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Testing Fuel Injectors


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ratrace2
User

Feb 17, 2012, 4:18 PM

Post #1 of 14 (2429 views)
Testing Fuel Injectors Sign In

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.


Hammer Time
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Feb 17, 2012, 4:47 PM

Post #2 of 14 (2401 views)
Re: Testing Fuel Injectors Sign In

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.



ratrace2
User

Feb 17, 2012, 6:56 PM

Post #3 of 14 (2379 views)
Re: Testing Fuel Injectors Sign In

(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?


Hammer Time
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Feb 17, 2012, 6:59 PM

Post #4 of 14 (2373 views)
Re: Testing Fuel Injectors Sign In

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.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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.



Discretesignals
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Feb 17, 2012, 7:06 PM

Post #5 of 14 (2368 views)
Re: Testing Fuel Injectors Sign In

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.


ratrace2
User

Feb 17, 2012, 7:19 PM

Post #6 of 14 (2361 views)
Re: Testing Fuel Injectors Sign In


In Reply To
Do you hear the pump in the tank run for a few seconds when you turn the ignition on?

NO, I didn't......

And, I didn't see any fuel pussing up against the lines when I took them off the throttle body.......

I think the filter should come off. it's an old truck with old gas tanks......

Tomorrow I'll work my way through the system.......

Key on: Listen for pump.
Change fuel filter.
Key on: look for fuel coming out of the engine bay fuel lines.
Key on: fuel pressure test.....if I can get fuel that far................


Thanks guys............Sandman is calling................


Discretesignals
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Feb 17, 2012, 7:30 PM

Post #7 of 14 (2354 views)
Re: Testing Fuel Injectors Sign In

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)


ratrace2
User

Feb 19, 2012, 7:48 AM

Post #8 of 14 (2325 views)
Re: Testing Fuel Injectors Sign In


In Reply To
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.......


Hammer Time
Ultimate Carjunky / Moderator
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Feb 19, 2012, 7:52 AM

Post #9 of 14 (2322 views)
Re: Testing Fuel Injectors Sign In

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.



ratrace2
User

Feb 19, 2012, 8:07 AM

Post #10 of 14 (2316 views)
Re: Testing Fuel Injectors Sign In


In Reply To
I don't see anywhere that you tested for power arriving at the fuel pump before condemning it.

You are right.

We looked at what was involved at getting to the pump and decided to send it out.
The Tow truck was parked in a gravel lot; and it's February in NJ; we didn't want to pull the fuel tank in those conditions so we just stopped
and called someone with the right equipment and shop space for that sized truck...G30 w/tow package in bed.


Hammer Time
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Feb 19, 2012, 8:10 AM

Post #11 of 14 (2312 views)
Re: Testing Fuel Injectors Sign In

You don't have to pull the tank just to test the wiring. I've seen many pumps replaced that weren't actually bad.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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.



ratrace2
User

Feb 19, 2012, 9:12 AM

Post #12 of 14 (2304 views)
Re: Testing Fuel Injectors Sign In


In Reply To
You don't have to pull the tank just to test the wiring. I've seen many pumps replaced that weren't actually bad.

this pump is half under the cab; given the weather, the location, the hassle, we decided to send it out.......But you are right.
They (STS) can check the wiring with the tank out..


Hammer Time
Ultimate Carjunky / Moderator
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Feb 19, 2012, 9:20 AM

Post #13 of 14 (2304 views)
Re: Testing Fuel Injectors Sign In

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.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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.



ratrace2
User

Feb 19, 2012, 9:47 AM

Post #14 of 14 (2293 views)
Re: Testing Fuel Injectors Sign In


In Reply To
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.

I'm, actually, not.
Me and my friend got to the part where we had to test the wiring around the fuel pump and decided to send the truck to another shop.

As for testing the power, I can barely get my hand near the top of the fuel tank, let alone unplug the harness. And, the truck is an 1988.
Everything that is plastic or rubber is just about gone--as far as the wiring harness goes going to the back of the truck.....
Plus, personaly, I don't want to work on the truck out in a gravel parking lot in February in NJ.......

We just decided to send it out...........






 
 
 






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