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YOUR RESEARCH996 Cranks but doesn't start
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car cranks
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Leading evidence: 'car cranks' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'car cranks' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Check evap purge valve located over the alternator' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Reported cause
In my case it was the wiring that was smashed and I was actually able to save the sensor.
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I see you checked the relay and fuses, but something is not right.
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Performed · outcome unconfirmed · Original poster
The cannister looks okay although for the life of me I couldn't figure out how to remove it, so I disconnected all the hoses and reconnected them.
Check fuel rail pressure first, was showing stepson how
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I recommend checking the fuel rail pressure first, was showing stepson how to replace his failed fuel pump, all worked good for two months, towed back home and found rail press.
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You can just check it with a small screwdriver at the driver side fuel rail shreder valve and can check the injectors (the one on the drivers side is the easiest to get to) if they get power with a noid light.
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I have new crank sensor, but it did not fix the problem.
Need a little help figuring out a starting point for chasing a starting problem. The problem is the car cranks but doesn�t start. This happens randomly and can occur with the car hot, cold, first starting of the day or after several starts with minutes or hours in between running. The cranking cycle is strong and does not spin slowly.
Okay the next description is strange but it is what happens�.
The engine cranks and eventually will start but it sounds like it is not getting fuel, but then gradually starts. Is reminds you an old carbureted car that you pump the gas and it finally �catches� and starts.
First thoughts point me to the crank position sensor, but the way the car starts could point to a fuel issues. One more fact, when first starting after a failed crank cycle, the car hesitates when the pedal is depressed.
1999
No CEL, no codes on the Durametric, and some days it starts right up and drives fine.
Chuck
Did you notice if the tach needle bounces when the no start happened? If it does not, it points to the crank position sensor. If it does, it's not conclusive.
My next guess is the fuel pump and fuel filter. You may need to check the fuel pressure when it doesn't start up. Do you hear the fuel bump priming at all when no start happened?
Also have you cleaned the idle stabilizer and throttle body?
The tach needle only bounces when the cranking results in starting. There are moments when the car initially cranks and almost starts, the tach will move slightly then not move until the car starts.
I recently moved and no longer have access to my tools and garage, this greatly hinders my ability to troubleshoot. I will pay attention to the fuel pump priming during the next startind cycle.....I didn't think of that...Thanks
Nope, and that needs to be done. I will do that tomorrow..
Sounds like a bad crank sensor to me because a healthy one will bounce noticeably until the engine starts, at which point it just shoots up to 1k+ rpm then settle back down to 900 or so.
When you turn the key to the last position before crank, you should hear a brief a ~2s fuel pump priming. If you don't, you will need to check the fuel pump relay and fuel pump itself.
I agree, CPS. I had a similar thing happen with my Infiniti G35. The sensor took a beating from a large rock or something that was thrown under the carriage. If the car was exposed to water at all it would not want to start or would take considerable amounts of cranking.
It actually shut itself down in a rainstorm while I was on the interstate doing 70mph! In my case it was the wiring that was smashed and I was actually able to save the sensor. Very similar symptoms...
I had similar symptoms in my car. When stopped after short drive, engine needed long crank before it started. Pushing the throtle to the floor helped, so I think that plugs were wet.
I have new crank sensor, but it did not fix the problem.
I now use plugs with only one ground electrode and had no probles after that.
My coilpacks are old and cracked, and needs to be replaced. I think that this is the reason why the engine had starting broblems with stock plugs with larger gap. (more resistance to get stromg spark)
So, two theories now - Crank Sensor or Plugs.
My initial thoughts were on plugs too - see my other post.
Jake Ruby once replied suggesting Camshaft Hall sensor , saying that when they fail, engine does not go into "fast start" mode - I've no idea what it means though.
Is there a way to test one of those sensor without PIWIS ? And if they "fail" - I suppose a CEL or Freeze Frame of some sort would be registered, I had none. Which leads me to spark plugs, in many cars I had, sparkplugs were always the issue.
A failing crank shaft sensor does not affect emissions so there is no OBD2 error code/freeze frame data available. There may be a Porsche proprietary error code logged but to obtain this would require PIWIS or perhaps a Durametric.
Plugs would have to be pretty bad to cause a crank but no start problem.
