I am helping a friend get his fuel injected 62 back on the road. It starts and runs, but has a fuel leak from the fuel meter area, seen as a small drip off of the bottom of the fuel meter, The engine is not correct but the FI unit appears to be the original 7017360 unit, which was used for most of 62. The leak appears to be coming from where the main fuel line from the fuel meter to the spider (aka the "nozzle fuel distribution line") is connected to the fuel meter. The small-diameter copper line has a shoulder built into it close to the end and the O-ring goes up against it on the fuel meter side. That end is inserted into the fuel meter and tightened with a retaining slip nut on the line upstream of the shoulder. We tried replacing the existing O-ring with a generic O-ring that appeared to be the right size, but that just made the leak worse. I am looking to replace that O-ring with the correct part, but so far I have only found it as part of a complete rebuild kit for $200-$300.

I am hoping some of the 57-65 FI experts on the Forum can direct me to where to source that O-ring, or at least provide specs for ID and OD and material of construction to source it from a generic supplier. I found that Zip Corvette sells an O-ring set for the injector nozzles, but I have no idea if those would be the right size.

Thanks in advance,
Gary

 

Any auto parts store can sell you a single fuel-rated o-ring with 3/16 ID which should work.

If the leak worsened when you attempted to replace it, one possibility is there is a bit of o-ring debris down in the hole where that tube/o-ring go. Get a small pick and a bright light and make sure the threaded hole is free of debris.

Another possibility is that the new o-ring got cut upon installation. Any time you install an o-ring, first slather it with wheel bearing grease so it glides into position. That's the best way I know of to minimize the risk of cutting the o-ring.

Good luck.

 

Responding to my own post, I just remembered sumpthin'. Years ago some anti-siphon solenoid valve kits included a reproduction copper tube with a flange that was TOO SMALL to effectively capture and seal the o-ring.

If the flange-end copper tube for your FI is an original GM piece you are OK. But if it's a repop, check the diameter of that flange. It needs to be the same as the diameter of the o-ring, never smaller.

 

Thanks for your replies, Jim. The replacement O-ring we tried was from a parts house carded batch of O-rings that were reportedly fuel resistant, and we just picked the one the seemed closest to the size of the one that came out. The old one was of unknown origin. There was no residue remaining in the opening that we could see with a bright flashlight.

While I would normally lube an O-ring before installing it, the 62 Rochester Fuel Injection manual says "Install the "O" ring absolutely dry to prevent the ring from rolling over the shoulder on the nozzle distribution line." We hesitated to go dry, but went with the manual guidance. The replacement O-ring we tried was apparently damaged by my tightening it too tight. The manual says to start by getting the retaining nut finger tight, but there was enough friction and difficulty getting arthritic fingers onto the retaining nut that it took a 1/2-inch open end wrench to make up the threads, and that went from being an easy turn to suddenly stopping. The new-O-ring had a part of it pinched off on the ID, possibly by partially rolling over the shoulder as that last increment (~1/12th of a turn) went tight.

We were working in my friend's garage 35 miles from my home, and I did not have my calipers or micrometer with me to get dimensions. Your idea about the shoulder on the line not being tall enough could be right. I have no idea about whether that line is original or replacement. I'll need to bring my measurement tools next time I go out to his house.

I am hoping to find a source of an O-ring of known correct materials of construction, ID, OD, section width, and durometer hardness for this specific 200 psig max, E10 gasoline application. If I need to design the O-ring myself, I'm a Chemical Engineer and I think Buna-N/Nitrile/NBR is an appropriate material, but I'll need to ask my Mechanical Engineer friends for help on the details of the O-ring dimension and durometer specs to meet that pressure rating.

Thanks again,
Gary

 

I'm impressed that you've taken the time to read the shop manual for that 7360 unit and have even noticed that obscure warning to install the o-ring dry. Being an engineer, you are at risk of over-thinking this problem so let me try to short circuit that before it happens. (I'm also an engineer so I recognize the signs. )

Some points:

1. I've got FI units here which work just fine with Buna-N o-rings. However, o-rings made from Viton are preferred for their even greater tolerance of ethanol than Buna-N. If you see a brown o-ring, it's Viton. Black o-rings could be either material.

2. The actual area of the o-ring which is exposed to fuel pressure is exceedingly small. So even at 200 PSI, the developed force is also exceedingly small. Any o-ring made from a fuel rated material which has 3/16 ID and an OD the diameter of the flange on a GM copper fuel tube will withstand the developed force.

3. By design, the underside of the hex of the tube nut will bottom out against the side of the fuel meter. In doing so it provides the right amount of o-ring crush. The point being that you can't over tighten that tube nut unless you are stripping threads.

4. I've never understood the recommendation to install the o-rings dry and I've never heeded it either. I always slather every o-ring with wheel bearing grease. I have yet to have one roll over the flange on the fuel tube.

5. I'll measure an original GM fuel tube flange tomorrow so you'll have a way to assess the fuel tube you're working with. You may need to remind me.... I tend to forget.

I hope this helps and keeps you from re-inventing the wheel.

