idle problems

[geoffdown]

hi guys renewed fuel pipes from tank to filter and every so offen it sounds like its running on 3 cylinders but only when it comes back to idle will do this then after 5 secs or so will idle correctly also if i blip the throttle will rev fine did the fuel pipe thinking it was leting in air, was wanting any guys with a tdi to compare if ur idle is same as this when rev to 2k let of throttle does it drop quickly to 1k then slow quickly to 750 or so please help no warning lights at all:nenau

 

[R1cho]

mine did that after the fuel lines were changed also developed a misfire it all corrected itself after a couple of fillups

 

[extreme-4x4]

does yours have the throttle valve on the inlet manifold side of the intercooler.

is yours hitachi or bosch system

 

[clivvy]

at idle, if I rev to 2k and let off the throttle, it drops quick 1k, then slow to about 750 ish., not sure that actually helps you though!

 

[geoffdown]

thanks guys it has no butterfly in the inlet system it sound to me like 1 of two thing the the return valve that badger had in the banjo of the return for the pump or no.1 injector i can get this for about £125 +vat new so might get it thanks for they replys so far will try the return valve problem first

 

[Timbo_1975]

The usual cause of this is you have a touch of air being sucked into the system.

That said, it can be a characteristic of the TDi. - mine does it.

 

[badger]

Hello Timbo,
I have read with interest various people saying it is on all (misfire), I accepted that at first but mine got worse, the air in the system is indeed a possible cause and likely candidates are fuel filter or filter housing, I checked these by bypassing with a inline filter, still the same.
I then by chance realized the amount of fuel being pumped through the pump was huge, I came to the conclusion that the pump was cavitating due to the overflow valve failing, very little info on this item in the uk, but the states are full of failures and new valves, the pumps need to be at about 15psi but with lower pressure the injection will be retarded and cause misfires, the proof on mine was in the eating, and I have no misfire no matter how slight whatsoever, the power delivery is smooth and precise, and mpg has increased as well, starting is quicker and towing is a dream, all other things must be checked first, but again from my experience and that of some others who have emailed me, the valve is an issue.
The tuning people in the states even have variable overflow valves to give more power, I played with the pressure and got loads more power but was unhappy to leave high as was unsure of outcome, the overflow fuel cools the pump and as such must be maintained, but if break point of valve is low problems with power will occur.
Here is a link to a website that has investigated the problem where the pumps are fitted to Cummins pickup trucks, the page is showing a new vp44 valve, which should I believe fit terranos with bocsh pumps? http://www.torkteknology.com/
explenation of fault here http://www.torkteknology.com/products/TORK-TEK-CUMMINS-ADJUSTABLE-OVERFLOW-VALVE-OFV020.html

Would Nissan and ford have allowed all these 1000’s of cars to do this from new? I believe it is something that has happened over time and miles, does not diesel bob say on his website about springs in pumps? Is it not possible it is the spring in the valve? I had real problems getting a dealer to sell me one, only when I quoted full part number did they get it, best £16 I have spent this year.

steve

 

[Timbo_1975]

For the benefit of the forum, could you post the part number of the relief valve so we may all use it?

My truck only occasionally 'splutter's just as it returns to idle like yours, usually when piping hot, although i am not running a stock management or tune, so I would not like to say that the valve is the cause of the splutter.

Low (inj pump) case pressure caused by air or relief valve issues will DEFINATELY cause timing irregularities and more splutterings.

