I am in desperate need of help finding a fuel leak in the engine compartment of my NA 300ZX. It only occurs when the temperature falls below about 32 degrees. It stops when the temp warms, or when the engine has time to fully warm up.

I have replaced the o-rings and hoses on the injectors and rails, and even after removing the intake I cannot find any leak.

The leak occurs before the engine is even started if the temp has fallen below freezing. I can smell the odor of raw gas before I even start the engine.

My car is in the shop now and the mechanic cannot find th leak. Any help is greatly appreciated! My email is visions2001@att.net

Thanks!
Johann

 

fairly common on the z32. the fuel hoses shrink when it gets cold. there are a few threads about this and the fix for it around here somewhere. i'm too lazy to do the search right now.

 

Thanks... I appreciate it. After I posted, I did a search, and found several posts on this... but my mechanic says he has done everything suggested, and I STILL have a leak. Either he's lying, he doesn't know what he's doing, or he just plain can't find the leak for whatever reason. So far I'm out about $1,000... and still have not fixed the problem. They want to give up.

 

i've got the same problem. really not worth spending any money on. you can can replace every single fuel hose yourself. look for fuel wash on those little fittings in the fuel line around the manifold and on the fuel rail. i know you changed the o-rings, but bad mechanics can mess that up. good ones can too even.

 

I reallt hope your kidding...let's do some basic math here. Engines get hot. Fuel + hot manifold = fire. I would say that's worth spending money on.


Johann....if you've paid some $1k to try to find a fuel then you need to have your head examined....so does your mechanic because he's clearly a retard. You both need to look a little harder....this is not rocket science. Look for the hose that is wet. It's probably the fuel that connects the two halves of the fuel rail....it's below the plenum.

 

The $1k was for parts and labor to replace the o-rings, hoses, fuel damper, and intake gaskets, along with a ruptured water hose under the plenum. I thought it was a little high myself, but he showed me the chart for the labor and it was inline with what he charged me.

After he said he could find no leaks, I said I wanted to look myself while the intake was still off. I could find no evidence of any leaks... just as he did not either. All the hoses and fittings were dry... and I could see no stains or evidence of any fuel anywhere. I am a fairly good mechanic myself ,and this has me stumped worse than anything I have ever come across in more than 40 years of working on my own cars. This is my only transportation and it's driving me to drink!

 

I've had a couple fuel leaks on my Z and they were a pain to find even thoguh they were right there when I found them. Do this, pop your hood, start your car and book your *** around to the front and check from teh fuel filter on teh right side and trace the fuel lines all the way left. I'll be very surprised if you don't find a drip or at least some wet somewhere near a hose clamp. And, even if you dont, grab a screw driver and tighten those buggers down.

Between the cold and the amount of vibrating the Z does under the hood you should strongly consider checking each hose clamp every 2 or 3 months.

If it's something more serious than that, well...I'd find a mechanic that specializes in Zs, the one you're going to now sounds like a jack off.

 

Tis the seasons! for fuel leaks.....

I bet it's the one towards the front of the plenum, the short one about 3 inches maybe.

 

i just noticed that my post was challenged. what i meant was that it wasn't worth paying a mechanic a lot for, because it's not that hard to do it yourself. a little money, yes it is worth. the money that he's paying the mechanic, no, it's not worth

 

KasbeKZ... Indeed your post could have been more clear, but simple reading comprehension should have helped 91zxtt understand what you were saying. Clearly you weren't saying "Don't worry about a fuel leak" as he portrays your post.

From the other thread: https://www.zdriver.com/forums/300zx-z32-performance-technical-47/turbos-27537/

From this thread:

Again, simple comprehension (AND ACTUALLY READING THE PREVIOUS POSTS) shows that Kasbek was trying to say that the OP didn't need to spend $1k when he could do the job himself.

AYE AYE AYE!!! Some people....

 

Many thanks for all the suggestions. I have the skills and tools to do the work, but I paid a mechanic to do it because I'm not up to doing the work myself... due to physical limitations, and because I only have an open carport to work in. I assume most of you guys are younger than me (I'm 57). I didn't mind working on my cars when I was younger... but it's not fun now that I have a bad back and arthritis.

 

some things will limit us, however no fuel leak is worth 1k you could have replaced the entire delivery system tank lines pump and rail for that price almost. labor rates are a bitch and get the best of us. however after that much money sunk into im sure almost only labor because the parts named are fairly inexpensive they should fix that leak no matter what it takes. it is probably a small leak and more than likely fumes right out of the line and leaves little to no traces as to where its from. now, silly question.... your SURE its coming from the engine bay?

 

The smell of fuel is strongest in the engine compartment... and once - when it was very cold - it actually leaked enough to drip on the concrete floor under the engine... that's why I believe it's somewhere in the engine bay.

