80 911sc will not start hot

silas · 06-22-2009, 11:37 AM

i have a 1980 SC. it starts grate wen your first get in it. but after it heats up and it sites for about 30 min it takes 6 to 8 long terns to get it to start.
have you had this problem?
how did you fix it?

Scott R · Scott R's Garage

You're going to need to test your fuel pressure during this event. I've had this problem twice now, both were different issues.

kodioneill · kodioneill's Garage

Fuel accumulator is a very common problem when trying to start a hot engine.

porsche930dude · porsche930dude's Garage

Quote:

Originally Posted by kodioneill

fuel accumulator is a very common problem when trying to start a hot engine.

x2

dave944cab · 06-22-2009, 12:37 PM

had this problem with my 2.7 and it was fuel accumulator.

mine wouldnt start at all after about 20 min sitting

docrodg · 06-22-2009, 12:46 PM

I saw similar problem in a mid-70's VW Fox or something (can't remember the model right now, probably because the horror of finding a good air door has blocked it form my mind) with CIS, fuel accumulator got hot and nothing for pump to push around. Owner was tired of problem and asked if I could come up with a "Creative" fix... moved the darn thing to the trunk and repiped the fuel system with a pump at and below the tank as well... once out of the heat no more problems. Not sure if this will work on the P-car tho, even tho the original system in that VW was all P-car parts the car is set up differently.

rwest · rwest's Garage

Hi,

I'll side with the fuel accumulator also, I just changed the one in my 77s a few weeks ago!

My car behaved as follows: Would start great after sitting for days, overnight etc. ; I could drive it as long as I wanted and it would be fine; If I started it within a short time after(few minutes or less) it would start fine, but if I tried to start it a half hour to several hours after driving it, I would have to crank it for a long time and then it would try to start and I would have to keep cranking to get it to stay running. After checking around with a couple of mechanics and some books, they explained that the accumulator's function is to keep the fuel under pressure for a short time after the car is shut down so that the residual heat in the engine compartment doesn't cause a vapor lock. They also said that is a fairly common problem on many fuel injected cars.

Hope this helps, Rutager

longhornchris04 · longhornchris04's Garage

It could also be the check valve... the fuel accumulator won't work if it can just feed the pressure back through the pump into the fuel tank.

I'd check the accumulator first. I'm not sure if the 80 Check valve is built into the fuel pump or not.

GothingNC · 06-22-2009, 04:27 PM

Did you recently fill wiith gas containing Ethanol?

Also, is your battery fully charged?

I would change the check valve first and if that doesn't solve it test the residual fuel pressure.

diy83sc · 06-22-2009, 04:44 PM

I had the same problem, spoke to my mechanic, and it was suggested to be the check valve... and it was.

On my 80SC, the valve is external to the pump.

rwest · rwest's Garage

Just a thought on the check valve, if it was bad, wouldn't you have to crank the engine for a long time to build the pressure back up, after it sat overnght? The problem is only when the car is hot.

GothingNC · 06-22-2009, 05:23 PM

Quote:

Originally Posted by rwest

Just a thought on the check valve, if it was bad, wouldn't you have to crank the engine for a long time to build the pressure back up, after it sat overnght? The problem is only when the car is hot.

Cold start injector is activated when the engine is cold since most of the fuel pressure is bled down after sitting overnight.

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by silas

i have a 1980 SC. it starts grate wen your first get in it. but after it heats up and it sites for about 30 min it takes 6 to 8 long terns to get it to start.
have you had this problem?
how did you fix it?

Silas,

Whether the problem is the fuel accumulator or the FP check valve, these components could be bench tested individually. Do not replace suspected component/s unless verified defective. Your '80SC should have the three-port FA. Pressure test the upper chamber with about 10-15 psi air pressure. If the diaphragm is ruptured or broken, air will be blown out from the bottom port (return line). Another method is running the FP for a very brief moment (2 sec.) with the bottom port of the FA disconnected. But you need some precautionary method to collect the discharged gasoline during the test.

The FP check valve could be tested by checking the residual pressure with a known good fuel accumulator. Or without a FA hooked up to the system to lessen the variables. Keep us posted.

Tony

Aurel · Aurel's Garage

Easy to way check the fuel accumulator: unscrew the gas line at the bottom of it, and if you see gas dripping from there, it is toast (It is not supposed to leak gas back in the line that feeds it).

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by Aurel

Easy to way check the fuel accumulator: unscrew the gas line at the bottom of it, and if you see gas dripping from there, it is toast (It is not supposed to leak gas back in the line that feeds it).

Aurel,

The bottom port of a three-port FA is the return line as you mentioned. There will be fuel in the line because it is connected to the main return line. To disprove this, try to disconnect the bottom line of your FA. You'll be surprised to find that your bottom line will have fuel even if the FA is 100% healthy.

Fuel coming from the bottom chamber does not indicate you have a bad fuel accumulator. Unless the diaphragm is ruptured. It is normal to have small amount of fuel in the lower chamber. What is abnormal is fuel coming thru the diaphragm.

Tony

Aurel · Aurel's Garage

Quote:

Originally Posted by boyt911sc

Aurel,

The bottom port of a three-port FA is the return line as you mentioned. There will be fuel in the line because it is connected to the main return line. To disprove this, try to disconnect the bottom line of your FA. You'll be surprised to find that your bottom line will have fuel even if the FA is 100% healthy.

Fuel coming from the bottom chamber does not indicate you have a bad fuel accumulator. Unless the diaphragm is ruptured. It is normal to have small amount of fuel in the lower chamber. What is abnormal is fuel coming thru the diaphragm.

Tony

I see you have investigated this topic more than I have, therefore I bow to your expertise

.

silas · 06-23-2009, 10:49 AM

wow that all is such good advice. thanks so much. i will start checking the Fuel accumulator and check valve...

1980 911 sc · 06-23-2009, 04:01 PM

I happened to have a used FA from my 80 SC. It worked fine when removed a few years ago to install my varioram motor. PM me if you think you need one.

silas · 06-24-2009, 01:04 PM

ok so i disconnected the bottom port of the FA and ran it for 2 sec. when it was cold and wen it was hot. wen it was cold it pored gas out wen it was on and then stoped after a short time. wen i did it after it was hot it slowly leaked out the bottom and did not seem to stop.
is the an indication that it the diaphragm is ruptured?
silas

GothingNC · 06-24-2009, 02:16 PM

Quote:

Originally Posted by silas

ok so i disconnected the bottom port of the FA and ran it for 2 sec. when it was cold and wen it was hot. wen it was cold it pored gas out wen it was on and then stoped after a short time. wen i did it after it was hot it slowly leaked out the bottom and did not seem to stop.
is the an indication that it the diaphragm is ruptured?
silas

I think you need to replace if it's slowly leaking .

Only about $110 for a new one for the 78-79 version, will work on the later years since it has the lower return fitting. Only difference between this and the 80-83 is the size, pressurization time and about $200 more