Trouble starting

J

Justin S.

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Kansas City
Having some trouble with my 4.0 getting started. Pretty much happens all the time, cold or after driving a bit. I made a video you can see here. First start was cold, second was after driving for about 15 minutes. Both of these starts are actually better than it usually is. Sometimes I go through 4 rounds or trying to get it going. It feels like if I try and drag out the first crank too long, then it takes even longer to get it going. If I just let it crank 3 or 4 times and stop, I can typically get it going on the next turn.

I've read a lot of posts about this and I know it can be a number of things. The engine already has the heat shield, and it probably isn't that anyway since it has the same amount of trouble starting cold as after warming up. The previous owner claimed to have put a new fuel pump in, but who knows. That would be my guess at this point, either he put a crappy after market in there or it was bad when installed. Not sure if it's related but I'm throwing a warning code for the Evap system too. Haven't really tried to figure that out much, I was guessing he didn't hook everything back up just right when installing the new pump.

Also, you can hear it at the end of the video. When the car is running there is something that cycles on and off constantly. Not sure what that is, any ideas.

Thank in advance for any insight!

 
Justin S. said:
Having some trouble with my 4.0 getting started. Pretty much happens all the time, cold or after driving a bit. I made a video you can see here. First start was cold, second was after driving for about 15 minutes. Both of these starts are actually better than it usually is. Sometimes I go through 4 rounds or trying to get it going. It feels like if I try and drag out the first crank too long, then it takes even longer to get it going. If I just let it crank 3 or 4 times and stop, I can typically get it going on the next turn.

I've read a lot of posts about this and I know it can be a number of things. The engine already has the heat shield, and it probably isn't that anyway since it has the same amount of trouble starting cold as after warming up. The previous owner claimed to have put a new fuel pump in, but who knows. That would be my guess at this point, either he put a crappy after market in there or it was bad when installed. Not sure if it's related but I'm throwing a warning code for the Evap system too. Haven't really tried to figure that out much, I was guessing he didn't hook everything back up just right when installing the new pump.

Also, you can hear it at the end of the video. When the car is running there is something that cycles on and off constantly. Not sure what that is, any ideas.

Thank in advance for any insight!
Click to expand...
First off the easiest answer to all of your questions... The "something that cycles on and off" is the A/C compressor clutch. When you have your A/C turned on or the vent selector set to any of the defrost settings it will run the A/C.
 
Justin S. said:
Having some trouble with my 4.0 getting started. Pretty much happens all the time, cold or after driving a bit. I made a video you can see here. First start was cold, second was after driving for about 15 minutes. Both of these starts are actually better than it usually is. Sometimes I go through 4 rounds or trying to get it going. It feels like if I try and drag out the first crank too long, then it takes even longer to get it going. If I just let it crank 3 or 4 times and stop, I can typically get it going on the next turn.

I've read a lot of posts about this and I know it can be a number of things. The engine already has the heat shield, and it probably isn't that anyway since it has the same amount of trouble starting cold as after warming up. The previous owner claimed to have put a new fuel pump in, but who knows. That would be my guess at this point, either he put a crappy after market in there or it was bad when installed. Not sure if it's related but I'm throwing a warning code for the Evap system too. Haven't really tried to figure that out much, I was guessing he didn't hook everything back up just right when installing the new pump.

Also, you can hear it at the end of the video. When the car is running there is something that cycles on and off constantly. Not sure what that is, any ideas.

Thank in advance for any insight!
Click to expand...
On to the Evap... is it an intermittent code that pops up or does it happen all the time. I had an Evap code that was caused by a wire that broke inside it's insulation right at the plug for the sensor. that's not to say that is or isn't your problem but from what I read it's a fairly common problem
 
You need a fuel pressure tester. Hooks to schrader valve on fuel rail. Key on engine off should be over 50psi. next key off, pressure should stay up for at least 10 minutes. To many people do this test with engine running. you can rent pressure testers. You didnt say what year. Newer jeeps don't have schrader valve s
 
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Oldguy said:
You need a fuel pressure tester. Hooks to schrader valve on fuel rail. Key on engine off should be over 50psi. next key off, pressure should stay up for at least 10 minutes. To many people do this test with engine running. you can rent pressure testers. You didnt say what year. Newer jeeps don't have schrader valve s
Click to expand...
X2, on the pressure tester. To add to that you need to be able to isolate the injectors from the rest of the fuel system and test both sides. Could have leaky injectors or leaky check valve in the fuel pump.
 
