Intermitent hard start problem

[tjbjday]

I have had my 1999 Boxster with 90K miles now for almost a year. Of course I love it, but I have a problem I cannot get resolved. If I drive for a while and then let the car sit for 30 minutes or more, sometimes it does not want to start. Turns over fine, just does not start. After cranking for a while, it finally starts, coughs a few times and then runs great.

It has been worked on by two different garages.

I have had the crank shaft position sensor, ignition switch, coils and oil separator replaced. Fuel pressure tested fine.

Now dealer is suggesting mass air flow sensor.

[milliemax]

My 99 at 90k needed a new fuel pump. Initial start after pump replacement took a short while to get fuel to engine. After a few coughs and rough running it smoothed out and now is fine. I always turn key on and wait a few seconds before start. Sounds like a fuel problem. I do not know if the fuel system has a check valve to hold pressure to the engine ? I suspect it is in the pump. I saved the old pump to dissect but have not had the time . Hope you find the problem and please let us know .

[Dale_K]

You can disconnect the MAF sensor connection and see if the car works better. The computer reverts to default values if it can't communicate with the MAF so the engine will still run adequately. When I read threads about hard starting even though the car cranks well it seems like many times the original poster reports the problems were corrected with a new fuel pump. I know your mechanic says the fuel pressure is OK but maybe the fault is intermittant. You'd have to perform a test while the car was in a hard start condition to know for sure.

On the other hand I've had some mystery ailments clear up after I replaced my MAF sensor. It's kind of expensive but very easy to change so I guess it depends on your willingness to risk the money without knowing if it's really the problem. My car always started OK when the MAF was bad.

[blue2000s]

It's in the fuel system. Fuel pump is a good first place to look.

[milliemax]

This is a DIY project ! Go and search back to "car dead wife mad" 11/9/11 as I got alot of help on this project. I did enjoy changing the pump. Total cost $216.00 Dealer ? $1200/1500?????? I do not know. Max

[tjbjday]

:troll:Well, the Porsche dealer said they found the problem, a valve in the fuel return system. Another $500. Seems like any repair costs $500 at Porsche! They returned the car, and 15 minutes later it was getting towed back to the dealer. Started up and started making LOUD noise from engine area when backing out of parking space.

The dealership is really trying... gave us a new Jaguar XJ to drive but we are running low on patience with the car. What could it be now! A blown engine? Another $500 + repair?! For all the repair costs, I could have bought a new one!

[milliemax]

I am so sorry that I have not disected the old fuel pump yet. BECAUSE I wanted to know if the "CHECK'' valve was bad. (internal) and to see it it was a 2 stage pump with a good or bad motor seal. As I said the pump was "flooded" with gas. So, So sorry for your pump problem. I just do not think there is a seperate "valve" (check) between the pump and the motor. I could be wrong. John 99, Danger, please help me out !!!

[milliemax]

John99, Danger ??? Need some help here !!