non start td5

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vougese39

vougese39

Well-Known Member
Posts
1,039
need some help please guys one of my customers td5 disco cut out whilst driving has been in to various garages localy and apart from a crank sensor nothing has been changed.
i have a t4 testbook and use this for diag testing
here what i have found
no faults in the ecu apart from sensors being disconnected.
new fly wheel fitted 3 months ago
crank sensor ohms tested within tollerences.
removed injector harnes and engine loom cleaned contacts checked all wire for continuity all ok. ecu has been stripped and cleaned!
tested system found no injector firing
checked for feeds at the injectors found 3,4 not reciving a signal
replaced ecu with a good used unit coded in imobiliser and injectors retested pulse feeds at all injectors
vehicle will run on cold start sounds ok so discounting timing problem.
fuel pump works and can be heard, have fuel coming out of fuel cooler to tank return pipe so it has flow round the head, replaced the fpr as noisy gurgling noise from head all quiet now still no start
any ideas would be great cheers stuart
 
Have seen injector harnesses going faulty without throwing up any codes. TBH, id try changing that first...

Also thought of injector seals, but wouldnt normally cause cutting out when driving...
 
it cranks over happy as larry. if the injecor seals have failed could/would all five fail at once? and if the seals are leaking would it not at least try to fire with the fuel in the combustion chamber? am getting no smoke from the exhaust even removed the down pipe incase of cat failure still no smoke.
and the harnes and loom are all ok as the switching voltages are all the same
 
vougese39 said:
it cranks over happy as larry. if the injecor seals have failed could/would all five fail at once? and if the seals are leaking would it not at least try to fire with the fuel in the combustion chamber? am getting no smoke from the exhaust even removed the down pipe incase of cat failure still no smoke.
and the harnes and loom are all ok as the switching voltages are all the same
Click to expand...


At risk of sounding stupid- have you put crank sensor on a scope-seen the output? or a milivolt/frequency meter? reason I say this is you may not be getting pulses (having never worked on a td5) is the air gap adjustable?
 
air gap is fixed! have as posted checked the ohms resistance of the sensor have whatched the crank sensor output on t4 and it is sending a signal
 
vougese39 said:
it cranks over happy as larry. if the injecor seals have failed could/would all five fail at once? and if the seals are leaking would it not at least try to fire with the fuel in the combustion chamber? am getting no smoke from the exhaust even removed the down pipe incase of cat failure still no smoke.
and the harnes and loom are all ok as the switching voltages are all the same
Click to expand...
Stuart,you are missing the point - it may well crank over fast enough,but spikes from the starter can get sent back up the battery lead and corrupt the crank sensor signal,so the ecu cant work out when to inject.As for the injector washers,it only takes one to fail to stop it running.Combustion pressure is forced past the leaky washer up into the fuel rail - only a tiny quantity is needed to stop it from running.Try letting it go through its bleed cycle a couple of times and try again.
As said before you really need to scope the crank sensor to prove its worth,the resistance check does not mean it will work.
You really ought to check the fuel pressure too,4 bar all the time the pump is running.
 
went back today and retested and checked the pressure i have .5 bar prepressure then 4 bar when cranking it drops then rises again strangly so i suspect the pump is at fault.
have done a rail pressure bleed done test and have no leak from the injectors or the seals so going for the pump cheers for the input
 
FWIW, the pump should have 4-4.5 bar of pressure as soon as the ignition is switched on. If it takes a while to rise that far, or doesnt hit 4 bar, or drops while cranking/running, the pump is fooked
 
has anybody got a spare pump to test with a the customer is reluctant to by a unit and i'm not spending on a new one and he refuses to pay
 
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