Engine turns over several seconds before starting

[Tyler_Smith_28]

Hello,

 

My engine cranks over ~5 seconds before starting. It is a 91' comanche. I have replaced the fuel pressure regulator, associated vacuum line, and the fuel filter. I do not believe there is an issue with the fuel pump, because once the key is turned to the on position (before attempting to start), the fuel pump will come on and turn off very shortly after signaling that enough pressure has been built up. I believe the issue lies on the fuel side versus electrical. I have already replaced the distributor cap, rotor, spark plugs, and spark plug wires. It is a 4.0L I6.

Thanks in advance!

Tyler

[pizzaman09]

I'm guessing you have a 4.0L?

[Tyler_Smith_28]

Yes.

[75sv1]

Some might disagree. I think you should check the timing chain. 

[cruiser54]

CRUISER'S MOSTLY RENIX TIPS

THROTTLE BODY AND IAC CLEANING

OCTOBER 30, 2015 SALAD 26 COMMENTS EDIT

Originally by TJWalker of CherokeeForum & JeepForum

The Idle Air Control (IAC) is mounted on the back of the throttle body (front for ’87-’90).

The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is retracted, the air control passage flows more air which raises the idle speed. When the valve plunger is extended, the air control passage flows less air which lowers the idle speed.

Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea. This should be part of a normal tune-up procedure and whenever idle/stalling issues are present.

CLEANING THE JEEP 4.0 IDLE AIR CONTROL

1. Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a Torx driver (2 bolts; one can be kind of hard to get to). On ’91 and later, it may be easier to just remove the whole throttle body. Be sure to use a new throttle body to manifold gasket when reinstalling.
2. “Gently” wiggle out the IAC from the throttle body. Gasket/O-ring on the IAC can be re-used if it is not damaged
3. Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and oxygen sensors. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.
4. Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner.
5. It is also a good idea to clean the entire throttle body bore itself, the butterfly valve inside of the throttle body and it’s edges, and all associated linkage as long as you have things disassembled.

[pizzaman09]

Bring that this is a 91, it is an HO engine, which I'm a bit less familiar with.  Making sure everything is clean, the vacuum lines don't leak and having decent park plugs would all be on my list of things to check.

[JeepSchmidt O'Guinness]

Might check the vacuum reservoir for leaks. Stock/oem location is passenger side front corner, tucked in behind the bumper.

[zomeizter]

Fuel pump may be the issue, you can verify with a pressure gauge to see if fuel pressure is getting built up quickly. Alternatively, activate the pump with the ignition switch two or three times, then crank the engine immediately after. If it starts in less time than before, the pump is weak and should be replaced.

[fiatslug87]

I know when I replaced my dead starter with a new AC Delco it cranked and started much faster than before.