Code 51

abed

New Member
Joined
May 15, 2023
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7
Location
Israel
Below are some symptoms that occur with fault code 51:
1. Poor acceleration
2. On the highway, the engine temperature rises a bit
3. The jeep is weak when going uphill.
4. Difficulty starting

From Where should i start?
 
If you have a code 51, that signifies a lean air/fuel mixture. I would start with a new oxygen sensor and see if that fixes it.
 
Fuel filter I replaced before month.

additional for symptoms, the engine over heated than normal in high speed.
On the original issue try cleaning the fuel injectors. Also, if you have low pressure it could be the fuel pump. If you replace that be sure to clean out the gas tank. Overheating issue you just added needs more detail
 
I Checked the fuel pressure,
When the switch is open the pressure is 10 and when the engine is on the pressure 25 psi.
And when I disconnected the vacuum the pressure did not change

Is the problem definitely in the fuel pump?

After I turned off the engine the pressure rose to 35.
 
Hmm. The pressure should definitely be 31 with vac connected and 39 disconnected. Since it is not reaching above 25 psi, I would say the fuel pump is weak.

However, with the pressure going up to 35 with engine off, that doesn't really make sense. I'm not sure how the pressure could be rising like that.
 
I checked another time , after the engine turn off the pressure didnt go up.
And after 20 min go to 0
 
going to 0 in 20 minutes is about normal, means pressure is not bleeding off too quickly.

If it were me, I would try a new pump. It could also be the regulator limiting pressure too much, but it's more likely to be the pump. Regulator would be easier and cheaper to try though.
 
I recommend replacing EVERY soft rubber fuel line when you replace the pump.

There's one that's ⅜" on one end and 5/16" on the other end. You should order that one with the pump so you have it on hand.
The rest you can replace with bulk fuel line from the parts store. Make sure it's rated for fuel injection
 
I recommend replacing EVERY soft rubber fuel line when you replace the pump.

There's one that's ⅜" on one end and 5/16" on the other end. You should order that one with the pump so you have it on hand.
The rest you can replace with bulk fuel line from the parts store. Make sure it's rated for fuel injection
There are two, the supply and return lines from pump to frame hard lines are 3/8 and 5/16 and supply and return are opposites.

My problem with replacing the lines is the bends they have to make without kinking. The little elbow at the fuel filter I buy the Mopar part for, but the ones from tank to frame I left alone on mine because they still looked new and I'd rather use them with the correct ends than anything I've been able to find at stores.

Did you not have any kinking issues or anything? They take some pretty hard 90s coming from the frame crossmember to the hard line connection, but maybe it's less of an issue than I think.
 
Maybe disconnect the duel line by the engine and check the flow rate into a glass jar. Just be careful with raw gas and don't start a fire or blow anything up.
I don't know what the rate is but it's a lot more than a trickle.
 
I checked th fuel pressure rgulator , I blocked the excess pipe and the pressure did not rise.

Is the pump ?
 
There are two, the supply and return lines from pump to frame hard lines are 3/8 and 5/16 and supply and return are opposites.

My problem with replacing the lines is the bends they have to make without kinking. The little elbow at the fuel filter I buy the Mopar part for, but the ones from tank to frame I left alone on mine because they still looked new and I'd rather use them with the correct ends than anything I've been able to find at stores.

Did you not have any kinking issues or anything? They take some pretty hard 90s coming from the frame crossmember to the hard line connection, but maybe it's less of an issue than I think.
Weird. I just had the one hose with 2 different ends. I made a custom braized brass adapter, mostly because I had it apart and didn't want to wait for shipping.

For the 90° elbow, I inserted a spring in the hose to keep it from kinking. That's a good point though, that hose would probably be better to buy than build.

The rest of the hoses were pretty easy
 
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Weird. I just had the one hose with 2 different ends. I made a custom braized brass adapter, mostly because I had it apart and didn't want to wait for shipping.

For the 90° elbow, I inserted a spring in the hose to keep it from kinking. That's a good point though, that hose would probably be better to buy than build.

The rest of the hoses were pretty easy
Interesting. If I recall, mine are: supply - 3/8” at pump and 5/16 at frame, while return is 5/16” at pump and 3/8” at frame. Others I’ve seen on forums and FB seemed to be the same. Anyways, it’s a pain for sure. The adapter sounds like a good idea.
 
Running lean will cause an overheat condition. Fix your fueling issue first and see if that fixes the overheating problem.