The only reason your engine should experience vapor lock is if your fuel system has extremely low fuel pressure.
This can be caused by a clogged pick-up at the fuel pump, a weak fuel pump, a clogged fuel filter, a leaking fuel pressure regulator or leaking fuel injector.
And your issue does sound fuel related, so in combination with your "vapor lock", I'd look first at the pick up/fuel pump and fuel filter.
You can check this by hooking up a fuel pressure gauge. With your key on/engine off, you should have 39-45 PSI of fuel pressure and hold steady.
If it doesn't reach that pressure, your pump is weak. If it does reach that pressure but bleeds off, then your fuel pressure regulator is bad, you have a leaking injector or a bad check ball in the fuel feed line.
First check the vacuum hose that enters your FPR for any sign of fuel. If there's any, then there's your leak. If not, pinch off the return line and turn the key off, then back on. If your pressure builds and holds steady, you have a leaking FPR. If it does still bleed off, then you've narrowed it down to the injectors or a check ball in the feed line.
To check the injectors, you can either use an automotive stethoscope to listen to each injector while repeating the procedure for each one, or you can pull the plug to each cylinder and check for the presence of fuel on the plug.
If pressure is good at the beginning of your test, start your engine. If pressure drops more than 8 PSI below specs, then you either have a clogged fuel filter or a leaking injector.
With the engine off, a clogged fuel filter will allow the pressure to reach spec. But as soon as your engine begins running, the filter won't be able to supply the demands of the injectors, so pressure will quickly drop.
If I've helped you, please take the time to vote for me, as my reputation pays my bills. Thanx, Ernest.
Thursday, February 11th, 2010 AT 6:15 AM