Tapping sound on my 7.3 idi

[mustangmalibu]

Hello all, lately I have developed a tapping sound on my 73 IDI 1992. At first I thought it was my injectors and I tested them they were popping at about 1400 PSI. So I ordered brand new ones from stanadyne and it came brand new in the box. I put those in and nothing changed I failed to mention that I have a brand new injection pump also. Well after I installed the injectors nothing changed. The same tapping sound was there, and it's only when I'm accelerating and when it's hot it doesn't do it when it's cold. Well the next thing I thought was timing so without a meter and I know this truck pretty well. I started trying different timing settings when I tried retarding it it just sounded horrible and had no power and smoked so I tried some advanced settings, and that seemed to help. The truck ran great and didn't smoke, and fired right up. it's still fires right up doesn't smoke runs great, has lots of power and it is set at about 8.5 TDC. So everything feels great, runs great except I have this tapping noise that will not go away. When I accelerate especially at low RPM. When it gets to higher RPMs it seems to just blend in with the engine and I don't hear it at all. I removed the valve covers and looked for valve train problems. Everything was clean as a whistle all of them. In fact this engine I got out of a truck that had only 48000 miles on it.
Still had remanufactured stickers on it, and the whole engine inside and out looked brand new, and still does I've tried everything I can think of. I have owned this truck for quite a while and I know quite a bit about IDI engines but I cannot for the life of me figure this tapping sound out.
Any help would be greatly appreciated, because my business counts on this truck I give horseback rides on the beach in Monterey and I haul horses around everywhere and without this truck, me and my horses will starve. So time is of the essence... Thank you

 

[Macrobb]

Change the oil every 2.5k miles or so, and add a quart or two of MMO.
Mine ticks a lot worse if I let the oil change go much longer, and the marvel mystery oil does seem to help a bit.

 

[YJMike92]

A video of the noise would help. You might try loosening each injector line one at a time and see if the noise goes away. If any particular loosened line makes the noise go away at least you know what cylinder to further investigate.

 

[mustangmalibu]

A video of the noise would help. You might try loosening each injector line one at a time and see if the noise goes away. If any particular loosened line makes the noise go away at least you know what cylinder to further investigate.

 

[mustangmalibu]

Thank you for responding I appreciate it. I have loosened the injectors many times, hoping to get some sort of response but it just wasn't there. When it's cold you don't hear it at all you go two miles down the road and as soon as you drop the RPMs down it starts tapping and as it gets warmer it gets worse. When you get above 1500 RPMs it goes away or Blends in with the engine sound and you can't hear it at all. It's dark now but in the morning I will take a video and post it again thank you for response and any other help you can maybe be able to give me I would certainly appreciate it have a great night!

 

[mustangmalibu]

Change the oil every 2.5k miles or so, and add a quart or two of MMO.
Mine ticks a lot worse if I let the oil change go much longer, and the marvel mystery oil does seem to help a bit.

 

[mustangmalibu]

I just changed the oil not too long ago and I've only put Maybe 20 miles on it since I did and it was all trying to solve this problem. I have use Marvel Mystery Oil in the past and it does seem to help a lot of things. But this just seems more than that I mean, it doesn't Rob the engine of any power whatsoever it's got plenty of power other than the tick it runs perfectly. I will post a video in the morning of the sound and anything else I can find but I've been searching for 2 months or an answer to this problem thank you again for your reply and have a great night.

 

[Thewespaul]

Welcome to the forum, with the engine running look down the driverside of the injection pump, you will see a a little arm that pivots with throttle and actuates on a small pin on the lower side of the pump. At engine idle push this arm in all the way gently and you should hear the sound of the engine change the rpms decrease. Listen for the tapping noise and see if it changes as well. This will tell you if there is an issue with the pump causing the issue, or a valve train problem. Ive seen the thrust washer fail and stick behind the advance piston which wont allow the cam ring to travel back to its idle position. If the engine tone and speed doesnt change with the arm movement, that is your problem.

 

[mustangmalibu]

Thank you very much! I will try it today, and let you know what happens...