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I have a 1991 camaro z-28 5.7 tpi.The problem is it will not start after sitting in the hot sun.The reason is that the engine is flooded with fuel. Also the engine oil has a STRONG smell of gasoline. After cranking it several times raw gas can be seen dripping from the exhaust.It does not matter if the engine is cold warm or hot,if it sits in the HOT sun this problem will show up.The car will start on a hot day as long as it has not been in direct HOT sun light. The fuel pressure with the key on and engine not running is 45 psi after five minutes the fuel pressure drops to 21psi and holds steady.With the engine running the fuel pressure is a steady 40 psi.If the vac line is removed from the fuel regulator the fuel pressure jumps to 50 psi.If the fuel return line is pinched off the fuel pressure jumps to 80 psi.the fuel injectors all test between 15.4 & 15.7 ohms of resistence.I have replaced the fuel regulator even though the fuel pressure readings lead me to believe the fuel pressure regulator was not the problem.I have also replaced the engine temp sensor even though the old one tested out ok. The same goes for the fuel relay.Map sensor tests ok,air temp sensor tests ok,throttle posistion sensor set correctly at .540 idle control valve tests ok timing dead on the mark compression all cylinders test ok vac lines all routed correctly no obvious leaks at intake manifold or plentum gaskets.The car starts idles and drives perfect after its sat out of the sun. The car has a bbk throttle boby and msd ignition with 3" k&n exhaust other than that it is stock.I for once am completly stumped. Is it possible that the diaphram in the new fuel pressure regulator is leaking by some how when the fuel in the gas tank builds pressure from heating up in the sun? Or maybe the pcm is shot and allowing the injectors to stay open to long and is some how triggered by the heat of the sun.
Hello!
When it does not start, can you spray some starting fluid in the intake to get it to start?
ALso, when it does not start, does it have spark?
To get it started I disconnect one or more of the fuel injectors to allow the flooding to partially clear. And yes it has spark.once started it idles and runs perfect.
After the fuel pressure drops and you try to crank it over, does the fuel pressure immediately go back up? Or does it take a little bit?
I was tipped by another expert to have you look for leaky injectors. This would make a lot of sense. Pull the fuel rail up a few inches with the injectors still connected and turn the key on to prime the fuel pump. Just watch for any gas dripping out of any injectors.
It immediately goes back up to 40 psi and runs perfect.Thats right now while its cool out side and the cars parked in the garage.If you are asking this question in regard to when its in the direct hot sun I do not know.I have not run a fuel pressure test yet when the car was sitting in the sun.
I have changed all eight fuel injectors.I dont believe they are the problem.
What about a noid light? Have you had a noid light on the injector connectors when this happens? DO you know if you have fuel trigger?
Reply to AMEDEE's Post: the fuel injectors are not leaking
I am wondering if the fuel injectors are getting a signal to open up when this happens?AMEDEE39632.9851434838
I dont know.How can i check? Would this indicate a problem with the pcm?
Fuel trigger is the signal from the computer to the injectors. You would use a tool called a noid light. It simply plugs into the injector connector after the fuel injector is unplugged and should blink when the engine is cranked over. It looks like this.
Reply to AMEDEE's Post: I hate to sound like a idiot, but i already know the injectors are receiving a signal because when the engine is running i can plainly here that each injector is pulsating. if i plug a noid tool into a injector and it is receiving a signal and the light is flashing it would mean the electric connector to the injector was ok if the light was not flashing the electric connector would not be good therefore the injector would remain closed.If I am correct how do you explain the flooded engine and what would the noid tool prove?39633.3208381134
Are we absolutely positive the engine is flooded when this happens?
My guess is that, when it does not start, the injectors are not getting a signal. We need to test this theory and check for fuel trigger when this happens.
ALso, I would rec to check the coolant temp sensor resistance.
177 ohms at 212 deg F 241 ohms at 194 deg F 332 ohms at 176 deg F 467 ohms at 158 deg F 667 ohms at 140 deg F 973 ohms at 122 deg F 1459 ohms at 104 deg F 2238 ohms at 86 deg F 3520 ohms at 68 deg F 5670 ohms at 50 deg F 9420 ohms at 32 deg F 16180 ohms at -14 deg F 28680 ohms at -4 deg F 52700 ohms at -22 deg F 100700 ohms at -40 deg F
Reply to AMEDEE's Post: the coolant temp sensor checks out ok and yes i belive the engine is flooded because raw fuel can be seen dripping from the exhaust and the engine oil has a strong smell of gasoline. i am waiting for it to heat up out side so i can test your fuel trigger idea when the no starting problem actually takes place.it is currently 10:20 am here in california i will test car at 12:00 noon after its had a chance to get hot in the sun.Iam still leaning to a fuel regulator problem!
I think that is a good possibilty! It is located on the fuel rail. It is round, about a quarter size and has a vacuum line going to it. If the regulator is leaking gas than it can cause this problem. Pull off the vacuum line that goes to the regulator. Be absolutely sure there is no gas in the vaccum line. If there is, the diaphram has ruptured and there is gas entering the engine that is not accounted for and the regulator will need to be replaced!
ok i finally got the problem to show up.its currently 2:00 pm sunday and 102 degrees outside i have a fuel pressure gauge connected to the test port on the fuel rail. when the key is turned on fuel pressure goes to 40 psi as soon as the fuel pump shuts off fuel pressure drops immediatly to 0. key off then on again fuel pressure 40 psi fuel pump off again presure immediatly back to 0 and raw fuel is dripping out of the exhaust.THE VAC LINE TO THE FUEL REG DOES NOT HAVE ANY NOTICABLE FUEL SMELL.i have disconected all 8 wire connectors from the injectors with no change key on 40 psi fuel pump shuts off IMMEDIATLY back to 0 and alot of raw fuel dripping from the exhaust
This is just an assist to amedee since he is not online. If we find the problem click accept on one of his answers.
While it is dropping out to zero clamp off the fuel return line and see if it still drops. If it doesn't drop the check valve in the pump is hanging open.
Pull all the plugs from the injectors and ohm them out. They should read 11 - 12 ohms across the terminals. You have either an injector hanging open intermitently or a return problem.
when the fuel return line is clamped off the pressure still drops back to 0 psi after the fuel pump stops.it still happens VERY fast but slightly slower than when no clamp is applied. the ohms reading across each injector are #2- 13.6 #4-16.9 #6-13.1 #8-15.1 #1-16.8 #3-17.0 #5-16.8 & #7-16.9
THanks for the help LSX! I think your right on track! Thats exactly where I was going next! THis is very common! The fuel pump does have a check valve inside that holds the fuel pressure steady. Prime the system and quickly crimp off the return line and see if the pressure still drops.
Let me know!
YUP!
The injectors are not leaking, the regulator is not leaking, and the fuel is not leaking through the return line. THe only thing that is left is the fuel pressure side. The fuel pump check valve is leaking! You are going to need to replace the fuel pump.
ASE MASTER TECH
CAR TECHNICIAN ADVANCED LEVEL SPECIALIST ALL MAKES AND MODELS