Liqui Moly Diesel Purge Gone Wrong - Now barely starting
 

Hello all,

Hope everyone's doing well.

I attempted a Liqui Moly Diesel Purge recently. As the title suggests, it didn't go too well, and am looking for advice on what to do. Prior to attempting the diesel purge, my D5 163 ran just fine (albeit with ECM-6805 saying hello occasionally), always a quick starter.

I'll try to detail as much as I can, so be warned, this might be a long read.

TL;DR: Did Liqui Moly Diesel Purge, now D5 barely starts.

After plumbing the fuel lines into a jar of Liqui Moly Diesel Purge, I managed to get the engine started. But not before:

1. Destroying the small-length hose on the injector return line during the removal; replaced with a portion of the hose I bought for the diesel purge process.
2. Priming the inlet hose and diesel purge filter to the LP/HP pump, including pulling a vacuum via the return line.
3. A few cranking attempts before the engine "happily" ran on the Liqui Moly Diesel Purge.

+ YouTube Video

After about 30 minutes of idling with the diesel purge, I tried to gradually raise and hold a steady RPM. I only got to around 1100 rpm before the engine died. A buzzing could be heard from the LP/HP pump area for around 30 to 40 seconds after the engine died.

At that point, I decided to give up on the diesel purge process and plumb the fuel lines back to the original setup.

It took a few cranking attempts to get the engine running after returning everything back to stock. When it did eventually fire, I noticed that starting was not as quick as it was before, taking just that bit longer of cranking before firing. I experienced something similar during a fuel starvation issue not too long ago, so I wasn't too concerned, yet, as I was just playing around with the fuel system after all.

This is a graphical representation of the engine parameters after that start:
https://live.staticflickr.com/65535/...b9b3591e_b.jpg

I let the engine idle for around 4 minutes and revved the engine a couple of times after that. At around 350 seconds into the log, I tried to gradually raise the revs, but just before reaching 1000 rpm, the engine died, just like it did whilst running on the Liqui Moly Diesel Purge.

I cranked the engine again, and it fired back up. I tried to gradually raise the revs again hoping to replicate the engine dying but it didn't happen again. I gave it a few more revs just after the 500-second mark and everything seemed to be just fine.

I ended by shutting off the engine and restarting a couple of times, and again, everything appeared to be just fine. Because of the slightly longer cranking time before firing and the engine seemingly starved of fuel at low-ish revs, I didn't take it for a test run, for fear of stalling in the middle of the road.

Fast-forward 18 hours later, it was early morning, not much traffic to hold up in case things go wrong, I thought I'd take it for a short run to the shops. The slightly longer cranking was still there, but everything else seemed to be just fine (data below):

https://live.staticflickr.com/65535/...62c2058e_b.jpg

Went into the shops and came back out 5 minutes later. Cranked the engine 1st time: no start. Cranked 2nd time: still no start. Cranked 3rd time for a longer period: started. Unfortunately, I forgot to log the engine parameters this time. Quickly drove back home and the car sat still for about 5 hours.

I came back out to the car to investigate further, this time not forgetting to log the engine parameters:

https://live.staticflickr.com/65535/...20a25819_b.jpg

The engine fired on the first try and I let it run for around 170 seconds, gradually raising the revs at around 90 seconds in.

I then turned the engine off and tried to restart it again. But after 7 starting attempts, the engine barely fired for a second or two but died immediately afterward. As you can see, the fuel rail pressure during this didn't indicate more than 200 bar during this time.

I've had a look around (and still reading) the forums and several issues have been mentioned (loose ECU connections, FP sensors FP regulators). I'm inclined to think I might have a leak somewhere in the plumbing to the LP/HP pump and/or rail, as I've been messing about with them and especially after discovering this on the inlet hose to the LP/HP pump:

+ YouTube Video

Is the hose supposed to be 'twistable' like that? I imagine that would allow air to be sucked into the LP/HP pump, no?

That said, I'm more than happy to be corrected and pointed in the right direction.

Lastly, I hope this doesn't put off others who are interested in doing a LM diesel purge. It's been done successfully by many others with good results, just not on this occasion.

Please help!

I'll start with the absolute basics.
Clean all fuel unions with brake cleaner so they are bone dry and look for leaks.
Can you hear the in tank pump running with ignition on?
When was the fuel filter last replaced and with what brand?

