gagliano7

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

gagliano7

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.

Compsystems

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.

gagliano7

Thanks I will check that tomorrow. I checked with key off the ground of two injector plugs to battery positive and I get 10v battery was 11.8v

smokeshow

iTrader: (17)

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...

gagliano7

I will check that tomorrow thanks

gagliano7

I checked all injectors to battery ground and no reading. I then checked all injector grounds to pcm and all were in .5-.7 and I checked all pcm grounds and they were all from.5-.7. This is ohms on the lowest setting. I checked the ohms on a few injectors and they were 12.5 which they should be.

joecar

Key off: there should be no voltage at any injector connector.

Key on, engine off: there should be 12V at all injector connector pins, try measuring with injectors plugged in, if you can.

gagliano7

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.

joecar

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).