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Discussion Starter · #1 · (Edited)
I am contemplating changing my 1973 1800ES's fuel filter and need some advice.

My records show current fuel filter installed about 46,000 miles ago. I realize the book service interval is 12,000 miles so I'm technically way overdue. Yet I wonder whether today's fuel is cleaner than that of 1973 and thus whether a new filter is still needed that frequently.

Questions:

-How often do you P1800 maintenance enthusiasts change fuel filters?

-Should I do mine ASAP or can it wait?

-When disassembling hoses around the filter, how much latent fuel pressure to expect? Manual says to clamp lines up and down of pump and filter but in my car these lines look fragile and I hesitate to clamp for fear of breaking them. Should I clamp?

-Should I replace the lines around and/or between the pump and filter?

Glad of any advice from experienced hands.

Lev

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I would continue changing the filter per the schedule. If you're afraid of clamping the hoses, I would be concerned driving the car. I don't think you want a fire. Replace both hoses and filter. And I think todays fuel is worse, with the added Ethanol in it. The fuel breaks up and it gunks up.
 

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If you have no symptoms, I would not say it needs to be done immediately - but I would definitely do it. If your car is FI - any junk in the system can really screw the FI's up. If your fuel hoses are so brittle that you fear touching them, then they should be replaced as well.

I'd probably drive the the car until you are fairly low on gas - then drain the tank, install new hoses and filters.

I don't think the cleanliness of the fuel you buy is the issue - but rather the state of your gas tank. It can deteriorate/rust. These rust chunks clog things up, and cause all sorts of problems.

If I remember correctly (I went through this about a year ago) there is a drain plug on the tank, and there is an internal tank filter, and a post tank filter. I've heard some recommend getting rid of the internal filter - but I put a new one in there. Mine was totally gunked up. To open the drain plug you can buy a special tool - or just grind down a socket until it fits into the bottom of the plug. Overall the process feels good to do - but also is one of those 'infrastructure' type improvements, that noone notices. You should just sleep better knowing that your fuel lines are not going to leak out on you. Also - if your car is FI, make sure to get the proper hose - that can handle the pressure.

Good luck, and let us know how it goes.
 

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Time is equally important. If that is 46,000 miles of infrequent use, you have had lots of time to accumulate sludge in the fuel system due to the inevitable temperature cycles that the fuel system has been exposed to and the fact that it is not a sealed system. SF has a fairly mild climate so the ethanol blend fuels should not suffer the phase change problem that occurs in colder climates. I assume that the car is running currently, so its not an emergency; but, I would plan for it sooner rather than later.

The Bosch fuel pump has a check valve on the discharge which is supposed to maintain fuel line pressure when the car is parked to minimize cranking on restart. As these cars age, those check valves get leaky. If you allow the car to sit parked over night, the pressure in the fuel system will probably be fairly low which facilitates removal of the filter. The best place to 'release' any residual fuel pressure is to clamp the line to the cold start injector, pull the hose off the cold start injector and then release the clamp allowing the fuel to drain into a small container. Once you release the pressure, you are still going to have to clamp the lines around the filter or make provision for catching fuel since you are going to have a lot of drainage when you yank the filter.

If the rubber fuel lines are original, I would definitely be planning for their replacement. 5/16" works just fine for the supply and return hoses. The Bosch pump is metric and the suction line from the tank to the pump is 12mm or 13 mm as I recall. I think 1/2 in worked OK. As a final note, don`t use a generic plastic fuel filter. A generic metal filter might work in a pinch; but, I suggest that you get the proper fuel filter for the Bosch D jet. Slightly more expensive; but, worth it.
 

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Discussion Starter · #5 ·
Thanks y'all for the advice. I've been on the road and haven't yet done the project. Some more questions if you don't mind:

-looks like the fuel filter that's already in there has a 1/4" inlet, smaller than The 12 or 13 mm that 142 Guy recommends. I checked and this is the stock filter (I don't have the part number handy). Is it a bad idea to go down to a 1/4" line to match the filter or is it better to have a wider line going into a smaller opening?

-should I replace the in-tank filter while I'm at it? Another guy I asked said he just rinses his. In any event, draining the fuel tank seems like a pain.

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In my post, 12 or 13 mm referred to the size of the suction line from the pump to the tank (if you were going to consider replacing the fuel lines), not the lines connected to the fuel filter. The supply lines connected to the fuel filter and the fuel return line should all be 5/16". If you have the OEM filter, it will have barbed fittings for 5/16" fuel line.

If you are going to the trouble of draining the tank to replace the filter sock on the suction line, have a new one on hand. Mine fell apart when I removed it from the suction line.
 
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