 

[badger]

Mine is zexel pump, all is in the post here, http://www.nissan4x4ownersclub.com/forum/showthread.php?t=11236&highlight=fault+codes&page=1

One member got one from an agricultural company, so must be common to lots of things.
And also contact details for company I got part from.
But a vp pump is a vp pump, just googled overflow valve bosch diesel and got lots of results.
Also on ebay I found this, which for bosch owners maybe a good starting point? http://cgi.ebay.co.uk/Mercedes-Dies...arts_Vehicles_CarParts_SM&hash=item1c18f0345c

I did read one usa post where a truck driver said they used to put a clamp on the return fuel line to get places quicker, but he didn’t care what the resulting damage would be.
I put a kink in the return pipe under the driver wing and held it in place with a zip tie, no idea how much pressure this created but the performance was like a race car, did this whilst I was awaiting the part to arrive was sad to loose it with correct part, and did have a slight diesel leak from where the hose clip was loose on the supply hose.
Again well worth looking on Cummins forums, loads of stuff on the return valve and symptoms.
The valve forms a oneway valve when engine is off, so starting is much improved as you do not have to crank up the internal pressure lost otherwise overnight.

At the end of the day lots of same symptom faults can be caused by lots of different things, this is just one and not a golden fix all, air in clear pipe test showed loads pre new valve, none after fitting, so back to original post, fault is caused by air in fuel, but not as such a leak.
I agree with your thoughts on air, and would advise anyone to check filter and housing first, you will see in my post on the subject I was originally convinced a faulty filter was the culprit.
Old cars, just trial and error, I cant imagine a main dealer changing this bit, new pump would be quoted.

 

[badger]

5th post down appears to give part numbers for bocsh may be of use.
http://www.cumminsforum.com/forum/98-5-02-powertrain/234058-funky-fuel-pressure-overflow-valve.html

 

[geoffdown]

Mine is zexel pump, all is in the post here, http://www.nissan4x4ownersclub.com/forum/showthread.php?t=11236&highlight=fault+codes&page=1

One member got one from an agricultural company, so must be common to lots of things.
And also contact details for company I got part from.
But a vp pump is a vp pump, just googled overflow valve bosch diesel and got lots of results.
Also on ebay I found this, which for bosch owners maybe a good starting point? http://cgi.ebay.co.uk/Mercedes-Dies...arts_Vehicles_CarParts_SM&hash=item1c18f0345c

I did read one usa post where a truck driver said they used to put a clamp on the return fuel line to get places quicker, but he didn’t care what the resulting damage would be.
I put a kink in the return pipe under the driver wing and held it in place with a zip tie, no idea how much pressure this created but the performance was like a race car, did this whilst I was awaiting the part to arrive was sad to loose it with correct part, and did have a slight diesel leak from where the hose clip was loose on the supply hose.
Again well worth looking on Cummins forums, loads of stuff on the return valve and symptoms.
The valve forms a oneway valve when engine is off, so starting is much improved as you do not have to crank up the internal pressure lost otherwise overnight.

At the end of the day lots of same symptom faults can be caused by lots of different things, this is just one and not a golden fix all, air in clear pipe test showed loads pre new valve, none after fitting, so back to original post, fault is caused by air in fuel, but not as such a leak.
I agree with your thoughts on air, and would advise anyone to check filter and housing first, you will see in my post on the subject I was originally convinced a faulty filter was the culprit.
Old cars, just trial and error, I cant imagine a main dealer changing this bit, new pump would be quoted.

right put mig tip in return fuel line it was a .8mm not a .6mm like you did and think it made things better but there is at times air in fuel as i have put a clear pipe to the injection pump. how much air should be in there and how can i test the fuel filter or housing i put an inline filter to by pass the orginal filter and still got air in the fuel line so help

 

[badger]

if putting a restrictor in made a differance you may be on the right lines, i dont have any air in clear pipe now pre pump, any air is bad as it is not fuel.
have you looked for valve or restrictor in pump, sorry i dont have a bosch one, but i think it is a vp37 in 2.7 and a vp44 in 3ltr?
bocsh manaul says either a restrictor or valve can be fitted, early manual says 12psi minimum internal pressure, later manaul says 5psi, dont know why, but on cummins site they explain in more detail.
main reason for any flow from pump is to aid cooling, but huge flow will add to air and cavitaion in pump, you havent changed fule pipes have you?
just had a thought, if nissan relied on small bore return line as restriction, i changed my supply pipe and return and used 8mm on both, didnt see a problem with it, until just now, worth a thought!

steve

 

[Timbo_1975]

right put mig tip in return fuel line it was a .8mm not a .6mm like you did and think it made things better but there is at times air in fuel as i have put a clear pipe to the injection pump. how much air should be in there and how can i test the fuel filter or housing i put an inline filter to by pass the orginal filter and still got air in the fuel line so help

There should be no air in the fuel lines.

