Recurring fuel leaks (not a Pontiac)
 

I'm having recurring fuel leaks at various locations feeding the fuel rail and injectors on a 1980 Datsun.
The leaks always occur at a hose clamp and can always be stopped by tightening the clamp a bit.

The locations vary from injector to injector, to the output of the fuel filter, the input of the rail, etc.

No real pattern to it. I find one of these leaks probably 5 to 10% of the time that I run the car. It can go for weeks without any leaks and suddenly somewhere I will find one.
I have swapped between injector hose clamps and worm screw type clamps.
I now have to check this car every single time I start it for fear that I will have a leak possibly leading to a fire.
The hoses and clamps are all new, replaced while I was doing other work on the car and I never had this problem before that.
It's standard parts store injector hose.
Any ideas?

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Greg, if your using worm gear clamps, you might try another type of clamp. although worm gear clamps are used in many automotive applications, they aren't the best type of clamps.

These are clamps used on fuel injection hoses other than worm drive styles:

Also the real fuel injection hose is fairly expensive, last time I bought any it was about $8 a foot, probably twice that now.

https://www.google.com/search?q=the+...hrome&ie=UTF-8

The Nissan/Datsuns are pretty notorious for leaks on the fuel rails and injector plumbing. I had a neighbor back in the 90s that had one that would leak after shutting it down, he'd get a definite fuel odor in the car, and after looking at it myself, it had leaks in the fuel rail area. Not severe, but you could see the damp areas after it was shut down for a few minutes.

We had a similar 'house plumbing' issue. Had a drain pipe that was leaking, the only way to make the connection was with a 'fernco' clamp. I figured the band clamp wasnt doing its job so I added another. Come to find out the pipe fitting itself had a hairline crack which was causing the leak.

I would check the lines. My guess is that the clamp is doing its job but the leak is elsewhere.

The locations randomly occur at different places but always after the fender mounted filter and before the injector itself. Thats 12 clamps just for the injectors, not to mention several other locations.
The consistent thing is that it has always occurred at a clamp and can always be stopped by a quarter turn or so to tighten it.
I actually started out with the fuel injector type clamps. I went to worm gear clamps in desperation and thought they had solved the problem for a while but I still get leaks.
I can always spot exactly where the fuel is coming out so it's not like some mysterious crack somewhere. It's always a very thin, hair thin, stream shooting from the end of the hose where the clamp is. It's literally coming from between the outer surface of the fuel rail and inner surface of the rubber fuel hose where the clamp is. A quarter to 1/2 turn of a screw will always stop it and it's good for weeks, possibly months.

That doesn't mean that the next week will be in the same place though. It will be at another injector, or the inlet to the fuel rail the exit from the fuel rail or even on the engine side of the filter.
I guess the simplest way to describe it is that it's as if the clamps are loosening but they are not. Each time I tighten it I'm getting closer to bottoming out the adjustment.
Its a weird problem that l've actually been fighting for quite a while.

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The only thing I can think to do at this point is to start documenting each time it does it to see if there's any kind of pattern or repetition of the failure at certain clamps even though every single one of them has been changed over the last year or so.
If I have the space I'm thinking about putting two clamps on each one. Sounds stupid but I don't know what else to do at this point.
Here's another thing that sounds stupid... Is it possible that if the injectors were slightly stopped up it could cause a back pressure situation? Doesn't seem likely since there is a return line.
I still have 3 or 4 of the injector type clamps in place and you can see that one has been tightened enough over time to be near the end of it's travel.https://uploads.tapatalk-cdn.com/202...8a6487fcce.jpghttps://uploads.tapatalk-cdn.com/202...903c7d2861.jpg
https://uploads.tapatalk-cdn.com/202...b4fac16815.jpg

I would follow Sirrotica's advise Greg. There is better quality hose for that, the worm clamps are temporary in my mind. The other type hose clamp you have on there is correct but needs to be tightened until the ends butt together, and that should also compress the hose properly.

John

I would try using a smaller worm clamp. If they are too large for the hose they don’t clamp evenly and will leak under where the worm is as it is fairly flat there. I always use gear clamps that just fit when fully open

I have an entire set of the other type of clamp as that was what I originally used. I did not know that they were supposed to be tightened until the ends butted together so thanks for that info.
Now, you say that there is better hose available? Do you have a part number or link?
The stuff I have on there is the high pressure fuel injection hose. I made sure of that.

