mechanical fuel pump questions!

[kickitandholdit]

So, I don't know anything about "mechanical" fuel pumps. I half to replace mine and im not sure about the steps and would love a detailed process and pics. Do I need to drain the oil? Does it just unbolt and slide out and the new one just slide back in or does something half to be in a special position to go back in. Your replies are greatly appreciated!

 

[derf]

Fuel pumps are pretty easy. Usually there's no need to change the oil.

First thing to do is to use a very good quality flare wrench to loosen and remove the hard line(s).

Then remove the rubber hose(s) if any.

Next, unbolt the pump. Pay attention to how it comes out. There will be an arm sticking into the engine block. The camshaft has a lobe that pushes on this arm so you need to make sure the new pump goes in the same way the old one comes off.

Clean up the surface of the block. Make sure the old gasket comes off, spray some brake parts cleaner on a rag or paper towel and wipe the area down.

Put new gasket over the arm on the pump, slide arm into block and get it seated reasonably well. It may not want to sit flat because the lobe on the camshaft may be pushing against the lever.

Put the bolts back in, making sure you get them through the holes on the gasket. Tighten them until the pump sits flush against the block. Torque them to 16 ft-lbs or whatever your manual says. This is not really all that tight. It doesn't have to be.

Connect the fuel lines to the new pump. I would recommend that you replace the rubber hoses with new ones if you can. Also, use new hose clamps.

Double check that everything is reconnected.

Check again. You're working with gas so triple checking doesn't hurt.

At this point, have someone there to help you. One person needs to crank the engine and work the pedal while the other one is watching under the hood to make sure you're not dumping gas all over the place.

Crank the engine for 10-15 seconds. Pump the gas pedal once. Crank it again but if it doesn't try to start, don't keep going for much longer than 15 seconds. Repeat the pump pedal once/crank again a couple of times if you have to. It may take a few cycles to get the fuel all the way through the lines into the carb. You may also get it to run for a couple of seconds but have to do it again. Air pockets in the line may disrupt gas flow until you work them all out.

If you crank more than half a dozen times and it doesn't even try to start, come back for suggestions on how to diagnose this.

 

[CJim7]

...And just to reiterate...
Make sure the fuel pump arm is underneath the eccentric when you put it on the block.

 

[derf]

...And just to reiterate...
Make sure the fuel pump arm is underneath the eccentric when you put it on the block.

Yep. I don't replace them often enough to remember so I make sure I pay attention when I take it out.

 

[kickitandholdit]

Yea, im OCD especialy when im working on MY jeep haha so I will probably check 5-6 times. So im guessing eccentric is the lobe on the camshaft? so the arm on the fuel pump just needs to be down or just the same way as the one I take out is? Is there any way I can check to make sure its under the eccentric before I crank?

 

[mylittlecj5]

you should be able to feel the spring pressure when the arm makes contact with the eccentric. As you tighten the pump up, the arm will align itself to the lobe if its even close.
Not too much you can do to screw up with this install! Its 2 bolts and 2 fuel lines. And make sure the fuel lines go back on the same way.

 

[derf]

Yea, im OCD especialy when im working on MY jeep haha so I will probably check 5-6 times. So im guessing eccentric is the lobe on the camshaft? so the arm on the fuel pump just needs to be down or just the same way as the one I take out is? Is there any way I can check to make sure its under the eccentric before I crank?

Yes, the eccentric is the lobe on the camshaft.

It really is not hard to make sure it's underneath. There's plenty of room to move it around when you're putting it in. Just make sure it's pointed slightly down when you put it in and you should have no problems.

And honestly, I think if you get the arm on top and try to bolt it down you won't get it to even seat right. You might not even be able to start the bolts if it's wrong.

 

[kickitandholdit]

haha ok I really appreciate the help!!! I get worried im gonna screw something up whenever I do something for the first time. I have done eletric pumps and im just glad i dont half to spend 120 bucks and take the gas tank down