The long crank mystery

Josh Harder

Josh Harder

Member
Joined
Dec 15, 2019
Messages
47
Location
Alberta
So I realise this has been discussed often. I cant seem to find a situation like mine tho...
Let me set the scene
Saturday mornin rolls around and I'm gonna hit the trails with the boys this weekend. The lj has sat for 2 weeks as it's not my dd. I hop in and turn the key lighting quick. Its starts quick. I dont even have time to hear it cranking. I spend the rest of the afternoon wheeling down the local trails. We stop for lunch and upon my return to my steed I turn the key over to start only to be welcomed back by the drawn out sound of the 4.0 turning over. For a while. Like too long.

Now that I have that out of the way here are some things I know.
-4.0
-always starts quick when it's been sitting overnight or longer
-will always start after about 3 seconds when warm
- the priming trick does not work
-it runs perfectly other than that
it's an 04 with no pressure release valve on the fuel rail
-it has a new fuel pump
- I dont know the brand of fuel

SEND HELP
 
If starter is turning the motor over strong and battery and starter are eliminated, then a couple things come to mind.
1) electrical issue related to fuel delivery, perhaps fuel pump relay etc, acts up when hot only. You should notice the drop in fuel pressure when cranking when it is acting up, but not when it is running fine.
2) air/fuel vapor somehow being pulled into fuel delivery line when it sits after hot. Winter gas (higher volatility) used on unseasonably warm days, or sitting your Jeep in the sun would cause this type of issue to be worse. Fuel pressure will be fine in this case, but the engine won’t start on the vapor until it cools and returns to liquid form.
 
Just resolved a similar starting issue that Josh has been experiencing.

To recap, when engine was cold it would start right up. If I drove the car to the store, turned off the engine and cranked it right away, it would start right up also. However, if I went into the store and came out 15-20 minutes later, it would crank for 5-7 seconds before starting. It would alway start, but was a little embarrasing with the long crank prior to the engine starting. My wife and I like explore remote areas like Coyote Buttes and Death Valley and it was always a little nerve wracking to shut the engine off and go hiking or have lunch and have the extended cranking make me question whether or not it might start this time.

What was discovered was that when the throttle body was removed from the intake and the engine was hot, you could hear a slight sizzle and fuel vaporizing in the intake. The #2 fuel injector was leaking drops of fuel which was vaporizing and causing a rich mixture. Over night it would clear on it own, but 15-20 minutes after the engine was stopped, thought is that the mixture was rich enough that it would not start until the rich mixture was cleared by continued cranking. I noticed that after the 5-7 seconds of cranking and the engine started, you could smell raw gas from the tail pipe area possibly confirming the hypothesis.

All 6 injectors were replace with the 12 hole injectors and the problem went away immediately. The Jeep seems a little peppier too.

Not sure if this is the solution to your problem, but it worked for me. I am not a mechanic, so I might not have explained the fuel system operation exactly, but you get the idea.

Larry
 
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LarryV18 said:
Just resolved a similar starting issue that Josh has been experiencing.

To recap, when engine was cold it would start right up. If I drove the car to the store, turned off the engine and cranked it right away, it would start right up also. However, if I went into the store and came out 15-20 minutes later, it would crank for 5-7 seconds before starting. It would alway start, but was a little embarrasing with the long crank prior to the engine starting. My wife and I like explore remote areas like Coyote Buttes and Death Valley and it was always a little nerve wracking to shut the engine off and go hiking or have lunch and have the extended cranking make me question whether or not it might start this time.

What was discovered was that when the throttle body was removed from the intake and the engine was hot, you could hear a slight sizzle and fuel vaporizing in the intake. The #2 fuel injector was leaking drops of fuel which was vaporizing and causing a rich mixture. Over night it would clear on it own, but 15-20 minutes after the engine was stopped, thought is that the mixture was rich enough that it would not start until the rich mixture was cleared by continued cranking. I noticed that after the 5-7 seconds of cranking and the engine started, you could smell raw gas from the tail pipe area possibly confirming the hypothesis.

All 6 injectors were replace with the 12 hole injectors and the problem went away immediately. The Jeep seems a little peppier too.

Not sure if this is the solution to your problem, but it worked for me. I am not a mechanic, so I might not have explained the fuel system operation exactly, but you get the idea.

Larry
Click to expand...
This makes alot of sense and I'm suspecting I have I same problem. Not sure if I should pull the trigger on a set of six or diagnose and find the problematic one and replace it?
 
LarryV18 said:
Just resolved a similar starting issue that Josh has been experiencing.

To recap, when engine was cold it would start right up. If I drove the car to the store, turned off the engine and cranked it right away, it would start right up also. However, if I went into the store and came out 15-20 minutes later, it would crank for 5-7 seconds before starting. It would alway start, but was a little embarrasing with the long crank prior to the engine starting. My wife and I like explore remote areas like Coyote Buttes and Death Valley and it was always a little nerve wracking to shut the engine off and go hiking or have lunch and have the extended cranking make me question whether or not it might start this time.

What was discovered was that when the throttle body was removed from the intake and the engine was hot, you could hear a slight sizzle and fuel vaporizing in the intake. The #2 fuel injector was leaking drops of fuel which was vaporizing and causing a rich mixture. Over night it would clear on it own, but 15-20 minutes after the engine was stopped, thought is that the mixture was rich enough that it would not start until the rich mixture was cleared by continued cranking. I noticed that after the 5-7 seconds of cranking and the engine started, you could smell raw gas from the tail pipe area possibly confirming the hypothesis.

All 6 injectors were replace with the 12 hole injectors and the problem went away immediately. The Jeep seems a little peppier too.

Not sure if this is the solution to your problem, but it worked for me. I am not a mechanic, so I might not have explained the fuel system operation exactly, but you get the idea.

Larry
Click to expand...
Also thanks for sharing, I was at a loss
 
I can’t find the receipt yet to quote you the cost of the six injectors, but it was reasonable. The new injectors each have 12 holes to atomize the fuel instead of just one for the OEM. My thought was that if one injector failed, another might fail and I would be back with the same issue again.

The issue was driving me crazy and there are a multitude of potential fixes on the web from heat shielding to fuel pump replacement depending on the root cause. It is so nice to have it start right away all the time.
 
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Yes it did! I had Bosh Style Upgraded 12 hole fuel injectors installed the the material cost was $82.35 for the 6 injectors. I am not sure where my mechanic got them.
 
K Suspension fab sells remanufactured injectors. I replaced mine with a set and it fixed the long crank issue for a time, but it comes back intermittently 🤬. Larry's explanation and symptoms are right on.
 
Replaced mine with 12 hole, did the insulation (and I did a new entire pump assembly about 3 months ago) and I still get a long crank. I guess I'll check the starter but first start of the day is always instant. Like always always.
 
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