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How to test NA 2.5 diesel fuel pump? (and other newbie ???)


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Hi all,

I bought a project Series 1 88; it came with a diesel Defender motor (either 2.25 or 2.5 NA, I don't know how to find out which). The original motor had been traded away for this diesel.

While the truck was still in Oregon I got some help from some great LR people there getting the engine mated to a Series 2 transmission and the whole of it fitted to the truck. When I tried to test fire the motor the starter was bad. I hauled the truck back home to Colorado. Fast forward several months. I finally have it in the garage and I'm working on it. I had the starter rebuilt locally and it appears to work pretty well. I tried to test fire the motor but it wouldn't fire up. I re-plumbed the fuel system with clear nylon lines so I can see what is going on. I can't seem to get all of the air out the line. I found a lever on the forward side of what I think is the lift pump but it doesn't seem to do anything. If I crank over the engine for a while it pulls fuel into the lines but there are still air bubbles and most of the lines are nowhere near full.

I should mention that I found the fuel solenoid and connected it to power -- it makes a solid click so I guess it works.

How can I test that the lift pump works? Can it be rebuilt if it doesn't? Which shop manual should I get? I just care about the engine sections because I have some pretty good books for the Series Truck. I'm looking for something that would tell me torque settings for the waste fuel bolts and how to test the fuel pump. Ideally it would tell me things I probably should know already such as which position to leave the manual pump lever in when not in use.

I'm hoping I can get the motor started soon because I think that it will give me a big motivation to get the truck on the road.

Thank you in advance,

Brad Guillory

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You need to identify which engine you have - the 2.25 and 2.5 engines are very different visually. On a 2.5 the injector pump is bolted to the rear of the timing cover, so is horizontal. The 2.25 injector pump is on the side of the engine and is vertical. The 2.5 has a large flat timing case and has a camshaft drive belt inside it, whereas the 2.25 is chain driven and has a small steel timing case. 2.5 has a vaccuum pump for the brakes, whereas the 2.25 doesn't. The lift pump has a lever underneath, which when operated - sucks fuel up from the tank and pumps it to the fuel filter and then to the injector pump, where it is further pressurised for the injectors. If the lever is sloppy and appears to do nothing, then rotate the crank 180-deg and try again - the foot of the pump may be on the cam, so may appear not to work. If however, the lever is still sloppy, then the pump may be broken, and the lever mechanism can't be repaired as far as I know. There are two valves inside the pump - one to allow fuel into the pump from the tank and one to allow it out to the filter. These can also fail and then you will get little or no pumping, or fuel will drain back into the tank when the pump stops. Check also the fuel pickup pipe inside the tank - if it has corroded, then it may also be perforated - allowing air to be sucked-up along with fuel, giving you the air bubbles you describe.

Les.

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I'm looking for something that would tell me torque settings for the waste fuel bolts

Not sure which you mean, and it depends a little on which engine - See Les's descriptions. The 2.25 diesel and 2.5NAD workshop manual is available for download from here (also linked from the technical archive under "manuals").

Ideally it would tell me things I probably should know already such as which position to leave the manual pump lever in when not in use.

Up, I'm pretty sure.

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Les,

Thanks for the great description; it sounds like I have a 2.5L. I don't have the fuel tank mounted yet so I just ran my fuel line (and return) into a fuel can. I will try advancing the crank and manually pumping again. What is the preferred method of advancing the crank? I will use the starter for now. If the lift pump is bad will the injector pump provide enough lift to pull some fuel into the lines?

errol209,

Thanks for the links. The workshop manual is very helpful. Though I didn't find many torque specs. The bolts I am referring to are the ones that hold the return line on top of the injectors. They appear to be pretty special in that they allow fuel to pass through them.

Thanks again,

Brad

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Yep - spill rail it's called. Those little bolts are hollow to allow fuel to pass through them, so be careful about tightening them up too much. 11mm or 7/16" spanner and there should be a small copper or alloy washer either side of the fitting.

Les.

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