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Curtis B.
Curtis B., Technician
Category: Small Engine
Satisfied Customers: 13581
Experience:  have worked on and around most engine models for 35 yrs./Polaris ATV expert
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I'm working on a JD 425 EFI. It hunts. I unplugged the

Customer Question

I'm working on a JD 425 EFI. It hunts for fuel. I unplugged the Manifold Absolute PSI sensor & it ran fine. Replaced the MAP sensor & plugged it in. It still runs the same. Not flashing any codes.
Submitted: 2 years ago.
Category: Small Engine
Expert:  JohnF2015 replied 2 years ago.

Hi, my name is***** will be assisting you.

On the EFI machines it is really hard to troubleshoot the problem if you don't have the diagnostic software to hook the machine up to. You could have poor fuel pressure, clogged fuel injector, temperature sensor that could cause the problem.

Exactly what is the engine doing?

Customer: replied 2 years ago.
It will start & die. Once it stays running it hunts (pulsates) on the hi & lo end & accelerates roughly. I guess I'll drain the fuel & put some fresh fuel in it. What threw me off was when I disconnected the electric plug from the map sensor it ran great....One thing I noticed is when you remove the fuel cap there is a lot of fuel recirculating in the tank... Is this normal? Could there be some kind of return ck valve that is letting off to much fuel PSI.?
Expert:  JohnF2015 replied 2 years ago.

The fuel recirculating is normal, the pump is pushing fuel to the engine at the same pressure constantly, anything that is not be used or burned by the engine will be returned to the tank. If you have poor quality fuel or high ethanol content it might cause the problem. Have you replaced the fuel filters? You may have air in the fuel line, have you tried to bleed the air line at the fuel rail?

Customer: replied 2 years ago.
I'll check the fuel issues & get back w/ you.
Expert:  JohnF2015 replied 2 years ago.

That is fine, just let me know.

Customer: replied 2 years ago.
What do you think about the fuel PSI regulator?
Customer: replied 2 years ago.
it's a 445 by the way..
Expert:  JohnF2015 replied 2 years ago.

I have never had one go bad so I am not really sure how the machine would react. What engine is on this machine?

Customer: replied 2 years ago.
wtf ? I'm journeyman machine repairman im a former certified jd tech. i want my money back!
Expert:  JohnF2015 replied 2 years ago.

I will forward your request to a moderator, someone will be getting back in touch with you.