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Hello I am new to this forum and diesels so sorry if I miss anything. I just purchased my first diesel truck 1990 f250 xlt lariat with a 7.3l non turbo idi with a 170,xxx miles. It also has a manual transmission and f350 axles and suspension. I just bought it about two weeks ago and did my first oil change on it this week. I used a motorcraft oil filter and Delo 15w40 for diesel motors. After filling it back up with oil I started it back up, and it ran horribly rough as if oil was not getting somewhere or something. After Reving it up to about 1200-1500 rpm the noise went away and the truck ran perfect. Now on cold starts in the morning when it dips below freezing at night I have the same rough idl noise. Temps are below or at freezing at night and 40 to 50 degrees during the morning it is in the Bay Area of California so it’s not a cold start by any means, but basically I was wondering if anyone had suggestions on what might be causing the weird noise on start up. Me and my buddy who is in school to be a mechanic think it might be the oil pump but we do not know much about diesels. I also saw another thread about a cold idle sensor, could that be it? The original owner also told me to run the glow plugs twice, and when it is cold but I often cycle them 3 to 4 times on a really cold morning. It seems to help.

Also if anyone could let me know how often to replace my fuel water separator. I did that with the oil change but do not know the intervals. Also any tips for a new diesel owner would be greatly appreciated.
 

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It's normal for any old non computerized diesel engine to knock, run rough, smoke and smoke some more on a cold start up. Oil pumps do not make noise. Owner's and shop manual say open the petcock and drain any water from the fuel filter at every 5000 mile oil change. Manual says change the filter at 50000 or 60000 miles, forget which, but 25,000, 30,000 makes more sense and that's what most of us do.
 

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Thanks a ton I really appreciate it. Glad to know it’s still running good. Okay I’ll probably change it out rn so I know when the filter was changed and I’ll be sure to drain it on oil changes. Really appreciate the help.
 

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It is not the oil. Check the glow plugs. That motor has 30 years on it, It will start at 30 degrees but not happy if all the glow plugs are not working. Have you been plugging it in?
DENNY
 

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Hello I am new to this forum and diesels so sorry if I miss anything. I just purchased my first diesel truck 1990 f250 xlt lariat with a 7.3l non turbo idi with a 170,xxx miles. It also has a manual transmission and f350 axles and suspension. I just bought it about two weeks ago and did my first oil change on it this week. I used a motorcraft oil filter and Delo 15w40 for diesel motors. After filling it back up with oil I started it back up, and it ran horribly rough as if oil was not getting somewhere or something. After Reving it up to about 1200-1500 rpm the noise went away and the truck ran perfect. Now on cold starts in the morning when it dips below freezing at night I have the same rough idl noise. Temps are below or at freezing at night and 40 to 50 degrees during the morning it is in the Bay Area of California so it’s not a cold start by any means, but basically I was wondering if anyone had suggestions on what might be causing the weird noise on start up. Me and my buddy who is in school to be a mechanic think it might be the oil pump but we do not know much about diesels. I also saw another thread about a cold idle sensor, could that be it? The original owner also told me to run the glow plugs twice, and when it is cold but I often cycle them 3 to 4 times on a really cold morning. It seems to help.

Also if anyone could let me know how often to replace my fuel water separator. I did that with the oil change but do not know the intervals. Also any tips for a new diesel owner would be greatly appreciated.
Howdy,
I've got the same kind of problem; DIESEL RX glow plugs cured it...
:geek:
 

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I'm with Dannys' post: glow plugs. Diesel RX glow plugs cured the problem for me. Also check the glow plug controller, and the relay. It actually sounds like it's glow plugs because what you're describing is the sound of a starting diesel that doesn't use glow plugs, just compression to ignite the fuel, rough then smooth when warmed.
 

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I too would say glow plugs, but I disagree on the brand. I don't trust anything but Motorcraft ZD9 glow plugs because the rest seem to have problems swelling, and breaking tips off down in the engine. I am lazy, I don't like doing unnecessary work any time, but especially not on my own stuff.
 

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That's for sure.
I too would say glow plugs, but I disagree on the brand. I don't trust anything but Motorcraft ZD9 glow plugs because the rest seem to have problems swelling, and breaking tips off down in the engine. I am lazy, I don't like doing unnecessary work any time, but especially not on my own stuff.
 
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