 

Thanks Jim. Words of advice from a voice of experience! I am a vintage Carter AFB/Holley 4150/Rochester Q-jet carburetor guy so this is new territory for me. I always strive to learn, which includes reading the manuals and also getting advice from those more experienced than me.

While I'm at it, I am also trying to talk the owner of this car into replacing the hokey manual choke cable to control the "fuel enrichment valve" that someone put on this car many years ago with the correct choke cover with a thermostatic coil and electric heat element. Would you agree this is worthwhile to restore to original operation?

Gary

 

I may have one in this pile of FI parts leftover from a few years ago. I'll check later. But I too may need a ping reminder as Jim said.

 

Here is a picture which shows the difference between the fuel tube flange on a poorly made reproduction tube (left) vs. that on an original tube (right). The flange on the repro was too small to keep the o-ring from rolling over and a leak was the result:



I still intend to measure the flange of an original tube later today.

 

Thanks Jim and Rich. Based on my recollection of how the end of the line on my friend's car looked, it probably has the original line like the one on the right in the photo. It would be good to measure the flange to confirm that, though. Also, based on the photo above it looks like the reproduction retaining nut has a smaller diameter head than the original. The one I am dealing with takes a 1/2-inch wrench.

Thanks,
Gary

 

1/2 inch is the correct wrenching for that tube nut.

 

I found these in my box of stuff. Are these the ones?

OD apx 0.310"


ID apx 0.180"

 

Those are the ones, Rich. Any autoparts store will have fuel rated o-rings in that size.

 

Ok. I thought so. Those are extras that came in the kit from John D a few years ago when i did that 61 unit you and JD helped me with. Memory jog Jim... recall the FM leak I had after break-in? It was the FM body and I had to pull it apart and resurface the pump mating surface per your guidance how to do it. You were my Obi-Wan-Canobi...

Would the auto parts shops have the brown Viton? My Napa doesn't.

Gary, if for some reason you can't find them locally let me know and I'll drop the 2 I have here in the mail to you.

 

Thanks Rich for digging those out and making the measurements! I'll see what I can find in Viton either locally or online (e.g., McMaster-Carr). I'll try not to impose on you any more than I have already.

I'm not 100% certain that the original leak, before our failed attempt at replacing the o-ring, was actually originated there. If we get a successful o-ring replacement but still have a leak dripping along the bottom of the FM I may need to reach out to you and Jim again about your pump body leak repair.

Best regards,
Gary

 

Rich, all of the fuel-rated o-rings at my FLAPS are black, which could be Buna-N or Viton. I don't know how to tell the difference.

The key point is that they are fuel-rated and that they do withstand E10.

Thanks for the kind words.

 

Yes hopefully it's the o-ring seal. In my case it was the FM body.

Yes I'm not really up on o-ring technology either. ​

Kind words aren't enough. Jim you were instrumental helping me diagnose and repair it. I'll be forever indebted. Here's where I found the smoking gun that you taught me about. I found a few old videos I forgot I had that I guess I never posted on my YT channel. Not to scare Gary, just for fun.... RIch.


These were the Before and After photos.


Area at 10 o'clock was high.



Here you can see how the casting pulled out on both sides and left gaps at 12 and 6 o'clock.



Had to remove a substantial amout of material to get it flat.


Flat again.


Terrible audio but the car sounded awesome close up. 283 Duntov solid lifter cam 315HP with Off-Road exhaust.


A few days later I trailered it to a friends shop to run it up on a chassis dyno to mainly put some miles on it as it wasn't registered. This was inside during one of several runs. Nice car, I restored it for a friend, gratis.




...

 

Clean off all fuel moisture and observe where you first spot any fuel weeping.

There are four areas where you could see fuel:

1. At the exit point for fuel going to the spider.
2. Around the spill valve cover
3. At the pump-fuel bowl mating surface
4. At the pump weep hole on the bottom of the pump.

Additionally, sand cast fuel meters and '58 4900 fuel meters have a gasketed cover on the inboard vertical wall which can also be a source of a leak, altho an unlikely one. Your 7360 does not have this. I mention it only for the sake of thoroughness.

#1 and #2 above can almost certainly be resolved by installing new o-rings.

#3 is due to the fuel meter gasket surface warping due to continuous stress from the pump mounting screws. The right way to address a leak there is to lap that gasket surface back to flat on a piece of sandpaper on a surface plate. Note, however, that doing that procedure creates debris in the fuel path which necessitates further disassembly of the fuel meter to clear it out.

#4 is symptomatic of a worn pump shaft seal and almost certainly a worn pump shaft. A total pump rebuild is the right way to address this. Maddingly, R&R-ing the pump, even one which was NOT leaking at the fuel meter gasket surface will nearly always result in a leak at that surface after re-installing the pump. What this means is that you need to preemptively address leak #3 any time you R&R the pump for a rebuild.

 

Excellent pics, Rich. I had forgotten about that exercise you went through. Your pictures perfectly illustrate what I just described.

 

Many thanks again, guys! I copied Jim's list of four potential leak locations and Rich's photos into a Word file for future reference as needed. If the leak ends up being at the pump housing flange I'm not convinced I want to get that far into someone else's fuel injection system (although I would have no qualms if it were my own car). My cars are carbureted.

Best regards,
Gary