1988 911 full batttery charge wont turn over?

[996AE]

Battery fully charged, cab top goes up and down, but wont crank?

DME relay?

I dont hear the fuel pump click

All fuses look good

Ideas welcome

Update

Headlights dim so I jumped the car battery and she turned over fast as she should be no fire. Usually first bump of starter and she lights

Two issues?

Under load 5 year old battery on garage queen on tender 11 mos a year toast and a bad DME relay?

Ordered UFO Relay

[GH85Carrera]

Try to jump start it with another car. 12.7 volts is after a fresh charge is meaningless if the amps are not there. I had a battery die, no crank, but a jump start got me home. I took it to the battery store and it tested as bad.

[Duc Hunter]

If the battery has lost a cell or two it will have voltage, and as GH85 says, no amperage to crank. My 996 Turbo just did this. Cranked slow at times fore 2 years, but started, then would not start. Down 1 cell it would crank slowly, it lost a second and would not crank. Charger charged it fine. New battery, problem solved.

Go to an Advanced Auto Parts, Napa, Autozone etc and they can test your battery. My guess, it's down a cell or 2. They will test it for free.

[996AE]

Jumped it and it turned over as it should but would not fire. Ill test battery and replace as necessary.

Ordered new DME Relay and no fire when jumped. Odd. Ive had the car for 6 years and this is a first.

We will see tomorrow with new battery and new DME Relay.

[996AE]

Jumped it and it turned over as it should but would not fire. Ill test battery and replace as necessary.

Ordered new DME Relay. Ive had the car for 6 years and this is a first.

We will see tomorrow with new battery and new DME Relay.

[Duc Hunter]

On one of my cars the DME died. Swapped to a new one (solid state DME with prime function). Car cranked great but not catch. I realize the fuel pump was not priming.....tried to figure out why...the wire in the DME plug that powers the fuel pump came off it's connection some how, in side the plug (maybe when I put the new relay in?). I re-soldered that end together and put an inline blade fuse in the wire right after it leaves the DME plug "just in case."

You might check the power from the DME to the fuel pump. Normally the pump only runs when the engine is cranking or running I believe. Part of why I love the solid state DME, it does a 5 second prime of the pump ever key turn. I can hear my pump run (our not) without the engine.

Good luck.

[996AE]

Update 3

New DME, jumped car nothing, battery shows 14.7 volts

Wont crank or spin starter

[Duc Hunter]

Won’t even spin starter…..hmmm…..starter solenoid? Strange.

[996AE]

Ignition switch is my guess. Lights not coming on with key on, and the door buzzer is intermittent.

Changing the switch is above my pay grade so off to shop Monday.

Thanks for the comments.

[PeteKz]

If it won't crank when jumped, try several things:
1. Make sure the jumper cables are well-connected. They just have small contact points at the jaws, so be sure those are tight on the battery cable terminals.

2. Clean and put some grease on the battery terminals and ground strap in the frunk, and on the battery cable connection to the starter and the ground strap from the transmission to the body under the car.

3. If the battery is 5 years old, that is about as much as you can expect from a lead-acid or AGM battery. Rather than dicking around with the old battery and jumper cables, buy a new quality battery. If you don't really "need" one now, you will very soon. Just bite that bullet now. Often, replacing the battery will fix "won't start" or "won't crank" problems.

If that doesn't fix it, then test the other things people have suggested.

[911obgyn]

Grounds, grounding ground ground. And clean battery terminals.

[996AE]

Wow I feel silly

After checking grounds, replacing DME, checking for power at starter etc... it was a bad battery

It showed full on the charger, tested at 14.7 volts

But one of you said it still could be a bad cell or two and when aload is put on it crashes and yep that was it

Pulled the battery out and took it in testing. New Interstate group 49 and fired right up

Thank you all

KISS is where you start

I hope this helps someone in the future

Thanks again all

[GH85Carrera]

I had the same thing with my daily driver. I had a jump start, and it ran and got me back home. I pulled the battery, and took it to Interstate. They used a battery tester. I showed a full charge, but the load test failed in a second. They replaced it with some warranty. The new battery works great.

I have had a battery fail so totally that even a jump would not start my car. I had to remove it in a parking lot, have a buddy take me to the Interstate store, have them test it, and sell me a new battery. The new battery fires the car right up.

I carry jumper cables always. And the tools to remove and replace the battery. In the past, batteries just got weaker and gave lots of warning they were dying. Now a battery works fine one minute, and is dead on the next start with zero warning.

At least with our 911s, we can do a push start.