Pierre, this is something that is harder to answer or offer advice on.

Unfortunately its really hard to know what you are getting when you buy a rebuilt pump. What sucks even more is I don't know of any source for new pumps so rebuilt are your only option. It is possible to buy new injectors easily for a moderately higher price, but not at any price for the injector pump it seems.

In your case, you basically just have a leaking seal at the timing advance/retard plunger, and the rebuilder probably knows its only a tiny O ring that costs pennies to replace. However, he makes more money with less time by simply replacing the pump with a rebuilt one he has on the shelf. Then he takes your old pump, replaces the seal and if the internals all check out, sells it to the next guy as a "rebuilt".

I don't know if this is breaking any forum rules, but there is a user by the name of Agnem on "oilburners.net" (VERY good forum like this one) that has access to a rebuilder who goes through the process of actually making the pump as good as new again (actual machining). So far he has sold to several members there and they all swear by it but the price is higher than what you would pay for something from pensacola diesel. Although with the exchange rate right now it might not be quite so bad.

He offers a high performance pump that will turn the sky black and blow the tires off with the settings turned up, but also sells a mild pump that is roughly under $600 USD. From the experience of current owners of the pump, the fuel economy is also slightly better than other "new" pumps because internal clearances are tighter. There is also the higher cost of shipping and you need to send your pump to be rebuilt into the performance or mild pump. He does not do a simple swap like others. I don't know if he can deliver in the time you need, but in my view he does offer the best pump you can buy. I'm probably going to buy one eventually, but am putting it off for as long as I can. Also, the price depends on what your pump actually needs replaced, so final cost is not fixed. I have a really hard time with that one. If you register on that forum, you can search the old discussions for the "moose pump" and draw your own conclusions. Registration is free just like here.

Most that buy from pensacola have good experience but some had nothing but trouble. The good news is they seem to honor their warranty and will refund or replace if you are not happy. Although if it breaks while you are on the road, that isn't much help. They do have the best price right now though. Really hard to beat $311USD.

Since pensacola does not require a core return, you could try installing one of their pumps and get a seal kit to repair yours as a spare for on the road should the new one fail. Actually, you should start a list of parts and tools you will need for a "just in case" scenario (filters, belts, etc).

Sorry I can't offer a more absolute answer. I'm not happy with the situation regarding injector pumps for our trucks, but it seems we have no choice but to buy rebuilt ones with 1 year warranties.