TJ hard starting

[Sid1966]

:???:I have a 97 TJ 4.0 3 spd auto, my starting problem is driving me crazy trying to find,it has been doing this for 6 months now.I try to start jeep it just turns over doesnt fire even if you crank for 30-45 seconds,release key from start position and retry to start it fires rite up.have changed cap rotor wires plugs clean air filter.i have noticed that when you first turn key to on and let the gauges cycle i dont here the fuel pump but when running if you listen close i can here the fuel pump working,about the same time it developed off idle stumble that only happens once within 1-1.5 minutes of starting then runs fine.this is more of an annoyance than anything any help would be appreciated

 

[Sid1966]

I forgot to mention that i have banks header with 2.5 " exhaust with a cherrybomb glasspack 62mm throttle body k&n air filter and home made snorkle but i have had these parts on for 2 yrs with no issues

 

[SteelHeadz]

Check the fuel pressure and test the fuel pump for a leak down after turning off the ignition.

 

[Bounty__Hunter]

Try this. Before starting the first time, turn the key to run and count 5 seconds, then start the jeep. Let us know if you notice a difference.

 

[Sid1966]

have tried that no difference seems to run fine after the start and stumble.I have listened to other jeeps and it sounds like the fuel pump cycles when key is first turned on mine doesnt do this it still pulls hard to 5000 rpm while driving it is the initial start and stumble thats bugging me,it always starts never stranded or anything just irritating

 

[Sid1966]

after the first start cycle doesnt work when i try the next time i can here fuel pump come to life engine fires right up this happens every time i start it doesnt matter if is shut off for 10 seconds or 10 hours i am stumped

 

[SteelHeadz]

Sounds like it's time for a new fuel pump.

 

[Sid1966]

i was wondering but it runs so good other than the starting issue no lack of power or hesitstion through out rpm range i would have though if it was the fuel pump that it would starve out at high rpms but it pulls right to the rev limiter even buried in mud

 

[SteelHeadz]

I agree however, whats in question is it's ability to hold fuel pressure in the lines after the ignition has been turned off. If the fuel drains back to the fuel tank after shut down, the lines will have nothing but air, hence a no start situation until the lines are primed again and sufficient for the injectors to spray the proper amount in the combustion chamber. In some occasions, if the internal leak is large enough to drain the fuel back into the tank , the engine will stumble on a WOT(wide open throttle) but will run normal at idle.

 

[Sid1966]

so basicly it is probably a check valve in the fuel pump and is internal to the pump so the whole unit has to be changed?a new fuel pump is almost$700.00 here. THANKS for the info i will do a pressure test and leak down test just hate to spend the money if is some thing else

 

[SteelHeadz]

so basicly it is probably a check valve in the fuel pump and is internal to the pump so the whole unit has to be changed?a new fuel pump is almost$700.00 here

Not nescesarilly, the last time i took one apart for inspection , the cause was an O-ring on the bottom of the fuel pump module. There was also one instance that the cause was the fuel pressure regulator which is on top of the fuel pump module. Those 2 would be my suspected culprit for letting all the fuel drain back to the tank.

 

[Team Twisted Off Road]

I'm with steelheadz it eather the fuel pressure regulator or the fuel pump..
you can get one at NAPA for around $270..

 

[abe]

i have the same problem. its the check valve. i have done some research and have found out that it could b a fuel pressure regulator/ fuel filter. they are one in the same, but only some jeeps have this. i haven't dove into it yet but i am planning on checking it out this weekend.

 

[Sid1966]

THANKS for the help,money kinda tight right now so i will probably run as is for now.A pressure and leak down test will be done .not looking forward to pulling the tank, tons of salt get dumped on the roads here so wrenchin on any thing under the jeep means 3-5 days of soaking with penetrating oil and still breaking bolts

 

[abe]

yeah tell me about it... i'm in ohio