88_N/A_GXL

iTrader: (3)

Hello, I have been searching this forum and haven't had any luck finding the info, so I just finished getting my post count to see if somebody could help me.

I have been looking at an '88 na GXL that my grandfather has for about 4 years now and he's finally decided that I could buy it off him, only problem is that it has a rusted fuel line that snapped when I was trying to replace the starter to get it running and accidentally bump the line causing it to snap, it was rusted because he lives way out in the country and has probably 8-10 miles of gravel road to get to paved goodness.

Well, I was just wondering if somebody knew a place that sells the line, preferably a stock line as I don't have much money, or if somebody had a line laying around after an upgrade that they would be willing to sell. If not, could somebody tell me what all would be involved in replacing the whole line and everything to something aftermarket.

Many many thanks in advance as this would be my first car, and for $3500 with less than 50k on body and motor, it sounds like a nice deal.

Evil Aviator

Just borrow, rent, or buy tubing tools and buy a spool of new fuel line. I think it is 5/16", but you should check and make sure. Example:
http://www.summitracing.com/parts/CMB-03-0080/

Yes, $3,500 sounds like a good deal, but it's not a steal. The blue book value of that car is probably around $4,000.

jjcobm

iTrader: (18)

Make sure to get F.I (fuel injection) rated line, alot of parts store employees don't seem to know the difference between 10psi and 40+psi and will try to sell you the low pressure lines. If you are replacing hard-lines only, ignore my comment.

clokker

iTrader: (2)

Wait a minute...
A low mileage car for $3500 that's so rusty underneath that a hard line breaks just by incidental contact?
What does the rest of the underside look like and how's the suspension?

$3500 is on the higher end of NA prices (especially since it's not a desirable model like the GTUs)
and if it's rusty below, the price should come down.

88_N/A_GXL

iTrader: (3)

I might be a little off on the miles but if memory serves me right it was right around 50k. As far as I could tell when I was putting the starter back on the rest of the underside was in great condition, but then again that was also about two years ago, and as it is currently in a nice steel barn that has 8ft+ of snow covering the doors and such, I cannot get there to snap a picture and post it here.

And about the suspension, I was more trying to get the 7 started than look at the suspension since it hadn't, at that time, been driven in probably 4-6 months. But, whenever the snow decides to clear enough up I will be going out there and taking plenty of pictures, hopefully with the old man's nice dslr, and only after I wash it down a little.

Evil Aviator, if I was to buy that kit how would I go about changing the old lines?

Evil Aviator

The fuel lines tend to corrode with age, while the underbody is usually pretty decent as long as the car was not driven in a salt water or salted road environment.

Sorry, but my friend replaced the lines on my RX-7s for me, so I'm not sure about the specifics or typical pitfalls of replacing the fuel lines. Hopefully one of the mechanics on this forum can help you out with that. I may replace the lines on my convertible in a few months, so I may find out myself pretty soon, lol.

clokker

iTrader: (2)

What is it that selectively targets fuel lines and ignores the rest of the undercarriage?
At the very least, I'd have to wonder about the hard brake lines as well.

Evil Aviator

My guess is moisture from the fuel. The brake lines are not usually as bad unless the car has been driven on snowy salted roads. However, you raise a good point that the OP should check the brake lines while he is at it.

88_N/A_GXL

iTrader: (3)

I shall check those lines too when I get to the car. But, he hasn't said anything about brake problems. That leads me to believe that they may be rubber lines possibly? At least where they are exposed to the gravel dust and whatnot.

I don't think he ever did drive it in the snow, probably figured he'd get stuck, he always had an international scout for that.

Edit: Would it be possible for you to ask your friend how he changed them and what all was involved? If not possible to ask, I could wait for a mechanic on the forum to help.

clokker

iTrader: (2)

Changing out the hard fuel lines is relatively easy...assuming the underside of the car isn't rusty and hasn't been undercoated.
The fuel lines and the brake line share common retaining brackets with nylon keepers.
Each bracket is held with one 6mm bolt and the plastic keepers are split, so removing them is quite simple and intuitive.

Once the car is in the air, you'll see exactly what has to happen.
Probably the hardest part will be separating the old, dried out soft lines from the hard line.
Up front it's an easy decision, just cut them off and replace the soft line.
In back it's a different story, I'd just go ahead and drop the fuel tank and replace all the soft lines there as well.
Since the car has been sitting, now would be the time to check the interior of the tank and the fuel pump sock- clean/replace as necessary.
Install new fuel filter.

You've just spent a day (assuming the tank didn't go out for cleaning) and your fuel storage/delivery system is good as new and you won't have to worry about it again.