It will not leak from about April all the way up until the first freeze... then, as soon as the temps start falling below freezing, it starts again. I first noticed it about 3 winters ago. It was very slight then. Last winter it got really bad, so I figured I better do something. I got out the invoice from the repairs and I just now noticed that he only listed the O-rings and fuel damper. I don't see any mention of hoses. If that's true, then that's probably why I still have a leak... since those hoses are more than likely original... and nearly 20 years old.

 

Many thanks to all who offered help with my fuel leak. After replacing the hoses on the rails and injectors, (which the mechanic should have done in the first place) the fuel leak is fixed.

I still have a problem though. The idle is rough... enough to feel it in the steering wheel... and even through the seat.

It's running the same way a carbureted engine would run if the idle mixture was out of tune... with a little uneven 'putting' at the exhaust. It's also noticeable at cruising speed... it's not smooth... almost like you can feel a slight miss or un-eveness.

My Z is a N/A '90 with automatic trans. It always ran great before the mechanic had his hands on it.

You guys have been a tremendous help so far... and any help with this problem would be greatly appreciated.

Johann B

 

Test the injectors. Resistance across the leads should be 10-14ohms.

 

how different does it sound? it sounds like you may even have a cylinder not firing (you probably know what this would sound like, but i've been surprised at the people that said it was just running rough and then it turned out to be running on 4 or 5 cylinders. including myself when i first got the car)

 

Are you running 91 octane or higher? I tried a tank of 87 once....ONCE...it ran terrible and I've not done it since. I also like ot run a bottle of injector cleaner and octane booster through every 4th tank of gas or so, despite wild public outcry here to specifically NOT do it, Ive honestly never had an issue with it.

If it's not something simple as that you may want to go get it tuned up, preferrably somewhere besides where you went for the fuel leak because those guys sound like they could find their asses with both hands and a map.

 

yeah i ran unleaded regular once, it idles like you describe, but also like Zlover said, test the injectors, could be one stuck open or something causing it to still fire but have a terrible burn so it makes it have a slight miss.

 

Yep... or the other way around... one that's hardly firing. I once had a customer with an injector that tested so high that my multimeter couldn't get a reading... it was still idling on all 6 though.

 

Once again, thanks to everyone for your suggestions. It's definitely not a dead miss like it would be if only firing on 5 cylinders. If any of you guys has ever had a carbureted engine with a bad idle mixture then that's the closest way I can describe it. It's not a dead miss, just running rough enough to be noticeable and aggravating.

It runs fine as long as you have your foot in it... only time it is rough is at idle, and at part throttle, like when you are in top gear and about 40 mph.

I only run premium fuel so that's not the problem. If it's an injector, I can't test them myself because I can't get to them... since they are under the plenum, and I can't tear all of the parts off to reach them... unless someone knows a way to do it without removing it.

From what I have learned, it could be one of several things... including the o2 sensors, or other things too. The thing is it ran smooth until that mechanic worked on it.

Thanks
Johann B

 

yes you can.... the injectors arent under the plenum they are inbetween the plenum runners. you cant remove them however without pulling the plenum, but for this check all you have to do is remove the electrical clip from the top of them then take an multimeter or something that will read Ohms (resistance) and measure what it is between the 2 terminals that will be exposed on the injector itself. its very easy. and if its running rough at idle AND half throttle i wouldnt be surprised if its a stuck open injector like i was suspecting especially since you say it runs fine at WOT. so check those first because a stuck open injector can cause damage to a motor. im proof of that. if they all read good then there are plenty of write-ups on TT.net to fix rough idles. bunch of sensors you can clean and re-adjust, works great

 

Thanks for the quick reply. I didn't know I could reach them without pulling the plenum, so I guess I can give it a shot and see what I find. I'll also have a look at TT.net and see what else I can find to diagnose the problem.

I'm very grateful for everyone's help on this... sales for my business has been way off this year... and I can't afford to pay a mechanic to do everything... especially when they don't even get it right.

Thanks again!
Johann B

 

I'm willing to bet one of your injectors is going to test really low on the resistance. It sounds like you're getting too much fuel, and that's why load on the engine helps (as Eric said).

Could also be a problem elsewhere in the fuel system (or possibly the ignition system even), but statistics says it's the injector.

And Eric, I can replace all 6 injectors without removing the plenum. All it takes is the right tools.

 

well la-dee-da mister fancy tools. I tried to pull mine with the plenum on, and it wasn't happening.

 

You need bent-nose vice grips to get the screws and hose pliers to pull the injectors out of the rail. And practice makes perfect.

Btw, I still prefer to remove the plenum to do it... but since a plenum pull on my Z takes a whopping 10 minutes compared to the 4 hour task that is a stock VG30DETT, the same may no apply to most people. Which option I choose ultimately depends on whether or not I feel like replacing the plenum gasket (which must be replaced with each plenum pull).

Also, to simplify the process, you can replace all the damn phillips screws (NO screw on an engine should EVER be phillips) with hex-head... then you can probably use a bending (swivel-head) wrench to get them... or possibly a 1/4" socket if it's small enough. I replaced them all with hex, but I haven't had to replace any injectors since.