Nissan Serena - Problems with diesel fuel system

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Tue 11 Feb 2014 19:53
Nissan Serena - Problems with diesel fuel system - neighbour

Hi all, Having sought help a while back overcoming startup problems I am back again after being stumped by yet another problem.

Helping my neighbour after his vehicle broke with what was initially thought to be ablown head gasket grew somewhat when it turned out to be a cracked head. Obtaining and fitting a replacement head took more that the production line fitting time. It was also pepered with a rash of ever other type of problem not least the weather over these past many weeks. The vehicle initially broke down in July 2013 and has stood ever since. I now believe that although the vehicle was in good order until it broke down when, attempting to re start after fitting the replacement head failed miserably. It was wanting to go but was clearly not getting fuel. Help was sought and eventually after much checking of fuses, supply, and imobilser etc, fuel was eventually delivered to the injectors and the engine now starts and runs well. But alas the spill line is being pressurised fron the pump body connection. The line back to the tank is clear. My guess, and I am clutching at straws, is that the cut off valve was stuck closed and caused the initial lack of fuel and now not fully open is allowing pressure out of the pump body connection which is shared by the spill line from the injectors. Anyone out there got any ideas which would help to sort this one please. The Nissan approach to help in such matters does not fit in the real world, have the vehicle brought in £180, run diagnostics until the fault is traced at £75 per hour.

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Wed 12 Feb 2014 10:19
Nissan Serena - Problems with diesel fuel system - neighbour

Hi All, apologies for the typo errors in the first edition and also for double entry. Hope it reads ok apart from that. Probably all the stress from too much thinking.

Had an e-mail back from Bosch Help who tell me that the flow back to the tank is normal and is designed to keep the fuel supply cool. Our problem seems to be that the amount being returned is greater than the return pipe will take and the result is that it is backing up to the spill line at the injectors making the joints, which are just push fit, at injectors one and two leak with a steady flow of diesel. Since the hose line from the pump and spill leading back to the tank connects to a steel tube held by a spring clip I am wondering if the answer would be to fit a further nine clips to the nine other joints on the spill line to make the lines reasonably pressure tight. Sounds a bit too obvious, but then why was it ok previously.

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Wed 12 Feb 2014 10:19
Nissan Serena - Problems with diesel fuel system - neighbour

Hi All, apologies for the typo errors in the first edition and also for double entry. Hope it reads ok apart from that. Probably all the stress from too much thinking.

Had an e-mail back from Bosch Help who tell me that the flow back to the tank is normal and is designed to keep the fuel supply cool. Our problem seems to be that the amount being returned is greater than the return pipe will take and the result is that it is backing up to the spill line at the injectors making the joints, which are just push fit, at injectors one and two leak with a steady flow of diesel. Since the hose line from the pump and spill leading back to the tank connects to a steel tube held by a spring clip I am wondering if the answer would be to fit a further nine clips to the nine other joints on the spill line to make the lines reasonably pressure tight. Sounds a bit too obvious, but then why was it ok previously.

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Wed 12 Feb 2014 12:34
Nissan Serena - Problems with diesel fuel system - thunderbird

The Nissan approach to help in such matters does not fit in the real world, have the vehicle brought in £180, run diagnostics until the fault is traced at £75 per hour.

That is the real world. It takes time to recover the vehicle and it takes time to diagnose the fault. The dealer has to pay his staff at the end of each week plus cover all his other overheads.

To me it looks fairly simple. The return pipe is returning more fuel that it should thus the pump is pumping more fuel than it should. Putting extra clips on the pipes to prevent the leaks is a bodge, find out why more fuel is being pumped, stop that and the leaks will also stop.

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Wed 12 Feb 2014 15:37
Nissan Serena - Problems with diesel fuel system - neighbour

Many thanks for your interest and input.

Looks simple - Yet set against their projected costs it hardly equates to customer help value.

The kind of help we sought was, hopefully, based upon their day to day knowledge and experience within their industry of what we could try or expect to find. Attempting to carry out work on the fuel pump is inhibited by tamper proof fixings as a hint or warning not to go there. So finding out why is a little tricky to say the least. The system was working perfectly well up until the failure of the cylinder head which should not have resulted in anything else changing. Regarding the fitting of extra clips, there are already clips fixing the return line hose from the pump to the return line to the tank. It will be interesting to carry out some testing of the flow rate and the pressure once this spell of bad weather is over. I suspect that the pressure might well be only inches water gauge and the flow rate may also be within the limits of the pump specification. Speaking with Bosch Help they have told me that there is an intended flow back to the tank which keeps both fuel and pump from overheating. Best regards

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Wed 12 Feb 2014 12:37
Nissan Serena - Problems with diesel fuel system - dieselnut

The spill flow from each of the four injectors should be about the same & certainly not enough to build pressure in the return pipe, as long as the return pipe isn't blocked somewhere.

If you have a lot of spill from the pump, it may have a leaking seal inside & would need overhauling. Alternatively you could probably find a used one quite cheaply on eBay.

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Wed 12 Feb 2014 16:19
Nissan Serena - Problems with diesel fuel system - neighbour

Hi, and many thanks for your interest and input to our problem.

One of the tests we carried out once we could get the engine to run was to pipe the spill output and the pump return flow into a container. The spill line flow was negligible and the pump return to tank flow was about half a litre per minute. The actual return line looked clear when diesel was fed down it by gravity from clear plastic tubing. Since speaking with Bosch Help they have indicated that there should be a significant flow of diesel back to the tank to keep both fuel and pump from overheating. I am planning to carry out flow rate and pressure tests on this line once the weather improves. Working on the fuel pump even with the aid of an internet manual will be an absolute last resort as I have noted the tamper proof fixings. Have spotted a replacement pump on ebay but I am not sure that my neighbours finnaces will run to it. However if the idea of extra clips will meet the need without causing any harm or other problems then that will be good. Such a shame that this problem has emerged as the restored engine now runs extremely well and starts in an instant.

Best regards.

Edited by neighbour on 12/02/2014 at 16:21

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Fri 21 Feb 2014 11:32
Nissan Serena - Problems with diesel fuel system - neighbour

Hi to one and all,

At long last all the issues are resolved and the vehicle is ready to be taken for its MOT and then back into service. Apart from the initial issue of the cracked cylinder head all the other side line problems related purely to the time the vehicle had stood out of action. The flow down the return line to the tank is within spec and the leaky spill connections were just a matter of getting correctly sized tubing. Alls well that ends well, but many thanks to all who contributed.

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