starting issues after car sits for a while - 986 Forum - The Community for Porsche Boxster & Cayman Owners

hi guys, 2000 base boxster, 140k miles on the clock. never failed to start since i got it 3 years ago. recently refurbished all injectors and mechanic had to remove the intake to get to the ones on the air box side. car starts first crank in the morning. once i shut the engine off and i come a few hours later it struggles to start as if it's not getting gas. acts similarly to when you run out of gas and you have to crank it for a few seconds until gas reaches the engine after refill. it typically starts after 3-4 seconds of cranking, most of the time depending how long it was since it ran when i return to the car. in the morning it starts perfectly. is all the gas going back to the tank somehow? mechanic did mention he noticed my gas pump was loose in the tank and he tightened it down. did he mess something up? where should i look first? thanks, Cristian

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I would start by running the car with a fuel pressure test gauge attached, reading the pressure. Then shut it off with the gauge still attached and let it sit to see if the pressure bleeds off. It should not.

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i'll order a fuel pressure gauge and test. i tested a few months ago and it was within specs but this does seem to be a fuel pressure issue somehow. could this be related to the fuel regulator in any way?

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Possibly.........

i did the fuel pressure tests. - ignition on without cranking the engine shows 52 psi which is on the lower end of the spec which i understand is 55 +/-3 psi but i'd say acceptable. - with the engine on at idle it sits at 46-47 psi which should be good as spec is 48 +/-3 psi - I pulled the vacuum out of the regulator as well, there's good vacuum, no leaks and no smell of gasoline on the regulator or line. fuel pressure jumps up a few psi when I pull it which indicates the membrane inside is working correctly. - here's a video of idle, steady revving at 3000 rpm and short revs. doesnt seem to indicate anything might be wrong with the fuel pressure. https://www.youtube.com/watch?v=j8OGCSFgcLY - lastly, i turned it off and left it for 30 minutes. pressure went down 1-2 psi which i think is ok? or should it not drop down at all? not sure what's going on, i was expecting a quick bleed out since it had issues starting after just a few minutes. weirdly enough yesterday while doing all these tests the car started fine. remember these issues started as soon as i refurbished injectors and the gas tank was opened as well by my mechanic who supposedly tightened down the fuel pump which was loose. car never had an issue starting up before. i heard if an injector o ring is pinched it could cause a slow leak. i also heard the gas pump has a valve that opens and closes when you start/stop the engine to prevent losing pressure. if that doesnt close it might cause a pressure bleed. any idea guys? thanks, Cristian

i'm starting to think it's not fuel pressure related, according to the above it seems to hold up just fine. someone correct me if i'm wrong. the strange thing is in the morning with the engine cold it starts perfectly, even after 3-4 days. if it was fuel pressure it should drop after not using the car for a few days. could this be starter related? a few weeks ago when i had injector issues and mechanic cranked it up a bunch of times when it was not starting it could have messed up the starter. what are the typical symptoms of a failing starter?

Have you checked your crankshaft position sensor?

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I did not. Is that done with durametric or how?

A failing starter should be easy to diagnose, it just cranks the engine over slowly.

Hmm.. I’m really starting to think it’s the crankshaft position sensor. A quick search reveals symptoms similar to mine where it would start normal when cold but once the engine was up to temperature it would have difficulties starting. It’s most likely on its way out. Since the CPS feeds info to the DME, I’m wondering if this could cause some of the long term trim issues I’ve been having for a good while?

so i went ahead and changed the crank position sensor and it did not fix it. i'm back to suspecting a fuel pressure issue. when testing with the gauge it did seem to drop 1-2 psi and from what i understand it should not drop at all. what i dont understand is why it starts perfectly every morning after sitting for a week? a fuel pressure issue should cause a starting issue after the car has been sitting for that long. could it be the fuel pump or some injector i recently refurbished? thanks, Cristian

Maybe a rich condition caused by the EVAP system? You could try blowing out or even disconnecting the EVAP purge valve, plugging both ends and see if that helps. I'm thinking that if you had a bad valve in the EVAP system that fumes could be flooding the intake, same as the "hard start when hot" issue. After sitting for an extended period, the fumes would dissipate and the problem doesn't occur.