Something you could try right now, without running specialty tools down, is cycle the fuel pump several times before starting it. Turn the key on, just enough that you hear the fuel pump kick on, and not turn the engine over. Then turn it off once the fuel pump kicks off. Do this 3-4 times in a row, then try starting it. If it fires right up, consistently, it’s the pump.
 
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TJBob said:
Something you could try right now, without running specialty tools down, is cycle the fuel pump several times before starting it. Turn the key on, just enough that you hear the fuel pump kick on, and not turn the engine over. Then turn it off once the fuel pump kicks off. Do this 3-4 times in a row, then try starting it. If it fires right up, consistently, it’s the pump.
Click to expand...
Leaky Injectors also bleed off pressure, though not as common a problem it has a similar symptom.
 
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reddvltj said:
On to the Evap... is it an intermittent code that pops up or does it happen all the time. I had an Evap code that was caused by a wire that broke inside it's insulation right at the plug for the sensor. that's not to say that is or isn't your problem but from what I read it's a fairly common problem
Click to expand...

It's continuous, never turned off. I'm going to run the codes again tomorrow just to see if anything new has popped up but I expect it's just that same evap code.
 
Sounds good, I'll do the fuel pressure test this weekend. Just out of curiosity has anyone upgraded their injectors before? I've seen a few reviews of guys going from the stock to a bosch model that has four holes to mist the gas in instead of the stock with one. Worth doing? Might be part of my problem anyway?
 
Justin S. said:
Sounds good, I'll do the fuel pressure test this weekend. Just out of curiosity has anyone upgraded their injectors before? I've seen a few reviews of guys going from the stock to a bosch model that has four holes to mist the gas in instead of the stock with one. Worth doing? Might be part of my problem anyway?
Click to expand...

The injector upgrade is pure bullshit on these 4.0s. That's some literal internet bullshit myth someone started way back when, and people who didn't know any better took it and ran with it.

"Upgrading" the injectors will do nothing at all unless you're running boost ;)
 
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Chris said:
The injector upgrade is pure bullshit on these 4.0s. That's some literal internet bullshit myth someone started way back when, and people who didn't know any better took it and ran with it.

"Upgrading" the injectors will do nothing at all unless you're running boost ;)
Click to expand...

HAHA, I had a feeling that might be the case. Thats why I like to run these things by you guys, you tend to see through the marketing BS.
 
Justin S. said:
HAHA, I had a feeling that might be the case. Thats why I like to run these things by you guys, you tend to see through the marketing BS.
Click to expand...

No problem. I always tell people that the 4.0 has more in common with a tractor engine than a Ferrari engine. That being said, getting power out of them isn't impossible, but it involves a lot of money and a lot of work (y)
 
I did the 4 port, also supercoil, 8mm wires and cap and rotor with copper not aluminum. Starts easier, idles smoother. No more power.
 
Did a quick pressure test on the schrader valve and turn the key to on causes the pressure to jump up to around 15ish and immediately drop back to zero. I haven't isolated the pump away from the injectors yet, got to go get the disconnect tool for the fuel line.

So that at least is consistent for why turning the key on and off a number of times to try and prime it isn't working, it's dropping straight down to zero in a split second.
 
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Well...I went to Orielly's to use their legit pressure test set. Bought one from Harbor Freight and not surprising...it was junk. Kinda odd though, when I turn the key into on position it registered nothing on the gauge. If I did it again it maybe jumped to 2 or 3, I had to turn it on 4 or 5 times continuously just to get it up to around 5psi or a little over. When the jeep started up it would get up to around 50.

I wasn't able to isolate the injectors and just test the fuel pump. For some reason with both my se from HF and the loaner from Orielly's the little nozzle to connect directly to the fuel line was too small, gas would just squirt out around the sides. Is there another part I need? Should I proceed with a complete fuel pump replacement?
 
Justin S. said:
I wasn't able to isolate the injectors and just test the fuel pump. For some reason with both my se from HF and the loaner from Orielly's the little nozzle to connect directly to the fuel line was too small, gas would just squirt out around the sides. Is there another part I need? Should I proceed with a complete fuel pump replacement?
Click to expand...
You can isolate the problem, to rule out the injectors, once you have your gauge hooked up to the schrader valve and not leaking.

Once connected to the gauge at the fuel rail start the engine. The gauge should read 49 psi plus or minus 2 psi

Turn the engine off and immediately clamp the rubber fuel line that comes from the pump. Watch the pressure gauge and see how long it takes to lose pressure.

If the pressure remains at 49 psi for an extended time then the problem is in the tank - probably the check valve. If the pressure falls below 49 psi fairly rapidly then the problem is in front of the tank - probably a leaky injector.
 
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