TJ won’t start unless I floor the gas pedal

Willhe

TJ Enthusiast
Joined
Jul 13, 2018
Messages
113
Location
Glencoe
Only had it about a month and today...It cranks great but wont start until I floor the gas pedal. Did it twice. Its a 4.0 manual. Runs perfect after its going. Thought about fuel filter or pump but It runs well after start. Any ideas?

Thanks
 
Does it do this every time you try to start it? Pumping the gas on an engine that doesn't have a carb doesn't really do much as far as I know. My guess is that the anti-drain back valve on the fuel pump has stopped working. Next time it doesn't want to start, just let it crank without touching the gas. See if it starts.
 
Only did it one of the last three starts...went to lunch and started fine until it sat for 5 min.
 
I have to pretty much prime my fuel system. Turn the key to on three times. Crank it on the last time. Allows the fuel pump to cycle a few times. I’ve been doing that since ‘10 I think. Hasn’t failed me yet! If it ain’t broke, then why fix it ‍♂️.


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Only did it one of the last three starts...went to lunch and started fine until it sat for 5 min.
If your drain back valve isn't working, fuel will drain back into the fuel tank and you won't have any fuel up at the engine. Then, the fuel pump has to pump fuel back through the fuel lines when you go to start the engine, which means it takes a bit to start.

On the fuel rail, there is a valve like you would find on your tires (schrader valve). Let the Jeep sit for a while then use the valve to see if there is any fuel in the fuel rail. If fuel comes out of the valve, then you have fuel at the engine. If no fuel comes out, then you don't have any fuel at the engine. If you don't have any fuel at the engine, then it has drained back into the tank and your anti drain back valve isn't working. This is probably the easiest way to test if your anti-drain back valve is not working.


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So you can release the valve same as a tire valve? Just by pushing in on it?

Yup. Just make sure to let the Jeep sit for a while so gas has a chance to drain back into the tank if your valve isn't working. Also doesn't hurt to hold a rag or something under the valve so you don't create a mess if gas does spray out.
 
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Thanks for the quick reply.
Ill try it this eve, assuming it starts to get me home from work.
 
If your drain back valve isn't working, fuel will drain back into the fuel tank and you won't have any fuel up at the engine. Then, the fuel pump has to pump fuel back through the fuel lines when you go to start the engine, which means it takes a bit to start.

On the fuel rail, there is a valve like you would find on your tires (schrader valve). Let the Jeep sit for a while then use the valve to see if there is any fuel in the fuel rail. If fuel comes out of the valve, then you have fuel at the engine. If no fuel comes out, then you don't have any fuel at the engine. If you don't have any fuel at the engine, then it has drained back into the tank and your anti drain back valve isn't working. This is probably the easiest way to test if your anti-drain back valve is not working.


View attachment 51337

They stopped putting Schrader Valves on sometime in late 2002.
 
Thanks for the quick reply.
Ill try it this eve, assuming it starts to get me home from work.

I would try it before you go home from work or before you try to start it tomorrow morning. It can take a while of sitting for gas to drain back into the tank. I had this problem on my TJ a couple of years ago. Gas would take a couple of hours to drain back. Would usually do it when I tried to start it up in the morning after it had been sitting over night.

Use this test every time is has sat for a while during the next couple of days. The anti-drain back valve can sort of be hit or miss when it works. On my TJ, it would work about half the time, meaning it was difficult to troubleshoot.

They stopped putting Schrader Valves on sometime in late 2002.

Well damn. I didn't know that. Never mind then. I guess the only way to test now is to cycle the fuel pump a couple of times before you go to start it. If that fixes your issue, then I'd guess it is the anti drain back valve.
 
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Ok... well... that seemed way to easy ....I never get that lucky. Glad a wasn't looking for ever thanks Chris!
 
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Also, I suppose this is obvious, but I would see if there are any check engine lights / error codes as well.

I agree with what @jodomcfrodo said above though.
 
Code and light free thanks....Turning the key on for a moment does it but.......It has started fine the last 3 or 4 times.
 
Code and light free thanks....Turning the key on for a moment does it but.......It has started fine the last 3 or 4 times.

You have to cycle the key about 3 or 4 times to get the fuel pump to prime the system. So turn it to one click before start (run position), wait a second or three, and turn it back to off. Do that 3 or 4 times before you start it. Do that every time you go to start it for the next week. Then stop doing it next week. If it starts fine this week, but not next week, you've found your problem. If it still doesn't start right after cycling the key, then something else might be wrong. The anti drain back valve won't throw any codes.
 
If your drain back valve isn't working, fuel will drain back into the fuel tank and you won't have any fuel up at the engine. Then, the fuel pump has to pump fuel back through the fuel lines when you go to start the engine, which means it takes a bit to start.

On the fuel rail, there is a valve like you would find on your tires (schrader valve). Let the Jeep sit for a while then use the valve to see if there is any fuel in the fuel rail. If fuel comes out of the valve, then you have fuel at the engine. If no fuel comes out, then you don't have any fuel at the engine. If you don't have any fuel at the engine, then it has drained back into the tank and your anti drain back valve isn't working. This is probably the easiest way to test if your anti-drain back valve is not working.


View attachment 51337
I know this is old, but thank you!!