HP pump appears to working fine so I'm guessing the issue is around fuel delivery/regulation.

There's either not enough fuel available due to flow/restriction somewhere or fuel is available and not being regulated correctly at the HP pump.

Given the work on the unions didn't go smoothly, it adds an extra level of possibilities.

Thanks, Si, for your reply.

I was hoping to get a strong smell of diesel around the unions, suggesting a leak in that area, but there was none. Nevertheless, I'll give the area a clean with brake cleaner and go from there.

I've never been able to firmly establish whether the in tank fuel pump is working or not. Would taking a voltage reading at the fuel pump fuse while key in position II tell whether it's working or not?

The fuel filter was last changed in June 2020, 4000 miles ago, with a Purflux C516 packaged in a Volvo box. There is currently just over half a tank of diesel in the tank and the car is parked level.

What are your thoughts on the last video showing the twisting tube to the inlet of the LP/HP pump? That can't be normal, can it?

I can't deny that I might have broken whatever seal might have been between the rubber tube and the LP/HP nipple (there's even a part number for it 30731749!) while taking off the other end. And since it's a pump inlet, there would be suction in that area, no?

That hose should not be free to twist. It could be drawing in air which would stop the car from starting. The movement of the engine when starting could be enough to move the hose, causing the engine to start sometimes and not start other times. Diesel purge is a very effective fuel system cleaner, and it contains enough additives to keep the components in the fuel system well lubricated, but you need to make sure the HP pump doesn't run dry at all. A few seconds is all it takes to cause irreparable damage to a HP fuel pump.

In your case I would hazard a guess that there's air getting into the HP pump via the loose supply hose. The hose clamps onto an adaptor that's threaded into the pump. Hopefully it has just worked loose and the threads are fine. If so then it should just be a case of removing the hose, tightening the adaptor then refitting the hose.

Thanks, Dancake, for your reply.

I've just been out to the car to have another look.

By the looks of it, the LP/HP pump nipple was still securely threaded into the LP/HP pump and it was the hose that was twisting around the nipple.

I undid the hose clamp and took the hose off of the nipple, looking to replace with another clamp and tighten the hose-to-nipple connection.

Before I did that, I decided to see if my electric fuel pump was working by feeding the disconnected hose into an empty jar and turning the key to position II.

No fuel came out, neither on the first turn of the key nor on any of the >10 key turns that I performed.

I replaced the fuel pump fuse (15 A, No. 21 in the engine compartment) with a spare, and still no fuel was flowing with key in position II.

I think that pretty much concludes that my electric in-tank fuel pump is not running. It probably hasn't been working for the past 4000+ miles since I couldn't get the engine started after a fuel filter change. On that occasion, an AA technician came out and, with the help of easy-start, got the engine running again. And it probably has something to do with the CEM-3F91 Fuel pump (FP) relay Shorted to supply DTC I have had on VIDA for a while now.

>4000 miles later, I decided to do a diesel purge and have probably disrupted any sealing between the hoses and the LP/HP pump in the process, allowing air into the fuel system.

I could tighten all the hose fittings and force fuel to the LP/HP pump again (as it has been for the past 4000 miles), or I guess the better option would be to look into the electric fuel pump issue.

Can anybody point to where I might find this fuel pump relay? EDIT: It's "located internally in the Central Electronic Module".

Can it be faulty and replaced?

https://live.staticflickr.com/65535/...fa33c62f_o.png

The Euro 3 HP pump is a tandem pump so if you can fully prime the system with diesel by vacuum pumping the return line at the front of the engine, it should run fine.
That's why Diesel Purge is possible on a Euro 3 D5 but not Euro 4.

My in tank pump has been dead for a couple of years now.
I keep it above a quarter of a tank and the car runs fine so I wouldn't spend too much time on that for now.
Having a working tank pump is ideal but not essential. .

The fact that you had revving issues during the Diesel Purge does suggest air in the system.

You could clamp the rubber feed line into the HP pump and pull a vacuum on the return and it should hold vacuum or point towards where air is being allowed in/out.

I have a starting D5 again.

