Ford 7.3 advice sought

[Blakers]

My dad has an 89 F-250 with 7. 3 IH naturally aspirated engine. It has developed a miss at about 2300 rpm and above. Idles fine and has power at lower rpm.



I haven't had time to work on it beside checking the lift pump pressure, which is ok, and the filters, so he took it to a local shop my uncle recommended.



The guy replaced the injectors and return lines (I've replaced the return lines several times when the begin to seep), but it still has the higher rpm miss. Now he's blaming the injector pump and wants to send it out to get rebuilt - a $700 price tag including his labor.



Personally I don't think it could have been injectors with only the high rpm miss and no miss at idle. I don't think he should have replaced them.



He said it's not air leaking into the fuel lines or diverter valve.



What are your thoughts?



Thanks,



Blake



PS - I am asking to get the injectors back so I can check them with my injector tester.

 

[forr]

Ask the mechanic if they found the bad injector(s) when they installed the new ones. While I am not familiar with the international diesels, I would think that your observation of no miss at cold idle would indicate the injectors are not to blame. Either way, the old injectors can be bench tested for break pressure and pattern.



If the mechanic can't answer your question about the old injectors, go to another garage.

 

[Evan A. Beck]

Seen this one before, and 99% of the time its the injection pump. However, there was one case where the injection pump gear had been incorrectly installed when the engine was built. It was one gear tooth off, and caused a high RPM miss. Ran real strong on the bottom end, but fell on its face above 2,000 RPM.

 

[Blakers]

Thanks guys. I guess the guy is right to want to go through the pump then. I guess he told my dad that the cheapest thing to "try" first was the injectors - that's why he replaced them. I still wish he had not done that - I told my dad I doubted it was an injector because no miss at idle. Oh well.



How much do those injectors cost anyway? I heard they are relatively cheap.



Blake

 

[Motorhead]

From what I understand of the inj pumps on the IH is that they have some plastic parts in them that wear out. The re-builds replace these with better parts.

IMPORTANT... Find out where he is getting the pump from and make sure that the re-build shop is reputable. A neighbor of mine changed out his on his '90 and he said that it wasn't hard. He is a great guy but his mechanical knowledge isn't alot. I think that it would not be hard to change it yourself. I believe he paid around $400. for his re-build.

Just a thought... has anyone checked to see if it has a broken valve spring?

 

[Bigramguy]

Injectors are usually cheap $25-30. 00 ea. So are the pumps $300-350. 00. See example below



http://www.dieselpage.com/fuel.htm



The pump is actually very easy to replace,take the old one off,put the new one on,set the timing by feel (you'll know when it runs right),and set the fast idle.

 

[Barry]

Follow these steps:



1. With a warm engine, bring the rpms up to 2000 and hold it steady for about 30 seconds.



2. Bring rpms up to 2500 and hold steady for another 20 seconds



3. Finally, bring rpms up to 2800 and hold steady.



A. Watch tach carefully. If tach starts to vary 200 to 400 rpms you have got a injector pump problem.

B. Also, have the right mirror positioned in such a manner that you can observe the exhaust pipe. If the tach starts fluctuating, generally you will also be billowing clouds of smoke. You have an injector pump problem. It's a cheap field test, but it works!

 

[drees1]

I had one of these trucks. My friend owns it now with about 260,000 miles on it.



99% sure is injector pump, governor section. These pumps last from 50,000 to 80,000 miles and then go out. A good rebuild will replace the plastic parts with metal and sleeve the housing. should be a little over $400. 00 pump only no labor, from a diesel shop, not Ford. Easy to change yourself, read the manual.



Good time to do the injectors, too, $30. 00 - $40. 00 ea.



If you rack it open at high idle, (floor it in neutral) and it rolls the black smoke, it is shot. Lots of people keep driving them that way though.



Good luck



Doug Rees