Tonight I attempted to fire up my LQ4 swap for the first time. I got a little bit of backfire out the exhaust, and what sounded like a couple feeble attempts at combustion, but not much else.

Every time I stopped cranking the engine, I heard a hissing sound from what seemed to be the front passenger side of the engine, possibly in the area of the fuel rail. Does this sound like the symptoms of a leaking injector? It's loudest as soon as I stop cranking, then slowly dissipates over 30-60 seconds. Or is this the normal sounds of the fuel pressure regulator relieving pressure (or something else?)?

 

That's probably a piston on the compression stroke and it's leaking down. Pull a few plugs and see if they are soaked if you want to be sure.

 

I was told to soak my injectors in Marvel Mystery oil to clean any deposits before trying to fire.

 

Quick question- when you turn the key to the on position, it runs the pump for a couple seconds. If you then crank the engine, it doesn't start, and you stop cranking- is the pump supposed to run again for another two seconds? I thought this was weird, so I bypassed the crank position of the key (thinking it was cutting power to the RUN/ACC circuits when in the Crank position, shutting off the PCM while cranking) and wired in a pushbutton switch instead. However, even with this switch it still does that.

Is it normal for the pump to kick back on for 2 seconds after failed cranking?

 

My pump does that (continues after failed start). I have a Gen IV, L92.

I believe the PCM triggers the fuel pump so it runs if the crank position sensor sees crank rotation.

Doug

 

Ok, so this is just bizarre. I tried starting it again after work, no luck again- seems to just fire roughly one cylinder per rotation, acting like its about to start...but nothing.

So I start checking things, spark first. Pull the fuel pump relay, pull the wire off cyl #2, put an extra plug in it, ground the plug to the exhaust manifold, turn the key to on, and use an external starter button to turn it over. Goes around once...got spark! ...and immediately after #2 fires, the engine starts.

With no fuel pump.

On 7 cylinders.

And it proceeds to run for at least a good 15 seconds. Seemed fairly smooth for 7 cyl, but couldn't really tell, as I was in a state of shock.

So I put everything back together, and.....back to square one. Still won't start again. Even re-created the scenario that it started in, and it won't again. What the hell?

 

Are you sure your pink ignition wires are hot in both run and crank positions?

 

This was my first thought, as I had read other people having that problem. I've tried testing it, and the results were inconsistent- it almost seemed like the key was still putting out juice to the pink wire sometimes, depending on how far into the Crank position I turned the key.

I'm going to sort that out better once I get everything running, see if I need a later model switch.

I've bypassed the crank position for now though, I have a pushbutton temporarily wired in between 12v keyed and the starter relay so any key-related issues should be eliminated.

 

I'm thinking about picking up some noid lights to test the injectors, but first I think I'm going to try to clean them. My thought is that they're probably not all working right now, which would explain why it seems to just be firing on a couple cylinders/inconsistently while cranking.

Any recommendations on injector cleaning? Solution/method?