P0093 code and repeated replacement of SCV

[johnmcface81]

Hi,

I wonder if someone might be able to help, I have had a Navara D40 (57) completely standard (no chip or fuel changes) for many years now and pretty much ever since I have owned it I have had an ongoing fuel problem with it. It seems to be the standard common issue of P0093 (Mass fuel leak). Over the years I have tried many different things like fuel filter replacements, all being genuine, ecu resets etc but what seems to fix the issue has been the replacement of the SCV however it seems to only last for around 9 months.

Symptoms always start with the occasional going into limp mode, usually while cruising or under very little to no load. This begins maybe once a week and get's more frequent to the point where when it does it it will sometimes stall rather than just limp mode and then struggle to start.

While I don't mind changing the SCV every 9 months I feel like it might be just covering up the problem rather than resolving it.

It started again this week (SCV changed last September) so today I thought I would test the relief valve, it mentioned removing the pipe to it, adding a new piece of pipe and a bottle to see if the valve is opening. What I thought was strange and this might be normal is when I started the vehicle fuel came out of the pipe I had disconnected from the RV in what was a bit of a trickle, I would say maybe in the space of 20 seconds it would be around 100ml. Is this common and expected? As I thought this is the return pipe or does this indicate the valve has been releasing and so the fuel in the pipe was simply from previous runs?

Does anybody have any suggestions or have had similar experiences of replacing the SCV every 9-12 months?

Thank you and much appreciated.

 

[linked]

Make sure you tighten the bolts of the SCV properly when changing it. Also look at the hoses that go to the fuel filter, those clips start to crack the hose with time and age as you tighten them down. Just trim the old cracked ends and reuse the clips and clasp.

 

[johnmcface81]

Thank you for the reply, last time I did the change which was about 9 months ago when I did the boost pipes as they were worn slightly and replaced several of the fuel pipes and trimmed the ends of others in case it was that letting air in along with changing the fuel filter with a genuine Nissan one.

 

[Old.Tony]

My SCV has only been replaced once. I've had a fuel line issue - which I found using the primer bulb. Let me explain a little about it.

The fuel system - from the tank up to the pump's inlet - operates as a low pressure system, which means it usually can't leak diesel fuel out - but can leak air in. A leak at this point usually allows fuel to return to the tank, which causes hard starting. Specifically, the car will fire then stall after a few seconds (having consumed all the remaining fuel between the leak and the pump). Cranking the engine at this point makes the pump draw fuel from the tank again, yes, but it is now missing the fuel at this point, which it uses as a lubricant. As soon as you suspect this issue you should prime the system manually until the leak is found.

And that's where the primer can help us. If you have a normally-working system, 3 pumps of the primer should bring the bulb up to a considerable firmness. This may reach 4-5 pumps but that's perfectly fine.

If it goes past that - there's a leak somewhere. To find the leak - the easiest, quickest way is to just keep priming the system. This will pressurise the system between the primer and the pump and fuel will start coming out of the leak.

I'd try that at first, and see what result you get.

If it doesn't work, it's possible that your injector seals are faulty. Please check your oil level and monitor it to see if it's rising.