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Old 03-20-2020, 05:09 AM   #1
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Hard starting Lehman 120, again

I know this is a beat to death subject, but I cant seem to find any good answers yet that have worked out. I have two Ford Lehman 120s in my 1979 MT. Both original and circa 1979. One has been completely rebuilt, including a new injection pump. The other is original with 2400 hours. The one with 2400 hours starts easily, no issues. The rebuilt one is the problem child.



The rebuilt one simply does not want to start when cold. Tried all different settings to the throttle lever, no joy. Removed the CAV filters and installed the adapters. Bled the system, no joy. Installed a Facet electric fuel pump in line with the lift pump, no difference. Bled the system again using the electric fuel pump. Again, no joy.



Once running, it runs great. Runs out to 2500 if I want it to and sounds smooth. Have to use a short spurt of starting fluid most times. No smoke (other than the normal amount of light smoke from a 40 year old motor). Restarts easily when warm as well.


I do hear a slight tapping noise from the engine in question. Air trapped in an injector? Badly adjusted valve? Wouldn't the electric pump power me through any fuel leak issues? I'm stumped.....
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Old 03-20-2020, 06:09 AM   #2
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"Once running, it runs great. Runs out to 2500 if I want it to and sounds smooth. Have to use a short spurt of starting fluid most times. No smoke (other than the normal amount of light smoke from a 40 year old motor). Restarts easily when warm as well."

My guess would be a tiny air leak somewhere.

Use an outboard bulb and pressurize the system from the tank pickup, if the bulb stays hard O'nite its time to look elsewhere.

Usually a piece of paper towel tied to EVERY fitting or joint will show the leak.


Or you could install a gravity day tank.
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Old 03-20-2020, 07:08 AM   #3
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It also sounds like an air leak to me. I would check every fitting and connection by loosening and retightening.
FF's plan is a good one too.
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Old 03-20-2020, 07:44 AM   #4
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That tapping sound really might indicate the need to adjust the valves. Get a tech out to check and adjust.
I am assuming, when you took the valve cover off, there weren't any dry areas. Every valve rocker was lubricated well.
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Old 03-20-2020, 08:12 AM   #5
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When you are cranking the engine and it doesn't start, look at the exhaust. If heavy white smoke comes out, you are getting fuel but the injectors are worn and not atomizing the diesel properly or the rings are worn not providing proper compression.

If no smoke, no fuel so look for air leaks.

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Old 03-20-2020, 09:05 AM   #6
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Is it "cranking" as fast as the other? Sometimes a tired battery will not turn the engine quite fast enough to make it go. Try a jumper battery to the other bank or if they are on the same bank check the connections. Something might be loose or corroded. Especially check the connections on the starter.

As long as you are playing with the starter, put an amp gauge on it. I can't remember what it is supposed to draw but you can verify it against the other engine. Really not all that uncommon for a brand new starter to be bad.

Curious why you had to rebuild an F.L with 2,500 hours on it. I had to rebuild mine with around 4,000 hours but if it wasn't so expensive I would actually describe it as a comedy of errors.

Good Luck,

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Old 03-20-2020, 09:11 AM   #7
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Cranking speed ok?
Get a compression test.
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Old 03-20-2020, 09:52 AM   #8
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Been having what seems to be the same problem w/ one of my 120s since we bought the boat 16 years ago-colder the engine, longer the start. Can take up to 20 seconds of fast cranking w/throttle 3/4 open if it sits for week or more. Starts fine when warm or recently used and runs great. Called Brian @ American Diesel. He had me check timing. It was fine. I have installed rebuilt injectors and fuel pump with no change. Would think if it was an air leak problem it would have gotten worse enough to affect running. Always wondered if there was some small check valve that might be not operating correctly. Wondered about a compression ring that was worn or not setting properly when cold, but figured that would cause rough starting, not none starting. My feeling is that it's in the injector pump, and since it does eventually start and runs fine, I haven't messed further with it. I've put over 3k hours on since purchased.


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Old 03-20-2020, 10:15 AM   #9
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I had a similar problem on my FL 120.

The stop solenoid was out of adjustment. The engine would start if I pushed the stop lever. One turn on the adjustment solved the issue.
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Old 03-20-2020, 10:23 AM   #10
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So engine is cranking well, just not firing?

Second Dave on this: If you are not getting exhaust smoke (white fuel vapor) after an extended crank, engine is not fueling. Note you have to crank quite a bit for the fuel vapor to make it out the tailpipe. How long depends on how much volume there is in the exhaust piping and mufflers. Gut feel, about 20sec for most boats. Test no good if engine starts by then!!

