P38A Fuel line check valve?

P38Rover · Jun 21, 2020

Ive been having some intermittent stumbling to start issues. I put a gauge on the fuel rail today and everything checks out at 36psi +/- 2psi while revving\idle. Only thing is that the fuel pressure goes to zero in about 3 secs after I kill the engine.

Who knows of a good place to splice in a check valve? Just after the fuel filter? Or how do I replace the one that is malfunctioning? Couldn't really find any info..

Thanks in advance

RangeRoller dt · Jun 21, 2020

Search NRV in fuel line. Mine had one installed by PO after filter - useless took it out is better with a joiner. Is on return to tank they fit one but mainly for startup
Always worth checking spill pipes/bubbles in clear pipe.

P38Rover · Jun 22, 2020

Fit it to the return fuel line..Yup thats right.. durrr me..

I will be searching for a suitable in line NRV.

thanks for the reply

Mark Piercy · Jun 22, 2020

Is there one stored in the fuel pump on yours @P38Rover?

brianp38dse · Jun 22, 2020

@RangeRoller dt was talking about the pipes on a dozzel yours will not have spill pipes and is a different set up.

P38Rover · Jun 22, 2020

Mark Piercy said:
Is there one stored in the fuel pump on yours @P38Rover?

I believe so.. But I already changed out the fuel pump motor almost 2 years ago now. And I did it the proper way by completely dropping the tank. So....pretty much Im trying to avoid ever going back in there again if I dont have to. haha

P38Rover · Jun 22, 2020

I was thinking about finding an adapter for the connections on the fuel rail if possible, then adding in a non-return valve on the return to tank line so the fuel rail can always stay pressurized. The connections all "look" pretty standard like I could use something generic at my local fittings shop. But we all know how that can go..

The screw on fitting seems like the feed line and would be easy to retro fit a check valve. But the push to connect fitting which looks like the return, is where I might not be able to find the correct adapters. Can someone confirm?

marjon · Jun 22, 2020

P38Rover said:
Ive been having some intermittent stumbling to start issues. I put a gauge on the fuel rail today and everything checks out at 36psi +/- 2psi while revving\idle. Only thing is that the fuel pressure goes to zero in about 3 secs after I kill the engine.

Who knows of a good place to splice in a check valve? Just after the fuel filter? Or how do I replace the one that is malfunctioning? Couldn't really find any info..

Thanks in advance

What year is your P38?

You say “stumbling on start” hot, cold or just in general?

I wouldn’t be putting a check valve in the return to stop fuel going to the tank, isn’t that’s what it’s for? Have you got any diagnostics to plug in because there’s loads of sensor inputs it needs.

Is the fuel pressure regulator ok it seems ok while running but when you turn it off it’s letting all pressure out. You need to establish which way it’s venting the pressure when you switch off,

J

pwood999 · Jun 22, 2020

Might be worth checking the vacuum pipe to the fuel pressure regulator.

P38Rover · Jun 22, 2020

marjon said:
What year is your P38?

You say “stumbling on start” hot, cold or just in general?

I wouldn’t be putting a check valve in the return to stop fuel going to the tank, isn’t that’s what it’s for? Have you got any diagnostics to plug in because there’s loads of sensor inputs it needs.

Is the fuel pressure regulator ok it seems ok while running but when you turn it off it’s letting all pressure out. You need to establish which way it’s venting the pressure when you switch off,

J

98 gems

Randomly struggling to start. 60% of the time she starts up perfectly normal.

Check valve would be a one way valve so the line would stay full of fuel instead of draining itself so quickly. I dont believe that the small impedance in flow would matter especially on the return line. I could be wrong.

I would think that it couldn't be the regulator because it drops pressure after the engine is off. Although I did check for a proper vacuum at the regulator and it is functioning 100%. It will maintain 36psi very efficiently.

thanks for the reply

Mark Piercy · Jun 22, 2020

You don't lose any coolant do you @P38Rover?

P38Rover · Jun 22, 2020

Mark Piercy said:
You don't lose any coolant do you @P38Rover?

Nope

RangeRoller dt · Jun 22, 2020

Mark Piercy said:
You don't lose any coolant do you @P38Rover?

Cheeky

Can you get use of a Nanocom?

oakey · Jun 22, 2020

Afraid I would check CPS first

wammers · Jun 23, 2020

P38Rover said:
98 gems

Randomly struggling to start. 60% of the time she starts up perfectly normal.

Check valve would be a one way valve so the line would stay full of fuel instead of draining itself so quickly. I dont believe that the small impedance in flow would matter especially on the return line. I could be wrong.

I would think that it couldn't be the regulator because it drops pressure after the engine is off. Although I did check for a proper vacuum at the regulator and it is functioning 100%. It will maintain 36psi very efficiently.

thanks for the reply

You are wrong, fuel circulates constantly to keep it as cool as possible. When the ignition is switched on lift pump should run until fuel pressure attains 35 Psi then stop. And not start again until engine is running.

P38Rover · Jun 23, 2020

oakey said:
Afraid I would check CPS first

CPS was changed about a year or so ago. So Im hoping its not that. But it could be

P38Rover · Jun 23, 2020

wammers said:
You are wrong, fuel circulates constantly to keep it as cool as possible. When the ignition is switched on lift pump should run until fuel pressure attains 35 Psi then stop. And not start again until engine is running.

So putting in a check valve would cause additional issues then huh? My fuel pump does what it supposed to do and primes to operating pressure with the key in the accessory position. Its just that after I turn the engine or key to off, the pressure drops to zero in a couple seconds. It definitely 100% didn't use to do that when it was running healthy the last time I changed out my fuel pump motor.

I thought I was being clever and found a shortcut. Guess I might have to drop the tank again then.

P38Rover · Jun 23, 2020

RangeRoller dt said:
Cheeky

Can you get use of a Nanocom?

No nanocoms.Sorry. I have RSW software though and it doesn't show any faults.

I do have a weird ABS fault "no voltage at ecu pin1 with ignition on". And the ABS works just fine and no error lights on the dash.

P38Rover · Jun 25, 2020

So what part regulates the 36psi fuel pressure with key in the accessory position?

Pretty much I need to change that out...

wammers · Jun 25, 2020

P38Rover said:
So what part regulates the 36psi fuel pressure with key in the accessory position?

Pretty much I need to change that out...

The fuel pressure regulator ETC8494. Unless the lift pump has a leak back problem or is not being switched on start up.

P38A Fuel line check valve?

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