Thank you as well 66beaumont. I'll keep that in mind.

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No Greg, I don't have any part numbers or anything. I was just going by the appearance of the hose. The hose that I have used in the past has printing on it saying hi press fuel or something and has a smoother outer surface.
Yes, the clamps should butt together when the proper size hose and clamps are used, and final torque- tightening keeps it all good.

John

Ok, probably buy new clamps and redo as far as those go.
The hose does have that script, you just don't see it on those photos. Here it is-https://uploads.tapatalk-cdn.com/202...a72c18afa0.jpg

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You guys made me remember something that might be the whole problem. I remember being unable to find enough of the injector hose clamps in the size I was looking for so I went up one size. I'll bet they are the ones that are leaking.
I was looking for 11-13mm and wound up using a few 13-15mm clamps. I just looked at one of my original clamps which I kept and though it has no size printed on it, it definitely matches the circumference of the smaller of the two sizes that I bought.
I know for a fact that the most recent leak was from a 13-15mm clamp.
That's why I come here when I have beat my head against the wall long enough. Sometimes just discussing it with other people can jar the answer loose. Not saying I know for sure but I'm thinking that that is a real possibility.

I'm always afraid of a fuel fire in my vehicles. Dont take this the wrong way Greg I'd spend the money for the best hose(china ugh) I could get. I carry a minimum of 2 extinguishers. Norwalk I have 4. I've changed hoses on my classics at least once and I ck for cracks by flexing what I can touch easily.

I lost my first 68 GTO to a fuel leak fire so you're preaching to the choir there.
So, if that's not good hose what is?
I specifically bought fuel injection hose at the auto parts store because I knew that that's what I needed...and by the way, it's never leaked from the rubber hoses but always past the clamps.


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Greg, just perusing some of the Z car forums, the fuel line leaks are fairly common on those cars like I previously posted.

They say that when they sit and the ambient air temp goes down they leak at the connections. Not sure how cold it's been in the south lately, but up here in Ohio we've had colder than normal temps for this time of year.

It actually said in one post that years ago Datsun had recalled some years of Zs for fuel leaks due to faulty design.

The forum members basically said the minor leaks come with the territory, and frequent vigilance to snug the clamps up is part of the upkeep of these cars.

One other thing is some of those worm drive clamps in your pics are overtightened to the point of deforming the band. They will fail when they deform like some of yours are. I'd be looking at some of the other style clamps to replace those worm drive clamps.

I used to work at a Datsun dealer long ago, and I was never impressed with using fuel line hose, and clamps under the hood for routing fuel to the injectors. I prefer having flared fittings on fuel lines, just my personal preference.

One other thing is a pressure test on the system to make sure the regulator isn't set too high and also causing the leaks.

The old Datsuns are terrible for fuel leaks at outlined above. Common leak point also is between the inner and outer shell of the injectors themselves. (metal to plastic). But it seems you have isolated the problem to the hoses and clamps. You clearly have 5/16" hose you are using. While it is roughly equivalent to 8 mm, possibly this Datsun is extra annoying and needs the more correct 8MM hose it came with. Just a thought. The factory looking clamps, non-serrated are the best clamp type you can use. It looks like the worm screw clamps are cutting into the outer jacket and bulging the hoses some where you are using them. Great cars other than rust and fuel leaks. Those are definitely the trouble spots.

I've had three of these over the last 40 years. Never had a fuel leak in any of them including this one until I did a complete removal of the fuel rail and replaced all the hoses and clamps.
I'm going to go out today and grab about 20 of the 11-13 clamps and replace them all.
It did occur to me that maybe I need a metric size hose but it just doesn't seem logical. In fact, I'm sure that I will have to cut them off if I decide to replace them. They're very tight. However, you never can tell about these things. They'll surprise you sometimes.
By the way, one more strange thing about it is that the leaks always occur on the first startup after it's been sitting for at least a few days. I have never, ever had one of these leaks occur when I'm out and about in it once I've tightened that clamp screw on the initial startup.
Once I have parked it for the day and restart it maybe a week or two later, there is about a 20% chance that one of them will be leaking.

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