164 Firewall Fuel Hose Replacement - Alfa Romeo Bulletin Board & Forums
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post #1 of 8 (permalink) Old 09-21-2015, 08:14 PM Thread Starter
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164 Firewall Fuel Hose Replacement

The following info is available by PDF download at the bottom of this post.


This guide shows how to easily replace the two front fuel hoses that connect the underbody steel fuel lines to the upper engine compartment steel fuel lines. There are two lines, a feed line and a return line. The feed line is pressurized to about 45 psi, while the return line is under no significant pressure.

Failure symptoms of these rubber fuel lines (and any in the engine compartment), are outright leaks onto the ground, but more likely seepage with the smell of raw fuel being drawn into the passenger compartment. Any gasoline leak is serious and must be dealt with right away. With a flashlight, looking down the firewall from above with a good flashlight, you can see these hoses. If the hoses still have the pinch-on Oetiker hose clamps on them, the hoses are probably original and are in desperate need of changing, regardless if they're leaking or not. The hoses are not as hard to replace as you might think at first glance. With a couple of tricks, it's a relatively easy job.

It is my recommendation that when changing these hoses, that you renew all the rubber fuel line in the car, i.e. at the fuel filter, firewall, and engine compartment. Hose is cheap. Engine fires and tows are not. This guide only discusses the firewall lines. The rest are straight-forward, easy replacements.

Here is a schematic of the rubber hoses in the fuel system:

Supplies you will need:

1. About 6' of 7.5mm fuel injection grade rubber hose. This type of hose has a plastic inner wall to better resist the pressure of the fuel supply pump. On the return lines, since the pressure is much less, regular fuel line will do, but for the pressurized side, you MUST use FI grade fuel line. My recommendation is to use FI grade hose on everything. As an expedient, limp home measure, you may be able to use 5/16" FI grade hose, but probably will require double-clamping not to leak. Regardless, 7.5mm is the correct size to fit the metal fuel pipes and that is what you should use.

2. Fuel injection grade hose clamps/
Oetiker crimp-style clamps, NOT normal worm-drive hose clamps. The crimp-style clamps are very good and were OEM from the factory. Normal screw type FI grade clamps are cheap and available at any auto parts store. Size is "11-13mm."
3. Normal hand tools. If you chose to use the crimp-style clamps you will need the crimping tool, such as the Knipex Oetiker 1099 side jaw pliers.


Disconnect battery!

1. Bleed down fuel pressure from the feed side of the fuel lines. You can do this by letting the car sit overnight, or disabling the fuel supply pump (pull the relay) and running the engine until it dies of fuel starvation.
2. Disconnect the fuel feed pipe from the front fuel manifold.
3. Remove the mounting bracket for the rear fuel line (return line) from the false firewall.
4. Disconnect the fuel hose to the fuel return pipe.
5. Jack the front of the car and secure with jack stand(s).
6. Remove the right front wheel and plastic inner fender liners.
7. Remove the lower left timing belt cover to allow wider access to firewall hoses.
8. IMPORTANT: Determine which under body fuel pipe is the feed and which is the return. Mark one with ribbon or tape. When you go to install the new hoses, it'll keep you from hooking them up incorrectly.
9. Loosen/remove only the lower Oetiker clamps from firewall hoses. It's possible that you can just pull the hoses off the lower attachment points by having an assistant pull on the upper metal fuel pipes while you hold the lower pipes. If not, then take a pair of vice-grips and grasp the crimped part of the lower Oetiker clamps and twist them back and forth. It will likely pop-off or loosen to the point that the hoses can be pulled off with the top fuel pipes. If not, add a thin screwdriver to try and assist. You're not reusing the clamps, so don't worry about damaging them. The under body steel fuel pipes are pretty rugged so you can put pressure on them to reach them.

CAUTION: Fuel will likely leak out of the pipes when you disconnect hoses. Have an extinguisher close by, just in case.
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File Type: pdf 164 Firewall fuel hose replacement.pdf (1.57 MB, 306 views)

John Stewart
74 Spider
91 164S

Last edited by Roadtrip; 09-21-2015 at 08:32 PM.
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post #2 of 8 (permalink) Old 09-21-2015, 08:15 PM Thread Starter
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10. Remove the upper metal fuel pipes along with the firewall fuel hoses still attached to the upper pipes.
11. Pop the clamps off the firewall fuel hoses from the upper pipes and remove the old hoses.
12. Measure the length of the hoses and cut new ones to match length.
13. Install the new hoses onto the upper fuel pipes. Secure with proper clamps. Orient the clamps, either screw type of Oetiker type so that they can be reached from the wheel well area (perhaps future tightening) and so they do not rub on the other hose.
14. Position the lower clamps either on the new hoses or over the lower under body fuel pipes.

