ML 270 CDI High Pressure Fuel Pump Connections

[Martin Hall]

Hi Everyone,

I have just rebuilt the cylinder head on my ML 270 CDI and needless to say it won't start. Could someone please confirm that the pipe from the low pressure pump goes to the inlet nearest the head of the High Pressure Pump and the leak off connection should be fitted to the connection nearest the radiator. I'm waiting for the battery to recharge before another attempt, but would appreciate any thoughts.

All the O rings have been changed, there is a new fuel filter and the pipe from the filter to the low pressure pump has been replaced. Car suffered black death, damaged copper washers and one of the injectors was faulty. This has been replaced with a known good second hand injector.

I've got a code reader and will be plugging that in when the battery is up to fully charged.

Many thanks

Martin

 

[mersum1es]

there are arrows in low pressure pump to show flow direction, in hp pump front connection goes to rail.

https://forums.mbclub.co.uk/threads/ml270-high-pressure-pump-fuel-lines.245922/#post-2707255

Check all injector connectors, pins withdraw easily. Do a leak back test if pressure is not rising.

 

[Martin Hall]

Hi there, many thanks for your reply.

its the two connections to on the left hand side of the pump that I am trying to check. these are two plastic connectors, one from the low pressure pump (which I have got correct with respect to the arrows) The high pressure pump has two connectors, one coming from the low pressure pump and the second going to what I suspect is the leak off. I was trying to confirm that the pipe from the low pressure outlet goes to the connector on the rear of the high pressure pump, the one nearest the cylinder head. Appreciate that the high pressure outlet goes to the fuel rail as this has the metal high pressure pipes.

Thanks once again

Martin

 

[John Laidlaw]

Welcome Martin - how’s that ^ for service ?

 

[Martin Hall]

Brilliant thank you.

I cannot see any reason for the ML not to start apart from needing ages to pull through fuel. There are no fault codes apart from a faulty water temperature sensor. There are some air bubbles going along the leak off pipe from No 1 injector (i replaced the broken pipe with plastic fuel pipe) I have checked all the leak offs from the injectors and none of them are chucking a load of fuel out of the leak off union (barely a dribble) All the connectors are secure, including all the injectors, the two sensors on the fuel rail and the cam position sensor on the cam cover. I'm reluctant to use Easy Start but I may just have to. Engine turns over with a fully charged battery at the right speed, and the glow plug light goes off after about three seconds. Its got me beat at the moment!

Mart

 

[mersum1es]

Sorry I was bit unclear, as you see in picture from link I posted above, you have those hp low pressure lines correct (front line goes to rail drain line)

Limit for injector leak is 20ml/min per injector so it is not huge...

What does your code reader shows in rail pressure during cranking?

You can check if you are gettin fuel from tank, remove line between aux pump and hp pump and crank. If all is ok fuel should pour from line (use safety glasses even flow is not huge), and you can slam the line back to aus pump on the fly.

 

[vincentfishing]

Brilliant thank you.

I cannot see any reason for the ML not to start apart from needing ages to pull through fuel. I'm reluctant to use Easy Start but I may just have to. Engine turns over with a fully charged battery at the right speed, and the glow plug light goes off after about three seconds. Its got me beat at the moment!

Mart

one thing that's definitely going to get it going is eaystart, use brake cleaner(supposedly less harsh on engine) if your worried about easystart, once it gets the engine firing on it, it will resolve any air or low fuel rail pressure issues(crack open the first injector fuel injector nut to make sure air is all out)
air in leak off pipes is combustion gasses coming back through worn nozzle/needles,
As mention above leak off is minimal on a good injector 5ml ish , if you do a proper test with bottles over a minute you will have a better idea of condition of injectors,
excessive leak off will stop it starting , then only easystart /brake cleaner will start car,
So to rule out fuel rail pressure problems because of leakoff , easy start is the quickest and easiest thing to do

 

[Martin Hall]

Finally! Engine has started and sounds great! Had to resort to a sniff of Easy Start (engine not me!!!), but once it had pulled the diesel through (car is on an uphill drive which is probably part of the reason!) it started and ran without issue. Only problem is a duff temperature sensor for the temperature gauge and possible the water level sensor in the expansion tank. You cant buy the level sensor seperately so it would have to be a replacement tank. A new part is £230 so probably not!

Thank you to mersum1es for your input. You know when you doubt yourself which is exactly what happened with the pipes to the High Pressure Pump.

Mart

 

[Johan Naess]

Hi Mart and Vinsentfishing.

Have red your troubleshooting, good reading.

