77 Seville throttle body injection hose question

[MarkV]

So today I replaced the hoses on my Seville. Then I noticed the label “not for fuel injection” so I asked the local parts store where I got the hose and the man who has been running it for 50 years said I had the right hose. He said that the old Seville injection system used standard fuel hose. I checked the malleability of the original hose marked with gm labels alongside the new hose and the malleability was the same. So I guess gm used regular hose? The vent hose was also original and it was much more bendable even after 41 years than what I replaced it with. 

Edited October 29, 2018 by MarkV (see edit history)

[TerryB]

Should depend on the fuel pressure I would think.  The hose clamps you show in your picture would not be good for a high pressure system.

[MarkV]

5 minutes ago, TerryB said:

Should depend on the fuel pressure I would think.  The hose clamps you show in your picture would not be good for a high pressure system.

 

So this fuel hose has a psi of 50 the pressure at the injectors is 39 according to some research.

[TerryB]

Where is the fuel  pump?  In the tank or near the engine?  Normally you need a high pressure fitting on fuel injection fuel lines for safety.  Don’t want any leaks in the system that might lead to a fire.  If the fuel hoses you show are before the fuel pump you are ok from a pressure standpoint.

Edited October 29, 2018 by TerryB (see edit history)

[joe_padavano]

That car is NOT throttle body injection. TBI systems used only 15 psi and regular hose would be fine. Your PORT injection is higher pressure and needs EFI hose.

[MarkV]

So why was the original gm hose the same construction as the new one? 

[TerryB]

It’s the standard hose clamps that first got my attention for a system under pressure.  There are clamps made to do a better job of sealing high pressure hose than the ones you are using.  Even if you use the hose in your picture I would highly recommend using hose clamps for high pressure fuel lines.  Most auto parts stores have them in stock.

[TerryB]

50 PSI is sort of the cutoff between high pressure and regular fuel hose use.  I like some safety margin so I’d go with high pressure hose just to be safe.

[billorn]

I wouldnt use those clamps on a fuel injection system. They are not going to hold. What was there originally? Not just hoses clamped on. I bet GM had special clamps for the fuel injection system that snapped on or locked in place somehow. The metal fuel lines probably have special ends just for that purpose. You didnt cut them off to install those hoses, right? 

 

Use the hi pressure injection hose. Theres no way to know what GM was using in 1976 and how it compares to today and what the pressure ratings were. Comparing new hose to old doesnt tell you anything. 

 

Dont take chances use the right stuff. The piece of mind will be worth it and you will know it was done right so you dont ever have to worry about it again. Doing it right the first time is always cheaper then fixing the mistake later when something goes wrong.

[Bloo]

The hose shown in the pictures is not applicable to fuel injection of any sort, in 1976 or now.

 

This is a port fuel injection system. It is so called because the fuel injectors are in the ports. If it were a throttle body injection system, the pressure would probably be lower but you would STILL need fuel injection hose. 30 or 40 years ago some countermen may have been unaware. Today there is really no excuse.

 

The "fuel/pcv" hose in the picture is used for fuel line on old carbureted cars with mechanical fuel pumps or small electrics that don't have much pressure or volume. Even so, it is a miracle more of those cars didn't burn down.

 

One common place this type of hose was used was at the fuel filter or carburetor, where there would be one or two short pieces . The hose rots, and it doesn't take long. When it does, it develops tiny cracks along the reinforcement strings. Those turn into tiny streams of gas squirting out. Many times I opened the hood of some car that just rolled into the shop and found the top of engine drenched in gasoline, dripping around the valve covers and on to the exhaust. Fssss. Fssss. Fssss.......

 

A fuel pump in a fuel injected car is typically a rotary vane or roller type. It can empty a 15 gallon tank faster than you would believe if there is no restriction on the output. Imagine what would happen if a rotten hose broke in two or slid off. I hope I could get the seatbelt off fast enough.

 

In the 70s, 80s, and 90s fuel injection systems often had rubber hose under the hood. In the 70s, for instance, something like a Datsun 260z would have a 2 inch piece of hose on each injector, 2 or three more of them on the fuel regulator, and then 2 longer hoses connecting the engine to the car. This was fuel injection hose, and used fuel injection clamps, except maybe the connection at the injectors themselves. Those were sometimes crimped. The return line could be a lower grade of hose as there is no pressure, but it really shouldn't be lower grade. The cheap hose is prone to leak.

 

If there is any question about the age or condition of the hose, ALL of it needs to be replaced with fuel injection grade hose and clamps. Fuel injection clamps can be reused, at least if they are the right size for the outer diameter of the new hose. Years ago, the outer diameter of fuel injection hose varied a lot between brands, so more often than not all the clamps needed to be replaced too.

 

Worm-type clamps like the ones in the picture are not for use on a fuel injection system of any kind. The do not have a round cross section, and may leak. Also, most of them do not cover up the threads in the band, and extrude the rubber of the hose.

