Diagnosing Rod Knock
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Freshman User
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Diagnosing Rod Knock
My truck won't stay running. I hear a noise from what seems to be the front of the engine. I thought it might be the water pump but now am wondering if it's a rod knocking. Anyway it runs fine if I give it gas but when I take my foot off the pedal it soon dies slowly. Any ideas? How do you determine where the noise is coming from. It seems to be top of engine though??? I think I might have two seperate problems here.
Thanks-
Alan
Thanks-
Alan
Postmaster
Joined: Jan 2003
Posts: 4,417
Likes: 3
From: Durham, NC
Diagnosing Rod Knock
If you have a rod knock, you can usually diagnose it by pulling
spark plug wires while it is running. If you pull the wire on the
cylinder with the rod knock, the knock will usually go away...
spark plug wires while it is running. If you pull the wire on the
cylinder with the rod knock, the knock will usually go away...
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Diagnosing Rod Knock
-360 engine-
I need more time with the truck to better describe the sound but I'll try from what I can recall from last night.
I have been hearing a noise like a rattle up front for a while now. The last time I started the truck I tweaked (maybe f'd up) the carb. It was running as smooth as I have had it run at idle and while in gear. The rattle could be heard at startup but then would sort of dissapear. There is a bent ac pulley that I need to take off, I thought this might be causing something to rattle.
Well, last night I go to start the truck and it starts fine but has a sound like perhaps a marble rattling around inside the intake manifold. I feel around with a screwdriver (will try the broomstick when I get home) trying to pinpoint the noise. I had no luck but it 'seemed' to be stronger at the top of the engine where the water pump connects. As long as I gave it gas it ran and the rattle was sort of intermentent, but after I took my foot off the gas it would soon start to stumble and then die slowly.
Thanks for the help-
I need more time with the truck to better describe the sound but I'll try from what I can recall from last night.
I have been hearing a noise like a rattle up front for a while now. The last time I started the truck I tweaked (maybe f'd up) the carb. It was running as smooth as I have had it run at idle and while in gear. The rattle could be heard at startup but then would sort of dissapear. There is a bent ac pulley that I need to take off, I thought this might be causing something to rattle.
Well, last night I go to start the truck and it starts fine but has a sound like perhaps a marble rattling around inside the intake manifold. I feel around with a screwdriver (will try the broomstick when I get home) trying to pinpoint the noise. I had no luck but it 'seemed' to be stronger at the top of the engine where the water pump connects. As long as I gave it gas it ran and the rattle was sort of intermentent, but after I took my foot off the gas it would soon start to stumble and then die slowly.
Thanks for the help-
Senior User
Joined: Jan 2003
Posts: 148
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From: Longmont, CO USA
Diagnosing Rod Knock
Have you checked your fuel pump? I had a chebby once that it did exactlly what you described and it turned out to be the fuel pump. The float would open up on the carb and let fuel into the carb and the noise would go away but when the float would close it created pressure and made the noise. You also stated it is close to the water pump. I replaced the fuel pump and it stopped. My .02 cents.
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Diagnosing Rod Knock
Well, I got home, added some carb cleaner to the gas, and sprayed out the carb real good. The noise soon went away but the rough idle and surging remain. I'm thinking fuel delivery is faulty. When I am accelerating the truck is shaky until it gets high enough rpms then if I really floor it there's like a pause and then a big SURGE or power. Could this be faulty pump? I have of course replaced the filter I thinking next is a rebuilt carb and possible pump.
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Lead Driver
Joined: Dec 2002
Posts: 5,491
Likes: 16
From: Kuna ID
Diagnosing Rod Knock
Sounds like you might have a vacumn leak, I had the same problem with my truck about 2 months ago, it turned out to be the base gasket.
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Freshman User
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Diagnosing Rod Knock
Well I have been replacing vac hoses and plugging up ports etc. I have sprayed carb cleaner around suspect areas and there is no increase in rpms. Of course when I spray towards the top of the carb there is higher revs but not around the base or egr. Could it be that a carb rebuild is in order?? I have a Motorcraft carb but I'm not sure which one. I think I'm going to buy a digi-cam so you guys can see the things I'm talking about. Thanks everybody.