The inlet hose to the HP pump was secured using a new hose clamp but not before:

• Brimming the inlet line with diesel via a vacuum pump,
• Blocking off the HP pump inlet and drawing vacuum at return line to test for leaks, and finally,
• Pulling a vacuum via the return line to force diesel from the (brimmed) inlet line to the HP pump.

I thought I had the system sufficiently primed to have a firing engine from a single turn of the key, but it took 10, see below:

https://live.staticflickr.com/65535/...da161c2b_b.jpg

I let it idle for around 10 minutes while double-checking for any leaks, followed by some revving. I also stopped and restarted the engine a few times.

I'm still convincing myself to take it out, will report back later.

Here's hoping that the non-starting issue was leak-related and nothing else and that my HP pump is still serviceable.

Thank you, everyone, for your help.

Well done.
There's nothing in those figures that would concern me so hopefully you're sorted long term.

I took out the car yesterday and the engine cut out twice.

The only similarity between these two occurrences was that I was feather-light on the throttle (1st: creeping away from a traffic light, 2nd: creeping away from parking bay). On both occurrences, the engine speed was just creeping up to around 1000 rpm, stuttered, and cut out. I moved the gearshift back into P, cycled the ignition, and the engine fired again.

Looking back at the data on the first cut out (Run 1), I noticed that there was a fuel flow spike just as the engine was about to cut out, which I think is a bit odd:

https://live.staticflickr.com/65535/...a349d5ea_b.jpg

I have yet to look up how the fuel flow rate is measured. Is there a sensor? Or is it a derived value from several sensors? Could there be an internal leak somewhere?

On the second cut out (Run 2), upon starting the engine, I felt a slight misfire/hesitation that lasted for 1 to 2 seconds. At this point, the car had been parked up for around 5 minutes. I revved the engine a couple of times just to get things going. Moved the gearstick from P to D and feathered the throttle to get out of the parking bay, the engine stuttered, and cut out. Moved the gearstick from D to P, cycled the ignition, and the engine fired.

https://live.staticflickr.com/65535/...1c25f1c0_b.jpg

At this point, I had already noticed that it might be the light-throttling that was causing the engine to cut out. So, for the rest of the journey, I made sure to be a tad more aggressive with the throttle, and, thankfully, it got me home without any issues.

It might be time to break out VIDA to look for any stored codes. It's probably also worth looking back at those connections and give them a final nip.

In the meantime, if anybody has any thoughts, I would appreciate it.

Reading around the forum suggests several issues linked to a D5244T cutting out or going into limp-home mode.

When cutting out under load, it seems to suggest a fueling issue, the usual culprits being, as well-documented:

• Blocked fuel filter
• Inoperational in-tank electric pump + running low on fuel

.

When cutting out at low load/revs, electrical issues have been pointed out:

• Electrical connector going into engine bay fuse box (see e.g. this, this, and this).
• Failing/failed fuel pressure sensor (see e.g. this and this)
• HP pump and/or pressure regulator (see e.g. this, this)

.

As I can't discount anything, yet, I've done the 'free' stuff first:

• Checked all unions carrying fuel to/from HP pump and gave everything a final nip.
• Disconnected battery, disconnected grey connector to the engine fuse box to look for any loose connections.
• Using contact cleaner to clean the contacts on the HP pump regulator and fuel pressure sensor.
• VIDA scan revealed ECM-2505 and ECM-2503 (low fuel pressure), which were logged from the earlier cut-outs and have been erased.

Now, I suppose, it's just a matter of running it and seeing if the problem has been resolved.

No success yet.

Took the car out today to the shops. The engine cut out three times in the span of approximately 3 minutes/300 yards. Interestingly, no cut outs in the 2-mile journey after.

All cut outs occurred at low revs/load, either on engine overrun or just barely accelerating from standstill, where the engine had well reached its operating temperature. The engine would fire again first time, every time, after cycling the ignition, which on a Geartronic means stopping and putting the gear selector into P. There were no cut-outs while the engine was warming up.

A very similar issue was detailed in this post and was remedied (thus far) by fitting a replacement fuel pressure sensor.

VIDA scan revealed ECM-2505 and ECM-2503, both pointing to a damaged fuel pressure sensor as a possible source of the DTC being triggered; however, there are other potential causes as well.

Of the two DTCs, I suppose ECM-2503 is the key DTC to pay attention to as fuel is cut off when it is triggered (ECM-2505 only 'reduces' fuel).

