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Old 03-10-2012, 11:48 AM   #1
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Ford Lehman Fuel Injectors

I have twin 120 Ford Lehmans in my 44 ft OA.* For some reason the port engine has started to drop off 50 to 100 rpm routinely when running at 2000 rpm plus.* I have almost 4,000 hrs on the 1982 engines.* Is it time to rebuild th injector pump?* Clean injectors?
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Old 03-10-2012, 12:19 PM   #2
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RE: Ford Lehman Fuel Injectors

I was told on the Ford Lehmans to do the injectors at 4-5000 hours - rebuild with new tips.* Can't say about the pump.* Get a hold of Bob or Brian Smith at American Diesel.
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Old 11-19-2016, 10:45 AM   #3
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For peace of mind I recommend you pull the heads and get them rebuilt. Also good time to inspect cylinders, 4,000 hrs us a lot of run time. I did this at 4,200 hrs and discovered a pitted cylinder that can be sleeved and rebored as well as a malfunctioning exhaust valve.
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Old 11-19-2016, 10:50 AM   #4
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Quote:
Originally Posted by MVDarlin View Post
I have twin 120 Ford Lehmans in my 44 ft OA.* For some reason the port engine has started to drop off 50 to 100 rpm routinely when running at 2000 rpm plus.* I have almost 4,000 hrs on the 1982 engines.* Is it time to rebuild th injector pump?* Clean injectors?
When was the last time you changed your fuel filters?
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Old 11-19-2016, 10:59 AM   #5
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Also had injector pumps rebuilt. Unless you can say with certainty the injector pump oil was changed every 50 hrs a rebuild is likely needed.
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Old 11-19-2016, 11:51 AM   #6
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I would pull the injectors and bore scope the cylinders before removing the head.

And I would do a whole lot more diagnostics before rebuilding stuff.

4500 hours is nothing on a half way well maintained Lehman. I've seen injector pumps go damn near forever before a rebuild without having the oil changed in them on a regular basis.

So rule the simple things out first.
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Old 11-19-2016, 12:07 PM   #7
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I think you should just spend a dozen boat dollars and just rebuild them both because you'll get a groovy new paint job on them. You could even pick the colour.

Reread what Capt.Bill said and start with your fuel filters.

There is very little useful information in your initial post, such as why you are running over 2000 rpm, what is your WOT reading, what are the coolant temps at WOT? That would help a diagnosis. And reread Capt.Bill's posts.
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Old 11-19-2016, 12:15 PM   #8
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I would pull the injectors and bore scope the cylinders before removing the head.

And I would do a whole lot more diagnostics before rebuilding stuff.

4500 hours is nothing on a half way well maintained Lehman. I've seen injector pumps go damn near forever before a rebuild without having the oil changed in them on a regular basis.

So rule the simple things out first.
I'm dealing with all this now. Hence the recommendations.
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Old 11-19-2016, 02:09 PM   #9
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I'm dealing with all this now. Hence the recommendations.
Yes I get that. I'm just assuming at least you didn't just start pulling things off willy nilly and rebuilding them before having a firm handle on what needed to be done.
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Old 11-19-2016, 05:24 PM   #10
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The 50 hour injection pump oil change is a myth.

Even American Diesel and Bomac have put out different info on the topic.

As long as fuel isn't diluting the oil...it could go for thousands of hours....well if not thousand, many hundreds more than 50.

At least one member reported running it for many hours with no oil in it at all.

Like all mechanical things..it needs watching and regular maintenance.....not kissing it goodnite every day.
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Old 11-20-2016, 01:01 PM   #11
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I cruise in vrry rrmote locations and need reliability. My port injector pump locked up at WOT and caused a runaway. Very scary. So a rebuild was necessary. Being prudent I had starboard injector pump rebuilt as well. It was in better condition. Port engine developed a knock so pulled head and found pitting in cylinder next to exhaust elbow as well as exhaust valve carbon / distress. Replacing piston and sleeving cylinder is next step.
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Old 11-20-2016, 02:04 PM   #12
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Rear piston knocking?
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Old 11-20-2016, 07:01 PM   #13
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Probably number 6, most common.
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Old 11-20-2016, 08:47 PM   #14
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My Lehman manual says change the injector pump oil at 200 hours, other apparently say 50 hours. I figure changing it with changing engine oil is often enough.
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Old 10-05-2017, 07:03 PM   #15
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My Lehman manual says injector pump oil every 50 hrs, engine oil every 200. They also like to have their valves adjusted every 2000 hrs. That might be what the knock is.
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Old 10-05-2017, 07:06 PM   #16
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Greetings,
Welcome aboard.
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Old 10-05-2017, 07:18 PM   #17
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I took Bob Smith's Lehman seminar in Oct 2015. He said to change the oil in the 120s at 50 hours. He said that you could go a little longer if it was not diluted by oil. He said each engine has it's own personality and you should change the injector oil at 50 hours and see if it is diluted. If not diluted then extend the interval a little and see how it is. One member in the class said he has twin 120s. One needed changing at 50 hours and the other routinely goes 100 hours. Fortunately on my SP225s I don't have to change the oil in the injectors.
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Old 10-05-2017, 07:57 PM   #18
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Quote:
Originally Posted by new2trawl View Post
My Lehman manual says injector pump oil every 50 hrs, engine oil every 200. They also like to have their valves adjusted every 2000 hrs. That might be what the knock is.
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Originally Posted by Comodave View Post
I took Bob Smith's Lehman seminar in Oct 2015. He said to change the oil in the 120s at 50 hours. He said that you could go a little longer if it was not diluted by oil. He said each engine has it's own personality and you should change the injector oil at 50 hours and see if it is diluted. If not diluted then extend the interval a little and see how it is. One member in the class said he has twin 120s. One needed changing at 50 hours and the other routinely goes 100 hours. Fortunately on my SP225s I don't have to change the oil in the injectors.
Do you know if Bob still does those seminars or did Brian become the new teacher?
My twins - Lucy (Stbd) and Ethel (Port) - never run past 1900 rpm. <2200 hrs on both. Ethel has a little fuel leakage in her injector pump but nothing to get excited about right now. These old tractor motors run forever with a little attention.
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Old 10-05-2017, 08:34 PM   #19
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Unfortunately Bob Smith passed away. I am not sure if Brian is going to continue on with them. Bob was a wealth of knowledge. It was amazing in the class whenever anyone asked him a question, the depth of his knowledge was staggering.
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Old 10-07-2017, 12:27 AM   #20
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I have twin 120 Ford Lehmans in my 44 ft OA.* For some reason the port engine has started to drop off 50 to 100 rpm routinely when running at 2000 rpm plus.* I have almost 4,000 hrs on the 1982 engines.* Is it time to rebuild th injector pump?* Clean injectors?
Its time to check your fuel filters before doing any thing else also if still using the mechanical fuel lift pump check that as well,if it's a serviceable type they usually have a small very fine gauze inside which i have seen gummed up more than once, the injection pump requires a positive pressure from the lift pump to reach full RPM output, (low input pressure-low output pressure-reduced RPM),

OR perhaps few barnacles on the Port prop?

Check the simple things first , by the way 4000 hours for these engines is not a worry if serviced on schedule
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