Ford F-150 / 250 / 350 / 450:

Misfire at cylinder #8

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# 1  1/8/2012 12:48 AM

tech1diesel
New member
Registered: 1/8/2012
Posts: 7

Misfire at cylinder #8

2002 Ford F 250 7.3 L Diesel. Misfire on cylinder # 8. 400 lb compression. Passes buzz test. Replaced injector twice with OEM injector. Switched injectors #1 and #8 because #1 sometimes will throw a code for #8 still misfires.

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# 2  1/8/2012 4:11 PM

TechHelp2
Administrator
Registered: 11/24/2009
Posts: 1299

Re: Misfire at cylinder #8

Can you tell me what codes were stored in the ECM memory?

Check all codes and repair any codes that come up.

Did you check to see if there is an injector pulse signal at #8 cylinder?

Check wire connections at the injector and ECM for #8 cylinder making sure there is no break or corroded connections in the injector circuit.

If wiring is good and there is no signal from the ECM it could be a bad injector driver in the ECM and it may need to be replaced.

If all of this checks out then check the fuel pressure at the fuel injector. It should be between 45 and 60 PSI.

Try these few suggestions and get back to me with your results, we can go on from there.


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# 3  1/13/2012 12:19 AM

tech1diesel
New member
Registered: 1/8/2012
Posts: 7

Re: Misfire at cylinder #8

Thanks for the help! The fuel pressure test gave up the ghost. What happened is the customer put DEF in the fuel he was using thinking it would help. The DEF crystallized in the strainer of the new filter. Injector #8 ,the last in line to get fuel wasn't getting it.

Last edited by tech1diesel (1/13/2012 12:20 AM)

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# 4  1/13/2012 4:24 PM

TechHelp2
Administrator
Registered: 11/24/2009
Posts: 1299

Re: Misfire at cylinder #8

Thank you for keeping us informed on your diesel problem, your results will be helpful to others who may be having similar problems.


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