Tech Area

Bad Injector (4 Cyl)

Question: Ok Guys, I am beginning to not like my little car. We have worked on the car all day and nothing!!! Checked all the fuel lines from tank to TBI all clear. Cleaned the injector, and found the screens were damaged. Replaced it with a whole new injector. Fuel is going to the TBI but not in it. Now what do we do. I really need to get it going. I will be sitting here waiting. Thanks in advance. Please Lord, let it be some simple thing....

Answer:Rustie, the injector either has no power or is not being grounded (pulsed) by the ECM.

A 12v test light will do to find out if you have power. Red wire is power input from the fuse with key on. Blue is grounded by the ECM. If you probe the blue wire, the test light will also light up, since it is providing a constant ground. Disregard that as a symptom - it only shows that the injector has continuity. A noid light attached to the injector will actually show if it is being pulsed (yours obviously isn't). BTW, a constantly spraying injector is caused by the blue wire being grounded somewhere, or a bad ECM.

99% of the time an injector does not "fire" on the 4 cyl cars, the problem is a bad fusible link that powers that aspect of the ECM. The other 1% is a bad ECM. Check fusible links with a 12v test light to both sides and/or GENTLY pull the wire on either side of the link. Sometimes there are just enough strands left of the fusible link that the test light might light on both sides, but if that is the case the wire will usually come out of one end, when pulled on.

A fusible link looks like something a wire is going through. It is inline, round, about 1" long, and maybe 3/8" in diameter. They are found near the starter and the 12v distribution center near the battery (and elsewhere in the car for other circuits). We don't have an 87 Helms manual at home, so can't tell you which/where that fusible link is (Pontiac changed locations between 86 and 87 models). So, check them all, unless someone tells you exactly which one is the ECM feed.

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