Startup/Firing
 

Hey Guys - new to this forum. I've lurked for a while and I know there are a lot of sharp minds here, so I was hoping someone might be able to help.

Have a 99 Boxster. Recently developed a startup issue. From time to time, it won't fire. Car consistently turns over - that's never a problem - but some times, it won't fire and get going. I can't seem to recreate it.

Pressure test was done and it doesn't look pressure.

The only other real clues I can offer is that the car was recently transported from city to city (on a truck). Not sure if that's relevant but maybe climate change? Doubt it. The other thing is that when I have the issue - when it turns over and doesn't fire - if I wait about five minutes and try again, then it fires up.

Intermittently failing fuel pump? Maybe something in the EVAP system? I have no CEL, no faults on the computer and no pending faults.

Any insight would be appreciated.

There is a potential for a fuel pump issue, but you said you're getting fuel pressure. Always a possibility it could be the pump, and you could try a used one (since it's an easier/cheaper system to the later models). But I'm probably not correct on that.

Sounds like EVAP to me. Check the charcoal canister and all valves/lines.

The ECU compensates for temperature (both air temp and engine temp) so a change in location/weather shouldn't make any significant difference.

The ECU will also enrich the air/fuel mixture at cold start if it detects low battery voltage or if the engine doesn't "catch" right away to improve the conditions for the engine to fully start.

Thus, I'd start by checking the fuel system - when was the fuel filter last replaced? Do you have the ability to monitor the fuel pump pressure while cranking the engine (when it doesn't start)?

I'd also take a quick look at the intake for oil from the AOS and check/clean the MAF.

With the problem being somewhat unrepeatable, it can be hard to accurately diagnose the exact cause. The good (!!) news is that usually these problems get worse over time and eventually you'll be able to repeat the fault which will help with diagnosis.

When flailing & failing at a repair I am ashamed to admit I am clueless so deceive myself by doing maintenance. Amazing what you find - sometimes.
So I agree ,if it is due - replace the fuel filter,check plugs, air filter,vacuum lines and electrical connections, oil &filter change.
But that is appalling advice to give in Winter !
But why does it start after you wait? What happens during the wait ,that 'fixes' the problem ?
I have found my Durametric or a SnapOn scanner sometimes identifies a problem that simple code readers do not. Maybe paying for a Durametric/PIWIS diagnostic at your local Indie is the best solution?
Let us know what the culprit is please.

Does it tend to not start over more often once the engine is warm?

If so, could be a failing Crankshaft Position Sensor (CPS). They tend to get finicky when warm before failing completely, which could explain why waiting seems to resolve the problem, and they normally do not throw a code.

To answer some questions:

-I haven't replaced the fuel filter. I've done the water pump, MAF, spark plugs, fluid flushes but not the fuel filter that I'm aware of. However, I've only driven it 6,000 miles in the time I've had it.

-As far as I know, pressure was tested in every way. Tested over night and never lost pressure.

-I can't say it's temperature related. What's bizarre (or - should I say - not bizarre) is I left it with the mechanic for a week. He drove used it whenever they needed to do small errands. Started every time. Even left it in in the garage; no problem. Of course, I take it home and there's an issue.

One thing I might add is that parking in my garage, it fires up every time. Sometimes it seems like parking on an incline or decline, the issue crops up. When it's in my garage, it literally fires up as smooth as can be.

Hard starts when parked on an incline also points to the EVAP system. ;)

Odd question: what about a decline? Is EVAP still a factor in decline as much as incline?

And I know this quite specific, but to clarify, when I say incline or decline, I don't mean a hill. Just mostly something like a driveway.

Any non-level position can affect starting if the EVAP system is faulty.

We recently had a Thread on the "won't start on an incline" issue.Indeed ,it seemed to be an Evap issue.In such circumstances(on the incline& not starting) I would think that Durametric would identify the fault

Looks like it was the fuel pump - at least, that's hopefully all it is.

Mechanic said he kept testing it and finally had the startup issue occur for him. When he listened closely, there was no buzzing (before turning the key the whole way), which tipped him off.

Unless it is an ignition switch fault - very common. But just to do due diligence, connect the pump direct to 12v - does it work & what resistance is the pump?