TheSamba.com :: View topic - m-TDI (Landy pump) lift pump needed?

Mon Jul 22, 2013 2:05 pm

Drew, no I don't think the LR pump is an issue, its a bosch VE pump, could be a B3.9 for all I care.

I agree with you that if everything is working properly then a external lift pump shouldn't be needed. However a lift pump can mask or eliminate the symtoms of the real problem. I've used external pumps to diagnose IP problems.

Mon Jul 22, 2013 2:18 pm

Zeitgeist 13 wrote: I noticed that my ALH has one of those fuel coolers. I'm not familiar with these. Are they necessary?

I've been running an 11mm pump on my ALH for a long time with no fuel cooler and fuel temps are fine whenever I check with vagcom.

Mon Jul 22, 2013 2:19 pm

Sheesh, I wasn't even aware that the ECU bothered to check the fuel temps. Steep learning curve for the old school diesel guy

Mon Jul 22, 2013 2:41 pm

It checks fuel temp for emissions reasons. The fuel density changes with temp slightly and this can impact measured tailpipe emissions.

Its ALL emissions these days!

Mon Jul 22, 2013 5:02 pm

kgold708 wrote: It checks fuel temp for emissions reasons. The fuel density changes with temp slightly and this can impact measured tailpipe emissions.

Its ALL emissions these days!

Fuel expands and looses energy per density when getting warmer. The ECU compensates for power loss.

Ok, first test run done. First of all I was surprised when I cut off the fuel line to add the lift pump - it didn't squirt, it was empty. Both the return and the main line was empty. Still, the feeder hose between the filter and the VP was filled. Can it be on such a stupid level that the filter is leaking back? I already changed it, to the same brand as before though.
The engine started instantly as usual. The symptoms are still present...

The lift pump did help to some extent. It's one of those spring pressure based models (tock tock tock) and it is silent when the pressure is up. When I turn the ignition on it actually tocks once in a while, something really is dropping the pressure. If it's not the filter it's the pump.
The engine starts nicely, run a few minutes and it doesn't come up after a start. Now, it's enough just stop cranking and try again and it pops to live. Weird weirder weirdest bloody start problem ever.

Next step will be to cut the clear line in two and put one half on the return line to see if there are any bubbles. I've heard people having problems with leaking waste lines (those tiny hoses between the injectors) but I have clear hoses and no bubbles.

BTW, It's a 130 l/h 0.4 bar pump, I could smack it to rev stop with no starvation.

Mon Jul 22, 2013 5:22 pm

A leak at the main shaft seal, top o-ring on the pressure control valve or the outer timing piston cap o-ring can leak air in without leaking fuel out. I also use clear tygothane for the injector jumpers. Sometimes those will leak air in after shutdown without leaking fuel out when running. With the clear line there you can see the fuel move after shutdown which is a clear indication that one of the junctions is leaking. Oddly enough a leak there can drain the pump enough to make harder starts. I have also seen once where the little feeler pin o-ring inside the LDA actually allowed air in without leaking and the pump would lose prime when sitting. Often times those leaks will be temperature dependent.

Mon Jul 22, 2013 5:23 pm

svenakela wrote: kgold708 wrote: It checks fuel temp for emissions reasons. The fuel density changes with temp slightly and this can impact measured tailpipe emissions.

Its ALL emissions these days!

Fuel expands and looses energy per density when getting warmer. The ECU compensates for ...... .

Ok, good luck. Sorry I garbaged up your thread but there is some good info in it. Maybe reread it and sleep on it.

Mon Jul 22, 2013 5:37 pm

Andrew A. Libby wrote: A leak at the main shaft seal, top o-ring on the pressure control valve or the outer timing piston cap o-ring can leak air in without leaking fuel out. I also use clear tygothane for the injector jumpers. Sometimes those will leak air in after shutdown without leaking fuel out when running. With the clear line there you can see the fuel move after shutdown which is a clear indication that one of the junctions is leaking. Oddly enough a leak there can drain the pump enough to make harder starts. I have also seen once where the little feeler pin o-ring inside the LDA actually allowed air in without leaking and the pump would lose prime when sitting. Often times those leaks will be temperature dependent.

