450 sel wont start when warm

HELLO,I OWN A 450 SEL YR.1980,AND I`M HAVING THE FOLLOWING PROBLEM:THE CAR WILL START FINE ONLY WHEN ENGINE IS COLD OR LET SIT FOR FEW HOURS.
IF I STOP THE ENGINE AND RESTART RIGHT AWAY IS FINE,IF I WAIT 2 OR 3 MINUTES THE CAR WILL NOT START OR IT WILL WITH A LOT OF CRANKING AND START SHAKING, WHEN START FOR A LITLE BIT, THAN IDLES NORMALLY.
HAVE BEING TOLD SOMETHING IS WRONG WITH FUEL DELIVERY SYSTEM...........

THANKS

MARINO

[Tomguy]

Have you ruled out vapor lock?
It happens, especially in the winter, when your gas lines and tank heat up the gas expands, and then it cools off causing it to contract. When it expands pressure leaves the system through the pressure regulated/vented gas cap but air doesn't usually go in nearly as easily. Take the cap off when it's hard to start, if that solves the problem, you have vapor lock. If you feel pressure on the cap (pushing it out, not sucking it in) then look elsewhere, a dirty fuel filter, clogged/malfunctioning pump, or dirty injectors.

Probably the pressure regulator but you'll need to do CIS fault diagnosis first.

[ctaylor738]

What is probably happening is that you are losing fuel pressure as the car sits. For the car to start, the system needs to repressurize with the fuel pump. If the car sits long enough, though, the cold start valve will activate and supply fuel immediately and the car will start quickly.

You could be losing pressure due to a bad accumulator or leaky injectors.

Originally posted by mapab
Probably the pressure regulator but you'll need to do CIS fault diagnos
is first.

replaced fuel pressure regulator but no changes,what about warm up regulator???

[david brent]

i had the same problem took me ages to find out and a lot of elimination it was leaking fuel injectors replaced them had no problem after

[ctaylor738]

I guess in theory that the warm-up regulator could have a leak that would allow the loss of fuel pressure. But I cannot recall anyone describing that situation.

And isn't there a check valve in the fuel filter assembly?

It is very easy to check out the fuel pressure if you can borrow a test set. I can send you the section off the CD if you send me an email.

Originally posted by marinos
replaced fuel pressure regulator but no changes,what about warm up regulator???

Email me your email address (adam@hisoffice.com) and I will send you a URL where you can get a CIS fault diagnosis manual. It helped me solve my hotstarting problems.

[Toxicant]

I had the same problem with a '78 6.9

There is a check valve in the fuel pump that goes bad, I found that you can buy just the check valve and install it on the old pump with out having to replace the pump.

Tox

[psfred]

Bad accumulator -- this allows the pressure to drop as the regulator leaks down, and the fuel in the fuel distribultor boils. Takes a while to force liquid fuel up there.

Check it -- you should have fuel pressure almost indefinitely after shutting the engine off.

Peter