1986 Porsche 928s turns but will not start
 

I've been driving my 1986 Porsche 928s for about 6 months now. But if I let it sit for longer than 2 days the car will not start and I have to jump it. Sometimes it takes about 15 minutes on the jumper cables before it will turn over, always if it sits for several days.

However recently it just will not turn over. Here's what I've done:

1. Made sure there was gas
2. Replaced spark plugs
3. Replaced air filter
4. Checked for spark on spark plugs. I'm getting a infrequent yellow spark
5. Replaced horn replay with EZF relay, still same thing.
6. Seems like the following relays are replacements (I could be wrong):
   • LH fuel injection
   • Fuel pump O2 sensor
   • EZF Ignition System

It's been a pain so far to check anything as to get it to turn with enough juice I have to jump it for 10+ minutes.

I've attached a picture of my relays and a
Any recommendations are greatly appreciated but I am very new to this so keep that in mind.
https://forums.pelicanparts.com/uplo...1489857768.jpg

It sounds as though there's an unwanted path discharging your car's battery.... assuming the battery isn't at end of life. If it is left heavily discharged then this can damage it.

There are threads on here to help find what the residual current drain is, and whereto look if it is too high.

I was planning on tracing and finding what was draining the battery but right now I'd be really happy if I could get it to start.

The battery is new a few months ago. So you're saying all the times I've let it sit drained for a few days might have killed the battery? I can get it checked but I didn't think I would get that churning noise if the battery wasn't good anymore.

Do you own a battery charger? If not I would suggest you buy one. They're not expensive. Note that I'm not talking about a trickle charger / battery tender. Get a real battery charger. Then disconnect your battery and give it a full charge, which may take several hours. Then reconnect the battery and see if the car will start.

I have seen RL posters talk about damage incurred by the car's ECUs from jump starting, but hopefully that is not your problem.

I actually went to auto zone earlier today and they said the battery had no charge. They got it up to 82% by the time I came back to pick it up. I'll be dropping it back into the Porsche tomorrow and hopefully it works. Fingers crossed the multiple jump starts I've put it through haven't messed up the ECU.

It's a deep discharge that kills a battery.

Also bear in mind that even if everything to start the engine is in good order it can be quite easy to flood the engine.

Try to check for a spark, if that is good then check for fuel. The EZ-F ignition ECU is the more unreliable of the two ECUs in your model of 928.

WARNING do not attempt to jumpstart your car any more.
Spend some time reading the Workshop manual on the charging system and the do `s and dont`s of how to treat it.

Since you know you have a drain on the system you must remove the battery from the charging circuit till your ready to use it.

Before you attempt to start the engine the battery should be at full charge,
this could be tested by the FLAPS.
If you have a weak battery then you might consider replacing it with a new battery thats been fully charged.
NOTE common issues with starting include dirty contacts at the battery ,
a failed ground strap I would just replace the one you have now.
corroded fuses and CE panel pins .
cleaning the CE panel with Deoxit 100 should be performed before you attempt to run the engine.


You would be best served by disconnecting the battery and putting the keys away,
and reading the FAQ at the top of the page this will take about 4 days.

Jumping the battery can cause damage to the alternator diodes the engine computer, the relays and the fuses .

Not following this advice can result in a permanent shadow in the your garage

Got the battery charged and put it back in. Spark looks good now but still no start.

Since it is sparking can I rule out the grounds and battery terminals?

I'll go ahead and clean all of the relays but the ones I pulled out looked fine to me.

Lastly how do I check for fuel? Do you mean try starting the car and check for gas on the spark plugs? Or something else?

Please forgive my ignorance and thanks for the help so far.

Are the spark plugs wet?

Does the horn work? If so then pull that relay and put it in place of the one with the test port for relays. My 86.5 sat for months until I tried a different relay. (can be any 53 relay just horn is used most times)

Is it an auto? Mine did this because I put the wrong relay in the trans relay position.
(Ignore my sig, I just sold the auto)

Does the tach flicker when you crank the engine ?

Clean all of your grounds. First thing I did when I brought my non-runner home. Amazing at what doing this will "fix".

-scott

Went to autozone again and the guy said the battery wouldn't hold a charge. It was under warranty and I brought home a new one. I put it in and it is so close to starting now. It's like it is right on the edge of starting but then doesn't.

The only thing I changed before the battery were spark plugs and air filter. The sparks look more yellow than blue. I didn't check the gap before I put them in, they are adjustable but I thought they were pre-set. They may not be. Would that cause the car not to start? If so does anyone know the right gap?

I've also tested each relay listed below. And I jumpered the fuel pump relay. The fuel pump does run and I tried starting but still no luck.

Imo000 - I gave it a few good tries then checked the spark plug. It wasn't wet. But I could smell fuel on them.

joejoe - Yes the horn works. I've tried swapping with the following relays:

• Ignition relay-X
• Starter relay
• EZF Ignition System relay
• Fuel pump 02 sensor
• LH-Jetronic Fuel Injection

Not sure what you mean about the test port relay as my chart shows that one runs the Fog lights

eWolf - Yes it is an auto. However it has been running fine so I doubt it's a wrong relay. Unless I'm mistaken?

John Speake - The tach meter flickered quite a bit before around 1rpm I put the new battery in. Now it slightly does but not more than a notch.

drscottsmith - I'll try that soon. Do you know where I can find them on an 86?

Thanks for everyone's input so far.

Press the gas pedal down all the way while you start the car.