Hello,

 

I have a Transit CONNECT with a 1.8 TDDi 55kW engine. I bought the car with a broken high-pressure pump (Bosch VP30), which I had replaced with another one from a scrapyard.

 

The engine runs perfectly normally when cold and under load, but as soon as I let it idle after the engine has warmed up, the revs start to fluctuate and the engine starts to knock. When I increase the revs with the accelerator pedal, even by 1% the engine runs perfectly normally. I also noticed that when cold and idling, pressing the clutch pedal also causes irregular running. I blame this on the change in load and thus the change in injection.

 

Standard OBD diagnostics do not report any errors, and the check engine light is not on.

 

Video of the engine running warm at idle and at increased revs:

https://youtu.be/D_UVS9Rx0rI

 

I tried:

cleaning the EGR

 

testing the EGR (okay)

blocking the EGR

testing the return of diesel from the injectors (none behaved abnormally)

cleaning the frame groundingcontacts

Checking for vacuum leaks with a brake cleaner

Blocking brake booster vacuum line 

Checking air bubbles in fuel system (very few bubbles in the return line over time)

Unfortunately, none of the above helped.

 

 

I haven't tried yet:

replacing the fuel filter

replacing the feed pump

overhauling the injectors

overhauling the pump

 

It's not so much that the idle doesn't sound nice, but I'm worried about the MOT because of the unstable revs. According to OBD data, the rev range is between 760 and 850 when running 'well' and about +-50 higher when running unevenly. They probably won't take me anywhere with that.

 

Out of desperation and an effort to save the car, I'm writing here in case someone has encountered something similar and could point me in the right direction. I'd hate to change the pump a second time—it probably wouldn't even be worth it. I'm struck by the fact that

A small update:

 

I spent several hours today trying everything possible—from blocking the vacuum lines to unsuccessfully attempting to find the vacuum leak using a brake cleaner. All attempts were in vain.

 

After a long period of tinkering and searching, I came across this page: [url]https://www.roverdiesel.co.uk/index.php/vp30-fault-finding/[/url] . My problem is described here, although I still don't think the car is losing that much power (I had 2 tons of wood behind it and it didn't have the slightest problem). According to the website, the fault could be in the pump timing solenoid.

Before I remove the pump, I will try to measure the impedance and voltage, ideally over time, to see the pulses going to the solenoid.

 

If anyone more experienced knows where to get a replacement solenoid at a reasonable price (300€ on eBay is ridiculous, I might as well buy a pump from another engine), I'd appreciate some advice. Of course, I will have the solenoid cleaned in an ultrasonic cleaner if it has the correct impedance and I manage to remove it, but even so, I would prefer to have a replacement solution at hand in case any of the above steps get out of hand.

Further updates:

 

So I removed the pump mount from the rear so that I could remove the solenoid. That was probably the hardest part. The solenoid itself is held in place by two T30 Torx screws and comes out almost by itself.

What I really didn't expect, however, was the surprise in the form of completely stripped wires from the solenoid when I cut the wires leading to it.

 

The wire insulation was completely burned to ashes, with virtually nothing left of it. No wonder the engine ran the way it did when the wires could touch each other all the time.

After removing the solenoid and having four beers to recover, I cleaned the solenoid with ultrasound and tested it. The impedance is about 10 Ω, which should be correct. At 12 V, the solenoid responded with the expected click, so I assume that the solenoid itself is fine. The question now is whether the short circuit between the wires caused irreparable damage to the control unit or whether the unit is smart enough to anticipate this situation and disconnect the power supply in time in the event of high current.

The next steps will be to insulate the now bare wires with a material that will withstand the conditions in the engine compartment in the long term, to power the connector at the end of the wires for easier removal in case I have to remove the solenoid repeatedly, and to power the connector for connecting an oscilloscope so that I can measure the current flowing into the pump while the engine is running without need to strip the insulation again. 

Further updates:

 

I repaired the insulation on the timing solenoid and added a connector between the parent unit and the solenoid so that I could add a measuring link if necessary.

 

Despite warnings from some contributors to online forums, I soldered the connector counterpart directly to the pump wires and connected the connector after installation. After starting the engine, its performance did indeed improve, although it is still not completely smooth. According to the OBD data, the RPM range is between 830 and 890. In my opinion, this is still too high, so I will continue my investigation. Other suspects are the alternator and the fuel solenoid, which I have not checked yet and which will probably have similarly poor insulation as the timing solenoid. 

 

I also replaced the fuel filter, which had almost no effect on the engine's performance. The RPMs are now staying within a narrower range, but I can imagine that it is possible to stabilize them at least twice as much. If anyone has any available materials listing the RPM range for this engine or has experience with RPM stabilization, I would greatly appreciate any advice. Until then, I will continue to work on it. I still have the following tasks ahead of me:

 

 

Replacing the alternator

Re-sealing the intake and exhaust manifolds 

Re-testing for vacuum leaks