88_N/A_GXL

iTrader: (3)

Could I just rip out all soft and hard lines and replace them with just a steel braided line like this? Or is my thinking off and I would need a soft line somewhere?

Could this be done with a pair of ramps or would I need to lift the whole car up?

SPiN Racing

Hey all,

I replaced Evil Aviator's fuel system.

Clockker is right.. they are really simple to remove.. the hard lines that is. IIRC its a 10mm bolt that holds the bracket in. The bracket holds brake and fuel lines in it, and the fuel line snaps into it, as do the brake lines.

As far as why they failed... there is a curve in the hardline that runs up the firewall, near the frame rail, and if he drives on a gravel road.. and has for a long time.. its entirely plausible that the lines have been beaten mercilessly by rocks etc.
Also if it was cold as crap there the lines will be brittle, even though they are hard lines, and could snap off from the temperature, if also weakened by impacts.
If it was driven with salt on the roads on and off.. its entirely plausible the lines have rusted over the years and thinned.

As far as using soft lines.. Not a good idea. There are several reasons not to.

They Sag. Even if you were to hook them into the brackets somehow.. they will sag. Sag=snag.

THe next problem you will run into.. is diameter. The wall thickness on the hard lines is minimal, so the inside diameter allows for a large volume of fuel to travel. If you were using soft braided lines.. the braid, and thick rubber line will make it so that the inside diameter would be minimal and you would run into fuel starvation issues at higher RPM, if not just above idle.

For some of the cars I have done, that needed upgraded lines.. like FBs.. that are carburated. I have gone with 1/2" hardlines. Aluminum. THe biggest problem as pressure increases is the end of the line. A rubber line will pop off on a fuel injected engine from the higher pressure cause the line doesnt have a bead in it.

Solution..
Tube Nut http://www.summitracing.com/parts/EAR-981808ERL/
Tube Nut SLEEVE http://www.summitracing.com/parts/EAR-981908ERL/
-8AN to barb fitting http://www.summitracing.com/parts/SUM-220757/

Put those on either end, and hook them into the high pressure braided lines you have going to and from the fuel tank, and the engine.

SO you buy your aluminum fuel tubing... in 1/2 inch. THen you buy two of each of those above. And you buy/rent a flaring tool.
Remove the factory hard line.. and bend aluminum replacement to shape, cut to length.
SLip on the nut, then the sleeve properly.. and flare the end of the tube. Repeat on other end.
SNap it into the original plastic holders. YOu may need to massage the plastic with a round file to fit inside.
Then you slip on rubber lines on the ends and connect it all back up. Voila.


make sure to check your barke lines and be careful not to break them also.

The Shaolin

iTrader: (5)

Yeah, I am also replacing all the fuel hard lines....I went with steel lines...massive, massive pita to bend!

clokker

iTrader: (2)

Sorry to be a pedant but...it's a 6mm bolt- which has a 10mm head.
Metric bolts are designated by thread size, not head size.

OK, carry on.

farberio

iTrader: (7)

Mazda sells the lines, but when I bought mine it was one of the last two in the north American continent. Its also very expensive.

Evil Aviator

Thanks!

Also, here is a basic rule of thumb for fuel line sizing from A. Graham Bell:
1/4" OD - 165bhp EFI, 110bhp Carb
5/16" OD - 300bhp EFI, 200bhp Carb
3/8" OD - 500bhp EFI, 335bhp Carb
1/2" OD - 1000bhp EFI, 675bhp Carb

The Aeromotive catalog also has a nice "Power Planner" section for recommending fuel system components.

88_N/A_GXL

iTrader: (3)

Thanks spin racing, very informative. I've decided to reconsider hard lines. And, yes it snapped right near a bend in the pipe near the wheel.

Now, planning out future upgrades, and going with evil aviator's little chart would this kit have all the necessary items to change the line? Or would I need those parts you mentioned spin racing?

Edit: Actually I'm gonna have a look around and find an aluminum kit, just so it won't rust. But, would it be possible to not have any soft lines, or less soft lines than current?

The Shaolin

iTrader: (5)

You could replace the soft lines with braided, if you really wanted to. The system definitely needs some flex in it.

Rick Castro

I want to do this too, my lines are nasty looking, but they haven't broken or anything yet. There's a bracket for the lines above the differential area (up in there, follow from the panel in the back hatch) that's kind of a pain, but that's all. I went ahead and got the summit racing set with the tools and stuff. It works well enough to do the job, just practice making your flares before you get started. My only concern, is the the metal line itself. It's not consistent as far as wall thickness throughout the tubing, at some points it looks almost paper thin. Is that going to be okay? Beats a rust hole i guess. Anyway good luck with your replacement!

