Nissan Injector Pump

Depends on which seal is leaking, also the 1HZ (80 series) is a rotary pump while the GQ is an inline one.
The inline ones are generally much more complicated and more expensive to fix but do last much longer.
The rotary pumps are lubricated and cooled by the fuel flowing through them. Whereas the inline ones are lubricated by the engine oil and only slightly cooled by the fuel.
In simple terms think of a minature six cylinder engine for the inline and a distributor on a petrol motor for the rotary ones.
The older inline pumps will suffer leaks due to low sulphur fuels drying out rubber based seals whereas most of the rotary pumps have vitron seals able to withstand the lack of lubrication.

My GQ had a rotary pump (as does my GU) and it did leak after the introduction of low sulpher diesel in QLD and then again in NSW.

Original leak was at the top cover and had that refaced and repaired by a diesel mob in Townsville for about $200 dollars.

Second leak was from the outside/RHS cover plate of the pump assembly. Can not remember what was under it. I did fix this bit myself with a $3 o'ring in less than an hour or so as I am pedantic. Access was a problem to the inside/LHS one so I left it alone as it was not leaking at the time. Have since sold the vehicle. Would have attempted the inside one myself also if required.

JamieMac

Hi Batboy, Toyota 80's and GQ, GU 4.2 are the same Bosch VE pump, usual leak is from the top cover ,part is about $14 you can do it yourself but has potential traps! There is spring loaded parts inside and also the throttle arm has to be removed [to replace an o ring] and must go back in exactly the same position. If you do not feel confident hunt around for a mechanic that can do the seals with the pump 'in situ' there should be ptenty around as this is a common replacement.
Regards Ken.