fuel level in the carby. 

Colin
« Last Edit: November 19, 2019, 03:30:55 PM by Colin Edwards »
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LukeC

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Re: Fuel pressure regulator
« Reply #4 on: November 19, 2019, 11:38:32 PM »
Comes a time when you just have to realise that old school nouse is the way to go... But worth paying for!

Canberra: Not much choice...

Fernando Moro,

Chris Hedges,


And some other dude that a very temperamental but is booked absolutely solid for the next 6 months  :-X
Luke Clayton

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sudsy

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Re: Fuel pressure regulator
« Reply #5 on: November 21, 2019, 03:18:54 PM »
Thanks for all your replies..

All the basics are good

Compression test.
Point gap
ignition timing
Possible camshaft timing
Carby internal leakage.
Dist leeds
Coil
Condensor
ign advance..

Fuel pressure and volume never checked ..hence my original post.
idles well (7-800)  fairly promptly after cold start up..

They are Dellortos from an 84 from a good running donor so effectively on car tested (DHLA40L). I believe being later model carb that they will be a little more restrictive/pollution controlled, but I wanted to install a known to be good pair of carbs and work back from there..They were a great improvement and made the car actually perform..

I also have another good earlier set of carbs to go on, but I dont think that's the issue..

I'll get a fuel pressure tester, as it has now been made abundantly clear for the first time that this IS a crucial factor..
If I had been told, it was probably long enough ago that it slipped my memory..
It doesn't look like the fuel pressure regulator has any adjustment..am I correct...Are they a swap out?

I'll keep you all posted

 



« Last Edit: November 21, 2019, 03:49:54 PM by sudsy »
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74 Sud L
74 Alfetta
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86 75 2.5

Current
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sudsy

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Re: Fuel pressure regulator
« Reply #6 on: November 21, 2019, 08:45:29 PM »
Think I've found the solution..

So thanks to input here, I focused upon the fuel pressure regulator..

By pure happinstance, I found a replacement FPR in my spares from the 79 sedan that i bought...

This FPR is old school 1/79 AND adjustable.  :)

I installed it and by all accounts things are now lovely,,

As much as things were previously quite good, now it is more sublime..
Even easier starting and idling, no popping etc..

Still need to take car for sneaky unregistered drive but quietly confident.

I will keep you posted..





Gone not forgotten
74 Sud Ti
74 Sud L
74 Alfetta
79 Sud 1.5 Ti
78 GTV
86 75 2.5

Current
79 GTV
79 Alfetta