OK here's one for you. 2001 7.3 powerstroke, 250K. It has a fairly loud knock on one of the left injectors when the truck is under load. It is intermittent and sounds like a loud version of air bubbles in a steam radiator. The truck has a new HPOP, New Alliant injectors, new UVC wiring harnesses, fuel bowl rebuilt. There are no cracked injector cups as there is no fuel in the coolant. There is no blowby coming from the oil filler cap or engine crackcase vent other than what is normal. Fresh oil with Prolong additive. The only thing I haven't tried is changing the lift pump, and I have one ordered and on the way. Any ideas? BTW I have driven the truck about 100 miles since the HPOP change, so the air should be out of the oil system. Oh, I almost forgot to mention, it also has a stumble in the engine when it does it, almost like a gas engine with ignition problems. One reason I was thinking lift pump. Also, can these engine get out of time? I thought they depended on the CPS, PCM and IDM to take care of that, If it were a gas engine, I would be thinking ignition time too advanced.

 

I assume by Lift Pump you are speaking of the electric fuel pump not the LPOP? Our trucks don't really have a lift pump like the other trucks do. The fuel pump supplies the fuel and is usually pretty reliable. Have you monitored fuel pressure while driving?

Why do you use Prolong? Most people running these engines do not recommend oil additives as they simply are not required as long as you use the correct oil and maintain it.

It could be a bad injector. Pull the valve cover and see which one it is. I am guessing you have an AE injector at #8. That could be the one that is louder. You can run it with the VC removed too.

 

Yes, I am referring to the electric fuel pump. I know they are very reliable, but again, it has 250K on it, and because of the maintenance habits of the previous owner (or lack thereof) I have put new CPS, injectors, HPOP/w new IPR, and wiring harnesses on it as well as new up-pipes. (I was going to do the donuts, but the up-pipes fell apart while I was disassembling them, so I went with the IH Bellewed pipes). So as a result, I have decided to go ahead and replace the electric fuel pump.

What is crazy is that the bottom end is very tight. 3000 miles on the oil and I can still see through it. Holds great oil pressure. I put my AE diagnostic computer on it and I'm not getting any codes as of right now. That is not to say that the injectors do not have a mechanical issue. Dang, I hate to pull the VC back off, (A real PITA) but if the fuel pump don't do it, I guess I have no choice.

It idles beautifully, and when it is not under load such as accelerating or pulling a hill, it runs fine with an occasional stumble.

 

This will help, if not done already...

Welcome to guzzle's In-tank Hutch Mod Web Page

 

Yeah that figures, I just filled the tank.

 

Well you can test fuel pressure to make certain before tackling something that might not be your current issue.

 

It could be a lack of oil pressure to the rear of the left (driver) side bank. This can be caused by the firing order. Cyl 6 &8 fire consecutively, and oil isn't usually fast enough to re-pressure the rail between injections.
A low (relatively) cost fix is to provide a cross link of oil supply between the heads. I used KCM HPX Line SD to fix the issue I describe.
As an added bonus, it also smoothed out the engine shake on mine. I have about 252K miles on mine.

 

Got one already. That along with the new HPOP makes me think it's not the oil.

 

I'll probably do that next.

 

["Why do you use Prolong? Most people running these engines do not recommend oil additives as they simply are not required as long as you use the correct oil and maintain it."]

I have always used the product. It was recommended by someone with a fleet of diesels that usually went 850K before trade in. I do change the oil every 5K and use a quality oil. I also change the filter every oil change and also the fuel filter. I have taken very good care of this truck since I have had it, therefore this has me perplexed. It was running fine one day, then it started with a miss, or a stumble if you will at freeway speeds. It got better when I changed the injectors, but still has the rattle like air in at least one injector. Mercedes calls it "nailing". When I checked it with the dignostic computer the most the HPOP would put out was 1152 psi, hence the HPOP. While I had it apart, I went ahead and changed the exhaust pipes, rebuilt the fuel bowl and replaced the HPOP lines. I have driven it about 100 miles since all that and it did get a little better, but sounds like it still has air in the system.

 

Sometimes it takes longer then 100 miles. Mine was okay after 30 miles, T500. Have you done the Frx. It should quite it down alot. Other then that, you mit of damaged an o-ring and thats been known to make a fuel knock also. Or like stated, one bad injector. Fuel pressure is key, you got to know what that is.
Chet

 

Never use Prolong, or any other oil additive, in these engines. Period.

Any additive like that introduces the possibility of aeration in the oil is never good for performance and a reliably running 7.3L PSD. Remember that these injectors fire off of high oil pressure, so they absolutely REQUIRE oil that doesn't foam.

 

OK here's the scoop. The injector rattle is gone. I was driving the truck yesterday, had to really get after it to get out of a traffic mess (getting forced out of my lane by a semi) and afterwards the rattle disappeared. I talked with the International Navistar techs here in my area and was given some great information. Was told the rattle was probably one of the new injectors sticking and when I got on the throttle really hard, the additional oil pressure broke it loose. Also the intermittent miss and air bubbles are caused by air in the fuel and possibly some dirt in the system. He recommended checking the fuel pressure. It was fluctuating and when the miss would take place, it was when the pressure would fluctuate low. I was told that it was caused by the air and possibly by dirt in my fuel pump causing it to bind. I will be replacing the fuel pump as well as doing the Hutch in tank mod along with a pre-pump filter. Either the Baldwin 1212 or a Fleetguard equivilant. I will also be flushing out the lines. The International tech basically said that while Ford builds a great truck, they didn't set the engine up as well as they could have. He said that from the start, International recommended a pre-pump filter, but Ford opted out because of cost. I kind of think they did it for designed obsolescence. If the International engine lasted until it's design life, Ford would sell less trucks.