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My wife & I bought a 1996 'N' Reg 2.4 Diesel turbo 'Merlin http://www.vwt4forum.co.uk/images/smilies/wizard.gif Autoholmes' camper with 45,000 on the clock, back in March of this year. After picking it up, the fuel gauge + temp gauge was very slow to respond (sometimes not at all, and the garage that I bought it from said that they had put 20Ltrs in. Enough to get me home I thought)
Anyway, I ran out of diesel on the way home. http://www.vwt4forum.co.uk/images/smilies/redface.gif After getting it refueled I drove it home.
Merlin intermittently has had a loss of power when driving in any gear.
By dropping a gear or taking your foot off the accelerator, Merlin seems to pick up power again.
I assumed that the Fuel filter had picked up from the bottom of the tank and getting blocked, and needed changing.

I took Merlin back to the garage from where I bought it and they took it for a test drive and couldn't find the problem.http://www.vwt4forum.co.uk/images/smilies/dontknow.gif

With my hols looming and excitement over ruling common sense I decided that I could put up with this minor intermittent inconvenience until I got the Fuel filter changed. http://www.vwt4forum.co.uk/images/smilies/sign0075.gif

You can guess what happened next. Yep, It came to a stop with a loss of total power in the middle of nowhere. http://www.vwt4forum.co.uk/images/smilies/mad0235.gif I could not get it restarted and so called out the AA. He did the usual checks (checked the ?101 relay and couldn't find any faults.) So we got taken by transporter to a garage. I told them what had been happening and they changed the fuel filter and the leak off pipe.
They also couldn't find any electrical faults.
We then completed the rest of our holiday & had trouble free motoring for about 500 miles.http://www.vwt4forum.co.uk/images/smilies/thumbsup.gif
I used the camper for a short weekend break and the fault reappeared. http://www.vwt4forum.co.uk/images/smilies/frown.gif
Again, by taking my foot of the accelerator or changing down a gear seemed to alleviate the loss of power.
I again assumed that maybe the new filter had maybe got clogged again.http://www.vwt4forum.co.uk/images/smilies/dontknow.gif

I went out, bought a new fuel filter, a canister of fuel after looking up on these forums on how to change it. ( http://www.vwt4forum.co.uk/images/smilies/thumbsup.gif Thanks to 'twozup' for his photos, as I couldn't have told you where the filter was, being a newbie to the T4 and not very mechanically minded) http://www.vwt4forum.co.uk/images/smilies/confused.gif

We set off on another short weekend break and the fault appeared only a few miles away from home. This time, as I was pulling into a layby, Merlin would not restart so I changed the fuel filter, which took me about 45mins.
We set off again and all was fine for a few miles and then I had the loss of power problem again.

We decided to cancel the trip and was returning home and I had no further problems, so I was wondering if there was air in the system and maybe it had worked itself out. So we plodded onto to a nearby lake nearer home and gave it another chance. We got up the next day and was heading home and had no problems so decided to carry on with the trip. Still no problems and had a lovely day on the coast. http://www.vwt4forum.co.uk/images/smilies/smile.gif
The following day we headed towards my parents home and this time I had a total loss of power, when I wanted to see what would happen if I didn't change down or take my foot off the accelerator, as we were close to a layby. I coasted in and tried to restart it, several times. No joy http://www.vwt4forum.co.uk/images/smilies/bawling.gif. After leaving it for about 20 mins I tried to restart it again and it fired up on the first attempt http://www.vwt4forum.co.uk/images/smilies/applause.gif . So we drove home with the intermittent fault happening more and more regularly. Again by changing down or taking my foot off the accelerator for a second and Merlin carries on again.

I have spent ages looking through these forums, but can't seem to find anybody with exactly the same problem. I know that the fuel / temp gauge problem is probably due to a dry solder joint and I can get that sorted. Thanks again to this forum, as it does seem a common problem with T4s . I'm not too worried about that as I reset my trip every time I fill up and fill up again, when I'm about half full. The gauge does jump into life every now and again.

Further info / recap:-
The fault is intermittent.
Taking my foot off the accelerator briefly or changing down, seem to relieve the loss of power problem.
Only once has Merlin stopped whilst idling and I couldn't restart it until I left it for 20mins.
I have tried driving it like Miss Daisey, changing gear early as the problems seems to happen more regularly when I'm going over 50mph OR at the higher revs range in any gear.
I have whilst stationary, held the revs at about half power with the accelerator, and the revs will drop and go back up again, with there being no regularity or pattern in the dropped revs.

So I was hoping that somebody on the forums out there would be able to offer advice. Thanks in advance. http://www.vwt4forum.co.uk/images/smilies/Santa.gif
 

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so many of these things end up being electrical....I had a similar problem and immediatly suspected the fuel shut of solenoid....or more specifically the current to the solenoid coming from the ignition switch. In my case I just wired in a switch so I can control the solenoid from the dash.....I could have put a new ignition switch in but I like lots of buttons etc to push....If one of you gets close to the fuel pump and the turns the ignition on you should hear a distinct click from the solenoid at the FP. If not see if there is 12V getting to it if there is and it still is silent it has failed..
It is funny I got a mechanical diesel engine to avoid electrical problems, and so far the only problems I have had have been electrical. IMHO the fuel cut of solenoid while simple enough is an Achilles heel in this set up, I like diesels that require no DC whatsoever to keep running......
 

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Just a shot in the dark but a while back I had a similar problem on a different vehicle. The fault was a fuel pipe had perished on the inside and as it pulled fuel through it would occasionally block the pipe, check it all over for 10 minutes and she would fire up!
 
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