From VIDA:
It's probably time to start replacing parts now...

In the meantime, if anybody has any insight on the below, I would appreciate the advice:

• On VIDA, a live read of the "current through fuel pressure regulator valve" can be obtained. Can anybody point out to where this pressure regulator valve is? Is it the one on the HP pump? I have yet to look on VIDA, but are there nominal/reference values for it?
• Where are these so-called pressure control and/or safety valves? Are they within the HP pump assembly itself? Or are they external to it?
• Any thoughts on why it only happens (so far) once the engine has well reached its operating temperature and not on warm-up?

The fuel pressure regulator is bolted to the high pressure pump and has an electrical plug on it. They can be tricky to diagnose, but if they aren't working correctly they will cause fuel pressure deviations resulting in running issues. FPR's can fail in two ways. Either they won't allow enough fuel to cope with the need or demand, or they will allow excessive fuel to pass to the rail. Either way can cause running issues, including misfires and cutting out.

The cutting out symptom is normally as a result of a low pressure condition caused by a stuck or partially blocked FPR (when the FPR is the faulty component). You can unplug the FPR to see if the engine behaves any differently, but don't let it run for too long if it sounds like a machine gun. Of course the fault could also lie within the pump itself, but the FPR is quicker to check than the pump. You could try removing the FPR and cleaning it in something like an ultrasonic bath using a sensitive metals cleaning solution, or swap one out from a known working engine to see if it cures it.

Codes 2505 and 2503 don't necessarily indicate that your fuel pressure sensor is damaged. The codes have been stored because the fuel pressure has dropped below the parameters expected at a specific engine operating condition, perhaps at the point the engine cuts out. These codes sound like symptoms of another problem and not the cause. I'd try the FPR on the pump first and go from there. Volvo call it a fuel control valve for reference.

Have you checked your air filter? A clogged or partially clogged air filter can cause a myriad of problems

Today I managed to replicate the problem with VIDA connected.

As VIDA allows a higher data sampling rate from the sensors (compared to my ELM327 + Torque Pro setup), I thought it might give better insight.

As before, the engine would cut out seemingly randomly, but only once it had well reached operating temperature and only at low revs.

Below is the data from the run. The engine cut out whilst I was doing a 3-point turn (well, it's a P2, so more a 7-point turn :regular_smile:). Two stutters and the engine cut off. The FPR current shoots up immediately after ignition is cut, and stays that way until the key is cycled from Pos 0 to Pos II. As with previous occurrences, starting always 1st time with the key.

https://live.staticflickr.com/65535/...e756fdca_b.jpg

EDIT: Just noticed how the FPR current dropped "one grid line" during the engine stutter and cut out and increased again after the engine started again. FPR current would only reduce that much if engine revs are increased (see spike in fuel pressure and revs just before cut out). Hmmm...

Zooming in, you can get a better view of the (indicated) fuel pressure drop during the stutter and engine cut out and how the fuel pressure drops before the FPR current rise.

https://live.staticflickr.com/65535/...7dfdfcbb_b.jpg

Conversely, if the ignition is killed with the key, the fuel pressure drops after the FPR current rise. This is the same data zoomed in towards the end.

https://live.staticflickr.com/65535/...2355c0eb_b.jpg

If there are any D5244T owners who don't mind sharing what their sensors report in similar conditions, it would be interesting to compare.

And, no rush for this, as this has just got my attention:

+ YouTube Video

What are the chances?? Easy job, this?

Looks like a pin hole in the thermostat housing?

A thermostat is easy to replace on the euro 3.

It will be a while before I could get data on mine.
The FPR does sound suspect though so perhaps check Vida Information >Specifications Electrical for the available data to compare.

Re the thermostat, looks like it's been separated in the past and the seal has been breached. Best to replace the whole unit but genuine Volvo is £100 ish if not more.

I have a brand new Wahler Thermostat, housing and coolant temperature sensor unit you could have for £75 delivered.
Wahler make the genuine one and it's identical apart from "Volvo" is ground off the housing and it's in a Wahler box.
Still has the Volvo part number stamped on the housing and the coolant temperature sensor and comes with a new gasket.

I bought it a while ago but they're just too damn reliable so never needed to fit it.

