Diesel drain back XM 2.1 TD 1994

AdeU · Unread post by **AdeU** » 31 Mar 2004, 16:58

I have this problem with diesel drain back. I have changed fuel filter assembly and replaced split hose and clips. The only way to stop it from stopping is to crank/start the engine then stop and bleed the system. After that the car will be ok until it stands for several hours then I would have to repeat the process above. Can anybody suggest anything else to try or had the same problem.
AdeU

AndersDK · Unread post by **AndersDK** » 31 Mar 2004, 17:21

No matter what you have replaced -
You STILL have an air leak [;)]

NiSk · Unread post by **NiSk** » 01 Apr 2004, 00:05

The most common sources of air leaks on TD12's are:
1) Rubber pipe from metal fuel line behind engine (bulkhead) to preheater (if used) or fuel filter/water seperator. Cracks and lets in air.
2) Preheater - the lump of porous aluminium slapped on the L.H,. (gearbox end) end of the cylinder head. No amount of jerking around will stop that from leaking in air - bypass it!
3) Fuel filter/water seperator - did you change the gasket between bowl and head? are all the bleed screws fully tightened? Is the rubber (squeeze) diaphragm leaking?
4) Rubber hose between fuel filter and pump.
Those'll get you 95% of all air leaks.
Alternative - try fitting a one-way valve in the fuel line between filter and injection pump. The fuel saved there will get the engine started and running fast enough to suck out any air in the rest of the system.
//NiSk

Dave Burns · Unread post by **Dave Burns** » 01 Apr 2004, 04:50

Injector leakoff pipes are one of the most common problems that afflict these older engine types, they harden and crack with age.
Dave

NiSk · Unread post by **NiSk** » 01 Apr 2004, 04:55

Yes Dave, but that just makes them stink of diesel! (own experience)
//NiSk

AdeU · Unread post by **AdeU** » 03 Apr 2004, 03:57

Thanks for that NiSk, the Preheater was causing the problem. When I put some pressure in the supply line from the tank sender unit to the fuel filter with the filter clamped, fuel pouring out of the preheater. Thanks to all of you for your advice.
AdeU

Triumph · Unread post by **Triumph** » 04 Apr 2004, 22:06

AdeU - regarding your diesel drain back. If you could borrow a vacuum/pressure testing unit and first do a vacuum test from the inlet of the filter it will indicate if the leak is from that point on. If so, give a slight pressure test and you will probably find it is from the pre heater in which case you can by pass it. The MkII XM with comfort spheres is a brilliant motor