This intermittent no start seems to be caused by vapor lock. When she wont start, I check the fuel line by removing the high pressure side hose from the fuel rail just past the filter. No Pressure. When I reattach she fires right up and runs great. This seems like "vapor lock". Any Ideas....Thanks.

 

I have read here that it is impossible to vapor lock an rotory engine. Or hydro lock, or what ever. No pressure in the fuel rail sounds like a big problem though...later

 

All electronic fuel port injection systems continuously circulate fuel so any vapor bubbles vent right back to the tank.

The fuel pressure regulator can fail & block the flow.
That would allow a vapor lock.

But, you're getting no retained pressure at the filter.
Maybe a fuel pump power circuit problem?

 

yeh, could be,...but the ONLY time she fails is on startup and that is intermittent usually when it has run and cools down to a certain temperature range somewhere between hot and cold. I checked the wires last night and the ground on the fuel pump looked sort not up to par....we will see...other than the relay by the steering column what other location does the power supply for the pump come from...wiring it direct would keep it running all the time, eh? Thanks....

 

Why would you expect the fuel to come out the pressure line when you pulled it off. You did not mention jumpering the fuel check connector when doing that nor did you say a thing about having someone put the key to start when you pulled the line off.........therefore you should not have expected to see anything but residual fuel coming out of the line.

 

Doesnt the system hold pressure for a few minutes? I can pull the line off after she's been running and THERE IS PRESSURE on it, LOT OF IT...it sprays everywhere. However, during a non start episode, there is no pressure and the pump is running..

 

Yep. There should have been approx 39-40 psi rail pressure in the line for some time. You could help yourself if you had a fuel pressure gauge that you could look at so you could see what is happening. The fsm has a check where you turn the pump off and the rail is supposed to maintain pressure for??????period of time. I forget what period of time. It's to check for leaking injectors.

Sounds like some kind of blockage in the fuel pressure line. Either the fuel filter or the mesh filter on the fuel pump itself. Might change both???

 

You've already changed the pressure regulator, right?
Could a previous owner have installed that "fuel pressure bleed off" thingy in the circuit somewhere?
At least it sounds like you're getting closer to solving it

 

YEP, but no fuel pressure bleed off...I installed a kill switch for the fuel pump to test for leaky injectors...if it were a blockage in the system I would think that it would shut down sometimes when running or not ever start once not starting....thanks guys....between all of us we are getting close....and yes I did put a new fuel pressure regulator on and the fuel pump filter is OK as I looked at it last night when checking the connections there...its an new one anyway and the old one was doing the same thing...

 

Pull the mesh filter off the fuel pump itself. When you lift the pump out of the tank ....the filter will hold fuel. If the fuel does not drain out of that filter within a reasonable amount of time......buy a new one or clean that one with carb cleaner, acetone/whatever. FYI you'll be able to see the fuel level in that filter as you lift it out of the car.

 

Bump

 

Some thing like a check valve ball is getting stuck somewhere because of the fuel pressure remaining in the lines after shutdown, and not allowing pump pressure to overtake it until the car's been shut down for a while to allow at least SOME pressure to bleed off from the system. Sounds good, but what component could we be talking about? The check valve somewhere near the pump? Maybe a check valve in the main filter? Hmmm...

If the mesh filter was clogged, it would run good for about 5 min, then slowly lose power until she falls on her face. Been there, done that...

 

bump

 

You can vapor lock the engine very easily. If you think about where your fuel rails are, just above the exhaust manifold / header, the heat off of that could cause the fuel in the fuel rails to vaporize, giving you your vapor lock. It amazes me that in the summer, that if you run your '7, turn it off, and try to start it again after 5 minutes or so, it starts right up with the close proximity of fuel and heat described above. My advice, just wait overnight, or if you can't, get a bag of ice and put it over the fuel rails. and also replace your fuel filter, about $15 and that is always cheap insurance against problems