I have the same problem! Have this Jeep Commander 3.0 CDR where that worked fine. I had down the diesel tank in the same time I have overhaled the rear DIFF axle totally. After reinstall the tank I filled it half full, turned the ignition on and listen to the aux pump sending fuel forward and I heard the return spitted fuel and air back to the tank. Did this several times before I attempt to start the motor. But engine makes NO attempt to start.


I got a tip to hook up a vacuum oil drainer that creates vacuum to the return line in the engine room. This to help the diesel to drag out the air and so on. Have tried some start spray and the engine fires up a little. I have opened the high-pressure line from the HP pump to let out air, some time it bubbles out some air. Have done this on all the HP lines out of the rail to all cylinders. Now it starts to decrease and some of them only clear diesel coms out.


But even after 40 to 50 starts attempt no start. I was then interested to look how much diesel that the HP pump was giving, so I tuck of the HP line on top of the HP pump and cranked the engine. The strange thing is that the HP pump only gives a small spoon of fuel only for a milli second when the cranking starts and then completely stops. This is happening every time. Is it normal for the HP pump to only give a little at start of cranking and then stop, even if cranking continues? Is the HP pump kaput? Or have I just not cranked long enough? Maybe it only gives a little for each turn etc?


At this moment I am out of suggestions. And I do not like to feed the engine start gas or break keener (maybe break cleaner is better that start gas ether). Because there is high compression in diesel engines and can in worst case do some damage.


Any input here is highly appreciated.

Best regards

Johan Naess in Norway.

 

[Martin Hall]

Hi there,

One of the things I did was to rig up a fuel supply straight into the fuel filter. I used a plastic bottle and a bit of pipe so that there is fuel easily available to the low pressure pump on a gravity feed basis. However, since my last update, I found a few other issues which may be of help. Firstly, when I got the engine running, the high pressure fuel pump started to leak from one of the three covers. I got the fuel pump rebuilt to solve the problem. I could have attempted this myself, but I hadn't done this before and a fuel injection specialist turned the pump round in a day. The car still took a fair amount of starting with the rebuilt pump and I was getting exasperated as to what the problem was. From the internet, it was suggested that the fuel line between the fuel tank and fuel heater had become porous. I was all ready to put a new pipe in when I discovered that No2 injector was leaking, fuel coming out of the little hole in the injector body. A second hand injector was purchased and fitted and since then there hasn't been a problem. The car starts quickly and runs well. My advice is check the plastic pipes and their O rings, I replaced the lot as there was a crack in one of the plastic connectors. Rig up a local fuel supply to the fuel filter. Check that the pipes are connected correctly as above, make sure that there are no leaks of fuel from the injectors. Use some clear plastic fuel pipe for the leak off hoses on the top of the injectors so that you can see if there is any fuel and if so if there are any air bubbles

Hope this helps

Mart

 

[vincentfishing]

one other thing you could do as you had no problem before you took tank off is use the vacuum pump(assume it has a gauage/dial on it) to test your flow and return pipes individually for air leaks ,its extremely hard to 'see' a split/damaged pipe, its very easy to see a vacuum dial dropping, maybe clamp off one end and test from other, then clamp off after pump or filter and test again at tank , it sounds like air problem if there was no problem before you dropped tank Or you've disturbed crap in tank and its gone up lines but filter would have caught it(maybe change filter anyway)when messing around with rebuilding injectors and getting air out I have used copious amounts of brake cleaner in short bursts to get a diesel up and running, with no apparent ill effects(maybe I've been lucky)
The separate diesel supply to filter using a container mentioned as above will eliminate all pipes as leaking air after filter if car starts,(you will have lot of air in system so may have to bite the bullet and use more brake cleaner,) at least then you only have to test pipes from tank.
Good luck !

 

[Martin Hall]

Hi there,

Agree with vincentfishing about the vacuum gauge and brake cleaner. I almost resorted to fitting a fuel pump near the tank, however that would have only cured the symptom, not the root cause. One thing I did find was that once the glow plug light has gone out, turn the key and keep it turned until the engine starts or the battery starts to get exhausted. By doing this, you only have one glow plug heating cycle and the fuel system has the best chance to bleed air in a continuous manner. On mine, as soon as you stopped cranking, the fuel went back to the tank. Try the bottle of fuel straight into the fuel filter to see if you can get it to fire, then fault find the rest of the system

Mart

 

[ajlsl600]

Finally! Engine has started and sounds great! Had to resort to a sniff of Easy Start (engine not me!!!), but once it had pulled the diesel through (car is on an uphill drive which is probably part of the reason!) it started and ran without issue. Only problem is a duff temperature sensor for the temperature gauge and possible the water level sensor in the expansion tank. You cant buy the level sensor seperately so it would have to be a replacement tank. A new part is £230 so probably not!