Installing new hoses:

15. Have an assistant lower the upper fuel pipes down one at a time making sure that the feed and return lines are going to the correct pipes. You guide the hose ends onto the lower under body fuel pipes while the assistant pushes down on the fuel lines. A little lubricate helps get the hoses started. Also slightly flaring the ends of the new hoses helps.
16. Slip the new lower clamps down into place and tighten. A good technique for tightening the clamps in such a confined space is to use your right hand to hold the lower clamp in-place, while cross-handed, you tighten the clamp with holding the ratchet/screwdriver with an reverse overhand grip, as in the picture below. Also, I prefer to use a 1/4" socket with a ratchet to tighten screw-type clamps. A slot screwdriver is difficult to line up and keep in the slot. The socket is much easier and faster.
17. All other rubber fuel hoses on the car are easily replaced and intuitive. I would recommend that you also install a new fuel filter while you have the system open.
18. Reconnect the battery and start the engine. Keep in mind it will take a few seconds for the fuel supply pump to re-pressurize the system for start. Check for leaks at all connections, regardless of if you changed the hose there or not. If good, button the car back up and enjoy.


Type of fuel line required for high pressure side: 7.5mm SAE30R9 grade fuel injection hose.
Minimum grade of fuel line required for low pressure return side: 7.5mm SAE30R7, although much better to just use the same high pressure hose for the entire system.

Approximate lengths of fuel line needed for each connection (cut to length of old hose):

Upper engine fuel feed (high pressure) to rail: 10"
Upper engine fuel return (low pressure) from rail: 24"
Fuel manifold short hose at rail #1: 4 1/2"
Fuel manifold short hose at rail #2: 5 1/2"
Firewall feed (high pressure) hose: 5"
Firewall return (low pressure) hose: 5"
Fuel Filter under car: 12"

TOTAL: 6 Feet

Clamp size: "11-13mm"

Fuel Filter: NAPA 3156
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Luigim and Spitfire like this.

John Stewart
74 Spider
91 164S

Last edited by Roadtrip; 09-21-2015 at 08:30 PM.
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post #3 of 8 (permalink) Old 09-21-2015, 09:10 PM
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This is very good Mr John. Very good. ciao, chris

Maintaining my tenuous strain on reality.
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post #4 of 8 (permalink) Old 09-22-2015, 03:47 AM
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Many thanks, Roadtrip.

1995 164 LS 5 speed 78K
owned since new
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post #5 of 8 (permalink) Old 10-05-2015, 11:56 AM
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Brilliant info. :-)

Always wondered why the standard 5/16 fuel hoses I was putting on the fuel rails kept failing every couple of years.

Thank you.
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post #6 of 8 (permalink) Old 10-05-2015, 06:10 PM
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Thank you very much for the nice write up John! I see that I still have a few hoses to replace...The Oetiker hose clamps and 'side jaw' tool are extremely worthwhile getting and easily do a nice job.
Thanks again,
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post #7 of 8 (permalink) Old 10-10-2015, 07:24 AM
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Thanks John, for another great, classic, step-by-step by the numbers guide.

But for what it's worth, let me add my experience with trying to change these two hoses, of which I was only able to change one after a lot of effort, because, like everything else on these cars, this is not an easy job and takes longer for some cars than others, you need to allow a lot of time just in case.

- getting those original clamps of wasn't easy, and even when I bought one of those fine Oetiker clamp pliers, it didn't fit or work, and every foreign car shop I checked with in the area, not one mech had ever seen Oetiker pliers before and knew how to use them, although they were used on some 1970-80s Fords, Lincolns, and Mercury's.

- my rubber fuel lines did not pull off easy, worried in pulling I may have screwed somthing up, so if they don't pull off easy, quit pulling.

- Paul at Difatta said to leave these two lines alone, that they only change them when they have to pull the engine, which seems to be the first step on any maintenance job on a 164, "pull the engine."

- If I had it to do over again, I think removing the power steering pump would be a good idea.

- Two weekends ago I ended up finally replacing the original mechanical fuel pump and the original two short rubber fuel lines from the hard lines on my wife's 1976 Firebird (400 ci), and the thicker rubber in those line was still good, not leaking, after 40 years (unfortunately it looks like the fuel pump was OK and I have a clogged fuel hard line, any suggestions?) ,
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post #8 of 8 (permalink) Old 10-10-2015, 09:12 AM Thread Starter
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Replacing these lines was not hard, just a little tedious, and I saw no need at all to displace the power steering pump. You do need to remove the lower left timing belt cover to gain a little maneuver room.

The key points:

1. Don't try and remove the upper clamps in-situ. Too hard to get to. Pull the hoses up along with the upper fuel pipes.
2. Use a pair of pliers to twist the hoses free (break the stickiness) on the bottom under-chassis pipes. Then try and pull up on the upper pipes with an assistant while you hold the lower pipes fast.
3. If no-joy, then twist the hose around to get to the nub on the oediker clamp. Clamp a small pair of vice grips and twist the clamp back and force to release it.
4. You don't care about the old hose, so slicing it as necessary is ok.
5. It's ok to put some pressure on the lower pipes to get them to where you can work on them easily.
6. When replacing the hoses, do it opposite to how they came out. Fasten and tighten well, the hose to the upper pipes.
7. Tighten the lower clamps with a socket down tight.
8. Before you button everything back up, start the engine and run it to make sure you have no seepage.

Firebird clogged line . . . . mechanics wire and/or compressed air?

John Stewart
74 Spider
91 164S

Last edited by Roadtrip; 10-10-2015 at 09:14 AM.
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