Fuel Line Flush?

[BassettBritts]

I hope (fingers crossed) to be able to pick up a 1983 911 SC in a few days. My first Porsche. The car has not been started since 2008. I'm pretty familiar with bringing cars back to life but have never done so with one that is fuel injected. I plan on removing the injectors and having them gone over. I know I'll have issues with cleaning the fuel tank along with replacing the fuel filter and fuel accumulator.

My question is.......should I flush or can I flush the fuel lines before trying to start it? Or is it easier too just replace them.....which sounds difficult with the engine in place.

Thank you.

[GH85Carrera]

Replacing the lines is a pain when the engine in place. You have to support the transmission, remove the transmission cross member, and work with just the ends of your fingers. I did it, and it is not fun.

One regular on the board, Len Cummings, sell a nice replacement set. They are a hard plastic. If you plan on keeping the car long term, do it. If you are yet another flipper, you will likely not want to mess with it. They will eventually need to be replaced. A 37 year old car can use a lot of updates. It all comes down to what you want from the car.

Post some photos of the car, and tell us about you. You will get more replies if you are another Porsche lover, and not just a flipper.

[boyt911sc]

Get rid of the old fuel. Drain and inspect the fuel tank including the gas tank filter. If the fuel tank is free from debris and clean, put some fresh fuel in the tank. Leave the old fuel filter for the meantime and replace after you have purged the system.

Do not attempt to start the engine until you have completed a fuel pressure test. Why? There could be a fuel leak and you don’t know that. Test the fuel pump without running the motor. If you know how to test run the FP that’s great. If you don’t know the procedure, simply ask.

Before attempting to start the car, check the following:

• Engine oil level.
• A fully charged battery.
• Test for presence of strong ignition signal.
• Turn the motor by hand and make sure it is not seized.
• Inspect the spark plugs and plug wires.
• Etc.

Disable the ignition by unplugging the connector to the CDI, pull out the RED fuel pump relay, and crank the starter very briefly for a short test and stop. Engine sound OK? Keep turning the engine until oil pressure registers on the gauge. Do this a couple of times. If the engine sounds normal, connect the ignition system and plug back the FP relay. You are now ready start the motor. Wish you the best. Keep us posted.

Tony

[GG Allin]

My can had not run since around 1999- 2000. What I did was disconnect the lines at the tank, inject gasoline in to the lines at the engine compartment and blow it out the front a few times. What ever was in my lines either got blown out and/or filtered out after I started up the engine.

I also replaced the pump, sending unit, under tank screen and fuel filter.

[jlex]

If you're not going to do the lines, the least you should do is drain all the old gas and replace with new plus dry gas, then jumper the fuel pump so it can run without starting the car to circulate the gas thru the filter without old stuff flowing through the injectors. Don't want to start it up right away as junk can flow into the injectors and mess them up. If you want to be careful, change out the filter after circulating the gas via the jumper before actually starting the car.

[83_Silberpfeil]

Hi Tony - reviving/revisiting your post from 2.5 years ago. I wanted to ask how to "test run the fuel pump" procedures. Can you describe, or link me to a thread that explains?

Thanks!

Originally Posted by boyt911sc

Get rid of the old fuel. Drain and inspect the fuel tank including the gas tank filter. If the fuel tank is free from debris and clean, put some fresh fuel in the tank. Leave the old fuel filter for the meantime and replace after you have purged the system.

Do not attempt to start the engine until you have completed a fuel pressure test. Why? There could be a fuel leak and you don’t know that. Test the fuel pump without running the motor. If you know how to test run the FP that’s great. If you don’t know the procedure, simply ask.

Before attempting to start the car, check the following:

• Engine oil level.
• A fully charged battery.
• Test for presence of strong ignition signal.
• Turn the motor by hand and make sure it is not seized.
• Inspect the spark plugs and plug wires.
• Etc.