 

Real fuel injection clamps can be made many ways, out of round wire, out of a metal band with a "tower", and the most common kind, an overlapping metal band with a machine screw and a square nut. There are probably others. All of them have a much rounder clamping area than a worm clamp.

 

Most fuel injection clamps have a narrower range of size when compared to the worm clamps in the picture. It is important to get the right size. The tongue should slip under the band without walking up and bending, and the clamp should tighten firmly on the hose without running out of thread. Getting the clamps is much easier than it used to be. Today you can walk into an Oreilly or Autozone and buy a blister pack of assorted sizes.

 

The fuel injection hose itself, years ago, varied in construction. Some had a liner inside, some did not. Either way it was meant to last for ages without burning your car down. It also had a higher pressure rating (300psi IIRC), but the pressure rating wasn't the main thing. The main thing was that it wouldn't squirt gas all over the place like the hose used on carburetors.

 

American fuel injection hose today is sae-j-30r9, and it is lined. It is rated for gas, e-10, e-85, diesel, and some others.

 

Edited October 30, 2018 by Bloo (see edit history)

[joe_padavano]

8 hours ago, Bloo said:

This is a port fuel injection system. It is so called because the fuel injectors are in the ports. If it were a throttle body injection system, the pressure would probably be lower but you would STILL need fuel injection hose. 30 or 40 years ago some countermen may have been unaware. Today there is really no excuse.

 

The hose neither knows nor cares if the car is EFI or not. All it cares about is operating pressure.  GM's Throttle Body Injection systems operated at 15 PSI. "Standard" fuel hose is SAE 30R7, which is rated at 50 PSI for diameters up to 3/8" and 35 PSI over that. This is more than adequate for TBI systems at 15 PSI. 30R9 is rated at 180 PSI and 300 degrees. That's overkill for 15 PSI.

[billorn]

38 minutes ago, joe_padavano said:

 

The hose neither knows nor cares if the car is EFI or not. All it cares about is operating pressure.  GM's Throttle Body Injection systems operated at 15 PSI. "Standard" fuel hose is SAE 30R7, which is rated at 50 PSI for diameters up to 3/8" and 35 PSI over that. This is more than adequate for TBI systems at 15 PSI. 30R9 is rated at 180 PSI and 300 degrees. That's overkill for 15 PSI.

 

Overkill is my middle name!

[joe_padavano]

2 hours ago, billorn said:

 

Overkill is my middle name!

 

Until the added wall stiffness of the tube wall prevents the clamp from tightening properly on the barb fitting. Proper systems engineering seeks to ensure that ALL parts of a system are matched for an application. Selectively "upgrading" one part without properly accounting for it elsewhere is not necessarily a system upgrade.  How many disk brake conversion threads on this forum have pointed that out?

[Bloo]

5 hours ago, joe_padavano said:

The hose neither knows nor cares if the car is EFI or not. All it cares about is operating pressure.  GM's Throttle Body Injection systems operated at 15 PSI. "Standard" fuel hose is SAE 30R7, which is rated at 50 PSI for diameters up to 3/8" and 35 PSI over that. This is more than adequate for TBI systems at 15 PSI. 30R9 is rated at 180 PSI and 300 degrees. That's overkill for 15 PSI.

 

I think we are going to have to agree to disagree.....  Yes, the hose does not care what the application is, just as it does not care if it burns your car down. I don't want any of it on my car. When I was in the business cheap "fuel-emission" hose on any car with a "real" fuel pump was considered mickey-mouse and dangerous.

 

You are absolutely correct that 30r7 is the old standard (fuel-emission) hose, and not an earlier grade of fuel injection hose. I had that wrong, and now I can't remember what the old stuff was called. I have edited my post and removed 30r7.

 

On Continental's page for their 30r7 fuel emission hose it says:

 

"WARNING  Do not use for pressure lines or fuel injected engines."

 

http://www.continental-elite.com/Products/Automotive-Parts/Shop-Hose/Fuel-Hose/Fuel-Line-PCV-Emission-Control-Hose-SAE-30R7.html

 

 

 

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[joe_padavano]

2 hours ago, Bloo said:

On Continental's page for their 30r7 fuel emission hose it says:

 

"WARNING  Do not use for pressure lines or fuel injected engines."

 

 

I'm pretty sure that was written by corporate lawyers who have no clue as to the difference between a 15 PSI throttle body injection system, a 50 PSI port injection system, or a 3,000 PSI direct injection system.

 

Of course, this whole diversion is irrelevant to the OP's car, since that Seville is NOT a throttle body injection system.

[MarkV]

So I put on the hoses but I had to use the worm clamps. The fi ones had the screw either hitting the hose or the tank. I’m going to go tomorrow and see if there is another alternative or a slightly smaller size . FYI the original gm hoses had all worm clamps all over the car. 

