Turbo Diesel Xud7 Rough Idle And Bunny Hop On Starting

[BenC 6]

Hi all,

 

My XRDT is starting to exhibit some funny behaviour on starting. When starting from cold it doesn't idle normally, the revs hunt up and down and when you pull off it 'bunny hops' (not violently but it's noticeable) for the first 100m or so and then settles down. It also puffs out quite a bit of white smoke. After this behaviour it will drive fine.

 

The fuel filter was changed last week and I tightened up the belts which had been squealing. I hadn't noticed this weird starting behaviour before this. It has been gradually using coolant too - I have to top it up every 4 weeks or so. The clutch is probably on it's way out, the bite point is very high. I don't know if this information is relevant but I thought it was worth mentioning.

 

I really know very little about engines so any suggestions to what it could be or ways to narrow down the causes would be greatly appreciated.

 

Ben

 

[Anthony 1,000]

Dead/dying glowplugs would be my usual suggestion for the rough starting/idling and smoke.

 

Given that you've recently change the fuel filter, check for an airleak around the filter housing and nearby pipes - air leaks on the fuel system on older diesels like this cause all manner of running issues and it only needs to be the smallest leak to cause loads of problems.

[BenC 6]

Thanks for the quick response Anthony. Sorry to be dense, but how do I check for airleaks? Am I looking for cracks/loose hoses with the engine off, or run the engine and 'feel' for air leaks around the hoses?

[Anthony 1,000]

Given how small the leaks can be, with some difficulty is often the answer.

 

Look for any evidence of leaking diesel, of perished or loose hoses, and try pumping the priming bulb (or pumping the lever, depending on the setup on yours) repeatedly and looking for any slight bubbling or noise around any joints. If there's a section of clear fuel hose, look at that with the engine running to see if you see any air bubbles in it.

 

From what I remember, the fuel filter housing, priming bulb and the diesel leak off pipes (small pipes from the injectors) are the usual culprits.

 

If there's nothing obvious, change the glow plugs first of all as XUD's are very reliant on them to start in cold weather

[welshpug 1,621]

pump the primer if it has one, you'll hear the air/fuel leaking.

 

the leak off pipes especially at the age yours is can get especially brittle, the only correct sized replacement I have found is from a dealer, comes in a 1m length which is more than enough to replace all of them.

[BenC 6]

Ok thanks all, I'll give the leak finding a try first. Just to confirm, it's ok to try these tests with the engine off so you can hear the air or does it need to be running to get the fuel flowing around? I have got the lever style primer. It's an orange sort of pump handle sticking out the top of the housing.

[allye 530 3 Cars]

Put a 306 engine in it.

[BenC 6]

You're a funny guy Williams...