high pressure fuel coming out return lines?

[chrissev]

hello, I have a strange problem with a fuel injector.  It has been rebuilt with a new 155 bar nozzle, and it seems that high pressure fuel is somehow getting to the return line and also is leaking at the base of the injector around where the steel part protrudes from the injector body.  Is this possible?  The injector has a new nozzle so I want to use the thing, but it seems to have this fuel leakage problem.

[Master ACiD]

did you just unscrew the old nozzle and add a new one wihtout actually getting the injector properly rebuilt?

[chrissev]

did you just unscrew the old nozzle and add a new one wihtout actually getting the injector properly rebuilt?

no, the injector is  a rebuilt unit I purchased about a year ago from a place called vwdieselparts.com.  Guy called "Jack".  It came in a box indicating it was rebuilt by bosch.  He wouldn't take it back when I complained about it and I had no luck getting answers from bosch so I still have the thing.  Just wondered if it was possible that it was put together wrong.  Thanks for the info.

[Giles@PerformanceDiesel]

HI

JUST STOP BY MY SHOP AND I CAN LOOK AT IT FOR YOU
CALL ME FOR DIRECTIONS

905-475-1122

GILES

[Mark(The Miser)UK]

:?: Are you sure the problem is not simply with the fuel bleed off lines leaking? This has tricked me before when I thought an injector return nozzle [barb] was leaking and I recut the tubing several times on one rogue. The injectors xs fuel(at idle at least) is miniscule...
 Pull a return line and it will fountain up into the air. This is caused by back pressure of fuel returning to the tank.
 This occurs even though the return to the tank orifice is maybe 10 or 20 times as big as the 'return' orifice from the injectors. Considering the 1/2 mm dia of the pump return restrictor one would think the flow would be purely towards the 'large' bore return line.

Just found this info I researched back in 2004...

Banjo outlets...
To tank                     9/64" dia or 10mm square [not 10 x 10!!]

From injectors           2/25" dia or 3.25mm sq

Banjo bolt hole:        6/250" dia or 0.3mm sq

So bolt hole is 1/30th of  fuel return outlet. Whats the
pressure drop I wonder?
Rotweiller-Mark

So at the banjo;  injector return is 10x larger than that of the pump pressure restrictor and  return to tank is 33 x as big :shock:

Effect of 8ft or so of return line?
Sorry guys I've just gone off topic (just happy to have refound that info :twisted:


 :idea: I wonder if this is where the anomaly in Jake's pump bench test comes from? ie the pump internal pressure should be higher at the higher speeds due to the long fuel return line adding to the restrictor? :idea:

[chrissev]

:?: Are you sure the problem is not simply with the fuel bleed off lines leaking? This has tricked me before when I thought an injector return nozzle [barb] was leaking and I recut the tubing several times on one rogue. The injectors xs fuel(at idle at least) is miniscule...
 Pull a return line and it will fountain up into the air. This is caused by back pressure of fuel returning to the tank.

I originally thought that.  So i took steps to try to remedy the problem, I replaced all the bleed off lines, I put a long wire through the return line that goes to the diesel tank, I ran a second return line teed into the line that comes from the pump all the way under the car to the diesel tank, and I removed the one way valve at the back of the car that connects to the diesel tank (so fuel can't go back up the return line).  Still the one injector continued to run fuel down out of both return line holes.  So I removed the return lines from each injector in turn and I found that the two return nozzles on that injector were shooting out fuel way more than the other injectors.  I then removed the suspect injector and found that it was also leaking around the stainless steel piece that comes out the end of it (between the stainless steel part and the injector body, all the way around).  So then I decided that the problem was the injector.  At the moment I have three good 155 bar rebuilt turbo injectors and the one bad one, and I have four old 130 bar injectors (with a lot of kms on them) in the car now, so the situation kind of sucks.  I am going to call the guy in Markham who left his number and get him to have a look at it for me.  Hopefully it can be fixed so I can run four rebuilt 155s again because the car was much peppier and easier to start with those injectors than it is with the old 130s that are in it now.

[chrissev]

I hope that you reset your injection timing to the n/a spec if using the 130 bar injectors.  If not you can melt internals, as the lower breaking pressure will advance your timing significantly.

Andrew

it's advanced quite far right now as the 130 bar injectors are in poor condition and the engine misses if the timing is set normally.  I checked my bentley and it said that I can set the timing where I have it for "turbos and air conditioned cars" so I figure that if an N/A car with air conditioning can function with the timing set where I have it, so can this car.

[VWDieselDoc]

Just a note...  I noticed that the injectors were purchesed from vwdieselparts.com.  For those of you considering purchasing ANYTHING from these people... DON'T!!!!!!  

