VP37 Pump: Low Pressure? Troubleshooting Guide.

Hello!

I'm having the following problem with my Volkswagen Golf 3 1Z diesel (with AF engine control unit):

The diesel pump is no longer building up enough pressure, so that no diesel reaches the injectors. While diesel flows into the pump through the supply line and back out through the return line, the pressure seems too low for it to reach the fuel injectors. I have already checked the supply lines to the fuel injectors and even disconnected them, then tried to start the engine, but no diesel is reaching the top at all.

Does anyone have any idea what might be causing this?

Sure, here's the translation:

'I would need it relatively urgently.'

I've narrowed down the problem to the intermediate pieces between the pump and the fuel lines of the injectors. There are valve spring screws in there (sorry if I don't know what those things are called }). When I loosen them, diesel leaks out; when I tighten them, nothing comes out anymore, not a single drop...

The pump was replaced again, but the new one has the exact same problem.

Help!

Thank you very much.

Best regards,

m3nx wrote:

I've narrowed down the problem to the intermediate pieces between the pump and the fuel lines leading to the injectors. There are valve spring screws in there (sorry if I don't know what those things are called ). When I loosen them, diesel leaks out; when I tighten them, nothing comes out anymore, not a single drop... The pump was also replaced again, but the new one has exactly the same problem.

Hi,

Your valve spring screws are likely the pressure relief valves.

If a new pump exhibits the same problems, it could be due to the shut-off valve: either it's not receiving power, or it's faulty and was installed in the new pump.

-> Is there tension on the stop lever when playing the organ?

-> Disconnect the jumper cable and connect the jumper directly to Batt+: Does it click? [/list]

Hi!

Thank you for the tip. I had the same suspicion and already checked the stopper; it works perfectly fine. It also clicks when I disconnect and reconnect the ring cable. The test light is also working.

I'm just at a loss; I rarely get to the point of despair, but it's gotten that bad here.

Perhaps another idea?

I've already checked the engine control unit (ECU) and installed it in another vehicle; it works fine. I'm really out of ideas at this point...

m3nx wrote:

...I really have absolutely no more ideas...

Yes!
While it seems unlikely, it's still an idea: four stuck nozzles.
Have the nozzles ever been calibrated? If so, what was the opening pressure and spray pattern?

So, if a pump can't even achieve the 190 bar opening pressure for the first stage, then I start to wonder if everything was done correctly during the pump replacement.

Bertil wrote:

It sounds unlikely, but it's still an idea: four stuck nozzles.

Hi Bertil,

Then, when loosening the screws on the injector side of the fuel lines and removing the injectors, shouldn't some diesel fuel leak out?
It doesn't, according to the original post.

Could all 4 relief valves instead get stuck ?

@m3nx:
How did the problem develop? Suddenly or gradually? -> Please provide details.

Hello everyone!

Theoretically, it's also possible for the metering unit to jam in the zero-injection range, causing the injection amount to always be close to 0.
When releasing the pressure equalization valves, a small amount of fuel drips out of the openings with virtually no pressure. However, the pump cannot generate any pressure because the effective plunger stroke is practically zero.

What do you think of this theory? I find it more plausible that a stuck quantity setting device is the cause than four simultaneously defective pressure relief valves.

Regards,
Alex.

It's conceivable!

But what about the same problem and supposedly two pumps? That makes the control panel just as unlikely as the four nozzles.

Hi!

Oh, it's so nice that someone is finally trying to help me. The people at VW wanted to immediately take the car to the workshop and replace all sorts of things without any real reason, and everyone else I asked was also out of ideas.

I've been working on this car since Saturday, and it all started like this:

On Friday evening, I drove a lot on the highway, and quite fast. However, I kept the car idling while smoking a cigarette to let the turbo cool down. The car ran perfectly, no issues whatsoever. The next morning, I got in, pre-glowed it briefly as usual, started it, and... 'orgel orgel orgel' (the sound of the starter motor)... nothing happened. I wondered what could be the problem. So I tried again... 'orgel orgel orgel orgel orgel orgel'... still nothing, completely dead. And there was a massive amount of white smoke coming out. It almost looked like a fog machine .

I already thought the worst and called a friend, had it towed to the workshop, and tried to pull it along on the way. At first, nothing happened. Then, after about a minute at around 30 mph in second gear, there was a 'whuummm' sound, white smoke disappeared, and the engine started... very strange.

So, we went to the workshop and checked the injection timing using VAG-COM. It was measuring outside of the acceptable range, somewhere above the green line, around 1-2 degrees. We were both completely shocked. We turned off the engine, loosened the pump's screws, restarted it (it started perfectly), and adjusted the pump to be within the blue zone. We took a test drive, and everything was fine.