Evil Aviator

Warning, you are on the edge of the slippery slope to spending a ton of money on your fuel system, lol. For example, you currently plan on installing larger fuel lines for future upgrades. You now realize that you will also want some nice braided lines large enough to match the hard lines. Then you will realize that the large lines will not hook up to the smaller fuel pump outlet, filter, and fuel rail, and the stock fuel pump may have difficulty pressurizing that big line, so you will then want to upgrade the fuel pump, filter, and fuel pressure regulator. You are looking about spending about $1,000 for everything if you buy quality parts, which may be a bit much considering that simply installing 5/16" lines would work just fine for your current engine, a tricked-out NA street engine, or a mildly-modified TII engine.

If you want to go the fancy route, here is an example of an upgraded fuel system, although you wouldn't need any pulsation dampers as long as you stick with a good Aeromotive or SX brand fuel pressure regulator. Also, the return line isn't hooked up yet - it would attach to the barb at the bottom of the fuel pressure regulator.
https://www.rx7club.com/single-turbo-rx-7s-23/parallel-fuel-system-pulsation-dampers-check-out-824342/

Diagram of a typical upgraded parallel fuel line setup on an FC RX-7 using the stock fuel rails:
http://fc3spro.com/TECH/MODS/FUEL/pararail.jpg

No, you will want flexible lines between the firewall and the engine to compensate for the engine shaking, and probably also a foot or so at the fuel pump to make it easier to install and reinstall.

88_N/A_GXL

iTrader: (3)

What is the difference between fuel injection and carbs on rotarys? I guess I'm just too used to a piston motor to understand the exact differences. Or is my thinking off and it's basically the same?

Edit: So the 5/16" should fit and be fine and all for now and up to a mild tune? But still wondering if I would need the parts spin racing mentioned.

Evil Aviator

Fuel injection is under high pressure, while carburetors are low-pressure or suction. If you have a suction tube for an EFI fuel pump then that would fall under the "carb" guidance that I listed, and therefore you may have noticed that the input port is larger than the output port on most aftermarket EFI fuel pumps. The list I posted is actually for piston engines, but it still pretty much applies to rotary engines. The only difference is that rotary engines tend to have a slightly worse BSFC (fuel flow vs. horsepower), so they usually need just a bit more fuel to make the same horsepower. However, the rule of thumb that I posted is still generic enough to make up for this slight difference. This forum tends to be much more technical than other automotive forums, so that is probably why this is new to you.

It is unlikely that your NA engine would make over 220bhp in a streetable configuration, so the 5/16" lines will work fine for that. You could also run a second 5/16" line later on if needed. Some people claim to run their 500hp engines on the stock fuel lines, but I would imagine that is only for drag cars as the strain on the fuel pump would be pretty fierce for any application that needed to run at that level for more than a few seconds.

The tools and parts required to fabricate your lines will depend on how you go about it, but I can't really comment further on that because my background is in engineering and analysis as opposed to maintenance and fabrication, and I don't have any personal experience with any of the stock fuel components aft of the fuel filter. SPiN Racing was a fabricator on the #1 Porsche GT racing team, so I have him help me out with things like that.

88_N/A_GXL

iTrader: (3)

Okay, thanks. And 220bhp I'm guessing would feel like a lot for two reasons, I'm used to a lil 100hp dohc saturn and I know the rotary power comes a little smoother than a piston motor, that's just common sense. I guess I will just have to wait and see what SPiN says about those parts.

Evil Aviator

Forget all that technicall BS for a minute and lets look at some real comparisons:

Your current car will go 0-60mph in about 8.0 seconds with a good stock engine, a stock 182bhp S4 TII is rated by Mazda at 6.7 seconds, while an automotive magazine recorded a stock 200bhp S5 TII at 6.3 seconds. With 220bhp you are looking at about 5.8-6.0 seconds, less if you remove some weight.

Therefore, 220bhp would feel like a lot in your car because it would out-accelerate James Bond (63 Aston Martin DB5), Magnum P.I. (80 Ferrari 308 GTS), Smoky and the Bandit (77 Pontiac Trans Am 6.6L), James Dean (55 Porsche 550 Spyder), and Knight Rider (82 Pontiac Trans Am 5.0L).

88_N/A_GXL

iTrader: (3)

Yippie!! Lol, I always wanted to race 007, and Kitt. Maybe I'll just go bootleg some beer from Texarkana, Texas to Georgia.

Back on topic, It's been warming up a little bit the past day or so, I may be able to get out there and snap some pictures and show everybody what I'm working with soon.