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Kind of surging while driving


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Hey guys I have a 1995 GQ with a 4.2lt diesel motor as of late while driving at around about 3000rpm it starts a kind of surging wont go any faster then about 95km per hour and that's pushing it. Its fine driving around town but as soon as I need to go out of town it starts a kind of surging and blowing white smoke. I put a new fuel filter, air filter and ran some diesel injector cleaner through it which did not change a thing I have taken it to my mechanic where it ran fine  for them. the only problem they found with it was a hose clamp was missing on the injector pump which they replaced they then test drove it and it still rand fine for them. I got it back yesterday and it has started again. I was wondering if any one on here could point me in the right direction so I can get it fixed. 

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G'day, welcome to the forum.

Firstly is yours NA (naturally aspirated) or turbo charged motor?

Blowing white smoke is usually  unburned fuel from unfinnished combustion.

The description of the fault sounds it could be something to do with pump timing being retarded perhaps. Is your pump inline type or rotary? Inline pump should have timer mechanism aka timing adjuster perhaps is not working properly.



Edited by Rumcajs
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Inline pump will have 6 injecting elements "inline" in the straight line in 6 injector lines at the pump will be arranged on top one after another

Rotary pump will have injector lines coming out sideways towards back arranged in a circle


Here inline pump for 4.2L  ==>







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