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Check the fuel pump relays and fuses first, then check the connections on the fuel pump as they may not be hooked up as tightly as needed and/or the ground strap may be broken or loose
Check fuel line for pressure - there should be something like a bike tire valve on fuel line - press the inner part of it and see if gas spurts out hard. If so you have pressure , a working fuel pump, and gas is reaching the injectors.
Unfortunately the answers you have given for replacing a cap is too vague. Is it a gas cap, radiator cap, air conditioning service port cap.... Look the battery needs charged that is why the battery drops to 9 volts, a good charged battery should drop to 10 volts. Check your battery terminals or cables for corrosion. Do a voltage drop tests on both positive and ground cables. As far as not starting any more...do you mean not cranking as in no starter eengagement or cranking but not running? If it is not running listen to hear in the first 10 seconds to the fuel pump relay if it engages or listen for fuel pump...is the car getting spark?
My first guss would be a fuel pump, just would have to verify that when you first turn on the ignition to crank you can either hear the fuel pump turn on in the tank or not, if you cannot hear the buzz or whine noise from the pump in the tank you need a fuel pump. Fuel pumps are a very common problem with these trucks.
should have 12 volts at pump during engine cranking. with key in "on" position, the fuel pump only gets voltage for 2 seconds if engine is not running. Read voltage during cranking. Check fuel pump relay in battery jucntion box under hood.
Same problem with my 85 F-150 5.0 EFI---turned out that the fuel pump relay under the hood was teriffically corroded on the inside (I opened up the relay to look inside). When I checked the voltage at the fuel pump it would show 3.5-6 volts instead of 12 volts.
I was thinking fuel blockage or perhaps failure of the in-tank pumps. Sometimes the truck would start and run, othertimes it would neither start nor run. Typically, if running it would stay running until turned off (where the relay had to break).
Changing the green fuel pump relay fixed the problem--12 volts now at the pump and no reoccurance.
Hello, 9-10 volts is not enough to keep a modern vehicle running. Taking in consideration the age and model of this truck, it could easily be an alternator failure. I hope this helps. CYA Gator241
Need to get a scan tool and look at the data stream while it is running for alot more info.Also any trouble codes.Sounds like initially,the engine isn't getting any fuel.I would have a pressure gauge connected to the fuel rail on the engine,so i could monitor the fuel pressure while all this is going on.Items to look at on the data stream would be timing,what timing is the PCM commanding for the engine.Also,have you checked for continuos power feed to the coils during this no start condition,and fire at the plugs while cranking.You could possibly still have spark,but maybe it is extremely weak?I have seen bad ignition switches cause weird problems before too.Many things power up through the ignition switch,just a thought.Have also seen bad PCM's cause strange problems..38 volts is a little on the low side for GM.Usually see those at,at least .50 and up,and rise steadily while pressing the throttle,up to just under 5.0 volts.Potentiometer with 5 volt supply.Vacuum leak can be checked with engine running at a steady idle speed,spray brake cleaner all around the intake manifold and listen for engine speed change.
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