Idle Knock

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Aug 31, 2002 | 06:44 AM

Led_Foot

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From: Owensville USA

Idle Knock

I have a 94.5 PSD that has idle knock. Are there any modifications that can be performed to fix or quiet this? I can only hear this knock at idle. The engine performance appears to be fine--- just this dreaded knock. It has a totally stock engine with no mods.

Thanks

Led_Foot

Aug 31, 2002 | 02:04 PM

dale i

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From: Washington

Idle Knock

Do you hear it only at initial start-up? Or, do you hear it even after the engine has obtained normal operating temp?

Aug 31, 2002 | 08:42 PM

navtech

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Idle Knock

Have you checked your fuel pressure? If it is less than 20-25 psi
at hi-idle you need to find the cause. Usually it is debris in the
regulator valve holding it open or debris on the inlet line fittings
restricting the supply to the injector fuel rail. Low fuel pressure
can cause idle knock. Another symptom of low fuel pressure is white
smoke. I am not sure if the low fuel pressure is causing the idle knock, don't overlook checking it and ruling it out as a possible cause.

1 eng oil level and quality

2 fuel level, quality and pressure

Sep 1, 2002 | 06:30 AM

Led_Foot

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From: Owensville USA

Idle Knock

Good information. I hear the idle knock at cold start as well as at warm operating temps. I do not have any white smoke in the exhaust. I think this problem has exceeded my powers. As I am new to the diesel world, I do not know how to check the fuel rail pressure (nor would I know what is normal) The guy I purchased the truck from worked for a Baldwin filter dealer. He changed the fuel filter every time he changed the oil --- every 3000 miles. I need to find a powerstroke engine manual for dummies!

Thanks

Led_Foot

Sep 2, 2002 | 07:22 AM

rescuepilot

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Joined: Dec 2001

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Idle Knock

It's your #8 injector. If its under warranty have them replace it, if not let it go it won't hurt anything, it just sounds bad. They run on the average about $300-$350 installed.

Sep 2, 2002 | 08:48 AM

Quadzilla

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From: Bonney Lake, WA

Idle Knock

Led_Foot-
Checking your fuel pressure is easy. Remove the black engine cover, and you'll see a shrader valve, (tire stem) on the right front corner of the engine. That your fuel pressure regulator. Start the truck, and while idling, measure the pressure at that valve. It's best to use a liquid filled guage if one is available, but you can get a pretty good idea with a pencil guage. Wrap the business end of the guage in a rag, because the pressure you'll be measuring is fuel, not air, and it'll come out of there in a big hurry while you're measuring. Normal, according to Navistar, is 60-90psi. There's a way to increase it, if yours is too low. I'll give you a link to a thread that explains in pretty good detail how to do it, in case yours is too low. Click on this:http://forums.ford-diesel.com/ubbthreads/showflat.php?Cat=&Board=UBB35&Number=665595&page=& view=&sb=&o=&fpart=1&vc=1
I hope this helps.

Sep 2, 2002 | 09:50 AM

navtech

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Idle Knock

>It's your #8 injector. If its under warranty have them
>replace it

This is a MY94.5
1 Does not have Splitshot injectors
2 Is not a deadhead fuel system
3 Does not have Longlead #8 Injector
4 Does not have the 72psi fuel regulator (splitshot system only)
5 Minimum fuel press spec is 20 psi@Hi-idle (Wide open throttle,no
load) normal fuel pressure is about 45 psi@Hi-idle.
6 Engines with low fuel pressure will have injectors that fail
inj. contribution tests. So make sure they check out the fuel
system first. Otherwise you will give till it hurts from a poor
diagnosis.