I would accept a pump leak as a reason if the engine was hard to start after a while. Now it's the opposite - turn off, crank immediately and nothing happens. Stop cranking and retry right away and it starts.
If I for example stop at a gas station and refill and take a coffee, it starts like it was cold. Right away...

The last jumper is a clear hose (that's what I called waste line) and there's no leak as far as I can see. I haven't used a clear on the main return, will add one tomorrow.

Mon Jul 22, 2013 5:39 pm

You could pull the stop solenoid plunger and spring to eliminate it as fuel supply electrical fault. Then dump the clutch to stop it.

Tue Jul 23, 2013 12:00 am

svenakela wrote:

ALIKA T3 wrote: What type of return bolt do you have on the pump,the number is engraved on it:55 or 75?

Was that to me?

Yes sir.

The 0.55 return screw is no bueno and can cause problems,most likely you have the one from what was on your van from factory,a #55.

Also about that solenoid,take it apart,the rubber cone might stick inside the pump when it's hot, kinda coming apart...

It must be something that makes sense somewhere.

I know there are internal springs that are important and might matter for cold or hot start,but that's beyond my knowledge,I'm not very theorical on these pumps,mostly practical :lol:

Tue Jul 23, 2013 1:32 am

@Andrew; S.M.R.T! I'll do that right away.

@Alika; Will check that. But if my memory is correct I have the Landy return.

Tue Jul 23, 2013 3:32 am

Drum roll please...

And the winner iiis... ...ritch ritch... ...Andrew!

The bloody solenoid goes bananas when it turns hot. I ran the engine a bit and took it off (the person who decided on its position should have a salary post reduction). I ran it directly on the battery. Wonk wonk. It only opens half way and get stuck. I had to kick it on the battery several times to get it fully open. I took a solenoid from another pump and it bounces like a kangaroo on coke. I mounted the replacement valve and took it out for a ride, did at least 15 stop and go with NO HESITATION AT ALL.

In my profession I work with a system with 40 000 solenoids, one could think that I should have learned something about 'em...

The lift pump is already there and I have made a nice mount, I'll leave it. It doesn't hurt so to speak.

I must say I enjoyed every line of the discussion in this thread and your commitment is what makes me read this forum. Thanks all! :)

Tue Jul 23, 2013 6:40 am

Nice resolution!

Tue Jul 23, 2013 10:12 am

Well,that's the second answer you got on your post :solenoid.
I was thinking the rubber cone 'cause it happened before,like you said,I've never seen a solenoid work halfway :shock:
It happened to me once on a Renault SuperFive (SuperCinq),it wasn't shutting off the whole way,but would open the when ignition ON no problem.I had to stall the car to make it shut off,it was running like on 2 cylinders :lol: :lol:

I'm glad you can drive with a free mind now,those things are annoying :roll:

Tue Jul 23, 2013 10:54 am

I know. But I've had already tested the darn solenoid. This time I heated it up. A burnt coil makes them act like this. Why it burns you never know for sure but too little voltage makes the amperage increase and sometimes that's enough to kill the coil internally.

Whatever you do, change the solenoid first. :)

Tue Jul 23, 2013 5:49 pm

Good to hear it was somethign easy!

I also did suggest checking the solenoid in the first post of this thread :wink:

Tue Jul 23, 2013 8:49 pm

For posterity, tho, neither checking the voltage at the stop solenoid, checking the plunger nor running 12v directly to it would have shown the solenoid as faulty. Removing the plunger and spring would have.

Tue Jul 23, 2013 9:42 pm

Andrew A. Libby wrote: For posterity, tho, neither checking the voltage at the stop solenoid, checking the plunger nor running 12v directly to it would have shown the solenoid as faulty. Removing the plunger and spring would have.

Certainly, but if the voltage checked out ok I would have investigated the solenoid further, easy enough to swap one in out of a used pump and test it. The distinct "starts great" or "doesn't even cough" seemed solenoid related.

Wed Jul 24, 2013 2:56 am

Andrew A. Libby wrote: For posterity, tho, neither checking the voltage at the stop solenoid, checking the plunger nor running 12v directly to it would have shown the solenoid as faulty. Removing the plunger and spring would have.

Exactly. It all measured fine. If the solenoid did work on the battery test I would have proceeded with your suggestion to run without the plunger. Now I found the problem one step further, luckily, so it was easy to swap to another valve. These little bastards can be tricky.