Question about 1999 GMC Jimmy
Change the E.M.C. computer in this heat that's all it can be if no other problems existed before
Posted on Jul 18, 2010
This sounds like the main relay also known as PGM-FI main relay.
Main relay:--Its a fuel pump relay.
you should hear the main relay click. If it doesn't click, check
terminal seven on the main relay (fuel pump) for power and terminal eight
(computer) for ground. If you have no power and you have ground, the main relay
If the main relay is bad. You will lose fuel pressure. Or you will lose power to the injectors and the fuel pump but you may not lose fuel pressure in some cases because the injectors can't open without power. When the main relay goes bad and there isn't any voltage at the injectors, it will set a code 16 for an injector because the computer doesn't read voltage on the ground side of the injector.
Before you dive in too fast, it's also possible that the car has more than one thing causing a hard start. You could also have a bad ignition switch, a bad igniter or a bad ignition coil. To test for spark, you should first perform a simple spark test, and then you can test the coil itself. Unfortunately to test the igniter itself, you need an automotive oscilloscope, something you won't really need too much in a home shop.
The main relay will give you the same symptoms as a bad coil or a bad igniter. A main relay usually only fails when the weather is really hot. You might have a hard start every now and then, but not enough to really cause you any concern, but when an igniter or a coil fails, the car won't start at all until it cools down. If you've determined that the culprit could be the main relay, just check and replace the main relay.
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Posted on Jul 18, 2010
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Posted on Jan 02, 2017
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