Back in the workshop, the car was parked and attempts were made to start it... 'orgel orgel orgel' (a sound like a struggling engine)... nothing. Tried again... after a long hesitation and sputtering, it finally started. Checked the injection timing again, still too far advanced. However, the fuel pump hadn't twisted; it was still in the position we had set it to, so that was actually good. We loosened the fuel pump again and adjusted it properly. At this point, we were running out of space towards the later timing marks because we had to use every bit of available adjustment just to get it somewhat aligned with the blue line.

We then connected the VAG-COM and repeatedly turned the engine off and on. Surprisingly, each time we restarted it, the timing advanced further. So, we vigorously shook the fuel pump, and suddenly, the 'crosshair' in the graph jumped dramatically from green to red, indicating a very late injection timing. We only touched the pump; nothing else was changed. Then, we were able to adjust the pump properly with enough play forward or backward, but immediately encountered the same problem after turning off the engine again. It's quite strange.

And so it just kept happening, the pump definitely couldn't be adjusted properly anymore... for whatever reason. It would adjust itself however it felt like, so on Saturday I bought a new, used, and tested pump from the local junkyard.

This built-in organ... organ organ organ organ organ organ organ organ... nothing...
Organ organ organ organ organ organ... nothing at all...
Naja vielleicht Pumpe doch defekt, nochmal umgetauscht, gleiches Modell nochmal bekommen, eingebaut, überall OT geprüft, Kurbelwellenrad auch geprüft, alles in Ordnung, versucht zu starten.. Orgel orgel orgel orgel orgel.. Ni'chts..'

'Maybe there's a blockage somewhere... So, we loosened the first metal fuel line and tried to start it. We noticed that absolutely no diesel was reaching it – not even a drop. Then we removed all the metal hoses… still nothing, nada, zero. Now we checked the shut-off valve; it clicks and works fine when disconnected and connected to the battery.'

Okay, so here I am today... The diesel fuel is reaching the pump (without air bubbles) and also returning through the return line. However, it's not reaching the individual fuel lines because apparently the pressure is too low to activate these spring-loaded components. I've already replaced those springs with ones from my original pump, but that didn't work either. I put the new ones back in, still nothing... I just don't understand what's going on anymore.

If you remove the spring parts and start the engine, a significant amount of pressure will be released after just 2-3 revolutions of the motor. It's impossible to hold it back with just one finger because of the force.

I'm completely lost now. It was working before, and the pump used to be adjustable, but why isn't it adjustable anymore? Now it won't even start. I've checked all the fuses out of desperation, but that's not the problem either.

It looks like a KW screw and a damaged KW stub, doesn't it?

Hi!

Okay, I checked the screw, and it's still very tight and not wobbly. I was also thinking about that, but aside from that, wouldn't that be a reason for the pump not to build up pressure?

No, not that. But regarding your fog machine, and the fact that you can't adjust the feed rate, and that if it works now, the same problem will likely happen again next time you use it.

Hmm.. I thought maybe the pneumatic system of the old pump was somehow broken, but I'm happy to be corrected . So, ultimately, all that work was for nothing .

Okay, as soon as the pump starts pumping again and builds up pressure, I will immediately check the crankshaft . But right now, even a brand new crankshaft won't help me.

Here's what else just popped into my head:
- fuel tank vent
diesel filter

Hi,

Given the range of symptoms, I suspect there might be a "variable blockage" somewhere in the fuel suction area.
This disrupts the internal pressure of the pump and, consequently, the start of the injection process.

For a test, temporarily disconnect the suction hose between the filter and the pump, and let the pump draw diesel from a small container filled with clean/filtered diesel (ideally, also return the fuel to the same container).

If the engine then runs normally, the basic problem is solved.

Edit: Overlapped with Jörg's response...

Hi!

Okay, I'll try that. By the way, I already temporarily bypassed the diesel filter by using a piece of pipe. The return line was still connected to the diesel filter, and I plugged the two now-free lines in the filter with rubber stoppers.

It's also sucking properly, and I used a plexiglass tube as a 'transition hose,' but it seems like everything that goes in is immediately flowing back out through the return line.

'Still, thank you, I'll definitely try that first thing tomorrow morning... there's still a glimmer of hope.'

The engine should at least cough sometimes... but absolutely nothing is coming out.

'When I spray starting fluid directly into the intake manifold, the engine runs... however, it doesn't respond to the accelerator pedal and immediately stalls when I stop spraying the starting fluid. It simply isn't getting any fuel.'

Best regards,

Are all the electrical connections from the engine control unit to the fuel injection pump in good condition?