270 CDI failing to robustly start after injector seal replacement

Andy The Bubble

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Hello All.
I would appreciate some help.
I few weeks ago - I replaced injector number 5 copper seal because it was blowing gases and partial combustion tar. Before this - the vehicle started every time, even it is was a longer crank than originally known.
To remove the injector, I used a special toolset - all went well, however I was mindful that I was removing many small pieces of the injector solenoid mechanism.
Once the injector job was complete, the engine started eventually and ran smoother than ever. However, it would not re-start when the engine had been previously started, not just a warm coolant.
Therefore I am adamant that it is not building up enough fuel pressure to start sufficiently because it is pulling in air at some point.
So only when it is left alone (overnight - on charge, - will it start)
I have replaced o-rings on pipes, re-built the injector head, changed the crank sensor, but I have this issue.
Unfortunately my generic tool has not pulled any DTC's
Is it possible the injector is partially damaged, closed during cranking, causing a low pressure as it is spilling into the return line?
Whilst the engine was running, there were bubbles in the lines, but the cleared away....
 

malcolm E53 AMG

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I see you are Midlands based, County Diesels based in Syston, Leicester, are very good might be worth giving them a ring. They have sorted out my injector issues and rebuilt my HP fuel pump so can vouch for their work
 

alexanderfoti

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You probably have an injector that's leaking off too much. Likely unrelated to the fixing of the seals.
 

Roxie

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The injector you have taken apart is now destined for the bin.

I know specialists can now repair these injectors but the tool that you used to pull the injector out is the last resort tool intended to be used when you have a new injector ready to put in.

Perhaps a specialist will be able to do something with the old injector but he will probably just sell you a reconditioned one.
 
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Andy The Bubble

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Thanks for the advise.
One party believes it is related to the seal job, and the other does not...
So, is there a theory that the injector always had a high leak off, but with low cyl compression. Therefore it would start up because higher fuel pressure could be achieved because of higher crank rpm???

The other theory is that dismantling the injector head has simply thrown out any calibratable clearances, causing an issue...

What about the fact that the engine starts after a long soak, but not when it is warm?

Either way - I did not conduct enough research before attempting to conduct this seal replacement.
I'll see if this injector can be repaired...
 

alexanderfoti

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I did not realise you had removed the top of the injector. This will alter the calibration if you did not put the washers etc back in the right order. This will cause excessive leak off.

Test the leak off on each injector, you will find one is much higher, and this will be the one leaking off the rail pressure.

Its possible you had a higher cranking speed generating more pressure, overcoming the leak, but its unlikely.

Its likely that the injector leaks off a lot internally when it gets warm but is ok when cold
 


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