Question about 1994 Isuzu Rodeo

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No pulse at injectors

The 94 isuzu rodeo is giving me 12 v at injectors but it wont give a pulse so im not geting any gas at the ignition chamber

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The normal way that injectors are controlled is via the permanent application (ignition on obviously) to one side of the coil that operates the enclosed piston, and the precisely timed application of ground (negative) to the other side of the coil. The transistors that control this switching under the command of the engine computer are typically contained within the computer itself. Measuring the voltage at the injectors is not productive since the common multimeter is incapable of detecting the very short pulses that activate the coil. Some kind of visual means would be needed to observe this pulse such as an oscilloscope or an engine analyzer equipped with a 'scope.
It's unlikely that all of the switching transistors (or the injectors) have failed simultaneously so either the computer has a problem or there is no fuel being delivered to the fuel rail that feeds the injectors. You should find a pressure regulator that sits between the fuel line coming from the tank that controls the fuel pressure for the injectors. This device seem to be a sore point in many vehicles and can make it appear that the injectors are not working. Many fuel rails have a fitting similar to a tire valve to allow the testing of the pressure being delivered. I would recommend you check this before assuming that the injectors are at fault.  

Posted on Nov 14, 2008

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You should check it with a noid light for pulse, if you have a distributor the module is bad. Start there, that is the cheapest, if you checked your fuses already.Check your relays too.

Posted on Nov 19, 2008

  • Did you check to see if you have spark? Did one today with no injector pulse.Do you know how to change a distributor module? Disconnect negative battery cable.Remove air cleaner. Remove distributor cap with a flat tip screwdriver.Remove rotor button. Remove plugs off of module. Write on a piece of paper the color code of plugs and where they go. Take the 2 bolts out of the module. Probably 5 or 5.5 mm. Remove module and replace. Make sure to put the dielectric grease on the bottom of the module, then reverse process.


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