C250 Td funny noise

[91dm]

Cackling is the best way to describe the noise. It’s ok at idle just around 850-1200 and then goes again. Someone else did say to check the compression which I might do just to check.

 

[Number_Cruncher]

For cackling?

I can't see that.

It's an obvious possibility with a noisy diesel engine, and I'm surprised no-one has mentioned it earlier.

If the compression is marginal, you get a longer delay period, and hence noisier combustion when it finally happens.

At higher engine speeds, the compression doesn't get the same chance to leak off, and so, combustion happens properly.

One quick check which will give a strong hint is to energise the glow plugs while the engine is making its noise. We know the injectors are OK, so, if the combustion suddenly goes quiet as the glow plugs light up,...

 

[91dm]

Looking at my fuel pipes today I noticed air bubbles around the revs that it’s making the noise at.

Does any one know if Mercedes sell the o ring for the fuel pipes separately or do you have to buy the clear pipe as well?
There was a seller on eBay selling a full kit of o rings but I can’t find the listing anymore?

Thanks

 

[91dm]

I’ve replaced the o rings and still have air in the fuel lines. The o rings on feed pump pipe where the worst, hard and had a tapered edge. I tried a one way valve/bleeder which didn’t make any difference, blew back the pipes that where going to the tank and checked the filter and pre-filter.

Most of the air is in pipe 95 on the diagram. Is there any thing else to check?

.

 

[Number_Cruncher]

That's odd, because the system should be under pressure there - fuel should leak out rather than air leaking in.

Is the pipe routing correct?,... absolutely correct?

 

[91dm]

It’s the same as the diagram, I replaced the pipe exactly how it was fitted.

I took the feed/lift pump off to clean and it seemed to build pressure fine. There is also some air in Pipe74 but not as much.

 

[Number_Cruncher]

One of the possible ways that the routing might be wrong is at the lift pump.

The fuel input (74) should connect to the outer port on the pump which is furthest away from the injector pump body. The diagram isn't absolutely clear.

 

[91dm]

I checked the pipes are all routed the same as the diagram.

Can someone tell me what 155 is in the diagram, can it be bypassed so the fuel pipe is going directly to the pre-filter?

 

[Number_Cruncher]

It's a fuel heater - it helps prevent fuel waxing.

 

[JonathanC250]

Did you replace the Banjo bolt (125) when you replaced the pipes?

the ball bearing in mine was easy to press, so thought the spring must be worn.

Be sure to get the copper o rings for either side.

Hopefully this cures it for you!

 

[91dm]

Last week I replaced the delivery seals as the top of the pump was wet. The seals were badly worn, the pump is now totally dry.

After putting it back together it sounded as it should. None of the noise, then after a few minutes the noise started again. There’s less air in the pipes, just thinking if the problem is related to lack of pressure? Any suggestions welcome.

 

[johnsco]

Over the past 4 years, we have run two E300TDs.
One always ran sweetly (until a recent sad accident).
The other (same mileage) has always been ticky.
This happens especially when the engine is cold and especially when I take my foot off the accelerator going down-hill with light or no load on the engine.
My mentor (Richard at Rodley Motors) tells me that it is caused by the air circulating in the diesel fuel, and not to worry.
He owned the "sweet" car from new, until he sold it to me.
It's obviously not doing any harm.
The car performs and starts just as well as the other car that didn't tick.
Fuel consumption is just the same.
When warm or under load, the engine doesn't tick.

I shall leave well-enough alone.

 

[91dm]

I’ve come to a bit of a dead end with this. I fitted an electric pump which got rid of the air in the pipes but this didn’t affect the running or noise.

I then thought it might be the valves so I’ve done a compression check. Each cylinder gave a 400psi reading.

I’m now thinking that it might be a weak ip? I’ve checked everything else I can think of. Any help would be appreciated.

 

[Number_Cruncher]

It is good that the compression figures were OK.

One thing I should have mentioned earlier is the ball / pip in the prechamber. If this has burnt away, then the start of combustion won't be as snappy as it should be - you can see this with the injectors out.

Can you pin the noise down to a particular cylinder?, by slackening injector pipes while the engine is noisy?

 

[91dm]

I tried slackening the pipes off, but I couldn’t pin it to any particular cylinder. The compression clock went up evenly and each cylinder was more less the same.

I noticed while cranking the engine over no diesel was coming out of the top of the pump. Is this normal when the pipes are off?

 

[Dieselman]

I noticed while cranking the engine over no diesel was coming out of the top of the pump. Is this normal when the pipes are off?

If the ignition was on then no it's not, but if shorting the starter solenoid then yes it is.

 

[91dm]

I was cranking it from the ignition. Is there any special tools needed to remove the pump?

 

[Number_Cruncher]

I would find it difficult to believe that all the pumping elements in the injector pump had failed at once - unless there has been some comon factor at work, like comedy fuel, for example.

 

[91dm]

As soon as I took the pipes off you could hear the diesel going back. You could see the diesel at the top of the delivery valves but I expected more to come out when cranking.

 

[91dm]

I’ve had the car running for a few days now with the recon pump, the quantities weren’t even but the pump hasn’t made any difference to the noise. It’s still the same, clatter noise at idle and then goes after 1200rpm. Can’t think of anything else it can be? It's had recon injectors, pump, pipes & o-rings and checked the compression.