99 Boxster hot start problems - Vapor lock symptoms - 986 Forum - The Community for Porsche Boxster & Cayman Owners

gssereik · 01-28-2010, 08:17 AM

My 1999 Boxster recently began having a problem... The car starts fine when cold. But once the engine warms up and then is turned off, it will not re-start. When trying to re-start, the lights all come on and the starter turns the engine over briskly. But it will not start. Like it is not getting a spark or is not getting fuel. But then if you let it sit for a couple of hours or more it will start right up. And it will always start the next day! It just recently began doing this. The first time I got a tow home. The second time, I drove it around to warm up and it ran just fine but then when i pulled into driveway and shut it down, it would not re-start. Lately I don't drive the Boxter very much. I do drive it at least once per week but usually only drive it around for 10-15 miles max. The Check Engine Light has not turned on. I have an OBD-II code reader that works on my other (non-porsche) cars but I don't know if it captures Porsche codes. At any rate, i did run the code search procedure but no codes were found. Not sure that I trust it though... Is it possible for a code to exist in the Boxsters computer but no Check Engine Light? I am not sure where to begin... thanks, George

ARModen · 01-28-2010, 09:56 AM

The answer to the OBD2 question is yes and no. The OBD2 will read all of the standard codes related to engine operation and the emissions system because that is required by law. That's the yes part.

However, there are more detailed Porsche codes and many more modules that the obd2 reader won't even access. All those modules, alarm, ABS, airbag, display cluster, transmission, etc, aren't read by the obd2 reader.

There are definitely codes that the obd2 reader won't see, that will kill the car, and won't cause a CEL. For example the alarm module can disable the car in the event of it being stolen, or at least the module believes it is being stolen, that does just what you describe because it turns off the fuel system.

There is a home system that works with a laptop and will show you all of these codes and allow you to access them and reset them. It's sold by durametrics. www.durametric.com but it's a whole lot more expensive than the scanners. You might be able to find someone on here, or a shop that is close enough to come over and check. The computer stores the codes so even if the car is running they should be able to pull the codes up. The dealer can use their PIWIS or PCT2 terminals to do the same thing.

ppbon · 01-28-2010, 03:03 PM

... try disconnecting the MAF and restarting.
If it starts it's something relating to the engine compartment temperature.
Probably a bad temp sensor or a problem in the sensor's wiring.
If the ECU thinks that the engine compartment is overheated it won't allow the engine to start to protect it.
I had those symptoms in my '99 as well.
Happy Boxstering,
Pedro

gssereik · 03-09-2010, 12:06 PM

PROBLEM SOLVED! Based upon advice from many experts, I decided to purchase a new Crankshaft sensor. Access was a bit difficult but I got it in there and it fixed the hot start problem! And after shopping around online and finding prices north of $100 for the sensor, i checked with Advance Auto parts and they got the part for me for $70!! And although the packaging said some other brand, the actual part was the OEM BOSCH part with the bosh part number on it and everything. So I am a happy camper. Thank you for all your help and advice!

vipola · 03-09-2010, 12:16 PM

Can you give us more information about what was the problem? how was that sensor failing? and what guided you to that sensor? for future reference..
thanks

gssereik · 03-09-2010, 12:25 PM

Frankly it was a bit of a leap of faith... I described the symptoms in detail to a couple of local German car mechanics. Both of them indicated that it could be a sensor issue. Because the car ran perfectly once it did start. There were no drivability problems whatsoever. But the Crankshaft sensor in particular needs to get a reading on the position of the crankshaft or else the computer that control things will not know what position the engine is in and so it cannot make a judment as to when to produce a spark and/or fuel or what have you. But once the engine starts, it relies on other readings perhaps? I don't know... Looking at the old crankshaft sensor, there were no visual clues indicating that it was worn out or damaged. Just a bit of black soot on it. But not much really... I also posted the question online in many different Porsche and Boxster forums and there were some posts from people indicating that the Crankshaft sensor might be at fault. There are also two camshaft sensors but a mechanic mentioned that they were a less likely culpret. And there were two of them, so more expensive! ultimately when i found the $70 price at Advance Auto parts I decided that was a price i was willing to take a gamble on. I did not have a check engine light. And none of my OBD scanners found any codes. And i was not going to invest in the right scanner that finds all of the available codes for a boxster. I almost was going to bring it to the dealer or to a good mechanic and pay whatever fee to get it plugged in and tested. But for $70 and my gut feeling that the crankshaft sensor was a likely culpret, I went ahead and bought it. And it worked! More often when i have taken such a gamble I end up being wrong and just wast money. But the Porsche God's shone upon me this time! thanks

vipola · 03-09-2010, 12:40 PM

nice, I'm glad it worked out so well for you, it's always a pain to troubleshoot intermitant problem.. thanks for the info and enjoy your summer

root_werks · 03-10-2010, 07:01 AM

I've heard the crank sensor is one of those "Replace every xxx miles" sort of part. Kinda like the MAF, often times they won't just fail, but have degrees of failure kind of working most of the time just causing all sorts of issues.

