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ratrace2
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Feb 17, 2012, 4:18 PM
Post #1 of 14
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Testing Fuel Injectors
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Hello All,
Well, my budy at the body shop has a problem with tow truck, it won't run. It will start and run as long as you stand there with gas and poor it in. So, I need to fix the fuel delivery system.
It's a 1988 Chevy Scottsdale C30 with a 7.4 liter TBI engine.
First, I was looking at the injectors and they are not delivering any fuel.
Anyone know what the resistance on these injectors should be???
Second, Voltage to the injector harness, (12v)?
Third, Pressure regulator,
fourth, would be fuel pump.
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Hammer Time
Ultimate Carjunky
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Feb 17, 2012, 4:47 PM
Post #2 of 14
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Re: Testing Fuel Injectors
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You need to use a bulb called a "noid light" and plug it into the injector plug and it should flash when you crank the engine if everything is working. You should have constant 12v to one wire and pulsing ground signal on the other wire when cranking but don't use a regular test light on that or you can take out the computer.
If you have injector pulse, then you need to test fuel pressure with a gauge. It should be 9-13 PSI
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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ratrace2
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Feb 17, 2012, 6:56 PM
Post #3 of 14
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Re: Testing Fuel Injectors
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(I'll get those noid lights tomorrow).
Constant 12v to one wire means I should be able to put a 12v battery to these injectors and see if they click open?
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Hammer Time
Ultimate Carjunky
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Feb 17, 2012, 6:59 PM
Post #4 of 14
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Re: Testing Fuel Injectors
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You could but that really isn't where you should be putting your effort. You need to test the signals to the injector. You have 2 injectors, they aren't both bad.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Discretesignals
Ultimate Carjunky
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Feb 17, 2012, 7:06 PM
Post #5 of 14
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Re: Testing Fuel Injectors
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Do you hear the pump in the tank run for a few seconds when you turn the ignition on?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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Discretesignals
Ultimate Carjunky
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Feb 17, 2012, 7:30 PM
Post #7 of 14
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Re: Testing Fuel Injectors
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Well, if you don't hear the pump running, there isn't any sense checking for fuel pressure because it will be zero.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Feb 17, 2012, 7:31 PM)
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ratrace2
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Feb 19, 2012, 7:48 AM
Post #8 of 14
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Re: Testing Fuel Injectors
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Well, if you don't hear the pump running, there isn't any sense checking for fuel pressure because it will be zero. Yes, you sure are right about that.
Well, we started from the fuel tank and went forward today.
We started the truck and found NO priming from the fuel pump; then, we checked the fuses: ALL GOOD.
Next, we started to take the tank out of the truck and then quickly decided that it was not something we wanted to do in gravel parking lot and
decided to call a friend that runs a local STS shop and let him have it.
I did put a Noid light on the wiring since there had been a couple of fires--starter fluid--on throttle body.
I checked the injectors they clicked with a little voltage.
I checked the fuel filter...nice and clear---I hate the taste of gas....
So, we get a new fuel pump installed and we should be good to go.......................
Thanks, ALL.......
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Hammer Time
Ultimate Carjunky
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Feb 19, 2012, 7:52 AM
Post #9 of 14
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Re: Testing Fuel Injectors
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I don't see anywhere that you tested for power arriving at the fuel pump before condemning it.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Hammer Time
Ultimate Carjunky
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Feb 19, 2012, 8:10 AM
Post #11 of 14
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Re: Testing Fuel Injectors
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You don't have to pull the tank just to test the wiring. I've seen many pumps replaced that weren't actually bad.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Hammer Time
Ultimate Carjunky
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Feb 19, 2012, 9:20 AM
Post #13 of 14
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Re: Testing Fuel Injectors
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I don't know why you are fixed on removing the tank just to test power. There is an accessible harness leading to it somewhere.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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