Injector plug key on volts
Thread Starter
TECH Addict
Joined: Aug 2005
Posts: 2,305
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From: Monroe,NY
Injector plug key on volts I had a problem recently when I was working on my truck I turned the key off and on many times and my motor hydrolock the motor with fuel. I pulled my fuel rail put fuel pressure on it and it held 58psi for an hour. So no leaking injectors. I checked all my injector plugs with key on and they were all 12v hot side to battery ground. I then checked the plugs hot and ground and they all read 5v. I thought they should be 0? Any help would be appreciated. Thanks
Thread Starter
TECH Addict
Joined: Aug 2005
Posts: 2,305
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From: Monroe,NY
It's a 2004 5.3 with a 1999 5.3 pcm in a 1992 chevy pickup 2wd. It was just recently that I started having hot start problems. Swap was done in 2013 probably put 25000 miles in that time.
Staging Lane
Joined: Jan 2017
Posts: 67
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it sounds like your "key on" relay is sticking causing the injectors to get voltage. Its likely the contacts are worn with high resistance, and thats why you only see 5 volts.
What happens if you unplug your relay, does your 5 volts go away?
Also make sure you are not overloading your relay with too much current draw, they can overheat and stick.
What happens if you unplug your relay, does your 5 volts go away?
Also make sure you are not overloading your relay with too much current draw, they can overheat and stick.
Should have an open circuit on the ground side of the connector if the injector isn't being commanded on. Sounds like you've got continuity to ground on the injector circuit ground leads. Unhook positive battery terminal and measure resistance between negative battery terminal and ground side of the injector plug. Should be a pretty large number...
Thread Starter
TECH Addict
Joined: Aug 2005
Posts: 2,305
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From: Monroe,NY
Should have an open circuit on the ground side of the connector if the injector isn't being commanded on. Sounds like you've got continuity to ground on the injector circuit ground leads. Unhook positive battery terminal and measure resistance between negative battery terminal and ground side of the injector plug. Should be a pretty large number...
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TECH Addict
Joined: Aug 2005
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From: Monroe,NY
They all had 12v key on power side of injector to ground. But checking across injector positive negative I get 5v with key on. I thought I would get 0 since the pcm isn't pulsing ground.
TECH Senior Member
Joined: Apr 2002
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From: So.Cal.
The PCM turns on the injector by connecting the injector ground pin to ground i.e. 0 volts at injector ground pin;
when the injector is off, its ground pin should pull up to 12V, you should measure this with injector plugged into harness, and key on (engine off).
when the injector is off, its ground pin should pull up to 12V, you should measure this with injector plugged into harness, and key on (engine off).