My subordinate hydrolocked a Q45 with fuel... Need indepth technical answers...

[greyxjltd]

I'll start off by saying hello to everyone and that I am new to this forum. However, after extensive searching for this particular symptom I've gotten now headway, so figured I'd ask.

One of my employees pulled in a 1991 Q45 into the shop for a severe drivability issue. He replaced the 8 sparkplugs and the vehicle ran 10 times better, but with a slight miss. I hooked up my MODIS, and disabled eash injector one by one, watching for o2 changes and engine performance. As it turned out, injector for cylinder 2 was dead. Open resistance. Since the repair job was already sold, the tech wanted to save money and swapped in an injector from a 1997 Sentra!!! That didn't go over too well. He cranked over the engine, and I heard a loud thud and pop. It would not crank over anymore at that time. I took over the repair at this time. I pulled the injector back out and compared it with the old one...totally different in design. I didn't know exactly what happened, so I removed all eight spark plugs, and cranked the engine over by hand. Fuel started running out of cyl. 2 spark plug hole. I was then able to crank the vehicle over with the starter. More fuel squirted out and then started spinning more easily. I ordered and installed the proper bosch injector and reinstalled the plugs. Now, vehicle starts up, makes an awful noise, almost like a bent valve at the front right of the engine, around cylinder 2 and now I have fuel running out of the throttle body past the MAF sensor and into the airbox.

So...what happened here? I can crank the engine over by hand and don't hear anything. I can disable the fuel pump. Crank the engine with the starter and still don't here the noise. The noise only occurs when it is running. Possible timing chain tensioner? I'm open to any and all ideas. Even if I can figure out the noise from the timing area...does the explain the mass amounts if fuel coming out of the air intake? The fuel pressure regulator vacuum hose had fuel in it when I disconnected it...but what if the fuel from the manifold ran down the vacuum line to the regulator...and not necessarily from a blown pressure regulator up into the intake manifold?

Again, any and all suggestions or ideas would be greatly appreciated.

Thanks in advance...
Modified by greyxjltd at 9:16 AM 4/15/2008

[elwesso]

so basically what happened is a bunch of fuel leaked out from the lower O ring, either from it being improperly installed or not the right injector installed. Plan on having a bent rod or broken rod, ive seen it happen a few times...

I doubt you bent a valve, but I suppose its possible.

Honestly, it sounds like you guys trashed the customers motor, and its going to be quick and easy to just buy a new motor from Japan, throw it in and you should be all set.. I bet there is some sort of internal engine damage, whatever that may be. I wouldnt waste any more technician time and get a new motor.

not the news you wanted to hear, but lack of Q45 specific experience often results in bad news.

[Q45tech]

We've seen it happen to dozens of shops over the years, not understanding sidefill injectors and interfearence engines.

Replacing Q injectors requires serious skill to avoid leaks and engine destruction.

The problem with domestic and JDM takeout 90-93 engines is they rarely have the plastic chain guides replaced and are accidents waiting to happen.

When we receive a hand selected JDM engine we replace chain guides and oil chain, knock sensors and harness, $300 worth of hoses, swap exhaust manifolds, clean egr and throttle body, reseal valve covers replace spark plugs all this takes..............all this takes 1-2 days on an engine stand and cost us ~~$1,000 in parts above engine price......................25 hours by an expert who changes Q engines monthly.

Your trainee has just spend $2,000 of your money and 25 hours minimum

Pull the engine and transmission out the bottom as one piece after removing exhaust and driveshaft [be sure to mark]. so alignment is maintained front and rear.

Good luck find someone who has done it don't rely on untrained or you will really suffer with engine swap.

[Q45tech]

Failure to disconnect remove fuel pump fuse and crank the rail dry, then remove input/output hoses and blow out residual fuel prior to pulling an injector will fill the compressed cyclinder [55cc] a leak will fill the cylinder and back up the runner and fill plenum quickly.

When Q starts the pump goes into high speed mode and can pump 255 l/hr or 71cc per SECOND.................hopefully you see 1.0 second can fill a compressed cylinder and 1/10 of the runner , 5 seconds and the plenum starts to fill and run down into other cylinders .............10 second and everything is full of gasoline.

If valves close on 555 cc and it tries to compress into 55 cc the rods bend!

The starter has more than enough torgue to bend rods and destroy bearings, break pistions and bend valves.

We have tried replacing rods and heads but it always takes more time than an engine swap and there is always something else weakened and the engines fail shortly thereafter from unseen damage.

[qship96]

Cheapest option may just be to pay customer book value for their car, as it will be less than obtaining and installing a junkyard motor and having to provide some type of warranty.

[maxnix]

then repair the car for yourself or sale. You might be amazed.

[qship96]

Or keep the ole Q as a training tool for your techs to tear apart and put back together over and over...... and become the neighborhood Infiniti specialists!!!!

[ScottJackson]

If you've got lots of fuel coming up into the intake, you've still got a BIG fuel leak. At this point, it'd be very unlikely the engine is still fine. Pull the fuel pump fuse and spark plugs. Crank the engine a bit. Do a compression test on all cylinders. If by some freak chance all are good, pull the intake manifold (not an easy job the first time around so if you doubt your abilities... well, good luck) and then pull up the complete intact fuel rails with injectors in them. Put the fuel pump fuse back in and turn the key on while watching the fuel injectors. You'll see the leaker(s). Pull those and replace the o-rings with the proper Infiniti ones. Don't use Napa or Autozone or whatever replacements as they're often not the right size and leak profusely.

If you've not pulled the intake and only done the #2 injector, you could just pull that one again as that's 99% sure the culprit. Put on the Infiniti O-rings and check it again... not by sealing it all up and trying to start it, but by leaving the plugs out and cranking it to see if fuel is coming out the #2 plug hole.

The engine is probably screwed, but it's worth checking just to be sure. At any rate, if it does turn out ok, don't charge the customer anything and chalk it up to a very lucky and cheap lesson.