• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

1998, Long crank time, only some of the time?

Caribou Lou

NAXJA Forum User
Location
San Diego
Hey everyone. I've got a '98 XJ (obviously), 4.0, auto, 108k on it. Sometimes (only when hot), it will crank for about 5 seconds before starting, others its a half a second....any clues?

Thanks.
 
You do know you are not supposed to touch the gas pedal when starting right ?
 
Check valve on the fuel pump is most common on the 1997-01's. Heat soak is another problem. Leaky fuel injector is possible, but not very common.

Use the SEARCH function.
 
Most likely a fuel pressure issue. If you turn the key to on, you should hear a brief hum....that's the fuel pump priming the system. When that hum ends about 10 sec later, see if you still have the issue. My guess is that the problem will stop. I know it seems annoying, but I see the same problem in my '94 XJ and my '93 Honda Civic....so I don't think it's just a Jeep issue. I will say that I recently changed the injectors in the Jeep and it seems to be less noticeable. Perhaps it's just the 10 year old O-rings not sealing quite as well as they used to.
 
Intermittent long crank? Check the following:
  • Battery voltage while cranking should be 9.6VDC or higher
  • Grounds should all be clean. A valve cover leak can cause slow cranking - the battery-engine ground is near the dipstick
  • Check the rest of the grounds - a weak sensor ground can also cause you trouble
  • Make sure the starter motor is mounted tightly, and that the contact between the starter motor and engine is clean. That's the ground return for the starter motor...
  • "Heat soaking" an electric motor will cause it to slow down, if it's starting to get weak. Something else to think about - it is just about ten years old now...

To rule out loss of fuel pressure, turn the key to ON when you expect a long crank, and wait about two seconds. This allows the fuel pump to pressurise the fuel system - which will effectively eliminate that as a problem. However, my first thoughts are electrical, rather than fuel-related - I'd probably check the battery (especially if it's more than four years old) or the starter motor (if OEM) first.
 
I would probably have to go with the checkvalve on the fuel pump. Change quite a few of those around here for long crank times. you can hook your fuel pressure guage to the rail and turn the key on for a few seconds and then turn it off and see if the pressure holds.
 
B.RAIDER said:
I have a 1988 ...is the fuel pump checkvalve a separate enity or is it part of the fuel pump?

If you have an 88, you have a RENIX rig - and long crank times are a quirk of programming, so not a good deal you can do about them. Upgrading mains has been shown to help - if you're still running OEM mains, your connections are deteriorating (they're, what, 20 years old?) and that can make your starter crank slowly.

Most of the same advice given earlier applies - but moreso. You're twice as old! You won't be able to get rid of all the "slow crank" issues (the key one is programmed into the system itself,) but you can still do a lot.
 
It's got a new fuel pump, new battery, everything is tight and clean (haha). Like I said, it only does it once the motor is hot, and then, only some of the time...?
 
I bet dollars to donuts it has to do with your fuel preasure. It's either in the seals of your injectors or it's your preasure regulator. It's probably loosing preasure over time while its off. After it builds preasure its fine.
 
White1998XJ said:
It's got a new fuel pump, new battery, everything is tight and clean (haha). Like I said, it only does it once the motor is hot, and then, only some of the time...?

Only when it's hot? Ok, i'm stumped.. Unless it's vapor locking
 
When the motor is cold, it starts in less then 1 second. Now say I drive it for twenty minutes, turn it off, and come back to start it 15 minutes later, (not everytime...) it'll crank for like 5-10 seconds before starting.

This isn't my first XJ, but this is the first time one has ever done this....
 
White1998XJ said:
When the motor is cold, it starts in less then 1 second. Now say I drive it for twenty minutes, turn it off, and come back to start it 15 minutes later, (not everytime...) it'll crank for like 5-10 seconds before starting.

Instant cold start rules out the check valve. Heat soak and/or vapor lock can happen even in winter. Do you get winter blend gasoline ? Does it run roughly for 15-30 seconds and then clear up and idle normally ?
 
I suspect fuel. It could be a fuel injector issue. How many miles on your engine and or injectors??

Two things come to mind. One of them could be leaking into the cylinder which creates a rich mixture and therefore upon startup you get the short stumble OR possibly a vapor lock type problem which has already been mentioned by a few others.

There is a technical service bulletin about rough engine idle after restart following a hot soak. 1803103 is the number. It is for 1999-2004 4.0 engines but I suppose it's possible that it could be your issue too. Haven't heard about any holes in that TSB but could be. There is a very quick and cheap repair kit which consists of installing an insulator sleeve on the #3 injector. If you get stumped, may be worth checking into....

Good luck and post back what you find! :wave1:
 
It's got just under 109k on it. When I was poking around under the hood yesterday, I noticed the word "Mopar" on the very dirty red plug wires. I pulled one off, cleaned it up, to find the date "4-97". Pulled out the same spark plug...well, they're "vintage" too. Did the plugs and wires, and it's running alot smoother.

I did try the turning the key on and letting it build up pressure for a few seconds before starting it, and that seems to work - so far.

I'll keep you guys posted, thanks for all the help.
 
If you get the long crank time again, here's something else to try - release the key as soon as you sense it going past the usual half-second, then immediately turn the key again. It may start right away the second time.

That's what mine does. I don't know what it means, it's just something I've noticed and a way to reduce strain on the starter and the engine. Since I got my jeep, it usually takes a long time cranking (like 4-5 seconds) if you just turn the key one time (even after waiting the 2 seconds for fuel pressurization). But if you crank a half-second, let go, then crank again, it starts immediately.

Note: I replaced my engine at 150K miles and the starter around 200K (bought the jeep at 95K), and the starting behavior was the same before and after both those events. So whatever the cause, it's not the engine or the starter - it's fuel delivery, or the computer programming like 5-90 said, or something else along those lines.
 
92xjsp said:
If you get the long crank time again, here's something else to try - release the key as soon as you sense it going past the usual half-second, then immediately turn the key again. It may start right away the second time.

That's what mine does. I don't know what it means, it's just something I've noticed and a way to reduce strain on the starter and the engine. Since I got my jeep, it usually takes a long time cranking (like 4-5 seconds) if you just turn the key one time (even after waiting the 2 seconds for fuel pressurization). But if you crank a half-second, let go, then crank again, it starts immediately.

Note: I replaced my engine at 150K miles and the starter around 200K (bought the jeep at 95K), and the starting behavior was the same before and after both those events. So whatever the cause, it's not the engine or the starter - it's fuel delivery, or the computer programming like 5-90 said, or something else along those lines.

The programming thing only applies to RENIX rigs (1987-1990, gasoline engine,) and not to ChryCo-controlled rigs (1991-up.) So, if you've got a later rig, it's not programming...
 
Back
Top