How many miles on the plugs? Stock plugs IIRC are good for 60K maybe longer I forgot the change interval. Keep in mind non-stock plugs may not have nearly the same service life.
No need to over analyze this I guess. If you believe plugs are at the root cause of the symptom then replace the plugs. If the coils show signs of deterioration it is best to replace them too.
If the symptom was from the plugs (and possibly coils) you'll know soon enough as of course the symptom will be gone.
If the symptom persists afterwards well, you can then replace the crankshaft position sensor unless a more likely explanation comes to mind in the meantime.
I'm with Macster on this one. Based on my own experience, in general marginal spark plugs should give you a lot of trouble (misfires) under load way before they could stall the car or cause a no start situation.
To check the crank position sensor and cam position sensor, ideally you want to use an oscilloscope
https://rennlist.com/forums/996-foru...l#post11469612
Thanks Macster. The plugs and coil packs were replaced 40K ago and I used OEM replacement parts from Pelican. I'm leaning more and more towards the CPS and will have the indy replace it as well as clean the IAC and throttle body.
Chuck
Macster and everyone,
Aside for the CPS could it be a failing fuel pump? I�ve reached out to a local indy and the logic that I'm following/applying to this scenario is the car cranks and "catches" but fails to start because the pump has lost its prime.
The tach does move when cranking, which I misreported before.
Is it possible that pump must generate enough fuel pressure to eventually start if the pump loses its prime? Is it possible for the pump to behave in this manner? I tell you what; it sure reminds me an old car that you must pump the gas pedal to get enough fuel to start.
Thoughts?
The pump is in the tank, so it shouldn't ever need to be primed, but a failing pump can result in low fuel pressure.
How old is your fuel filter?
The ground strap issue that has been reported in various threads may also result in an occasional hard start.
It seemed progressive until I needed a tow because it decided it was kaput. This was over the course of a week or so.
The buildup was hard starts; the adios involved total power loss on the freeway at about 85. It kinda sucked.
Bummer on the when it failed, but your thoughts have pushed me to the conclusion that the pump needs replacement. Although the incident last night is also the "push" I needed.
Driving last night a new sound appeared which seemed to originate from the front of the dash (fuel pump location in tank if I had to make a guess). The sound is a whining that happens when I press the throttle and continues until a stopped idle but then returns and it is loud. The car also died 4-5 times while idling and took a lot of cranking to restart.
At this point, the dots connect and point to the fuel pump so I'll order one on Monday and make the change. The suck factor on this is I no longer have access to my nice garage in NC, so I'm doing the repair in condo complex parking lot....yippee!
Thanks to everyone that responded both on the thread and via PM, all the advice was great and I learned a few things.
Looking for a little more help/suggstions.
I replaced the fuel pump with great anticipation that if would solve my non start problem….and it didn’t. I’ve researched several forums over the last week and I’m no closer to a solution, but I have a bunch of ideas. I’ll try not to write a novel but here is what I’ve got so far.
Couple of CEL’s finally showed up and I’m hoping they are recognized by someone that has a suggestions or solution. Code P0455 and 446, which could be the canister, vent lines, gas cap, vent valve, or regeneration valve. Gas cap replaced a year ago, vent valve on the filler tube replaced about a year ago as well. I do not think it is the regeneration valve because most of the posts related to that part replacement suffer from not starting at gas stations. I am experiencing non starts when the car is hot when the car is cold, after long or short drives and also when cold after sitting for a few hours or overnight. The car also stalls when the gas pedal is depressed while accelerating from a standstill and hunts for idle while at stop lights.
All ideas, thoughts?
I would suggest the followng:
- remove the idle stabilizer and throttle body and give them a thourough cleaned
- remove the evap regen valve that's above the alternator and use a 9v battery to test if it's sticky. It should remain closed and sealed when no power is applied
- check presence of sparks when no start occurs
- pressure and flow test the fuel system
- test resistance of the crank position sensor. Use an oscilloscope to check its wave form
I posted some links on RennTech for you to help you run down your problem. I was also wondering if you have checked for a vacuum leak somewhere? Just wanted to suggest that with a hunting idle vacuum leaks are frequently the cause. Check your evap purge valve located over the alternator. I would just replace it. Also, carefully inspect your oil filler pipe for cracks. Mine cracked, power was down, car ran like crap, hunting ilde. Replaced it and the everything was perfect again.