I work for a VW Specialty shop and we have dealt with rebuilt parts from this  guy "Jack" on many occasions.  Customers have brought his rebult parts for us to install in the past... and there is not ONE instance where there weren't problems with the part(s).  The injection pumps I have seen have 'play' in the mainshaft, up to 5mm of axial clearance!!!!!  Perhaps .25mm is acceptable, but NOT 5!  Not one of these pumps has even made it past the warranty period.  Then when you try and return the pump under warranty, he ALWAYS comes up with an excuse as to why the pump failed...  and it's ALWAYS the consumers fault.  One pump started to run the engine uncontrollably after only TWO days of service.  He refused to warranty the pump, claiming it was installed incorrectly!  Hmmm... we've been working on VW diesels since the first one was built.  One would think we know how to install an injection pump!  By the way, we ended up disassembling and inspecting the pump.  The throttle shaft bushing had NOT been replaced...  (a $3 part).  and apparently no one inspected the pump housing for wear before "rebuilding" it.  The feed pump vanes had not been replaced and the input shaft was worn (it should have been replaced)

Be wary of this guy.  If you do purchase something from him, you WILL eventually have problems with the part... and usually within a year.  I'm just letting you know... it's your choice to throw your money away.

[Master ACiD]

interesting. i had purchased some parts from jack in the past. a headgasket, some valve shims, some other odds and ends. all new parts mind you.

i didnt have any problems with the guy other than the exorbantly  
 high part prices and shipping prices.

i know that jack doesnt rebuild parts if they dont need it. for example he will use old pistons and valves and such in a rebuilt motor if the parts spec out ok. he only replaces what needs to be replaced when rebuilding an item. but this is said right on his webpage.

[chrissev]

What spec does your Bentley give for the breaking pressures of the injectors in the air-conditioned cars?  I have the '85-92 golf/jetta Bentley and find no different spec for air-conditioned cars (timing or breaking pressures).  I have a vague recollection that VW used different injectors with higher breaking pressures for some of their n/a vehicles (I thought it was auto trans, but could have been A/C) and then bumped up the injection timing to compensate in order to meet emission standards.  Injection timing is a fuction of both the injector breaking pressure and the point where the pump develops that pressure.  If the injector breaking pressure is lowered injection timing is advanced.  It is inadvisable to mix and match injection timing specs with injectors of a different breaking pressure than what the timing spec is for, as you negate the timing spec by doing so.  The danger is that overly advanced timing can hurt things.  Do what you want, but eroding a piston top can cause a bad day.

-the timing is set at .004 inches.  It should be at .0037 (max for a 130 bar injector) so I'm not off by too much.  I bumped it up because the injectors are not that great and the engine runs very rough when it is cold if the timing is not advanced.  It is a temporary fix until I get the one leaky injector rebuilt or repaired.  The turbo setting is I believe 1mm or .0045 inches so I am not all the way there yet, just in the middle where it seems to run all right.  Desparate times call for desparate measures.    I watch the rearview mirror carefully and if I see smoke I let off the accelerator (smoke out the back of a diesel = you're melting your pistons with excessive fueling).  It's a turbo motor so it has the oil squirters so I should be OK with this temporary set up for a bit longer.

[dieselweasel]

You mean .040" and .037".  Everyone says not to set injection timing past .039", although you'll probably be okay.  The effects of lower NOP will tend to be offset by the coarser spray from the worn injectors.  Larger fuel droplets will have a retarding effect on timing since they take longer to vapourize, mix with air, and burn.  

With the timing too far advanced, you won't get more black smoke.  The problem with over-advanced timing isn't excessive fuelling, it's excessive pressure due to combustion beginning earlier.  Also, black smoke doesn't necessarily mean the engine is over-fuelled or that the pistons are melting.  Some smoke is normal depending on the engine and it's fuel system.  It's the opacity of the smoke that's the concern.

[VelocityConservation]

I have also gotten good service and products from vwdieselparts.com (Jack).

I recently bought a rebuilt pump for my car.  It is running excellently.  He does lock down (tamper resistant paint etc.) all of the adjustment (except for idle speed) and it is a very conservative set up.  But otherwise I have been very happy with my purchases.

[maxigaz]

hello
did you change the shims, down in the hole, where the injector seats?
they can only be used once, and if you didn't, compression passes through the threads, and can even enter the injectors.
i learned that this week as i changed the nozzles, but not not shims.now i have to remove the injectors again, dismantle them to clean them, and put new shims.they are elastic, and once they have settled, won't come back to their initial position.
cheers stef

[chrissev]

hello
did you change the shims, down in the hole, where the injector seats?
they can only be used once, and if you didn't, compression passes through the threads, and can even enter the injectors.
i learned that this week as i changed the nozzles, but not not shims.now i have to remove the injectors again, dismantle them to clean them, and put new shims.they are elastic, and once they have settled, won't come back to their initial position.
cheers stef

yeah I changed them.  I actually figured out the problem.  The injector seats in the head were bad so the compression was getting out, probably leaking into the injectors somehow.  I have the same injectors in a 1.9/1.6 combination motor (that I am tearing down tonight due to excessive smoking when cold) and they work fine with no leaks, so it was the head that was the problem.  Live and learn

Chris