Slow starting 2.5 td

[HughR]

Hi Everyone,
new to this but Ive got a starting problem with my 1995 XM 2.5 TD, French model and currently in France.

Problem seemed to begin after I took the fuel filter mountings off to make space to get at the starter motor (now sorted) but afterwards it took about 30 secs of turning the engine over to start.
Then it puts out some white smoke and runs normally. Engine is good and doesn't burn oil or smoke at any other time. Starter motor and battery also are good. Having started in the morning it restarts fine but left overnight it takes another 30 secs of running the starter motor. I changed the fuel filter and bled the unit but no change so I'm thinking that's a red herring. The fuel hoses that I can see look good.

Any ideas??

thanks, Hugh

[White Exec]

Hi Hugh, and welcome to the forum. Good to have another 2.5 in our midst. Do post some photos and car details when you can find time!

If you didn't open up the fuel filter when you moved it to one side, it's unlikely to be a problem with the filter unit itself, but check the pipe connections to it for tightness and tube splits.

The symptoms you describe could be air-in-fuel, which plays old harry with starting, but might allow normal running, if not too severe. Connected in series with the fuel filter is a fuel heater (block of aluminium, bolted onto the engine block, with fuel pipe in and fuel pipe out). It is located just behind and below the fuel filter. These items have a reputation for going porous, which allows air to be sucked in as fuel is drawn up under suction from the tank. Many 2.5 owners have simply jumped this unit out of circuit (leave it in place, but join the two fuel pipes to it together; obvious on inspection).

A quick test for air-in-fuel is the action of the priming button on top of the fuel filter. With regular car use, this should always offer immediate and firm resistance to be being pressed. First thing in the morning - when it's difficult to start - try pressing the button several times. If it goes down readily, and then stiffens up, then there was air in the fuel. If immediately stiff, everything was OK.

The other cause of what you describe - reluctance to start, but starting only after prolonged cranking - is that the glowplugs are not operating, or operating only partially. Prolonged cranking will heat up the air in the cylinders, enough to start badly (with white smoke), but not the immediate high-temperature start that the glowplugs would provide.

Bolted to the front of the battery box - and in the area you have been working - you will find the glowplug relay. Largish black box, with two heavy-duty cables connected, plus some smaller ones. Remove it, and clean up both the external and internal (easily opened up) relay contacts, back to clean metal. These corrode with age. Renew any cable connectors that look in a bad state; best soldered on to a clean cable end.

Also check for a decent connection main battery feed to this relay, and both battery terminal connections themselves. If the latter are the original lead (Pb) lump crimped-on connectors, it is a good idea to replace both of these with new brass clamp-type connectors, cleaning up the battery cable strand ends as part of the job. A poor battery connection may allow reduced-speed cranking, but will deprive the glowplugs of their full power. A symptom of a poor battery terminal connection is the connector getting warm (or even hot) during cranking.

Try that lot to begin with: I'd do the glowplug and battery checks first, but do check out that priming knob.

Let us know how you get on, Hugh.

Hope I've got component locations correct for you - ours is RHD.

[Dieselman]

The symptoms describe air in the fuel pipe exactly. Check the pipe connections where you moved the filter housing.

[HughR]

Hi guys, thanks so much for the quick response that makes perfect sense. I just got back from France but Ill ask a friend to check out your ideas and Ill let you know how it goes. Overall I really like the car, especially the way its lazy power from low revs in high gears.
Thanks again, Hugh

[xmexclusive]

The symptoms could describe fuel run back overnight or long period standing due to small volume air ingress.
Ability to restart when warm could just be feed pipe now charged with fuel as the system relies on the engine sucking fuel up from the tank.

There is one other place where small air leaks can happen on a 2.5TD.
There is a rubber to steel pipe connection down the back of the engine.
Rubber splits just above the clip, very difficult to spot.
You will never find fuel leakage on the suction part of feed pipe as any leaks are air in only.
If nothing else solves the problem put a length of clear pipe in just before the filter.
If its full of air each morning before you try starting you are looking for that small air leak in the feed pipe.

John