Thanks for the advice.The filler tube was replaced when it split during an alternator swap.
I have several new codes on the Durametric
To test a theory I disconnected the mass air sensor while the car was running so I attribute these three codes to that; P1125, P1123, and P102. Am I sound in my thinking or way off base?
P0446 is still present ( I rechecked all lines but don't have access to a compressor to blow the lines) along with a new code, P0444 -Solenoid valve 2 for carbon canister open circuit. Does this mean the valve has failed? If so is is valve #6 or #1 on the diagram (link to Renntech
http://www.renntech.org/forums/topic...code-is-p0455/
)
The cannister looks okay although for the life of me I couldn't figure out how to remove it, so I disconnected all the hoses and reconnected them.
Are the symptoms still the same that the car cranks but can't start randomly?
If you suspect the evap system is affecting it, you can disconnect the purge valve from the throttle body and use a rubber cork of the right size to plug the hole in the throttle body and then re-crank the car to see if it starts.
Thanks for the great suggestion....I will plug the hose today and take drive to test.
I've read what I believe to be every single tech article, DIY and forum thread even remotely related to my problem (CPS, EVAP system, fuel system) and I've decided chase the EVAP path as it seems the likely culprit.
With the fuel pump, fuel filter, gas cap, and operating purge valve being replaced, and cleaning the mass air sensor, throttle body, and IAC valve I'm confident I will find something soon.
Just one clarification. You need to plug the hole on the throttle body (and maybe the hose itself too as it will emit fuel vapor so it may not be safe to drive the car around with the open hose). I meant to say do the check only when the no-start occurs but turn off the engine and connect everything back if you need to drive the car.
Also, the crank sensor is still a suspect although usually it fails when hot but your problem does not seem to be temperature dependent.
It is still very random, but occurs more frequently when hot. I still suspect the CPS as well, so I will replace it. I was able to locate it when I changed the fuel filter, so it shouldn't be too much trouble.
as for disconnecting the valve, it's normal state is closed so I simply disconnected the plug and will see if that has an effect.
Thanks for all of your feedback. It's nice to have someone to bounce ideas against.
Additional question(s)
P0444 Solenoid valve 2 for carbon canister Open circuit...Can someone point out which valve this is?
P0446 Shutoff valve activated charcoal filter (function) below limit value. Same question, which valve is this.?
Check out this diagram of the carbon canister
http://www.autoatlanta.com/porsche-p...section=201-20
I think all that stuff is located behind the passenger side wheel liner.
Picture
http://www.renntech.org/forums/topic...anister-valve/
That may not give you conclusive result because the valve may have failed and is stuck open. The whole point of disconnecting that hose is to separate the throttle body from the evap system. If the valve is stuck open, the throttle body will suck in all the gas vapor and create a high vacuum in the gas tank that prevents the fuel from being pumped to the engine.
Another indirect way to test it is when the engine doesn't start, just loosen up the gas cap and that will release any vacuum.
The valve is stuck close. I can see the internal valve and it is in the close position and when air is applied to the inlet of the valve non passes through.
I see this is an old thread but just wanted to see if my situation of no start has any suggestions. My 1999 996 tiptronic had a new fuel pump and sender unit a little more then a year ago when I had a no start issue after that ran fine for a year. Sounds like same problem again but wanted to see if any other possible issue comes to mind from anyone. Relay and fuses are good if I spray starter fluid into intake car fires right up, thoughts?
thanks
Rich
Need to check the fuel pressure on the fuel injector rails. Check or replace the fuel pump relay. I see you checked the relay and fuses, but something is not right. Only a pressure check will tell you for sure. Could be the fuel pump or connections. Faulty fuel pressure regulator?
Besides checking the fuel pressure. You can just check it with a small screwdriver at the driver side fuel rail shreder valve and can check the injectors (the one on the drivers side is the easiest to get to) if they get power with a noid light. Is the tach needle bouncing when you are cranking the engine over with the starter? I had a failed crank position sensor that cut the signal to the injectors but it would start up with starter fluid.
I recommend checking the fuel rail pressure first, was showing stepson how to replace his failed fuel pump, all worked good for two months, towed back home and found rail press. is zero, had him pull the fuel pump and found pick up tube not connected. ouch
