Hey guys,

here is the situation.
A fellow Rennlister (Hans) picked up his car from my place today. The car had not run for a year.
Car started fine, with no weird sound, vibration etc.

Hans started the drive home and about 20 miles out of Corpus Christi, on cruise control, doing about 75, the ABS light went on and car started surging.

When he applied the brakes, lightly, to go to the shoulder, the 4 wheels seized.
He was able to make it to the shoulder unharmed.
Shut the car down. Now it will turn, but not start.

He is having the car towed back to my place, but neither one of us as an idea of where to start looking.

I assume that a malfunctioning ABS system can lock the 4 wheels, might also have been the reason for the surging, but can it also keep the car from starting?

Any other ideas?

Thanks in advance guys

Paul

 

The abs cannot keep the car from starting no, but check pedal freeplay for the brake issue.

As well for trying to start the car try holding the pedal to the floor and starting.

but as always check the relays.

 

I'm a novice to Porsche's but if its an automatic going that speed and locking up....killing the engine is no surprise to me. Holding the pedal down may do the trick...I wouldn't think its to major why it won't start...the ABS is another story.

 

The ABS has no effect on starting - whatever state its in.

The ABS should not be able to sieze the brakes either - in operation its job is to partially release the brakes - not the other way around.

Sounds like some other brake circuit or transmission issue here - if one of the brakes locked up or the transmission did something wierd for some reason and the ABS was unable to compensate or received what it considers "implausible sensor readings" it has various failsafe features to shut itself down (since its capable of disabling your brakes this is important...). In fact the ABS has lots of redundancy built-in and any time any of its inputs or its own actions are suspect it shuts down.

I suspect the ABS warning happened after something else went wrong...

Alan

 

What Alan has stated is the reason I said to check pedal freeplay, if there isnt enough play in the master cylinder the fluid port will close and not allow for any expansion of the brake fluid which will then boil (esp if sitting for a year in a damp area) and the only spot for expansion is the brake caliper pistons closing the brakes.

 

And he is a long way from Indiana... I suspect that the brake booster failed and was dragging the brakes BUT not sure why it would be turning over cranking on the starter but not starting... As stated the ABS only takes away braking pressure it never adds.

 

thanks guys,

Hans is not back yet, so there is a lot I don't know about what happened.

He did drive around for a little bit after the car was started. He told me that the brakes seemed a bit "funny" but good.
I offered that we put it on the lift, but he thought that everything was fine.

I am still puzzled by why the car would not start. It started right away when he first tried it, and then again after he filled it up. No issues at all.

More later once he makes it back

Paul

 

Hey guys,

Hans is in, we have determine that there is no power to the fuel pump.
we can't even jump the relay there is no power between posts 87 and 30.

Hans as a highly modified electrical system we will try to determine next where the power as cut off.

Can anyone tell me what the fuse for the fuel pump is on a 1989

Thanks

Paul

 

The chart for my 89 says the fuel pump is fuse #42. Good luck.

 

Further tests have shown that there is no fuel and no spark.

The current theories are either the crank position sensor, the ignition switch, problem with the brain maybe.

Now, to clarify: when Hans was first trying the car, he felt that the brakes were giving the same feeling as "warped rotors". But they worked nicely.

On the road, the car started surging. He describes it as when a cruse control looses vacuum. When the surging happened, he looked down and the ABS light was on.
He was already slowing down on it's own (was feeling like a fuel delivery problem), he started to go to the shoulder and as he "brushed" the brake pedal, it felt like the wheels locked up. He apparently left 4 impressive tire marks.

Hans doesn't really remember if the car stalled before, during or after the braking episode. All he knows is that once the car had stopped, it was not running anymore, and it would not start again.

Any other thoughts?

Paul

 

I have been talking to Hans on the phone about this problem. Refer to the other thread I started before I realized this one was going.
https://rennlist.com/forums/928-forum/417059-urgent-help-needed-928-died-on-interstate.html

 

Paul, tell Hans I am at the shop. I now have access to Mitchell and Alldata. Neither one has wiring diagrams though. I have found a pinout to the PCM though.

 

Crank sensor signal goes to the EZK which then feeds it to the LH.

You can pull the ABS relay in the CE panel and it should disable the power relays in the fender. I think the ABS issues are an effect, not a cause.

 

Very odd...... it must be more than 1 thing happening at the same time......I can't think of anything in the LH-EZK that would cause the brake issue at the same time.....the only thing that might do it is a bad ground point......

Does the ABS system and the CE share a common ground point.....that would be the 1st thing I check-clean?

Since there is no fuel-spark that tells me that the EZK is not turning on the LH...which all goes back to crank sensor...

http://www.electronikrepair.com/page6.html

Rich has lots of helpful tips for tracking down no-start issues....he does have a 9 page PDF file that lists everything...it helped me ALOT..but I can't find it right now.....try PM or emailing him!

 

Some kind of alarm issue? Aftermarket? Bad battery or alternator? It did sit a year. Aftermarket alarms are often the work of Satan.

-Joel.