Short version. After adjusting the valves and correcting the firing order on the 2.5 Lima engine I was having trouble getting it to run correctly. The issue was way too much fuel, would not idle and only somewhat happy above 3k rpm.
After trying a few sets of injectors, checking timing, compression, fuel pressure and vacuum/timing again I decided to try something. Fired it up, revved it up to where it was somewhat smooth and pulled the fuel pump relay which conveniently is under the seat. It not only did it not die but settled in to a perfectly smooth idle at 1800 rpm. Very confused as to how it was running with out a fuel pump I got out, checked timing and vacuum, locked the distributor down and began to rev it up a bit. It had great throttle response but stalled when I opened it up a bit.
Happy with the base settings I started removing the timing light and vacuum gauge when I noticed fuel in the vacuum line that goes to the MAP sensor. Thinking to myself, fuel doesn't belong there, I follow the line. Turns out if your fuel pressure regulator fails and you have a vacuum line going to the top of the intake just behind the throttle body it will suck fuel from the tank and run great once started.
P.S. is 185 -200 psi too much compression? I advanced the cam 4 degrees so now 2 degrees advanced instead of 2 retarded and got it down to 190 with fuel soaked cylinders.
I was wondering when I saw the title if this would be about a leaking fuel pressure regulator.
Yup. Seen the failure happen but never seen it actually do what you managed to do.
Compression is fine.
You should check out skinny G's video on the operating principles of a carb to compare notes.
Someone has the link I am sure...
I once had a driver pull the keys for an E-350 off the "Out of Service, do not Drive keyboard", walk out to the service lot, ignore to note that said "Don't Start, no Carb!" on the steering wheel, crank the 300 six over until it fired from the fuel being sprayed into the intake, throw it in drive and move about 30 feet until the flames started licking out from under the loosely installed doghouse. At that point he jumped out and let it burn to the ground.
MadScientistMatt said:
I was wondering when I saw the title if this would be about a leaking fuel pressure regulator.
My favorite weird failure was a report I'd read about a 5.8l F150 that was running extremely rich (when it would even run) but it would run just fine with the fuel pump disconnected.
The multi page head scratcher story short: You could starve it of fuel by pinching the fuel lines but it would run just fine on zero fuel pressure. The culprit turned out to be a bad ECM. It was opening the batch-fire injectors 4x as often as it should have. Intake vacuum (possibly Bernoulli effect too) and the extra on-time was sufficient to pull enough fuel through the injectors to allow the engine to idle.