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you might be on to something here! whenever i have the starting issue and the car eventually starts i do get this strong smell of gas fumes.

My son’s Boxster had same problem and it was CPS.

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wish i was in his shoes since i'm tired of chasing this issue but replacing CPS didnt do it for me

I'm ignorant of the cause... but I'd be running with Particleweave's recommendation. It appears there are no clues left.

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yeah im going with that, looking into how i can test

UPDATE: i went ahead and replaced the EVAP purge valve. i only bought the valve itself, not the whole valve and line assembly ($46 vs $200 difference) and from the source website it mentioned i should reuse the line. big fat lie as that line is plastic that i believe is heat shrunk on to the valve itself. i bought a $2 fuel hose and some clamps and made my own line for under $5. BUT! unfortunately it didnt fix my hot start issue. 2 hours after the car sat it still struggled to start a bit. ugh!! patience is running low on this one. very strange though, i drove the car for about an hour after replacing it and my god did it idle good! i'm talking not one dip on the needle, it was perfect! drove home feeling like a champ, patting my wife on the back who helped with the swap. half a mile from home i get the dreaded P1130 code which i've been eluding for a couple of months (somehow). i reset, idles like "meah" again, take it for a drive around the block, with durametric hooked on, check for codes again when i park and voile P1128 and P1130 lurking there, no CEL on the dash yet, but they were in the memory. oh man is my patience running low. didnt fix anything, still having hot start issues, and same old codes keep coming back for 2 years. i'm just about to call it quits and take it to a specialist, i have a road trip coming up in 10 days. maybe have it smoke tested again and see if they can figure out why the start issues. any other advice before i give into the darkness?? thanks guys, cristian P.S.: I miss my Honda S2000 days. CEL? what's a CEL? whiskey time to drown the sorrows! oh! another code in memory after replacing the purge valve was this guy: P1671. did some research and it's a weird one, most likely a fluke so i ignored it. didnt come back after reset. rom the 7.8 DME Manual: P1671 DME relay/control module faulty (computer monitoring: reset) – signal implausible Possible fault cause ◆ Undervoltage ◆ DME relay faulty ◆ DME control module faulty This fault may be entered if the control module has been operated with undervoltage. Affected terminals I/1 and I/8 Diagnosis/troubleshooting Note! • If no fault is present, erase the fault memory. 1) Check voltage supply, terminal 15 ◆ Measure voltage between pin I/1 and ground. > 11 V 2) Check DME relay ◆ Switch on the ignition ◆ Measure voltage between pin I/18 and ground Battery positive voltage Check triggering of DME relay Replace DME relay 3) Replace DME control module. 4) Perform adaptation. ◆ Switch on the ignition ◆ Wait one minute ◆ Do not press the accelerator ◆ Switch off the ignition for at least 10 seconds ◆ Read out the fault memory -> End -> End

Regarding the codes, do you have a Durametric to check fuel ratios? Have you tried disconnecting the MAF to see if it idles better? Smoke tested the intake for leaks (or sprayed with starting fluid)? Are you certain your new purge valve and lines are absolutely sealed? Since the injectors were just refurbished, there could also be an issue there.

I’m pretty sure new valve and line are ok, double checked everything and it was good. I did disconnect the MAF and doesn’t idle any better. I had it smoke tested a year ago came out air tight everywhere. I did think maybe injectors might be the issue since it started after replacing, like maybe a slow leak from a pinched o ring but that wouldn’t be the case since the car sits for a week and starts at first crank, pressure would be all gone by then. I have durametric, which values should I check and what am I looking for in terms of fuel trim?