Xantia 1.9td Idles But Won't Rev

[skysurfer]

Has anyone seen something like this before?

 

My Xantia 1.9TD SX will start (rather reluctantly) and idle (750rpm - it was normally 1000rpm) but the revs hardly change at all when the throttle arm moves on the injector pump, remaining at a slow idle even at full throttle. (No unusual noise, quite smooth running).

 

If the injector pump detects turbo boost then it will pick up and rev fairly normally, responding to the throttle arm on the pump.

Obviously there is no boost at idle, but it can be initiated in several ways:

1) Using ether (Easy-Start aerosol) to get the revs up over 2000 rpm.

2) Rolling the car down a hill and releasing the clutch in gear to get the revs up over 2000 rpm.

3) Connect a tube to the atmospheric pressure vent on the underside of the injector pump boost sensing diaphragm. Suck very hard on the tube with the engine running. After about 30 seconds the revs will build to over 2000 rpm and there is then no need to suck the tube.

 

So long as the revs are kept up then it will run indefinately and will respond to the throttle. I have driven the car over 10 miles like this. I don't think it has as much max power as it should. If climbing a hill the revs can be held as low as 1700rpm without dying back to idle but if there is no load on the engine then it will die back to idle if the revs are ever allowed to fall below 2000rpm.

 

It doesn't actually require turbo boost to run, it just needs the injector pump to think there is boost! I've run it with the inlet manifold disconnected from the intercooler ducting and squirted Easy Start into the manifold to get the revs up. Once over 2000rpm it can be reved on the throttle and no more Easy Start spray is needed.

 

When this fault developed I had run very low on diesel and it felt as though it was loosing power for the last half mile before filling up with diesel. It was still low on power after filling up. The idle was slower than normal and the throttle response was not normal. (Needed to press pedal further before it would rev). I kept the revs fairly high for the next mile before parking at the shop we were going to. When I came out of the shop and started the engine it would only idle and did not rev in response to the throttle...

 

On getting the car towed home I changed the fuel filter. It didn't appear to be particularly blocked and there wasn't much residue in the filter container. There was no water in the filter container. I could easily pump fuel into the filter chamber with the primer bulb before I put the lid on it with the new filter. I slackened the union at the injector pump inlet and could pump fuel free of air from it with the primer bulb. With the engine running I cracked the pipe connections at 2 of the injectors (1 at a time - couldn't get to the other 2). The revs dropped and the idle slightly rough and fuel leaked out for each one. With the engine stopped but the ignition on and the keypad code entered I slackened the injector diesel return union and could pump air free fuel from there with the primer bulb.

 

After looking at diagrams and descriptions of how the boost sensing works, I removed the dust cap from the top of the boost sensor diaphragm and adjusted the screw down by 3 turns. This made no difference. I then removed the 4 torx screws and removed the top of the boost sensor and its diaphragm along with the shaft with the offset cone on the end. The pin that rides on the cone was not visible, but it did pop into the central hole when the throttle was opened. I put a pen down the hole as a stop to prevent the pin from being pushed through too far and falling into the central hole where the cone should be. With this mod the revs now pick up from idle without any further trickery! Even with this temporary modification I can't continously HOLD the revs anywhere between 800 and 1600rpm although it idles ok at about 800 and I can rev it anywhere up to about 4800 and hold at any constant revs I want at 1600rpm or greater!

 

Is it definately the injector pump? Is there anything else I can dismantle/check with the pump on the engine?

Could it be the cam belt slipped? (This has happened before on this car and it ran ok then but it had more "diesel" noise than usual and the engine warning light was on. After running for some days it probably slipped another tooth and it would not start). I guess there could be different simptoms depending on which pulley slips on the cambelt. (Crankshaft/Injector/Camshaft). I've never managed to find the timing hole in the bell housing/flywheel on this engine. Is it just above the starter motor?

 

Could it be something electrical? This injector pump has a throttle pot on the top of the throttle shaft. There is a sense wire on one of the 4 injectors. There are 4 wires going into the end of the pump. (I think this is to do with the keypad imobiliser).

 

I've had this car from 65,000 miles and it now has 160,000 miles. The cam belt has about 40,000 on it.

 

The injector pump is Bosch 0 460 494 427 / R 601-2 / XUD BP 02

 

I had no replies on the GSF forum. I hope you guys can help me.

 

Thanks for any ideas!

[Johndouglas]

Have you put your problem on http://www.frenchcarforum.co.uk/ There are some very knowledgeable XUD enthusiasts on there.

[skysurfer]

I would like too but I haven't managed to complete the registration to join :P They havent sent me an activation email and my username etc isn't working. :huh:

[Johndouglas]

If you were a member of the GSF forum when it was Andyspares, you can use your old Andyspares login