vandal968

1993 968, daily driver since 2003, showing 158k. About two years ago it was running rough, low power. I swapped plugs and wires (no change), original fuel filter (no change, but the old one had rusty water in it), cleaned the MAF (no change), then swapped the TPS & O2 and the car totally came back to life. Fast as hell again, no roughness, runs like new. Not too long after that, I noticed that when the car was parked in the sun (100+F outside), it would need to crank for a LONG time to start, like 15-20secs it would crank and crank then eventually you'd hear it try a little and if you massaged the throttle it would fire up. It needed a little gas for maybe 10 secs before it would hold idle without adding a little throttle. This was ONLY when it sat and baked in direct sunlight. Wouldn't do it if parked indoors regardless of temp (110F in my garage sometimes), wouldn't do it if it was less than 80F. Only when sitting and baking in the direct sun so that you couldn't put your hand on the hood. I originally suspected that the 24yo original fuel check valve might be letting the car lose its prime when it baked (esp since I had just messed with fuel filter before this issue surfaced), but indy tested fuel rail said all was good and it even maintained pressure for 2days (when they stopped test). I just tested coil (in spec), checked & regapped plugs (look beautiful), inspected cap & rotor (look good), replaced DME temp sensor (only $7, so why not). Not really sure what else to check. Someone suggested idle air valve, but my idle is rock-solid. I looked at my DME relay and the contacts had that black/brown varnish deposit on them which I cleaned (no change). Any ideas what else to check? On my 944 the only thing that ever went wrong from 51k to 174k was when the cap and rotor were end of life it would crank and crank the same as what I'm seeing here BUT on that car it only acted-up when it was super-cold like 10F which was my indicator to change it (would start fine once the sun warmed the car and I could drive to the auto parts store for one). I experienced that several times with that car over the course of many years. This is a similar behavior but only at hot temps rather than cold which has me looking elsewhere, also the cap and rotor for the 968 is a lot more expensive so I don't want to replace them for no reason, and I don't think they're very old. (although as I type this, I am now starting to suspect cap & rotor.....)

I'd also like to buy a fuel pressure tester and I find it infuriating that instead of them telling you what thread adapters they include (968 needs M12) they say idiotic things like "fits GM!" Great! WTF thread does GM use? Anyone have a recommendation for a kit? I want to be able to test two Porsches and an Infiniti and whatever else that I might drag home.

Car runs absolutely fantastic other than not wanting to start after being parked in direct sun for a while.

cheers,
c

vandal968

As I read and re-read my post I'm struck by the fact that my 944 used to have the exact same symptom when it needed a cap and rotor. But it seriously ONLY did it in the very cold when I went skiing, and this car is ONLY doing it when it's hot. Ok, I'm doing it, I just ordered a cap & rotor from AutoHausAZ. I'd still like to hear ideas for what else it might be as well as a recommendation for a fuel pressure test kit.

cheers,
c

Jfrahm

Try leaving the gas cap loose. It might be the vapor purge valve leaking and flooding the motor.

vandal968

Joel,
I think you might be onto something. The cap/rotor arrived today, and it's a warm sunny day, so I took off the top of the air filter box for access to the screws on the cap. The gas smell almost knocked me over. Never had that before and I've been in there a lot lately, but today is the first time I've opened it after the car baked in the sun (as opposed to right after a drive). I decided NOT to swap the cap/rotor. I loosened the gas cap and left the air filter cover off for about 15 mins for the fumes to dissipate. Will report back findings.

Thanks for the help,
c

vandal968

It was still hard to start, but now that I know that I'm dealing with flooding I used the flooded engine start procedure (WOT until it started) and while it cranked for a bit, it took less time than it usually does under similar conditions. So, now the question is, does it only flood when it's parked and bakes in the sun, or is it always flooding, but doesn't mind the rich mixture when it's cold out?

The problem seems to be getting worse. What other things can cause the engine to flood while the car is off?

I'm hoping this isn't a leaking injector, although they are 24 years old...

cheers,
c

V2Rocket

first thought after reading this thread is see if you can borrow somebody else's MAF sensor...
my thinking is that the sensor is getting a little screwy with the high heat (baking in sun under hood), and when you try to start the car the MAF tells DME that the air is super hot (hotter than it really is) and the DME leans out the mixture = harder to start.

vandal968

But the MAF doesn't come into play while the engine is off. I smelled a VERY strong gas smell upon removing the airbox cover while the engine was parked and not run for the last two days. Seems to me that fuel is leaking into the intake manifold from somewhere. I wonder if a little piece of crap is keeping one of the injectors from closing all the way and it's drooling?

I'm considering pulling the injectors and sending them to http://www.witchhunter.com/injectorserv1.php

Even if that's not it, it might not hurt to clean the injectors once every 20 or 30 years.

cheers,
c

vandal968

I've got one of those endoscope cameras. I wonder if I can just pull the MAF and jam the camera up each intake runner and see if one of them is wet?

cheers,
c

Jfrahm

Try leaving the gas cap loose before you park in the sun.

vandal968

Yup, I'm doing that as well. I loosened it today and left the top of the air cleaner off for a bit to let the fumes dissipate. It was still hard to start, and seems to be getting worse. Went for a 20mi drive, cap is still loose and I'll see what happens tomorrow. If problem persists, I'll send injectors for cleaning as that's my next guess and it's never been done in 24yrs.

cheers,
c

Jfrahm

It could be a leaking injector. I switched my car to newer Volvo injectors, there are some threads on this with part numbers. I do not recommend putting money into the old-style injectors when an updated style is so readily available. I suppose if you have a leaking injector fuel tank pressure could force fuel out of the injector when parked in the sun. You should also check for a blown fuel pressure regulator.

thomasmryan

smell the vacuum line on your fuel regulator. if the diaphragm is bad, it can be dumping fuel straight into the intake.

get a spare rail cap and tap some threads so you can adapt your pressure tester.

probably not your issue but shake check the charcoal canister in the divers fender well. if the charcoal gets loose, it can foul the control valves open. take it off and shake it. there is an emissions valve at the tank that allows the expanding volume of fumes to be pushed into the canister when the car is off. if the symptoms subside with the cap loosened, suspect this part

witch hunters injection service is a pretty sweet deal with new O-rings.

Tom M'Guinn

+1 on the fuel pressure regulator and damper suggestion...

vandal968

That vacuum line smells strongly of gas. To be sure, I hooked a mityvac to the nipple on the fuel reg, pumped it down to 23" and held it there for 30secs (it didn't lose vacuum). Removed mityvac and put finger on nipple, got a drip of gasoline on my finger. So, looks like that diaphragm is leaking, I'll get one on order asap.

Thanks guys,
c

vandal968

AutohausAZ is my go to place and they don't have it. Googling around, it looks like $135 for Bosch or ~$80 for a generic. Recommendation?