Pistol Pete

Ok, so I have an '87 944, N/A. The previous owner mentioned that the car gets "vapor lock" in very hot weather, at which time the car will not start unless the pressure is drained from the fuel rail. This has happened to me several times lately. I can take a short trip, shut off the car, and it won't start 5 minutes later. It also smells strongly of gas after it has been driven. When I drain the fuel rail there is a ton of pressure and lots of gas. What can I do about this? Anyone have similar experiences? Quick help would be great. P.O. said a mechanic told him of the vapor lock, but could it be something else? I need to get this sorted out this week. Thanks.

SidViscous

Vapor lock in a fuel injected car? Helluva mechanic the P.O. had.

There is a thermo switch that changes stuff under hot engine tempratures. It's mounted on the back of the engine, possibly under the intake manifold (is on early cars). Has a vacumn line that goes to the throttle body, and another that goes to a vacumn thingy mounted on the drives side fender, behind the strut mount.

Check for loose, leaky lines. If not that replace said switch.

Bri Bro

Sounds like you may have several problems. One may be that the vapors in the fuel tank are not going into the carbon canister and then into the engine when it is started. Another issue sounds like a fuel or vapor leak and this needs to be addressed ASAP.

Lots of fuel preasure in the fuel rail is normal. There is a one way valve after the fuel pump to hold preasure in the fuel system. Without it, your crank times would be a lot longer before the engine starts. You could also have an injector that is dripping fuel under preasure. Lots of time a couple of Lucus gas cleaner treatments with a gas tank fillup will clean up this problem.

Pistol Pete

How difficult/expensive is the replacement of these valves and fuel lines?

Pistol Pete

I just popped the hood about a half hour after parking the car and I can still hear a loud hiss near the fuel rail, I assume of the pressure leaking out. Is this supposed to happen or is the rail leaky? I'm really frustrated with this whole thing and I need to sort it out quickly.

Manning

Hissing and fuel leaking out or hissing like vacuum pressure is leaking off? One of the culprits a lot of folks through out there is the Fuel Pressure Regulator. Maybe it is leaking internally or the vac line connected to it is and isn't holding pressure.

I had a similar problem last summer where no matter what if I drove my car for long enough to get to full temp and then shut it off to run into a store or something it wouldn't restart until it had cooled down. I never found what caused it and it hasn't happened a single time this year. Obviously that doesn't help your situation.

Bri Bro

Your nose will help determine if the sound is a fuek leak or a vacuum leak. Use a hose held to your ear on one end and were the sound is coming from on the other end. This will help detect were the sound is coming from. If it is a fuel leak, don't let it go. Lots of egine fires are caused by small fuel leaks. Look around the fuel injectors for leaks, each injector has a O ring seal and they are easy to replace. Also, check all the fuel lines in the engine for small cracks in the rubber or leaks in the metal crimps.

Pistol Pete

It does look like I'm getting some leakage around the injectors. I dont need a hose to hear the hissing, either. It is pretty loud with just the hood raised, standing near the engine. I'm reading up on the fuel system and I'll try to check some of the things you guys have mentioned. I'll look at hoses, check O-rings, etc. Is there a good way to check the fuel pressure regulator? It just seems like there is way too much pressure.

Bri Bro

Sounds like you are tracking the problem down. You need a manual gauge to check the preasure. I would suggest you go to your local reapir shop and ask them to do it, it is cheaper then buying a gauge and using it only once before you store it away. The preasure on the fuel system is high, around 35 psi.

http://www.clarks-garage.com/shop-manual/fuel-01.htm

Pistol Pete

Now I am more confused than ever. I just took it out for 45 minutes or so to get heat it up again. Parked it, tried to start 30 seconds later. Nothing. I unscrewed the end of the fuel rail and there wasn't anything to leak out. Previously, it has shot out of the rail and gone for several feet. I'm just confused now. I checked after the drive and the gas seemed to be leaking out of the fuel rail all over the rest of the engine. I don't know if that leak is the cause of the problem or merely a symptom of some deeper pressure problem in, say, the regulator. There are several things that could seemingly be wrong and I need to narrow it down a little more.

Bri Bro

Fix the leak first, I was able to pick up a kit for the Bosche fuel injectors seals from my local parts store. Lots of sources on the Internet for the parts. Then, do the preasure test in the link above. You can jumper the fuel pump to run without running the engine, don't want a fire.

Pistol Pete

Well, it looks like the leak is coming right from the end of the fuel rail. The thing seems to be misthreaded. From what I've read in some other posts, I assume I'll need to get a whole new rail. I think it might have gotten misthreaded during my battles with the "vapor lock" or whatever it is. So, in fixing the fuel rail I probably wont even be fixing the big problem. But, I have to start there.

phil0618

Fuel pressure regulator?

Pistol Pete

UPDATE: Turns out the gas smell/leakage was coming from the end of the fuel rail. The cap was misthreaded and not going on quite as far as it needed to. I retapped it today and now it fits. Gas smell is gone. Still though, I have the occasional starting problem in hot weather to worry about. I read somewhere that it could be a problem with the L-Jetronic fuel injection system responsible for maintaining a "hot-start" pressure for the 20 minutes after you shut the car off. Can anyone offer some feedback to this end?

Bri Bro

Two things maintain the pressure. One is a one-way valve after the fuel pump and the other is the injectors. The injectors should maintain the pressure for an extended period without an excessive leakage. Most injectors are graded by "drips per minute".

I would run lots of Lucas fuel injector cleaner though your system to try and clean up the injector seals. A leaky injector will cause a rich start condition in hot weather (flooding) but will have little effect on starting in cold weather.