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Changing the Primary Pump on a 6.9 IDI Engine Ford F250 Diesel: A Tutorial
If you are fitting a new diesel primary lift pump on a 1983 Ford 6.9 truck with the Navistar 6.9 or 7.2 diesel engine, then reading this article could save you a lot of work, grief, and big money, not to mention bad language!
1. Removing the Old Primary Lift Pump
OK, so let me start by saying that I am not a qualified mechanic so anyone following this advice does so at their own risk!
The primary lift pump on these engines is located on the right-hand side of the engine block near the front. It has two pipes attached. One is the feed from the fuel tank—it's a rubber pipe—while the outlet is usually a steel pre-formed pipe that goes up to the fuel filter.
- The first task (after removing the keys from the ignition) is to remove the steel bracket that clamps the battery to the starter motor cable to the engine cross member by undoing the two nuts. This gives you much better access to the pump.
- Next, you will need to have on hand a suitable receptacle to catch the diesel fuel that will leak out of the open fuel lines.
- Remove the rubber fuel feed pipe and then attempt to loosen the union nut on the steel line going up to the filter. (I must say that this proved unsuccessful in my case, as it had probably never been removed before and was seized solid—so solid, in fact, that I thought that the bottom of the pump would snap off before it came loose. So, my solution was to undo the steel pipe from the filter and remove the pump by removing the two retaining nuts, then lifting out the pump, taking care not to damage or distort the steel pipe that was still attached. Once the pump was removed I then clamped the union nut in a vice and unscrewed the pump off the pipe.)
- After removing the lift pump, you need to clean up the gasket surface on the engine block by removing any old gasket material with a scraper, solvent, or whatever you find works best for you.
2. Fitting the New Lift Pump—Getting It on the Right Side of the Cam!
Now Comes the Important Bit!
You REALLY need to make sure that the cam that operates the lift arm on the new pump is resting in the correct position (cam lobe pointing upwards) BEFORE you fit the new pump with the arm underneath the cam.
It is very difficult to see inside the pump aperture to check the position of the operating cam. My tip is to use a digital camera with flash to see what is what! The correct position is with the cam lobe pointing upwards (see picture above). If you find that the cam is not in this position you can "nudge" it round using the ignition key.
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Once you are sure the cam is correctly positioned, you can then proceed to fit the new gasket & pump.
The reason that you take all this care is that if you don`t ensure the cam lobe is pointing upwards it is quite easy to fit the pump operating arm above the cam by mistake. If you do that, then once the engine starts it wrecks the pump and dislodges the pivot pin, which then drops inside the engine sump pan—thus creating a lot of unnecessary work & expense.
The operating arm on the new lift pump may be a different shape (my old one was straight and the new one was shaped) but as long as it is the correct one supplied it will be fine.
Because it is not unknown for the operating cam to wear on these engines you may decide to use an electric fuel pump in place of the mechanical lift pump.
You could just cut off the pump operating arm and use the old pump body as a cover, but make sure that you bypass the lift pump with the fuel lines because you don`t want the diaphragm puncturing under pressure and filling the crankcase with diesel.
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Just for Fun: My Old Ford F250 Diesel Truck Videos
Starting Our 1983 F250 Diesel Truck
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.