Hello folks,

I am trying to help a friend who has been going through a horrible ordeal with a back yard mechanic..

To give a recent history of the vehicle, first was an intake mani gasket job which ended with a nut in the cylinder and a knocking motor. The guy tried to fix the knock but that didn't work out. Next was a new shortblock. After that was in the timing stuff had to be pulled back apart because the ck pos sensor and wheel weren't installed.

After that the vehicle started and ran fine for a few minutes and then shut down. My first look at the truck was that it would start and run if you pedaled the gas but it would idle high 2-3k rpm on it's own. I started checking out all important sensors map, clt, tps, iac, etc.. All checked out fine. After 15 mins or so of checking we tried to restart the truck but it wouldn't turn over. Tried again with the charger and still a no go. I suspected hydrolock and started pulling plugs. It was hydrolock.

So the problem is constant ground (no pulse at all) to the injector with the key on. I have pulled the ecu plug and there is no continuity to ground( not a shorted wire). When checking the injector signal to ground there is some continuity with the key off.

I'm abit stuck at this point and thinking the ecu is bad but I don't want to just start swapping parts. If anyone has any insight on this it would be greatly appreciated.

Thanks Sam

 

What are you driving? I'm thinking it must be a '95 cause you are talking about an injector (singular) and not injectors (multiple).

The injector is supplied ignition voltage by fuse #10 per the schematic I'm looking at. The ECU (or PCM if fully OBD2) then pulses the ground to the injector to open it. This pulse is fast enough that you may not be able to monitor it using a DMM. A noid light should be used to determine if the injector is properly being pulsed.

Even if the injector were open all of the time, it should not spray enough fuel to fill the cylinders unless the ignition sat on for an extended period of time.

 

Hi swartlkk,

I was hoping you would see this.

Yes it is a 95 and single injector.

As for a noid light, i don't have one but I am testing with a snap on vantage(digital graphing mm with pw capabilitys).

Even at initial key turned to on it goes to solid ground and stays there ie no shut off after initial prime pulse.

The amount of time for lock up was 15-30 minutes. Vehicle was running, we shut it off, turned the key on and I started testing. Attempted to restart but it was locked.

I'm hoping someone has experienced this before. I can't scan the ecu and don't have access to a fsm so this forum is my last resort befor ecu swapping.

Thanks, Sam

 

It is easy enough to pop the plenum cover off and have a look inside. If the injector is constantly grounded, then fuel should be spraying out of the poppet nozzles.

The pump should shut off after the initial prime which should limit the amount of fuel that can flow into the intake...

 

Update.. I've fixed a few issues and refined the symptoms for the main problem.

First the fixed..
1 spark plug cross threaded one loose
Cap and rotor were bad enough that the coil wire was arcing on brand new wires

And the remaining issue.. Fuel keeps on runing after the truck dies on it's own. It's only when the truck dies that the fuel runs on. It also seems to be running extremely rich. It runs well for a short time then loads up and dies and the fuel keeps on trucking.

I'm at the point now that the plugs are grossly fouled and the truck is very difficult to start. I'm about to clean the plugs and start fresh.

Can this be a cam or crank sensor issue? It's currently not throwing a code and even if it was my scanner wont read this truck.

Thanks for any help or advice.
Sam

 

Have you pulled the plenum cover and looked for a fuel leak yet?

 

Nope, I haven't. It's most likely headed for a shop tommarow.

It's funny to hear the injector clatterin away after the truck dies. If you open the throttle it even goes faster hehe. I want to find another 95 and see if they all do this. Seems very dangerous if it's normal.

I may still take it off but there is no fuel/starting issue if there is prolonged "on" time without running. That seems to eliminate fuel leak enough for me but it would be nice to wrap up one more possibility.

I'll keep ya posted.
Thanks for the help.
Sam