Thank you to mersum1es for your input. You know when you doubt yourself which is exactly what happened with the pipes to the High Pressure Pump.

Mart

• Have to buy expansion tank to get sensor!!! Plain marketing robbery, it's well time the regulators got a grip of this. I thought we supposed to be saving planet/resources/waste/money..

 

[Johan Naess]

Hi all. Thanks for input.

Just to clarify some issues. The tank was of the car and opened. Little or no dirt in it from before. But checked and 100% clean and the pump was refitted the tank. When I now have the external vacuum, tank hooked up to the main return line inside the engine compartment, without any vacuum applied, just so I can see the return fuel coming through the clear pipe, there is a fast return flow and no bubbles. When I apply vacuum, I get some bubbles coming, but this was earlier when I saw the return hose from the filter (between the cylinder heads) had a leak so it sucked inn air. This is fixed now.

When I study the flow and hoses, the fuel coms from the tank, into a Y split, where one goes to the left rail distributer pipe for the cylinders on the left side cylinders, the other one from the Y split goes to the low pressure part of the high pressure pump placed on the front of the left camshaft. Then the return hose from low pressure pump goes to the input to the filter placed between the cylinder heads. And return line from this filter meets up with all the return hoses from all 6 injectors and then back to the tank. This is the flow.

So at the moment I think, since there is so little coming out of the high pressure pump (only at start of each start crank) I attend to take of low/high pressure pump. Then when all hoses are hooked off, I will check the flow coming into the low-pressure pump to see the flow. If this flow is good, I will open the low/high pressure pump to examine this inside at my workshop.

But as Mr. vinsentfishing mentioned, I will make an attempt to feed the input to the low-pressure pump directly with a small tank with clean fuel and if this solves this problem I have to examine and change all the hoses in the engine compartment. This also because I attempt to remove the SVIRVL motor and remove the damper (if that’s the right word for it) and neutralize the input to the Ecu WITH A 4.7k Ohm resistor. And also change the O rings for the oil cooler underneath with purple O rings made of Viton.

I will make a summary of this issue after the car is running. In the meantime, thanks for input from you all.

Best regards Johan

 

[Doug1234]

Johan on your Jeep you do not mention any warning lights on or codes , you should be getting something at least fuel related such as low rail pressure etc etc.

 

[Johan Naess]

Hi Doug1234.

No, there is no faults codes to report. I have two systems for reading ODBII. Have the pump in the vise on my workbench now. Have also made me test probes so I can attach the PICO scope and a Fluke Volt/Amp meter to measure the quantity flow valve. Have done this measurements om my own car Jeep Commander Overland 2009 mod with the same engine that is running well.

This so I can use a power source to simulate the cars signal to the pump I have on my workbench. Also forced open a valve so fluid can enter the high-pressure pump part.

Have just watched some YouTube videos that show pumps in a testbench, there they run the pump all up to 3000rpm. For the moment I only have a drill to use, so maybe I have to rig me up at the lathe bench.

 

[Doug1234]

Are your code readers Jeep compliant ?,I use an icarsoft reader for my 06 Grand cherokee which is Jeep compliant as a standard OBDII will not do it

 

[Johan Naess]

Hi all.

The car is running!!!

I am almost too ashamed to tell the solution.


Since the return lines from each injector from each side comes together and ends up connected to the input hose from the tank that goes into the diesel filter, I assumed that this must be the return to tank. WRONG!!


I found it out after talking to a diesel technician that told me that the pump is supplied with minimum 0.3 bar input when they test the pumps in a testbench. So I put a clamp on the hose from the pump I assumed (at that time) was the return line. When I did that, the wrong pressure I had pressed inn trough the return port and created the needed pressure for the pump to start pumping.


So, by this I have learned much about this pump, have had it all to peace’s and together again. I have made me test probes so now I can hook up my PICO oscilloscope and test the fuel quantity valve on the HP pump (and other sensors) function to be correct.


Thanks for all input!!


And yes, I use a certified ODBII reader/writer.

 

[mersum1es]

so it was wrong piping after all... good you got it working (isn't that return line shown in attachment in post I linked?)

 

[Martin Hall]

Brilliant news that you have got it started. Like yourself, I have learned so much from fault finding!

Happy Motoring!

Martin