Edited October 31, 2018 by MarkV (see edit history)

[TerryB]

Even as the discussion bounces around on technical fine points, the thing to remember is we are all trying to keep you from having the “hottest” car on the block!  The pics show the fuel line near the exhaust pipe where any leaks would not have a good outcome.

[joe_padavano]

Here is yet another example of why it is not a good idea to provide technical information when one does not fully understand the particular car being asked about (and I put myself in that group, by the way). A little research shows that the 1977 Seville has TWO electric fuel pumps, a low pressure boost pump in the tank and a high pressure pump on the frame rail.  The line that the OP has replaced is a LOW PRESSURE line - about 15 PSI - from the boost pump to the high pressure pump.  The fuel line and clamps he has used will be more than adequate for that application. This, by the way, is why the OP correctly pointed out that the old hoses were comparable to the new low pressure hose. Problem solved.

 

Edited October 31, 2018 by joe_padavano (see edit history)

[MarkV]

5 minutes ago, joe_padavano said:

Here is yet another example of why it is not a good idea to provide technical information when one does not fully understand the particular car being asked about (and I put myself in that group, by the way). A little research shows that the 1977 Seville has TWO electric fuel pumps, a low pressure boost pump in the tank and a high pressure pump on the frame rail.  The line that the OP has replaced is a LOW PRESSURE line - about 15 PSI - from the boost pump to the high pressure pump.  The fuel line and clamps he has used will be more than adequate for that application. This, by the way, is why the OP correctly pointed out that the old hoses were comparable to the new low pressure hose. Problem solved.

 

 

I thought it was low pressure because when it was leaking it was a mere drip drip drip when the car was on and the old hose was pretty far gone. So I’ve wasted a bunch of time taking off the other hose and replacing lol I’m still going to get those other clamps I don’t like the idea of hose clamps cutting into the hose by the muffler. Years ago on my first Seville I lost one of these lines and was stuck at the side of the road! Lol

[Pfeil]

2 hours ago, joe_padavano said:

Here is yet another example of why it is not a good idea to provide technical information when one does not fully understand the particular car being asked about (and I put myself in that group, by the way). A little research shows that the 1977 Seville has TWO electric fuel pumps, a low pressure boost pump in the tank and a high pressure pump on the frame rail.  The line that the OP has replaced is a LOW PRESSURE line - about 15 PSI - from the boost pump to the high pressure pump.  The fuel line and clamps he has used will be more than adequate for that application. This, by the way, is why the OP correctly pointed out that the old hoses were comparable to the new low pressure hose. Problem solved.

 

Joe, thanks for the information. Is this boost pump in the tank a priming pump for the high pressure pump? Or is it running all the time supplying fuel to the high pressure pump?

 Food for thought if the low pressure hose is leaking because of age, I would replace all the fuel hose high pressure as well.

 Also; I worked for a auto manufacturer for 30+ years and at the time when the refiners switched from methanol fuel additive to ethanol ( by government order) we recalled cars that were 20+ years old to replace our rubber high pressure FI hose ( HYPREX "D") because ethanol eats this and all other hose up.

[MarkV]

All done! There are these two hoses passenger side rear, one on the drivers side that I replaced with fi hose and two on the passenger side that look newer, I also replaced all hoses under the hood.

[Larry Schramm]

Looks like you may have gotten the correct hose clamps. 

 

Here is what comes in a search for fuel injection hose clamps.

[MarkV]

Yes it is fuel injection clamp they only sell this size in the assorted pack

[joe_padavano]

8 hours ago, MarkV said:

Yes it is fuel injection clamp they only sell this size in the assorted pack

 

I don't know who "they" are, but Summit Racing (as only one example) sells clamps for 3/8" ID hose for $3 for a set of four. Sets to fit 1/4" and 5/16" hose are similarly priced.

 

[54vicky]

I agree with Joe I have never had a problem buying those in the sizes he showed at any local auto supply.

[MarkV]

55 minutes ago, 54vicky said:

I agree with Joe I have never had a problem buying those in the sizes he showed at any local auto supply.

 

Autozone and oreilly only had 1/4 in a multi pack

[MarkV]

55 minutes ago, 54vicky said:

I agree with Joe I have never had a problem buying those in the sizes he showed at any local auto supply.

 

Autozone and oreilly only had 1/4 in a multi pack

[Bloo]

If they are trying to sell them by SAE sizes, that is a good part of the problem. They are metric and will be marked 11-13, 12-14, 13-15, etc. When you ordered those clamps from NAPA back in the 90s, there was no telling which ones would fall out of the box. It seemed random.

 

One shop I used to work for used to order them by the box of 10, usually 1/2" IIRC, and sort them out into their proper sizes. Sometimes several boxes needed to be ordered to get enough clamps of the same size to finish a job.

 

FI hose varied quite a bit in outer diameter then depending on the source, and the clamps don't cover much variation in size. The sizes that didn't fit would get probably get used up with a different brand of hose later on.

 

I was elated to see those clear-packaged assortments hanging on the wall in Autozone and Oreilly.