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Checking injectors before putting on the UIM

ecgreen

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OK, so I am SLLLOOOOOWWWLLY getting my upperend rebuilt. I have the injectors in and all the fuel lines run. Here is my question: I would like to check and make sure the injectors are sealing well before I put on the upper intake manifold. If I turn the key to the "on" position, does that pressurize the whole system or do I have to turn it over?
 


Paulos

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You could check the fuel system for leaks with the injectors clipped into the fuel rail before installing it into the lower intake. That way you would see if they are actually closing completely and not leaking. If you cleaned the injector ports in the lower intake, used new o-rings and lightly lubed them (motor oil works, just don't use anything silicone based on the o-rings), it's unlikely that you'll get vacuum leaks at the lower intake.

To pressurize the fuel system, install a jumper as stated in the image below.

Fuel pump relay bypass.jpg


If you're rebuilding the upper end and fuel system, you may want to consider cleaning the fuel rail, as mentioned here.
 

bodyman46

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Not that familiar with yours newer than mine, but mine had flexible braided fuel lines that connect to the rail. If so just connect them to the rail wherever you can and then turn the key on. That will pressurize the system. My 4.0 has the injectors sandwiched between the upper and lower intakes, so they were held in place and I could see them. Fantastic thought to check them first. I'm overhauled my 92 4.0 twice this summer because I did not check the NEW injectors I had installed. Got about a hundred miles on it and had one dead cylinder and blowing blue smoke. One new injector was bad, would not seal at all, and washed down that cylinder and scuffed the cyl. walls. When I took it apart and checked the injector, that one looked like a lawn sprinkler. Very expensive mistake
 

adsm08

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Running the fuel pump pressurizes the whole system. That's how we checked the 5.4 injectors.

Also, if you have the rail and injectors installed already, the time to do this test was before that.
 

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