Good job on the fix!

masterbm · 07-25-2010, 06:16 AM

Hey,

I've got the same deal in my '99 with 140K. Think I'll try the sensor fix. Got a part #?

B

masterbm · 08-03-2010, 12:31 PM

Well, turns out it was INDEED the crank position sensor. Fixed, and now car runs great. No thanks to the shop that said it was the ignition.

B

craigf103 · 08-15-2010, 06:21 PM

Where is the crankshaft sensor located on the engine? I want to replace mine but don't have a manual to find where it is located.

Pianohawk · 09-29-2010, 11:51 AM

My 99 Boxster also has a hard start up issue. Every mechanic I ask about the CPS tells me that's prob not the cause, it's very frustrating. Please post some quick info on how to replace one. Thank you!

craigf103 · 10-10-2010, 07:36 PM

I replaced my crankshaft position sensor to try and fix my hot start problem and unfortunately it didn't help. It is relatively easy to do once you take the right rear wheel off. A few weeks later I got a CEL and took it in to my local INDE Porshce shop. The read the codes and initially told me the MAF sensor was bad which I was kind of skeptical about since the MAF seems to be often misdiagnosed as the problem. They replaced the MAF sensor and found it didn't solve the problem so actually started doing some more detailed diagnosis and found the fuel level sending unit and fuel pump and that did clear the CEL and solve my hot start problem finally! They took the new MAF sensor back out so I didn't get charged for that.

denvergold · 06-19-2012, 01:19 PM

Quote:

Originally Posted by craigf103

I replaced my crankshaft position sensor to try and fix my hot start problem and unfortunately it didn't help. It is relatively easy to do once you take the right rear wheel off. A few weeks later I got a CEL and took it in to my local INDE Porshce shop. The read the codes and initially told me the MAF sensor was bad which I was kind of skeptical about since the MAF seems to be often misdiagnosed as the problem. They replaced the MAF sensor and found it didn't solve the problem so actually started doing some more detailed diagnosis and found the fuel level sending unit and fuel pump and that did clear the CEL and solve my hot start problem finally! They took the new MAF sensor back out so I didn't get charged for that.

So you replaced the fuel level sending unit and fuel pump?

mikeboxster · 03-16-2014, 08:22 AM

I had the same hot start problem with my Boxster, 97(53k miles). If I start it immediately after switching off, it starts but will not if I leave it for 15mins. Changed the Crankshaft sensor but the problem reoccurs. The posts suggest replacing the fuel sending unit & fuel pump or disconnecting the MAF. Which should I try next?

Supersmarti69 · 05-15-2014, 12:57 PM

My '00 Boxster is having the same hot start problem. An independent import mechanic told me it was the ECU and to take it to the dealership. The dealership just took a look today. They refuse to change the ECU because they cannot be sure that is the problem... surely they have a way to know if it is bad without it throwing a code? There is another Porsche sitting there for 2.5 months with the same problem. I'll buy a crank shaft sensor and figure out how to swap it out myself. I am so frustrated with this car right now. At any rate, the dealership is still diagnosing.

jince · 02-23-2015, 07:05 AM

I'm having basically the same problem.
It will start right back up but if I go into a stor and come back out after 15 minutes or so...... makes a bad houre or so. Always at a bad time too.
I 've printed out schematics and did some tests. I ordered just the fuel pump to try because it's cheap (if it does fit and work). Universal Electric Fuel Pump E8016S for 1968-1981 Ferrari, 70-71 Dodge, 66-74 BMW etc ($23). Wish me luck.

jince · 02-23-2015, 09:38 AM

I'm having basically the same problems and I'm so over it. I'm going t try a new fuel pump. Basically because I found out you can just replace the pump only. I ordered a Universal Electric Fuel Pump E8016S. For a only $23, it's worth a try.

jince · 02-23-2015, 10:04 AM

I have the same problem as gssereik. I'm going to try a new fuel pump for $23. Hope it fits and works: Universal Electric Fuel Pump E8016S for 1968-1981 Ferrari, 70-71 Dodge, 66-74 BMW etc.
If that doesn't work, 'll try to clean and dielectric grease the ECU connectors in the rear trucnk and under the driver's seat.