XM 2.5 won't start

endorfin · Post by **endorfin** » Mon Apr 02, 2012 11:43 pm

Also could leaking seals in the injector pump cause these problems? Is the fuel return pipe on this pump the one coming out of the top, thinking of putting a clear hose on this to see if air bubbles coming out.

Post by **robert_e_smart** » Tue Apr 03, 2012 7:43 am

The expansion tank can be easily removed to moved out of the way to give you access to that one.

The glow plug controller is mounted on the front of the battery box. Its a black box with a wiring plug going in underneath it, and a couple of other wires bolted on if memory serves me correctly.

2point5XCL · Post by **2point5XCL** » Tue Apr 03, 2012 8:28 am

The 2+2 set up is two relay coils in the box each operating a pair of glow plugs. Later 2.5s reverted to single coil operating all 4 plugs. The plug behind the pump is the most difficult. A good selection of spanners/sockets should have something that works, otherwise customise a tool or two. Plenty of rags stuffed in gaps and a cloth over will help retrieve errant nuts etc.Saves time in the end as it is amazing how stuff disappears and is hard to find.

Roy

Post by **xmexclusive** » Tue Apr 03, 2012 8:50 am

The earlier 2.5's had a Glow plug relay with two seperate outputs.
Each output feeds a pair of glowplugs, hence the description 2+2.
Most diesels (and later 2.5's) use a standard glowplug relay with one wire feeding the 4 glowplugs.
On the early 2.5's there should be no wire joining the middle two glow plugs.
On no account try modifying the 2+2 setup to standard or using a standard relay.
The 2.5 engine ECU's monitor the glowplug setup and have different wiring and programming for each type.
The ECU's are not interchangable if you want a working car.

John

kenhall · Post by **kenhall** » Tue Apr 03, 2012 10:32 am

endorfin wrote:Also could leaking seals in the injector pump cause these problems? Is the fuel return pipe on this pump the one coming out of the top, thinking of putting a clear hose on this to see if air bubbles coming out.

A worn or hardened shaft seal might allow air to be drawn into the injection vane pump which would affect it's ability to 'suck' fuel from the tank+filters+lines. Depending on how accessible the shaft/seal area is, you could try flooding the seal area temporarily with some heavy oil while trying to start the engine as a check.

endorfin · Post by **endorfin** » Tue Apr 03, 2012 10:48 am

Have removed all 4 glows, actually one of the easier ones to do, I got the 1 behind the fuel pump with a S shaped spanner, incidentally that one was very loose could that be a contributing factor? Glows look in reasonable condition (see photo) and are Beru brand. I don't think the glows are the problem but since I've paid for 4 new Bosch ones & collecting them in a bit I may as well fit them. Didn't drop any bolts.....although that doesn't mean I won't when fitting the new ones!

How can I test the glow plug controller?

endorfin · Post by **endorfin** » Tue Apr 03, 2012 12:59 pm

Right, some success!

I fitted new glows and tried starting it and it wouldn't fire, thinking back now I probably didn't try for long enough. I then took out the plunger from the solenoid and tried again and after a lot of cranking it finally fired up. Don't know whether this is down to the solenoid or I was just allowing enough time for the fuel to get through. I've turned engine off now and going to leave it for half an hour and try starting again to see if it starts right away. I also changed all the leak off pipes as they were feeling a bit brittle.

One thing though, even without the plunger when I turned the ignition off it stopped, didn't need to stall it. What does this mean?

endorfin · Post by **endorfin** » Tue Apr 03, 2012 1:53 pm

No it's not the solenoid at all. I tried starting it again after half an hour and had to crank it for a bit before it would fire. Replaced the solenoid and tried again after 5 mins, had to turn it over for a few seconds before it would fire. If you turn it off and try it again it will start right away but after a short while such as 5 minutes it will need turning over for a few seconds before it will fire, the longer you leave it between starts it takes longer to fire. Obviously an air leak but where? The clear hose from fuel filter to the fuel pump shows no bubbles at all.
Problem must be at the fuel pump or above but I'm stumped.

marc61 · Post by **marc61** » Tue Apr 03, 2012 2:50 pm

Theres a chance it might just be that the glow plugs aren't getting hot enough due to controller problem. Could try putting a temporary thick wire to the chain of glow plug cables, hold it against the positive terminal on battery for 10 seconds, then jump in quick and turn the key. At least that way you'd be sure they were hot enough to ignite the fuel.

I haven't actually done this before so might be best for someone else to confirm ok.

Cheers

Marc

kenhall · Post by **kenhall** » Tue Apr 03, 2012 2:58 pm

One thing though, even without the plunger when I turned the ignition off it stopped, didn't need to stall it. What does this mean?

The ECU recognises when you have switched off and the engine is still running. After a short delay it turns the fuel delivery right down to stop the engine.

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