New engine doesn't start after warm up - help

Emi · 05-07-2016, 02:47 AM

Hello All,

I have a 75 911s it has an updated pump and as such I noticed there is no fuel check valve on the fuel pump - nor banjo bolt to install one? Car runs fine however and starts first turn when cold. It will however, not restart 20 after it has been warmed up - it needs to cool before it starts again. It is loosing pressure! Can I install a check valve ?Did this year have one? Finally how can I diagnosis my fuel accumulator its a two line in only version?

Thank you all in advance for your help.

Flat6pac · 03:10 AM

The 75 has the fuel pump in the rear. The banjo fitting connecting next to the pump is the check valve, not just the connection.
Use check valve 911 608 901 00
Bruce

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by Emi

Hello All,

I have a 75 911s it has an updated pump and as such I noticed there is no fuel check valve on the fuel pump - nor banjo bolt to install one? Car runs fine however and starts first turn when cold. It will however, not restart 20 after it has been warmed up - it needs to cool before it starts again. It is loosing pressure! Can I install a check valve ?Did this year have one? Finally how can I diagnosis my fuel accumulator its a two line in only version?

Thank you all in advance for your help.

Emi,

I am wondering how did you determine that the system is loosing residual fuel pressure? Did you measure the residual pressure? The FP for '75 is suppose to run when ignition switch is @ ON position (not start). Is this correct? The fuel accumulator is easy to test. Either pressurize with air or liquid to test the diaphragm. A broken or defective diaphragm would leak. Remove the tiny screw at the bottom during test.

Tony

Emi · 05-07-2016, 04:55 AM

Hello

Thanks for the replies, the issue is that the car has an upgraded fuel pump from an sc I believe ? There is no banjo bolt present on the car ? simply a straight line attachment on an open adapter. The car runs great, if it is shut off and left to sit for 20 mins or so it will not restart untill it cools off? Prior to that it starts up, be it with a bit of stuggle after the first 5-10 mins turned off - starving for fuel symptoms? Will that banjo (911 608 901 00 ) fit an sc pump or should I get a sc check valve and banjo fitting ? The car has a hard plastic line can the barb banjo line be fitted to this?

Emi · 05-07-2016, 04:57 AM

HI Tony,

Forgot to mention that yes, the FP runs with the ignition in the on position. Regarding pressuring the fuel accumulator would that require a fitting for the pump or would adding liquid to it be enough? If not how do I pressurize the Fuel accumulator?

Flat6pac · 05-07-2016, 05:07 AM

There are 2 fuel pumps used on the SC. 77/79 has an internal check valve, when it goes, replace the whole pump. The 80/83 has an external check valve that bolts to the nose of the pump and acts as Hali the banjo fitting.
Bruce

Emi · 05-07-2016, 07:52 AM

Hi Bruce,

the fuel pump does not have an internal check valve.

strictly · 05-07-2016, 08:01 AM

check engine compression/leak down test.

I recently has an sc, difficult to start when hot, started ok cold, a bit lumpy, went through the whole fuel system (new pump, new accumulaor, adjusted CCP, SP, etc, checked injectors, etc). Went through ignition system. Then Check valve clearances, checked head stud nuts (that a key point). Finally stumped checked compression.

cylinders 1 to 3 were all leaking, #3 was 90% leakdown, it turn out someone had done some "work" on it about 500 miles before, and i had one head stud at 10 degrees pointing out than the others. No Joke. See pick below :

I know you built your engine, but dont rule out compression.

The analysis of a problem with regard fuel/carbs should always be :

1. Check Compression/Engine Mechanicals
2. Check Ignition System
3. Check Fuel System

From now on, thats the procedure i follow. I should have known better, just did not expect it, the car had 36,000 miles on it!

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by Emi

HI Tony,

Forgot to mention that yes, the FP runs with the ignition in the on position. Regarding pressuring the fuel accumulator would that require a fitting for the pump or would adding liquid to it be enough? If not how do I pressurize the Fuel accumulator?

Emi,

Turn the ignition switch @ ON position and FP running. While the FP is running remove the bottom screw on the fuel accumulator (two-port). There should be no fuel coming out from the bottom of the FA and should be dry all the time. If there is a sign of wetness or fuel, the FA is bad.

Tony

Emi · 05-07-2016, 05:13 PM

Hi Strictly,

Thanks for the reply, I have checked the engine all was well for over a year. Untill recently this has happened. The engine has thousands of miles on it, prior to this issue and there is no fuel check valve at all on this car???? Go figure, not sure if the previous owner upgraded the pump with a 77-79 internal check valve ? However, pressure is lost after about 20min, How can I add a check valve to that plastic line? I know that GM has a repair kit and I have using a heard heat gun is effective

strictly · 05-08-2016, 12:18 AM

okay, good. Just wanted to be sure, ive learned the hard way to go compression, ignition, fuel for diagnosis.

So what not just change the pump to the one with an external check valve fitted? Your pressure loss in 20 minutes, you have confirmed that was a CIS fuel pressure guage/tester on the system pressure side, or is that a guess?

Im sure you could "fit a check valve" but better to do it right, with the right pump. Sell the old one on ebay. What if you need to unfit that new check valve.