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AMEDEE
AMEDEE, CHEVY TECHNICIAN
Category: Chevy
Satisfied Customers: 21894
Experience:  ASE MASTER TECHNICIAN ADVANCED LEVEL SPECIALIST. Wisconsin certified emissions state inspector
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87 Chevy: wont start..Replaced fuel pumps, relay, ecm !..injector

Customer Question

87 Chevy pickup won't start! Replaced fuel pumps, relay, ECM ! Have no fuel spray and no ground to injector plugs
Submitted: 2 years ago.
Category: Chevy
Expert:  AMEDEE replied 2 years ago.
Hello!

My name isCustomerXXXXX I can assist you with your question. I need ot get some information from you in order to steer you in the right direction.

Does the check engine light come on with the key on? Does the TPS have 5 volts going to it with the key on?
Customer: replied 2 years ago.
Yes, check engine light comes on. TPS has 5.04 volts
Expert:  AMEDEE replied 2 years ago.
EXCELLENT!

Does the engine have fuel pressure with the key on and cranking the engine over?

Do each of the fuel injectors have power with the key on?
Customer: replied 2 years ago.
No fuel pressure! Yes have hot to injectors!
Expert:  AMEDEE replied 2 years ago.
Is there power to the fuel pump when cranking? Do the fuel injectors get grounded when cranking the engine over?
Customer: replied 2 years ago.
Yes! No ground to injectors when cranking
Expert:  AMEDEE replied 2 years ago.
What is the TPS signal return voltage back to the computer with the key on engine off?
Customer: replied 2 years ago.
Tps has 3 prongs on plug I get 5.04 .02 .01! If I'm checking it right!
Expert:  AMEDEE replied 2 years ago.
It should be about a half of a volt with the key on engine off. Anything between .5 to 1.0 volt should be ok. But if the TPS is not even registering a half of a volt with the key on, the computer might go into clear flood mode when cranking and cut off all injector pulse.
Customer: replied 2 years ago.
Replacing tps if problem, ECM would send ground to injector plugs and kick on fuel pump? Tps signal return located on prong closest to fire wall? Prong closest to fan had 5.04
Expert:  AMEDEE replied 2 years ago.
The dark blue wire is the TPS signal wire back to the computer.

The injector ground from the PCM is completely different from the signal to the fuel pump relay. The PCM actually supplies power to the fuel pump relay to activate it to allow power to the fuel pump. The Tan/white wire leaving the fuel pump relay is the power wire to the fuel pump. This wire should have power when cranking the engine over. If not, try to power up this wire and see if the fuel pump comes on.
AMEDEE, CHEVY TECHNICIAN
Category: Chevy
Satisfied Customers: 21894
Experience: ASE MASTER TECHNICIAN ADVANCED LEVEL SPECIALIST. Wisconsin certified emissions state inspector
AMEDEE and 3 other Chevy Specialists are ready to help you
Customer: replied 2 years ago.
Tps blue wire is .55 volts!
Expert:  AMEDEE replied 2 years ago.
Ok.. good! Does the engine have spark when cranking it over?

Does it run on starting fluid?
Customer: replied 2 years ago.
Yes! Fires right up with lil gas!
Expert:  AMEDEE replied 2 years ago.
And there is still no fuel pressure correct?

Have you tried to power up the tan/white wire to see if the fuel pump will run?
Customer: replied 2 years ago.
I still have pickup bed off, at top of fuel tank I have plug with one purple and one gray wire that go to pump! I think purple went to sending unit and gray is power for pump! Didn't see tan/white wire off relay
Expert:  AMEDEE replied 2 years ago.
You said this is duel fuel tanks correct? Which tank are you testing currently?
Customer: replied 2 years ago.
Tank switch is on RH side! I'm not sure which wire to add my hot wire to
Expert:  AMEDEE replied 2 years ago.
The gray wire is the power wire to the right side fuel pump. Power this wire and see if the fuel pump runs and if the engine starts and runs.
Customer: replied 2 years ago.
Powered gray wire and truck fired right up!
Customer: replied 2 years ago.
Relist: Other.
I accidently pressed green button to soon
Expert:  AMEDEE replied 2 years ago.
Hello!

Sorry for the delay! Was spending time with the family.

If the truck starts up when powering up this gray wire, then we need to check the inputs to the fuel tank selector switch and or fuel tank selector valve and meter switch. According to my wiring diagram , this vehicle has both switches. The fuel tank selctor switch should have power going into it on that same tan/white wire we were talking about from the fuel pump relay.
Customer: replied 2 years ago.
Yes tan/white wire is hot on tank selector switch
Expert:  AMEDEE replied 2 years ago.
And does the black wire have a good ground?
Customer: replied 2 years ago.
Yes
Expert:  AMEDEE replied 2 years ago.
Ok.. and does the gray wire leaving the selector switch have power when turning the key on and cranking the engine over when it is set to the right fuel tank/pump?
Customer: replied 2 years ago.
No power
Expert:  AMEDEE replied 2 years ago.
IF there is power going into the selector switch on the tan/white wire and no power coming out on the gray wire with the selector switch in the "right selector" then the selector switch is bad and needs to be replaced. If you just replaced it, it should be under warranty.

You can jumper the tan/white wire going into the selector switch to the gray wire and see if the engine starts and runs.
Customer: replied 2 years ago.
Ok new switch is rocker style that you depress to desired tank, then it goes back to middle of switch. If I hold it depressed on RH it fires right up! You are awesome! Thanks so much!
Expert:  AMEDEE replied 2 years ago.
I think thats it! Glad to hear we got to the bottom of it!

Please let me know if you have any further questions!
Customer: replied 2 years ago.
For some reason I have only fuel guage working. My oil pressure, temp, and volts are not working! My guage fuse is good! Any thoughts?
Expert:  AMEDEE replied 2 years ago.
Does the fuel gauge work on one setting.. left or right side or not at all?
Customer: replied 2 years ago.
Fuel guage works fine on either tank!
Expert:  AMEDEE replied 2 years ago.
Got it! Sorry for the confusion. This is usually just a bad instrument cluster.
Customer: replied 2 years ago.
Is there a way to check to see if they are still good? I have them out? Temp,oil pressure,volt guages
Expert:  AMEDEE replied 2 years ago.
Not that I am aware of. All that I do is check the inputs to the cluster when I get one of these issues. If all inputs are good and the cluster is not working, the cluster is bad and needs to be replaced.
Customer: replied 2 years ago.
Ok! Thanks for all your help!
Expert:  AMEDEE replied 2 years ago.
You bet!

Have a great weekend!

AMEDEE

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