Rough idling due to TD pump tweaks?

[JohnCKL]

My 96 1.9TD has rough idling but smooth when on the move. I've tweaked my fuel pump and that may have something to do with it. Presumably more fuel but not enough air going in when the car is not moving. I would like to ask the opinions of others who have tweaked their fuel pumps, do you have the same problem of rough idling? I probably should detune my fuel pump to see if the problem goes away.

[XantiaMan]

Apart from the max fuel screw, all other adjustments should have no effect on the idle performance, apart from a slight rise in idle speed but even that should be minimal.

Adding more fuel to a diesel increases the engine speed, you definatly will not be able to make it over-fuel enough to cause lumpy running like a petrol engine.

[Peter.N.]

You cant alter the mixture by adjusting the pump, only increase the max fuel, the mixture is controlled by your right foot, the pump only controls the ammount of fuel delivered, it gets a full charge of air on every stroke.

Your rough idling is probably due to wear in the pump causing it to deliver differing ammounts of fuel to each cylinder. Just check that you havn't got a leak on one of the delivery pipe connections. The other possibility is an injector but its most likely to be the pump.

[AndersDK]

I agree with Peter ..

Most likely problem is air getting in on the pumps suction side.
Check your fuel lines and fuel filter.
It must be spotless all over.

You can tweak as much as you want, it wont affect the idle.
Only the running engine will smoke like a chimney if you get it too spirited, and performance will decrease a lot.

Remember that your diesel engine doesnt have a throttle or a carburettor for mixing air/fuel ...

[JohnCKL]

Thanks for your quick answers. Cleaed up some questions. I will check fuel lines n filter.

Happy New Year 2009!!!

[bonnyman750]

I have a similar problem with my Gold one. Erratic tickover and lumpy starting (i.e. starts at low tickover speed but once suspension pumps up to normal height increases slightly. I also need to check all the glow plugs as that could be contributing too!). However I did improve things when checking for air leaks. I read a thread on this forum about the valve at the bottom rear of the filter housing leaking air in when running. I fitted the obligatory temporary clear pipe between the pump and filter to check for air and found loads getting in somewhere. I found the leak by overpriming the fuel system while the engine was running. Behind the filter housing where I had cleaned up with a rag, was a new pool of fresh diesel. On closer inspection, by overpriming the system it was forcing fuel out past the valve body and the filter housing and collecting on the aluminium casting behind it. I dismantled the filter housing from the car and removed the valve (pop out the spring washer in front of it and pull it out of the housing). Fault was found to be flat hard 'O' rings on the valve body. I checked on service.citroen site and the valve comes as a complete unit from Citroen and the 'O' rings cannot be bought separately so I sourced some new ones from a local bearing stockist for pennies! Reassembled and restarted car. No leaks!! It still starts on a lower tickover than desired but at least it is now constant and doesn't feel like it is going to cut out all the time and no discernable air in the clear pipe...

HTH

Glyn

[Peter.N.]

If it ticks over OK when cold but becomes increasingly uneven as it warms up (down on one cylinder) it is in all probability the pump.

[CitroJim]

There's really only two things in a Bosch pump that can cause this. Either a broken plunger return spring or a worn timing piston. The timing is hydraulically controlled and if the piston is worn, the effects will be most noticeable at idle when pump transfer pressure is at its lowest.

The other possibility is very worn injectors that have a poor spray pattern and/or dribble at end of delivery.

Does the engine smoke (black) when idling roughly?