Fuel Injector Problem

[Guest]

Trying to get my 88 YJ running after supposedly sitting for 7 years. It has the 2.5 TBI and I just replaced the fuel pump and fuel filter and it won't start. It will sputter/run with a sprinkle of gas straight down the TB.

So I unplugged the fuel filter and had gas...unscrewed the line of the back of the TB and had gas...but nothing is coming out of the injector. I found the OHM rating for the injector online and it seems to be right (I also read that even if it tests right it still may not work)

Does anyone know a way for sure to test the injector before I run out and spend $140 for an injector that may not solve the problem? Does anyone have one laying around that I could possibly try?

[ericfx1984]

I know some shops have an injector tester

but this should work...

http://www.fierosails.com/InjectorTester.html

[reward_1000]

Or, you could remove the injector and check the screen, but you may ruin some gaskets like this. You could hook up a test light and you could test for power and ground at the injector while some one is turning it over. Usually you will have power all of the time and the PCM will pulse the ground causing the injector to work. You could also hook up a hose to the inlet of the injector housing and disconnect the connector at the injector, then hook it to full power and ground and try to blow through the hose and see if you can blow through it. If not you have a bad or dirty injector. Or you could make some crazy looking thing taking days to find all of the parts and build. That is just me though.

[Guest]

Or, you could remove the injector and check the screen, but you may ruin some gaskets like this. You could hook up a test light and you could test for power and ground at the injector while some one is turning it over. Usually you will have power all of the time and the PCM will pulse the ground causing the injector to work. You could also hook up a hose to the inlet of the injector housing and disconnect the connector at the injector, then hook it to full power and ground and try to blow through the hose and see if you can blow through it. If not you have a bad or dirty injector. Or you could make some crazy looking thing taking days to find all of the parts and build. That is just me though.

I'm glad you mentioned the screen...I pulled mine out and the screen appeared clogged, but since I don't know what a new one looks like I wasn't sure.

I did use a DMM and checked for voltage while cranking. It did show a change in voltage, but since I don't have a range to go off again I wasn't sure.

I also just read that the TPS has something to do with the injector firing, so tomorrow I was going to check the voltage at WOT on the TPS just to make sure.

[reward_1000]

Sounds like you are on the right track. If you have a test light try that at the injector, the meter will not be able to keep up. It will need 12 volts to fire and that is what most test lights require.

[Guest]

Sounds like you are on the right track. If you have a test light try that at the injector, the meter will not be able to keep up. It will need 12 volts to fire and that is what most test lights require.

I wasn't sure if it was something silly like only using 5v or something. I'll check it with a test light tomorrow. Along with the TPS.

[Guest]

Well I went back out and re-installed the injector. Looked up the wiring diagram in the service manual and began tracing and testing a few wires with a test light and here's what I got.

Injector has two wires...orange and blue

Orange is power and blue goes to the PCM.

Orange has power while cranking and blue has power while cranking...

unplugged the injector and tested again.

Orange has power while cranking and blue has a perfect ground pulse!

I would say the injector is shorted and allowing the power to back feed into the ground pulse. Sound right?

Going to go ahead and order the injector. Hopefully that does it.

[reward_1000]

That sounds like an injector issue from here, but I am not there to see it. You should have a pulse when hooked up so it sounds like you have found the problem.

[Guest]

Thanks a lot reward_1000! Put in the new injector and it fired right up

I was really surprised. After supposedly 7-8 years of sitting it fires right up and idles smooth and even has good oil pressure. Now to get the t-case in and fix a couple minor thing and drive this beast!

[reward_1000]

Glad to hear! Good luck with the rest of it.