95 4.0 starting issue

[Nascarnutz]

when i crank it up in mornings cold it will start then shut right off. crank it again runs ruff for a 2 or 3 seconds and clears out. get to work after it has sat for a few hours it cranks fine. if i stop on way home at a store more than once or twice it runs ruff for 15 seconds (longer than cold start )or so then clears up.
fuel pressure regulator is new and made no change with issue. fuel filter has been recently replaced. new plugs. any help will be greatly appreciated.

 

[RonD]

Welcome to TRS

Turn key on count to 3 then turn key off, repeat 2 more times then try to start engine.

The Fuel pump only runs for 2 seconds when you turn on the key, it won't run again until engine RPMs are above 400, so started engine.
But it runs for that 2 seconds EACH TIME the key is turned from off to on
You should be able to HEAR the fuel pump's HUMMMM from in the cab, it is not that quiet

You need about 30psi fuel pressure at the engine to get a good running engine.
2 second run time is about 10psi

So if your fuel system is losing pressure when it sits, engine off, then turning on the key one time will get 10psi so engine would fire but struggle to run since opening injectors drop the 10psi down fast.

So do the test, key on/off a few times, to see if that may be the problem

The Fuel pump has a check valve built in, it holds pressure in the system when pump is off, normally fuel pressure will hold for a few months, at minimum 20psi, so the 2 second run time is fine, if system is holding pressure

Fuel pressure regulator also holds system pressure, so thats both ends of the system, pump and regulator, in between are the fuel injectors.
A fuel injector can leak, this drops the pressure down to 0psi, engine off, but will also flood out the engine, and MPG would noticeably drop if that was happening, just a heads up

 

[Nascarnutz]

will do thanks. will update when i get home this evening.

 

[Nascarnutz]

Welcome to TRS

Turn key on count to 3 then turn key off, repeat 2 more times then try to start engine.

The Fuel pump only runs for 2 seconds when you turn on the key, it won't run again until engine RPMs are above 400, so started engine.
But it runs for that 2 seconds EACH TIME the key is turned from off to on
You should be able to HEAR the fuel pump's HUMMMM from in the cab, it is not that quiet

You need about 30psi fuel pressure at the engine to get a good running engine.
2 second run time is about 10psi

So if your fuel system is losing pressure when it sits, engine off, then turning on the key one time will get 10psi so engine would fire but struggle to run since opening injectors drop the 10psi down fast.

So do the test, key on/off a few times, to see if that may be the problem

The Fuel pump has a check valve built in, it holds pressure in the system when pump is off, normally fuel pressure will hold for a few months, at minimum 20psi, so the 2 second run time is fine, if system is holding pressure

Fuel pressure regulator also holds system pressure, so thats both ends of the system, pump and regulator, in between are the fuel injectors.
A fuel injector can leak, this drops the pressure down to 0psi, engine off, but will also flood out the engine, and MPG would noticeably drop if that was happening, just a heads up

tried your suggestion with no luck. same issue as before. still cranked the second time i started truck. on way home from work today i turned ignition on off 10 times and still stutters then smooths out after 15 secs or so. im thinking injector?
how do i test? or am i wrong?