The car crank but won't start. I am also getting a fast clicking sound near the IM area. No fuel pressure either. I took a look at the fuel pump fuse. Where else should I look?

 

If you get the fast clicking sound when you turn the ignition on (not trying to crank) your LH ECU has failed - classic symptoms - look at www.jdsporsche.com

 

Or it could be as simpkle as a dead battery. That is also a sound that is made. Start cheap and easy first. Battery charged? If so, do you have spark? Test by pulling a plug and grounding it while turning ignition. If spark, then fuel? You said fuse was good, try swapping the horn relay with the fuel pump relay and see if you get any result.

 

I would recommend troubleshotting step buy step so you don't waste over $1,000 in parts you don't really need (like myself)

 

Also, I saw/heard the same sypmtom on my former 86 and it was the nuetral safety switch. Fast klicking sound, no start. It is the electronic device that keeps the car from starting when it is in gear. Not as expensive as a brain.

 

When my battery goes low, I get a loud clicking sound and no start. This could also be caused by bad contact of the battery ground strap, or the ground strap between engine and body.

 

The battery is good. It is on a charger. The clicking sound with key turn to on but not crank. Why does LH brain fail. It was fine last week.

 

^^^^What Nicole said.

And, in the case of my avatar car, exactly that symptom was a loose/corroded ground for all the electronics in the engine management system. ( LH, O2sensor shield, MAF, etc ) Location is rear valley of engine, under the fuel regulator/damper system (hard to reach, but critical). One on each side of the valley.
https://rennlist.com/forums/928-foru...d-mp-viii.html

 

If the fuel injectors are clicking with the ignition switch turned on, but the engine not turning over, the LH ECU has failed.

There is a "hybrid circuit" solid-state device in the ECU that is almost invariably the cause. A rebuild of your ECU is the best option, a used ECU is a poor second choice, and a new ECU from Porsche is really, really expensive.

This is a common failure.

 

Just for clarity.

Injectors clicking at ignition on is relatively quiet and you will not hear the sound if you just turn the key straight to the crank position. So if no start - turn the ignition on and listen very carefully. The frequency of clicking is at a guess 20-30 clicks per second. The sound is probably best described as similar to the sound of all 32 lifters sticking a bit but much quieter at idle speed.

If you try to crank the engine and all you get is a very loud clicking sound (about 1-2 clicks per second) that sounds like an on beat then an off beat (da dum da dum)

This means that there is not not enough volts/current getting to the relay on the side of the starter for it to engage properly - so it just keeps trying on/off on/off.

Not enough volts/current is due to either a flat battery or loose/ corroded cable connections - bat terminals, starter terminal or engine grounds.

 

^^^ What he said...

If I read this correctly, you are saying the clicking is when you have the ignition on, but you are NOT turning the key further to start the engine.

Is that correct?

Or is the clicking ONLY when you turn the key all the way to the "start engine" position?

IF the latter is the case, then you have a weak battery or weak connection - usually ground strap, but it could as well be the starter wire. Easiest is to clean the ground strap contact in the trunk, and the battery terminals as well.

Otherwise it could be a failed LH brain. But I'm not qualified to diagnose this properly.

 

Please say more about the source of the clicking.

We had to actually jam our earr to the CE panel with start attempts to isolate the demon because the sound antenuates and its hard to find the source.

Is that what you are seeing/hearing , or is it something else?

The LH relay can click like crazy if the valley ground is corroded or loose. And it can show that behavior intermittently with respect to frequency. In other words, depending on engine bay temperature, humidity and god knows what else, that ground makes variable contact. Sometimes the LH relay will click fast, sometimes slow, sometimes not at all during attempted starts. Sometimes the car will run perfectly, then not restart warm. Sometimes it won't start cold.

Its best to run-through the cleaning regimens for CE panel and ground points. And looking for a broken CPS connector and especially shorted MAF connector.

Otherwise, you'll end up like a bunch of folks replacing the brain and still having the issue.

 

Landseer, I don't deny what you say and they are all valid points. However if the OP has identified the source of the sound as coming from the injectors - once you are somewhere quiet with the hood open and you can get your ear near the injectors there is no real doubt - then the next step is take the suspect LH ECU and put it a known running car to see if it replicates the symptoms. If it does it in the otherwise known running car detective work over.

AFAIK (Confirmed by JDS) there is no known way that an LH ECU that exhibits these symptoms can damage an otherwise healthy car. That is why the first test is to put the suspect LH in a "good" car. If that proves the suspect LH is duff then assuming the original car was running fine before LH failure it should be reasonably safe to swap a known good LH into the non running car.

However I would not swap a known good LH into a non running car (maybe one that has no known history or has had had a major rebuild) where the cause of non running was not known without further diagnosis - ie testing all inputs into both EZ and LH for the correct signals and voltages.

 

I agree if the sound is at the injectors.
Didn't know what he meant by "IM". Thought that meant ignition management system.

That said, we've all seen some weird behavior when CPS ground, MAF plug & ground and LH ground are in-play. Some of it didn't follow the "if A, then B" troubleshooting rules of thumb.

My main point is of course to clean grounds and do it an a regular (annual or so) basis, plus check the integrity of straps, because it has been proven to be a problem across the LH EuroS, S3, and S4. So that's what I'm doing first now. I've had my hands into a few of each over the last 12 months and am starting to form opinions that may ultimately be still from too small a data set. Have not, for instance, run into a bad LH yet, but we know they have weakness and many have been the root cause. Same with MAF. Ran into the first bad one a couple nights ago. Thank goodness it had been already identified by somebody else shifting back and forth between cars and a known good unit, because I'd still be out there on the driveway scratching head over ground points!

Back to the program.... Mr. Jthwan, what else can you clarify / tell us?

 

I thought IM meant intake manifold???? Go figure