Disable the ignition by unplugging the connector to the CDI, pull out the RED fuel pump relay, and crank the starter very briefly for a short test and stop. Engine sound OK? Keep turning the engine until oil pressure registers on the gauge. Do this a couple of times. If the engine sounds normal, connect the ignition system and plug back the FP relay. You are now ready start the motor. Wish you the best. Keep us posted.

Tony

[83_Silberpfeil]

jlex - In the procedure you describe below, when you run the fuel pump w/o starting car, where does the fuel end up? I see you mention that fuel will pass through filter. Are you disconnecting the fuel line at exit/discharge of fuel filter?

Thanks!

Originally Posted by jlex

If you're not going to do the lines, the least you should do is drain all the old gas and replace with new plus dry gas, then jumper the fuel pump so it can run without starting the car to circulate the gas thru the filter without old stuff flowing through the injectors. Don't want to start it up right away as junk can flow into the injectors and mess them up. If you want to be careful, change out the filter after circulating the gas via the jumper before actually starting the car.

[boyt911sc]

Originally Posted by 83_Silberpfeil

Hi Tony - reviving/revisiting your post from 2.5 years ago. I wanted to ask how to "test run the fuel pump" procedures. Can you describe, or link me to a thread that explains?

Thanks!

Jonathan,

Every CIS troubleshooter should know this basic CIS test of running the fuel pump with the motor off. There is a thread by DKLever48 about fuel pump relay and socket. This is a very interesting subject that I strongly recommend to people to read. There are 5 terminals in a FP relay/socket namely:
87a
87
86
85
30

Best way to understand how these 5 terminals work is making a sketch for your notes.
87a-30...........NC (normally closed).
87-30.............NO (normally open).
86-85.............terminals of magnetic coil that switches from NO to NC and vise versa.

With the ignition switch @ ON position, power is supplied to terminals 87a and 86 (bridged at the socket side). Use a 12-volt test light to confirm it.

To run the FP, you need power at terminal #87a and #30. With the FP relay removed from the socket, you can use a jumper wire between #87a and #30. And turn the ignition switch to RUN position. With the jumper wire installed and ignition switch @ RUN, the fuel pump will be energized and run.

Tony

[HarryD]

Check posts 20 and 21 of this very informative thread. Winter storage checklist?

Ignore Grady Clay (RIP) at your own risk.

[83_Silberpfeil]

Thanks for posting the instructions, Tony. I do aspire to be a "CIS troubleshooter" since my 911 is an 83 SC. But for now, just a newbie WRT the fuel/delivery system. I'm going to print this out and look under the frunk to see all the terminals you mentioned. that's my next step, then go from there.

PS >> hope that your May 1 ~ 2 engine rebuild course will also cover CIS..

Thanks!
Jonathan

Originally Posted by boyt911sc

Jonathan,

Every CIS troubleshooter should know this basic CIS test of running the fuel pump with the motor off. There is a thread by DKLever48 about fuel pump relay and socket. This is a very interesting subject that I strongly recommend to people to read. There are 5 terminals in a FP relay/socket namely:
87a
87
86
85
30

Best way to understand how these 5 terminals work is making a sketch for your notes.
87a-30...........NC (normally closed).
87-30.............NO (normally open).
86-85.............terminals of magnetic coil that switches from NO to NC and vise versa.

With the ignition switch @ ON position, power is supplied to terminals 87a and 86 (bridged at the socket side). Use a 12-volt test light to confirm it.

To run the FP, you need power at terminal #87a and #30. With the FP relay removed from the socket, you can use a jumper wire between #87a and #30. And turn the ignition switch to RUN position. With the jumper wire installed and ignition switch @ RUN, the fuel pump will be energized and run.

Tony

[PeteKz]

I’ll add one small thing to the others’ excellent recommendations: remove the spark plugs before cranking the engine to make sure you don’t have hydraulic lock from oil seeping into the cylinders over almost 20 years. This will also run down your battery less while cranking to test oil pressure.

[PeteKz]

Originally Posted by 83_Silberpfeil

jlex - In the procedure you describe below, when you run the fuel pump w/o starting car, where does the fuel end up? I see you mention that fuel will pass through filter. Are you disconnecting the fuel line at exit/discharge of fuel filter?

