CDI/Fuel issue ('77 911s)

[kiwicobber]

Hi everyone,

After getting the car running again after an engine-out clutch replacement, it ran perfectly for about 3 weeks and now the car simply won't start.

I have checked and there is spark at the spark plug end
No fuel coming from injector when I crank the car though but the injector end was wet with fuel when I removed it to check
No whine from the Permatune CDI....
No fuel pump noise either
Checked all fuses, all OK (repaced the two fuses in the engine compartment just to be sure)
One of the cables in the CDI loom was a bit melted but it is intact so that may just be a function of age and exposure to heat in the engine compartment
Cabnnot find any relays or the like under the driver's seat
Have CRC'd the various electrical components

[pa911]

Permatunes do not whine like a Bosch CDI..you will need to take the air filter top off and lift up the air sensor plate to get fuel..Have you checked the fuel pump relay in the front trunk? (the red one)

[HarryD]

Check for fuel flow:

1-Remove air Filter;
2-Put key in RUN position;
3-Slightly lift the air flow sensor arm inhte air box and if youhave fuel flow, you will hear a buzz/whine from the injectors.

Check Ignition:

This thread may be helpful: Ignition problem troubleshooting (electrical)......

Also, from another thread (How do i check a coil with a timing light??

Originally Posted by HarryD

To get a spark to the spark plug in the engine. Several things need to happen. First, you need power to the CDI. Next you need to have a way to trigger the CDI (the points do this by opening and closing). Then the CDI will then send a pulse to the coil which will increase the voltage and send it through the high tension lead to the rotor and to the selected spark plug. You need to verify that each step in this chain is working.

1) Verify that the CDI is getting power (Unlike the Bosch unit, there is no whine). Pull the 3 pin connector. Put the key in the RUN position and check the center pin for 12v power.

2) Verify that the CDI is producing power to make a spark. You can do this with a "telegraph" test. Take the high tension lead off of the center of the distributor and put a spark plug on it. Ground the threaded part. With your plug attached to the center lead, open the distributor, remove the rotor, place your key in the run position, and manually open and close the points. Each time you cycle, you should see a spark from the plug. If you do not, you may have a bad CDI.

3) Verify that the coil gets a signal when you crank. Replace the rotor and distributor cap. Leave the plug on the center high tension lead. Crank the engine. Do you see a spark? If so, you are getting spark to the distributor. If not, your point gap may be off or there is some other problem with the connections.

4) Verify that the spark goes to the spark plug wires. Reattach the center lead to the distributor. Attach you spark plug to one of the leads going to the cylinder spark plugs and ground. Crank engine. If you see a spark you may have a timing problem. If no spark, you have a problem with your rotor or distributor cap or your wires are improperly seated.

Do a search here as there are many threads on this topic. Look especially for the ones by early_s_man. Warren (RIP) left a great deal of knowledge on troubleshooting this problem.

[kiwicobber]

Hi, checked for fuel flow and no, there's no whine from the injectors..... There was a little resistance the first time I lifted the airflow sensor but no noise at all from the injectors......

[HarryD]

You may have a clogged fuel filter, clogged screen in your tank or a dead fuel pump.

Remove the line from the fuel pump that feeds the accumulator in the trunk. Get some line to direct the flow out of the engine room. disconnect the power to the CDI Box and put the car in run. See if any fuel gets pumped out.

[kiwicobber]

repleaced the red fuel pump relay and hey presto.... all running again. Thanks for the advice team....