No fuel pressure, injectors dripping fuel

Tiny
JOE UTLEY
  • MEMBER
  • 1989 CHEVROLET 1500
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 206,000 MILES
I have changed the fuel pump twice, rebuilt the TBI with new injectors, new fuel filter, new distributor and changed a bunch of sensors/ECM. The injectors are still dripping fuel. I hooked up a fuel pressure gauge right after the fuel pump and I’m not getting any fuel pressure. So I’m stumped. What do I do next?
Monday, July 6th, 2020 AT 5:55 PM

23 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Good morning,

I attached a wiring diagram for you to view. We need to verify power to the pump to find out why you have no pressure.

https://www.2carpros.com/articles/how-to-check-wiring

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

By dripping, do you mean the injector is dripping from the pindle or the mounts?

With no pressure, they should not drip at all.

Roy

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Tuesday, July 7th, 2020 AT 6:10 AM
Tiny
JOE UTLEY
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Hello. Thanks for the reply. The injectors are dripping from the pintle.
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Tuesday, July 7th, 2020 AT 9:46 AM
Tiny
ASEMASTER6371
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If you have no pressure, they should not be doing that.

Did you do a pressure test? You can rent a tester at a parts store.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Roy
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Tuesday, July 7th, 2020 AT 10:25 AM
Tiny
JOE UTLEY
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  • 13 POSTS
So I went to start it up with the fuel pressure gauge attached and the truck won’t crank. I had the starter tested and it’s not the starter. So now I’m going to change the ignition switch. Could the two issues be related?
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Tuesday, July 7th, 2020 AT 12:43 PM
Tiny
ASEMASTER6371
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Maybe but in my first response, I asked if you checked for power to the fuel pump. Did you ever do that?

Why do you think it is the ignition switch?

Roy
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Tuesday, July 7th, 2020 AT 12:52 PM
Tiny
JOE UTLEY
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Yes, the pump is getting power. The meter said it’s receiving 7.95 volts. That’s at the pump connector. I think the starter solenoid isn’t receiving power from the ignition switch. That was my first thought because the starter is good.
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Tuesday, July 7th, 2020 AT 1:01 PM
Tiny
ASEMASTER6371
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That was not the pump. That was for the sending unit.

The fuel pump must have battery voltage to work.

With the key on, it will have power for 2 seconds for priming. When cranking, it will have power all the time.

It should be the purple wire.

Roy
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Tuesday, July 7th, 2020 AT 1:09 PM
Tiny
JOE UTLEY
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It has power from the purple wire “0.35.
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Tuesday, July 7th, 2020 AT 1:33 PM
Tiny
ASEMASTER6371
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That is not power. It needs a minimum of 12 volts for the pump to work.

I attached a picture and location of the relay. We need to find out why there is no power at the pump.

Do you have a test light or voltmeter for some testing?

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Roy
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Tuesday, July 7th, 2020 AT 1:42 PM
Tiny
JOE UTLEY
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Yes, I have a voltage meter.
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Tuesday, July 7th, 2020 AT 1:43 PM
Tiny
ASEMASTER6371
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Go to the fuel pump relay and remove it.

Test for battery voltage with the key on a one terminal.

If you have power, then you need to test for power when the key is first turned on to another terminal. It will last for only 2 seconds.

Roy
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Tuesday, July 7th, 2020 AT 1:48 PM
Tiny
JOE UTLEY
  • MEMBER
  • 13 POSTS
Okay. I found a constant power on the fuel pump relay connector and it has 12 volts. I also found the 2 second source and that one has 11.75 volts for 2 seconds.
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Tuesday, July 7th, 2020 AT 1:59 PM
Tiny
JOE UTLEY
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I cannot try to start the truck though because the truck won’t turn over.
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Tuesday, July 7th, 2020 AT 2:23 PM
Tiny
ASEMASTER6371
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Okay, good.

Put the relay back in and turn the key to on and see if the relay clicks.

Roy
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Tuesday, July 7th, 2020 AT 2:49 PM
Tiny
JOE UTLEY
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Yes the relay clicks.
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Tuesday, July 7th, 2020 AT 2:51 PM
Tiny
ASEMASTER6371
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Okay, with the relay in have someone turn the key to on and test the purple wire when the relay clicks in.

Roy
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Tuesday, July 7th, 2020 AT 2:54 PM
Tiny
JOE UTLEY
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I have 0.35 at the purple wire, but I can hear the fuel pump turn on for those 2 seconds. I also have 8.5 volts coming from the pink wire that connects to the purple wire at the connector.
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Tuesday, July 7th, 2020 AT 3:24 PM
Tiny
ASEMASTER6371
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The purple wire should have battery voltage, not.35 volts. The pump will not run with that voltage.

Please recheck.

Roy
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Tuesday, July 7th, 2020 AT 3:49 PM
Tiny
JOE UTLEY
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I cannot get my prob to go in deep enough to get a good reading. Any ideas on how to get a good reading?
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Tuesday, July 7th, 2020 AT 5:34 PM
Tiny
ASEMASTER6371
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You need a set of back probes. They are thin enough to get to the wire while it is hooked up to the relay from underneath.

You can get a set of them cheap at a parts store.

https://www.harborfreight.com/test-probe-set-5-pc-61872.html

Roy
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Tuesday, July 7th, 2020 AT 5:38 PM

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