Water in fuel system

Disconnect the fuel line at the fuel injector and crank there should be fuel spray if none the pump needs replacement.

I just have one suggestion, after what all your mechanic already did. I would want to know the fuel pressure reading WHEN IT WON'T START. So you would need a fuel pressure gauge handy, for that time it won't start. Hook up the gauge and turn the key on- if at 59 psi, when the engine won't start, then you know the fuel pump and the relay sensor is not the problem. And so probably not a fuel problem, although you haven't checked the injector circuit, but likely that wouldn't exhibit a problem as you have.
So if not a fuel problem, check for spark when it won't start. Maybe the problem is in the ignition system. Buy a spark tester from a parts store, use it when the **** engine won't start- simple and easy check of your ignition system.

I'm going to assume you mean Chevy Suburban.
Did you check fuel pressure before and after you replaced the fuel pump ??
Are you getting spark to the plugs ?

try some starting fluid, see if it will fire, if it will then yes theres a problem in the fuel lines inspect the lines all the way back to the tank also check and see if its not a cloged fuel filter, if you spray starting fluid and it wont fire up then check your ignition system spark plugs wires ect.

Turn off all your accesories and turn the key forward, but dont start it. You should hear the pump kick on for 2-3 seconds. Prime the system a few times then start it. This will narrow your diagnosis

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It's when the security light starts flashing that the infamous "chip" in the key becomes a nightmare to many. Gradually the car begins not cranking anymore or if it cranks it would start and die in a second. Randomly it will do this more and more often until it won't start anymore. VATS, PASSkey and Passlock immobilizer systems are killing cars all over North America, they have a short lifespan and are certainly more effective against owners than thieves. Here is how you save your car
1st trick, (if not starting) turn the key forward 2 clicks till right before it would normally start, leave like that for 10 minutes. ( no less ) After 10 minutes, turn key back then forward and your car might start. I did this in my regal for more than a year. If its shuting down while running, im sorry i have no quick fix...

Cheap fix: Bypass the chip in your key. Temporary, but effective. Until the TDM (theft deterrent module) in the dash poops out, then you're kinda screwed. I was told that these types of key security systems have a 7-10 year life span. Sucks for us. This link explains the "Key Issue" pretty well.
----- http://vats.likeabigdog.com/


Never worry again fix: Bypass the whole VATS/Passlock/passkey I or passkey II system entirely. Literally take it out, and throw it away. I just did this in my Regal. Took about an hour. Took longer to find the thing than it did to fix the problem. For a list of cars effected by this problem. See the NEWROCKIES link on the right side of their page......... They sell a unit for 200 bucks to totally bypass this system FOREVER. life time-money back and all that. Finally did this in my car. Well worth the 200 if you've looked into getting this replaced... Anywhere from 600-1000 bucks.
----- http://newrockies.ca?ap_id=judd0081
----- With this fix, you can take that whole Vats, passlock, passkey **** system out of your car all together. Good info on both sites

cam sensor,
crank sensor,
theft system

the fuel system is seperate from heating system.check water pump the impeller could have deteriated i have seen this in another cavalier,once i removed water pump the blades that move the water were full of holes.but first make sure ther is good flow to the heater core.also hope you used a 50/50 mix of antifreeze because solid antifreeze wont heat up.

I hate to be the one to tell you this but if there is fuel,oil,water getting into your plugs than you have bad rings. the vehicle will not start because it is not getting enough compression to do so. If you love the car and would like it to run again it will cost about $1000.00 to have the rings done if not more. But since there is water than fuel getting into your plugs than it is a defenent sign that your rings are bad.

if your caddy detected a key that was used but not 4 your car the system shuts down the fuel flow 4 security messures