If the filter head is not drawing air, then either the rubber pipes or steel chassis ones are leaking it in.

Remember there are two rubber pipes ontop of the tank too, but these rarely give problems.

 

[badger]

if you read my post where i had fault under load, i had changed my fuel pipes, just remembered it got worse after this, over the lengh of the return pipe the small bore would be a restrictor, i just used same size hose for both, more i think about it more i think i may have caused fault :doh by doing this, valve was u/s but partialy masked by small bore pipe, first post in this thread says changed hose, now missfire, what size pipe did you use?

 

[geoffdown]

if you read my post where i had fault under load, i had changed my fuel pipes, just remembered it got worse after this, over the lengh of the return pipe the small bore would be a restrictor, i just used same size hose for both, more i think about it more i think i may have caused fault :doh by doing this, valve was u/s but partialy masked by small bore pipe, first post in this thread says changed hose, now missfire, what size pipe did you use?

i have only replaced suply with new rubber fuel pipe from tank to inline bulb primer near the fuel filter i am in the middle of fitting a twin tank to run 100% veg oil all year round so surply goes from tank to bulb primer to small heat excahnger (which is near fuel filter ) to orginal fuel filter to injection pump will try tomorrow and take out bulb primer but have tested it and does seam air tight

 

[badger]

is the primer a mod? as my primer is in the filter housing.
when i was testing for my "leak" i put a large inline mower type filter and ran hose from tank direct to it and then another new hose from filter to pump, just to eliminate all others, then decided must be return.
if you have done these svo mods then i think you have got an air leak somewhere, or is hose/pipe bore to small? somthing like rust moved when you change metal pipes?
good luck

steve

 

[geoffdown]

is the primer a mod? as my primer is in the filter housing.
when i was testing for my "leak" i put a large inline mower type filter and ran hose from tank direct to it and then another new hose from filter to pump, just to eliminate all others, then decided must be return.
if you have done these svo mods then i think you have got an air leak somewhere, or is hose/pipe bore to small? somthing like rust moved when you change metal pipes?
good luck

steve

would be nice if it was like that but the can had problem before i fitted any svo mods, tomorrow will by pass filter and try that then i will by pass the tank aswell as might be pick up pipe draging in air at the top of tank . but that return valve for my bosch pump is £60 + vat from electro diesel part no. is 2467413025

 

[geoffdown]

well dare i say it the air leak has gone, bypassed the fuel filter and stoped the air entering the system, phoned up nissan for fuel filter head and the f**kers wanted £120 +vat so went to a diesel injection place i bought new filter head with out primer and spin on filter for £35 ( i no i now havee to get a diff fuel filter from the 1 stated at motor factors but no way i was going to pay £120 or so for that )and so far its doing what it should do:thumb2 so just a warning to any1 else that if they vac tested the fuel filter unit and it was holding a vac it could still be the fuel filter unit best thing to do is put a clear fuel pipe before fuel filter and 1 just before the pump on the surply line and the smoke has also stopped:clap thanks for all the surport and thanks to badger too will run the truck now for a couple of days and let u know the results.

 

[spudd]

bobbin rastards.i put a ford primer on my navara.ive just bought another from ebay for the terrano with water jacket for svo £44.50.hope it will sort mine out.

 

[geoffdown]

bobbin rastards.i put a ford primer on my navara.ive just bought another from ebay for the terrano with water jacket for svo £44.50.hope it will sort mine out.

my twin tank set up is all working. brill now 100% svo all year now love it