Thanks!

The pump provides a constant pressure that is above “system pressure.” The pressure regulator (on the fuel distributor) constantly bypasses excess fuel to maintain the correct system pressure. The bypassed fuel flows back to tue tank via a “return line.” That’s why the tank has two fuel lines. By simply running the pump, you circulate the fresh fuel from the tank, through the supply lines, pump, accumulator, filter, pressure regulator and then back to the tank.

[LazorJ]

Great info here. I have a 77 here with similar issues, sat for 20 years. lines and tank were trashed, (will be replacing) however, is it to be assumed the accumulator is also junk? Doesn't look terrible, but is it possible to clean?

[PeteKz]

The accumulator will get flushed out by fresh fuel. However, if it's the original accumulator, it's probably starting to fail by now, so consider replacing it proactively.

After draining the old fuel, remove the fuel sender from the top of the tank and look inside. How much crud? Flush out the tank and lines as best you can. Then I would add a can of fuel system cleaner, drive the snot out of it, and then change the filter. Then peek in the tank again to see if you got it reasonably clean.

[83_Silberpfeil]

Thanks PeteKz. I'll see if I'm able to reach the plugs. My 83SC is fullly stock, w AC and all the HVAC ducts/flaps. Getting to plugs is not easy task.

I was able to turn the engine using the hand-crank tool to turn the fan pulley. Does that mean I don't have hydraulic lock?

Originally Posted by PeteKz

I’ll add one small thing to the others’ excellent recommendations: remove the spark plugs before cranking the engine to make sure you don’t have hydraulic lock from oil seeping into the cylinders over almost 20 years. This will also run down your battery less while cranking to test oil pressure.

[83_Silberpfeil]

Following up on this thread --- I further inspected the fuel tank, after completely draining it from the bottom. There are some visible rust in there, but doesn't look too bad. I'm going to proceed as is.

I did swap out the fuel screen/filter for a new one (w new o-ring), the old one had disintegrated. And at the top, for the fuel level sender, replaced the gasket as well.

Next is to change the fuel filter. I bought a Bosch K22 fuel filter from our host here. In my 83 SC, it looks really tight in there to change the filter. So, I plan to remove the air duct (outlined in red). I see there are two fastners to remove (blue outline), on hose clamp at the bottom of foto, and a hex bolt on second foto below. Are there any others that was not visible to me?

Also should I remove the fuel filter and accumulator together? I didn't procure a new accumulator but have read here that removing both together makes for a simpler job.

Thanks!

[PeteKz]

Yes, you will have to remove that air duct. As for removing the fuel filter and accumulator together, I've generally just removed the filter, but do whatever looks easiest to you. Be sure to use two open end wrenches and orient them so that all you have to do is squeeze them in your hand to loosen the fittings. Avoid applying torque on the fuel lines. When you install the new filter, do the same in reverse.

[83_Silberpfeil]

Thanks for confirming PeteKz. I was wondering if just two fasteners to remove (that I mentioned) or are there more that is not visible?

Appreciate the tip/advice for using two open end wrenches. I will follow that.

Originally Posted by PeteKz

Yes, you will have to remove that air duct. As for removing the fuel filter and accumulator together, I've generally just removed the filter, but do whatever looks easiest to you. Be sure to use two open end wrenches and orient them so that all you have to do is squeeze them in your hand to loosen the fittings. Avoid applying torque on the fuel lines. When you install the new filter, do the same in reverse.

[83_Silberpfeil]

@PeteKz - I stumbled upon a YouTube video that demonstrates removing this heater duct. It's always helpful to see it done. Although, I noticed in this video the 78 SC Targa had two hose clamp fasteners, different from my 83 SC: with one hose clamp and a hex bolt.

https://www.youtube.com/watch?v=KhCw5lP0-js

[PeteKz]

As you should be able to see, the fuel filter is held at the top and bottom by the full line fittings, and in the middle by a hose clamp around the filter and bracket.