It does, yeah. It seems that access to the bottom bolt of the thermostat housing is a bit tight and involves moving the power steering components, aux belt, etc. out of the way, something I don't have a problem with; it's the putting things back together that gets me nervous!

It seems there is a resistance measurement that can be made; should be around 3 ohms.

My local Volvo dealership wanted £104 for it and were happy to have it ready for me sometime in May. I followed a link you posted on another thread and was just about to purchase it. I'm happy to take you up on your offer. PM incoming!

On another note, what do you guys think about using a primer bulb on the inlet line to the HP pump to prime it, as opposed to pulling vacuum on the return line. Something like this, perhaps with some clear tubing:

https://i1.adis.ws/i/washford/221868...5&fmt=webp&v=1

I prefer vacuuming.
Those cheap eBay/Amazon kits usually come with a jar which will catch the drips until you pull through a good solid stream of fuel.
https://images-na.ssl-images-amazon...._AC_SL800_.jpg

The FPR could test ok with the resistance check, but it won't tell you if there's a blockage or mechanical wear within the regulator. I've fitted hand primer pumps to a few engines over the years, mostly diesel Fords as they can be awkward to start after changing the fuel filter. They should be fitted to more engines in my opinion, as when needed their convenience can be a great time saver. You can place it on the supply line to the HP pump no problem.

"It does, yeah. It seems that access to the bottom bolt of the thermostat housing is a bit tight and involves moving the power steering components, aux belt, etc. out of the way, something I don't have a problem with; it's the putting things back together that gets me nervous!"

I understand what you mean. Its one of those jobs where you just have to take your time or even take photos so you have a reference point to go back to.

The thermostat's on the euro 5 models (2009 onwards) are a right pain! Some genuis thought it would be a good idea to put the thermostat in the most awkward place, literally at the back of the engine! You have to remove the battery, air box, throttle body, the EGR valve, some of the wiring loom & then you'll see the part! So much so, a dealership will charge around £300-£400 to replace it! :shocked:

Quick update:

1. Thermostat housing (and thermostat) replaced (thanks @cheshired5).
2. Replacement FPR installed.

Engine cutting out behaviour unchanged (cut out during 3-point turn, engine at operating temperature).

Update:

Fuel pressure sensor replaced; engine still cutting out at coasting/idle, although it no longer takes the engine to reach full operating temperature to do so!

There are not many parts left to replace if I'm right in thinking; it's either the HP pump or the pressure safety valve. Or it could be an electrical gremlin somewhere!

Is it still possible to obtain a new HP line from the HP pump to the rail? It's supposed to be replaced upon removal, right?

Thoughts, anyone?

The high pressure lines are supposed to be replaced each time they are removed. This is because they deform when tightened in order to provide as secure a connection as possible. You can reuse them a number of times though, providing you don't overtighten the nuts. Unless the pipe is damaged or leaking I wouldn't be rushing to replace it.

My recommendation to try the FPR was based on trying the easiest thing first. It obviously didn't work despite some of the symptoms matching those created when a fuel pressure regulator starts to play up. The fuel pump is a strong possibility, but before you go near it I would pull the fuel filter and check for swarf in the filter housing. If you see any take a picture and post it up.

I would have done (and did) the same: easiest thing first.

Seeing as there are not many things left to swap out and test, and that my FPR (or inlet metering valve (IMV), as I've been reading?) came with a HP pump attached to it, I'm going to see if I can swap it out.

I'm very fortunate to have had the time and opportunity to investigate this step-by-step. But I think it's been going on for long enough and I need to know whether this will potentially cure the problem or not.

Either way, next week's school run will not be on public transport! :soccer_ball:

I've just had a look at the spare HP pump and tried rotating the input shaft by hand.

I couldn't.

Can anybody advise if that's how it should be?

Thanks.

EDIT: Nevermind, I got an adjustable spanner on it and it moved freely.

HP pump replaced and fuel lines system primed with primer bulb and monitoring return line for bubbles.

Still summoning the courage to turn the key, while contemplating what might go wrong, and more importantly, whether I'll be able to cope with it!

Good luck..... You deserve a positive outcome.

After 200 trouble-free miles on the replacement HP pump, I'm hoping the issue has been resolved.

Thread closed (for now!).