Fuel level during rebuild
 

OK...finally got the nerver to drop the engine and do a top end but the fuel tank (88 Carrera, if that matters) is down to about 3-4 gallons. I expect it will be 2-3 months before it's done since I'm not in any hurry. How full should the tank be and what should I do to prepare it? Should I fill it up and add gas treatment or add gas treatment and leave fuel level as is?

TIA

I'd put in some fuel stabalizer with a couple of gallons of gas. Drive it a few miles to distribute the fuel stabalizer, then drop your engine. Once you get it finished drive straight to the gas station to fill up with fresh fuel.

-Andy

thanks...so just having a few gallons, say 3-5 is not a big mistake. Are you saying though that, ideally, it would be better to have it full during the rebuild? I can get it to the gas station but I can't turn it off since I have a worn spot on the ring gear and if it stops on that spot the starter won't engage. I'll have to fill it up while it's running which I know is not safe, or legal for that matter, although I see people do it all the time.

I'm saying I think it's better to not have it full. That way you only have 3-5 gallons of old gas when you go to drive the car instead of a full tank of old gas.

-Andy

Got it...thanks for the clarification.

I'd recommend pumping out the remaining gas (use the fuel pump), then spray some kerosene, WD-40, ATF or equiv. inside with a garden sprayer or nozzle to protect against corrosion. While you're at it, remove and clean the filter screen at the bottom. The tank also might have sediment you'll want to remove. Seal the openings until you reinstall.

Sherwood

When I was done my rebuild I drained the tank by jumpering the fuel pump on and emptying it into 5 gallon containers. (which i used in my truck). Then I put a new fuel filter in.

Its nice to have fresh gas when you start up that expensive motor.

Kirk

Another option is to do absolutely nothing about this.

I've had fuel in my fuel cell over the winter many times, and can't say that I ever had anything bad happen that I could connect with "stale" fuel.

You follow my lazy suggestion at your peril, of course. But the only times I have removed all the fuel have been times when the tank had to come out.

Walt Fricke

Kirk,

How did you jumper it? My gas is going on 18months old and I suspect it wont be soon when my engine is finally running. I would love to drain the fuel out with the pump.

Best regards,

Michael

I added a large jug of Methyl Hydrate to my tank before I let my car sit for 18 months, I figured it would act as a solvent and disolve or at least thin any heavy stuff that phase seperates in the tank over time. You hear stories of gas turning to varnish, leaving deposits, etc.

The good thing (unexpected) was that the gas didn't stink so much when I re-set the float levels in my carbs. I usually end up using 1/2 a tank just doing that!!!

My car is a 964, so my procedure would be different from yours.

Although I would guess it should be a simple jumper across two pins of the DME relay. (My 1984 944 was similar to my 1989 C4, so I would guess yours would use the same procedure)

Just check your wiring schematic, and it should be obvious which 2 pins are required.

Kirk

Michael

On your SC this is easy. You can either turn the ignition on and hold the air flow plate up after removing the air filter, or you can reach behind everything and unplug the safety switch connection and control the pump with the ignition switch.

Or you can jumper the fuel pump relay, though that is more work because you have to identify the proper pins and bend some single strand stiff copper wire so it will do the jumpering.

Walt Fricke

Thanks Kirk! SC has no motronic ;)

Walt:
Intake is totally disassembled so no lifting of the air plate ;) I'll have to jumper the relay... Not looked at the diagram yet. Any guesses off hand which pins?

Best regards,

Michael

If the intake is disassembled and sitting on your workbench then you have removed the interlock connector wire/plug from its proper home over by the air measuring plate. Turning the ignition to "on" should cause the fuel pump to run (not a good thing in general, unless you have a jug under the end of the fuel line you disconnected when pulling the intake).

Walt

Walt

Good discussion here and lots of good advice.

There are several issues:
-The age and condition of the fuel when you restart the engine.
-Preservation of all the fuel components.
-Condition of the fuel tank, screen filter and fuel filter.
-What to do on start-up.

To start a fresh engine you need higher than normal octane fresh fuel. I just discussed with a Pelican his using 112-114 octane race fuel on his 10.5:1 CR engine. The reason is that oil (from assembly lube and not-yet-sealed rings) effectively lowers the octane of the mixture. Starting a fresh engine is not a time you should tolerate detonation.

While an engine is disassembled for work, you don’t want to leave the fuel system subject to damage. There are two issues; evaporating fuel leaving “varnish” and corrosion from moisture in the air. Choosing the right fuel before shutdown can include draining the tank and installing a few gallons of aviation gas. This is far more time-stable than automotive fuel and doesn’t contain ethanol. Stabil additive is additionally very useful. Just before shutdown, I like to add Marvel Mystery Oil and then shut off the engine when it starts to smoke. (If you have a cat and good muffler, it is best to remove them first so they don’t get oil contamination.)

Some time during the engine process it is a good idea to drain the old fuel, inspect (or clean) the tank, clean the screen filter and replace the fuel filter.

When starting a fresh engine it is important for it to start and run properly on your first attempt. This means the fuel and ignition must be exactly proper. With CIS and DME it is easy to have the nozzles in containers and purge the fuel system with fresh high octane fuel. It is a little more difficult with MFI and carburetors. With EFI it depends on the system.

Every first attempt of start-up should have tested good fuel and ignition systems.


So … to answer your question, you can use your fuel system to pump the old fuel out and do whatever maintenance and prevention you want. You can even fabricate a fuel hose at the engine bay so the fuel circulates.

I suppose with some creative work you can reinstall the DME and trick it into flowing fuel. Can you can take some bailing wire and reinstall just the DME hanging in the engine bay?

As always, be extremely careful with gas. Gasoline (and particularly vapors) are the most dangerous substance you normally come in contact with.

Best,
Grady