1979 911 starting problem and spark plug wire problem

porcomar · 03-29-2015, 04:53 PM

My car cranks but doesn't fire up. I have not had a problem for years till now. My friend told me to ground a spark plug wire to make sure the spark plug was getting a charge. I grounded the end of the wire and saw sparks coming from the spark plug wire five inches from the end. Does that mean its time to get a new spark plug wires? The wires do look old. How hard would it be for a novice to change the wires with new ones? Any help would be greatly appreciated.

hansv123 · hansv123's Garage

How old are your wires? Spark from the end of the wire would seem to be good (if i read your description correctly), sparks arcing from the wire itself - not good. Try having a helper crank the engine in the dark garage, you watch at the engine/spark plug wires and see if there is arcing from the wires, will be a light show if your wires are bad. Not to say this is your non-start issue, but should help you determine if wires are a problem.

I just replaced the wires on my '85 3.2 and it wasn't too complicated; routing properly was the only challenge. For your '79 it may require removal of an item or two to make it easier; on my 3.2 I had swing the A/C compressor out of the way, made life a lot easier.

If you decide to replace the wires, my recommendation is Beru.

H

DRACO A5OG · DRACO A5OG's Garage

Couple of things:

What is the voltage on the battery before start? It should be 12.4+ volts

Also when you cranked it, did you smell unburnt fuel? make sure Fuel Pump is working.

Report back.

wwest · wwest's Garage

Quote:

Originally Posted by porcomar

My car cranks but doesn't fire up. I have not had a problem for years till now. My friend told me to ground a spark plug wire to make sure the spark plug was getting a charge. I grounded the end of the wire and saw sparks coming from the spark plug wire five inches from the end. Does that mean its time to get a new spark plug wires? The wires do look old. How hard would it be for a novice to change the wires with new ones? Any help would be greatly appreciated.

Check the fuel pump fuse in the frunk for good contact on both ends, contact looses its "springiness" over the years.

ossiblue · 03-30-2015, 06:10 AM

Sparks from the wires is a sign you need new wires, but it is not likely a reason for a non-start.

I'd advise you follow the suggestions to look at the fuel supply. Try this simple test: Remove the air cleaner and look inside the intake--you will see a metal "plate." Turn the ignition switch to the running position, and gently push up on the plate. Once the plate moves up, you should hear the fuel pump running. If you don't, that is your problem. If you do hear the pump running, hold the plate up for 2-3 seconds until you hear the injectors vibrate. Let the plunger go, move to the driver's seat and try to start the car.

If you choose to perform the above check, please report back with the results.

porcomar · 03-30-2015, 02:49 PM

I charged my battery fully and put it Back in my carxand the lights radio or anything else would not come on except the light in the trunk. The ignition key wouldn't even turn to start the car. I brought the battery to get checked and they said it was fully charged but was only showing 400 of the 660 amps. The guy said the battery was bad. Last year was the time when I cranking the car and it wouldnt start. He said the battery probably didn't have enough juice to get the car started. Does the ignition need to have a good battery to turn the key? For now I wwill try to get a new batterry to see if this fixes the problem. Thank you for your help.

ossiblue · 03-30-2015, 04:46 PM

Quote:

Originally Posted by porcomar

I charged my battery fully and put it Back in my carxand the lights radio or anything else would not come on except the light in the trunk. The ignition key wouldn't even turn to start the car. I brought the battery to get checked and they said it was fully charged but was only showing 400 of the 660 amps. The guy said the battery was bad. Last year was the time when I cranking the car and it wouldnt start. He said the battery probably didn't have enough juice to get the car started. Does the ignition need to have a good battery to turn the key? For now I wwill try to get a new batterry to see if this fixes the problem. Thank you for your help.

Yes, a low battery can prevent starting.

No, the battery has nothing to do with the ability to turn the key.

Clearly, there is something wrong with the battery installation if you get no signs of electrical except for the trunk light.

Please clarify the ignition switch issue for us. Does the key turn at all? It seems that it must if you claim that no lights come on. Are you saying the key cannot be turned to the start position, or are you turning it all the way to the right and nothing is happening? This is important because a dead battery could result in nothing happening when the key is in the start position, but not being physically able to turn the key all the way to "start " is something completely different.

Keep us posted after installing the new battery.

porcomar · 03-30-2015, 05:52 PM

The key will not turn at all. It would turn last year when I had the car cranking but no fire. Its strange but I tried wiggling the key but no movement. It seems to be locked up. The steering wheel has movement that my dad said shouldn't be moving. Had the car for years w/o any problems till last year. I will try again tomorrow. Thx again for your guidance.

T77911S · 03-31-2015, 03:33 AM

if he held the end of the wire close to the engine and it arched, that is good. that is what it is suppose to do. if the spark is jumping from the wire other than at the end, that is bad.
will that keep it from starting? probably not.

remove the air filter. on th eflat side of the air box you should have a "flapper". kinda looks like a small toilet seat. make sure that is seated properly and closed. if you do not have one, has the car backfired lately?

then turn the key on. reach inside the air box and push up on the arm, you should hear a squealing noise. try to crank after doing that.

porcomar · 03-31-2015, 02:25 PM

I just tried the key again by moving the steering wheel side to side. Now the key turns. I'm going tomorrow to get the battery checked again at one of the autozones. So if the reading comes back at 400 instead of 660 amps could that be the reason why I couldn't get the car to fire up? It cranked but did not fire up. I will get a new battery to see if that fixes my car issues. Thx

T77911S · 03:44 AM

its the voltage that matters in the end.
if it is cranking strong then that is not the problem. if it is cranking very slowly then the voltage could drop low enough so it will not fire the CSV. (rasise the sensor plate to give it a shot of gas like i said above).
you can put a multimeter on the battery to check the voltage while someone cranks it.

the AMP rating is the max current the battery is capable of putting out just like an alternater. even though an alt may be rated at 90 amps and a battery for 600, they are not putting out that much current unless something "asks" for it or needs it. for starting you may only need 200 amps, (i dont know how much) and just driving downt the road, the alt may put only 10 amps.
so if the cranking amps is down on the battery that IS a sign it is going bad BUT it may not be the cause of why it is not starting. it depends on the voltage that the battery can maintain when starting.

someone was going to eat my shorts for lunch if i did not elaberate on that one.

porcomar · 04-01-2015, 02:12 PM

The reading on the battery was 12.7 volts. Tried cranking the car again but no smell of gas in the engine. Removed the air filter but I don't see something that looks like a toilet seat. 1979 gargantuan porsche.

ossiblue · 04-01-2015, 02:19 PM

Quote:

Originally Posted by porcomar

The reading on the battery was 12.7 volts. Tried cranking the car again but no smell of gas in the engine. Removed the air filter but I don't see something that looks like a toilet seat. 1979 gargantuan porsche.

Read my post #5, above.