WG 2.7 CRD Rough idle hunting problem

[bodgie]

Originally Posted by Yes we bought one

So I have replaced all the O rings as the filter is about 5k old and genuine merc so should be ok. What filters are you guys using and have you had problems with them??

I haven't been able to find a test kit for 30 bux best i could find was bout $100 inc del. I will look a bit harder later.

Cheers

The Merc filters are typically Mann Hummel which are what I use, so far no issues to report.

Bay usually has some for $30, seems a bit slow at this time of year though.

Jason

[Yes we bought one]

Seems i have missed the fuel filter O ring (I remembered seeing one on the filter but now recall that was to seal the return valve thing) the one on the end of the fuel supply line. I have also spotted air in the same line (fuel filter to Lift pump). When the car is shut down the air travels from lift pump towards the filter. Could the filter still be the cause of my problem?

If I'm really lucky changing fuel filter O ring may fix my problem.

Thanks for all the help.

[drover]

Brand doesn't mean much nowadays, I use mainly Mann filters have had a dud which had only done a few thoa and when I swapped it problem solved.

A small bubble appearing in the line near the filter shouldn't be a problem as mine has had one there for about yrs and I can't get rid of it, runs like a dream so I don't worry about it.....List of filters that we generally use is located in the Everything 2.7 thread.

[Yes we bought one]

I have noticed air travelling from the lift pump to H/P pump on start up followed by rough idle/hunting. The air bubble clear after a second or two but the hunting lasts a little longer.

I connected my vacuum pump to the bleed valve and pumped till the hose flattened. I then drew a continuous flow of air travelling from the lift pump to the high pressure pump.

My question being can the lift pump draw air from somewhere other than past the O rings on the hose connectors? Does the pump have servicable parts inside it that if failing could be drawing air?

Cheers

[bodgie]

Originally Posted by Yes we bought one

My question being can the lift pump draw air from somewhere other than past the O rings on the hose connectors? Does the pump have servicable parts inside it that if failing could be drawing air?

Cheers

Yes, you could be leaking air on the rubber supply hose from the tank or on the return hose. I've seen this on another vehicle where there were no visible signs of diesel leaking but the hose was bad enough to leak air into the system as fuel slowly leaked back into the tank.

A quick and easy test to see if this helps.

It could also be a faulty return valve or filter for that matter.

Jason

[Yes we bought one]

[QUOTE=bodgie;1511275]Yes, you could be leaking air on the rubber supply hose from the tank or on the return hose.

Please let me know if I'm missing something but the air cannot be seen in the supply line between the filter and lift pump when I applied suction at the bleed valve. The air seemed to be coming from the lift pump not travelling through it via the filter. I hope this makes sense.

Cheers

[piper]

the lift pump has a 10mm seal, and oring around the lid, can send pics if you need