To unconfuse, fuel is forced throught the fuel pump to the fuel rail. The end of fuel rail has fuel pressure regulator installed - means it keeps pressure to a certain level and releases the excess through the return line. If you install non-return valve on return it won’t change anything as fuel pressure regulator is your non-return valve already there.
Fuel pump generates pressure while running, not sustaining it when off. Hence the idea of non-return valve to make sure your pump is not wasting time to replenish losses in fuel rail after long time off.
It’s like a tribe knowledge really, won’t bring much improvement in correctly working fuel system. People believe in holy trees, magic bugs and non-return valves…
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Maybe my memory of the placement in the return line is incorrect I KNOW it was placed in the engine bay maybe it was on the feed line. Cars long gone to a new owner and I don’t think I have any other photos.
Hi Everyone,
Thanks again for the feedback. The explanations make sense as I continue to figure this out. Just a point of clarification- I did state that key cycling did not help. I didn’t state however that I cycled the key two or three times. I just went outside and tried cycling the key 6 times, and the car started up on first crank. The current temperature is 28 degrees Fahrenheit, up from 15 this morning.
I’m fairly convinced that I have either a bad NRV or fuel pressure regulator. From all of your feedback it is clear that the NRV is a one-way (check) valve that allows fuel to flow from the pump to the fuel rail but not the other way. The fuel pressure regulator will open and close to maintain a constant fuel pressure, controlled somewhat by engine vacuum, but also to maintain a static pressure when the engine is not running.
As soon as the weather is more cooperative, I’ll remove the return line from the fuel pressure regulator and see if the fuel leaks back when the car is not running. If that passes the test, I’ll order an NRV and install it in the feed line.
I’ll keep you posted; thanks again,
Darren.
Darren, sounds like progress!
Unfortunately it doesn’t seem possible to provide the appropriate link in a new post but, if you click on “Old Site” at the top of this page, then select “Photo Album”, then “Search” you can select “XJ40 Section” and within that search for “fuel pressure”.
That should show you a few photographs, one of which is from me entitled “XJ40 fuel pressure readings”…
If you can lay your hands on a suitable gauge installed as shown you should get similar readings.
However, if after engine shut-down the hold pressure drops, you can determine which component is leaking back to the tank by clamping immediately prior to shut-down the feed OR return lines.
Obviously if clamping the return line stops the pressure from falling on shut-down the FPR is faulty. and if the feed line, the NRV is the problem.
Good luck!
Darren, when the non return valve failed in my car, Bryan suggested a fuel pressure test. I disconnected the feed line from the fuel filter and put it into a half a gallon bottle. Then I used a jump wire in the fuel pump relay base to make it run continuously. It has to fill the bottle in about one minute. That test confirmed a low fuel pressure. Now I have an inline one way valve.
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Hi Joe,
I’ve finally decided to order a new fuel pump since the fuel rail loses pressure during sitting and the pump is now becoming loud after driving for an hour. Now I have to look up how to change it.
Regards,
Darren.
Two options, the correct way, take the tank out or the hack of cutting the rear parcel shelf.
There’s probably a few videos on YT.
I removed the gas (petrol) tank to replace the pump and had a chance to clean the bottom of the tank as well.
I originally posted that the car would not start when cold. This was quite an odyssey but I finally solved it-here’s the list of what it was not:
Crankshaft position sensor-nope, I replaced it, no change,
Cap and rotor-nope, same as above,
Spark plug wires-nope, same as above,
Fuel pump-nope (the fuel pump was wearing out and getting noisy but changing it did not solve the problem).
So what was it…?
The fuel pressure regulator -not holding rail pressure after shut off, causing the need for priming the system after 4 or more hours of sitting. The car is running fine now.
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Very surprised that the key cycling trick that you tried in post 9 didn’t show up as being advantageous.
Well I thought the problem was solved. Today I went to start the car and it was back to its old tricks-acting like there was no fuel in the rail. It finally started and then 4 hours later it cranked longer than it should but finally started and about 3 hours later it acted like nothing was ever wrong. Here’s what I’ve done so far:
Replaced the crank sensor, replaced the fuel pump, replaced the cap and rotor, replaced plug wires, replaced the fuel pressure regulator, replaced the temperature sensor. What am I missing?
Any help would be so appreciated.
Darren.
Try another temp sensor or try fitting the old one again - In the past I’ve bought an after market temp sensor that was iffy.
As I was just replacing that single component at the time it was easy to identify the issue.
Worth a try?
Hi Larry,
I did that. They both have similar resistance readings within spec.
I’ll keep racking my brains.
Thanks though,
Darren.
Hi Everyone,
I’m going to order an in-line non return valve. Can someone please advise me on the inner diameter of the fuel supply line?
Thanks so much,
Darren.
i read your issue with the start problem.I have exactly the same problem that you describe .Have you solved the problem?And I want to ask you what was the cause of the problem?
greeting Walter from the Netherlands
Hi Walter,
I discovered that the fuel pump did not always receive power when the key was turned on. I connected a test lamp to the load side of the fuel pump relay and watched through the rear window as I cycled the key. I solved the problem by disconnecting the electronic control module and then reconnecting it. Apparently there was some oxidation on the connector. The car has been fine for over a year.
Regards,
Darren.
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ok thanx .i will look at that .when i read your first post with describing your problem it was exactly same as mine.when turning key it does not start when long cranking.when turn key back suddenly it give a little bit life.then by second attemp it will start but you have to give a bit gas and slowly it come to life.and then it runs fine.it only happens sometimes and always by cold start after that it starts super.so i think i have same problem as you have had.
so thanx for your reply
my english is a little bit poor sorry