To avoid killing your starter with lots of cranking, you can try this: Close sea cock. Take sea water hose off fitting on exhaust mixer. Aim hose into bilge or a bucket as some water will come out. Then crank engine. Watch the fitting where the water hose attached, this is now a clear shot into the exhaust. Won't need to crank extensively. No smoke (vapor, really) means no fuel. When I say vapor, I mean a LOT of vapor, even with no fuel being injected there will be a little fog. If fueling properly, it will be thick heavy vapor.

If not fueling, suggest putting a temporary clear hose between secondary filter outlet and injection pump inlet. May need to get creative with fittings to do this. Then that clear hose will tell you if air is getting in from somewhere.

A couple of cheap tests to focus the troubleshooting....
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Old 03-20-2020, 10:31 AM   #11
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Something that can happen with solid lifter engines is normal wear
tightening up the valve clearances. This can cause hard starting.
Make sure all the valves have the proper clearance.
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Old 03-20-2020, 11:57 AM   #12
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Same engine. Similar problem. After many trial & errors came down to a very small air leak at the lift lever of the fuel pump.
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Old 03-20-2020, 03:49 PM   #13
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As engines age and wear, compression goes down. Air increases it's temperature when compressed. A diesel must reach about 500įF to ignite the fuel. If too much air is escaping past the rings or valves, you won't reach ignition temp. If ether makes it start, then it's not a fuel problem. Ether increases compression beyond normal, thus increasing the temperature in the cylinder. A block or pan heater is the best solution. Don't run the engine on only ether when it won't start. Because it increases compression pressure beyond normal, large amounts of ether will crack rings.
In cold weather or especially non-use over winter, rings contract, some more than others. After firing and reaching operating temp, rings reseat and often will show normal compression when hot. Most rings are sold as cast iron, but in reality are made from scrap steel and the actual alloy can differ between rings from the same manufacturer. So they expand and contract at different rates. Just because an engine has hard starting when cold doesn't mean it's worn out.

Again, the best solution is to pre-warm the engine or start with warmer intake air. Glow plugs, bigger glow plugs, or even a hair dryer blowing into the intake are possible solutions.
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Old 03-20-2020, 05:01 PM   #14
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Spoke with Brian at AD. He was pretty positive it was a compression issue due to something going not so perfect with the rebuild. Instead of re-inventing the wheel, he suggested heating the block with either a heater, block heater or immersion heater. Boat starts perfect when warm. Runs great then with no smoke. Going to get a heater in there, adjust valves and re-torque head (this may have not been done when the rebuild happened. He also recommended to NOT go with an electric fuel pump or spin-on filters (which I just did both). Doh! I'll fill you all in on what I found.


Oh, and the engine was rebuilt as it was full of water. This MT was a complete basket case and had to have a complete refurb. All new decks, bulkheads, fuel tanks fittings, rebuilt gen, etc etc. Not stripped down and paint. Totally replaced. All of it. The only original piece in the boat st the bulkhead next to the rear sliding door. Otherwise a brand new boat. An 18 year project.
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Old 03-20-2020, 05:07 PM   #15
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Why not spin on fuel filters? I was going to do that this summer.

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Old 03-21-2020, 02:33 PM   #16
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Quote:
Originally Posted by Tator View Post
Why not spin on fuel filters? I was going to do that this summer.

Tator

He was saying that any modifications to the original fuel system is a potential new way for air to enter the system. They used to sell the CAV adapters years ago though. After putting the CAV spin-on adapters on mine, I have to say that the quality of the adapters really sucks. They are all made by the same place.



I installed electric fuel pumps in mine as well (Facet 4.5-5.5 psi). Right now the manual lift pumps are still inline. I am going with A1-rated 3/8 hose from the RACOR 1000 filter to the electric pump and from the electric pump to the filters. This will take several connections out of the equation on both motors.



I did install new batteries today (dual group 31s in parallel), re-torqued the head and adjusted the valves. Started without ether this time. A little bit of cranking, but getting better.
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Old 03-21-2020, 02:38 PM   #17
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Quote:
Originally Posted by Redhook98 View Post
Spoke with Brian at AD. He was pretty positive it was a compression issue due to something going not so perfect with the rebuild. Instead of re-inventing the wheel, he suggested heating the block with either a heater, block heater or immersion heater. Boat starts perfect when warm. Runs great then with no smoke. Going to get a heater in there, adjust valves and re-torque head (this may have not been done when the rebuild happened. He also recommended to NOT go with an electric fuel pump or spin-on filters (which I just did both). Doh! I'll fill you all in on what I found.


Oh, and the engine was rebuilt as it was full of water. This MT was a complete basket case and had to have a complete refurb. All new decks, bulkheads, fuel tanks fittings, rebuilt gen, etc etc. Not stripped down and paint. Totally replaced. All of it. The only original piece in the boat st the bulkhead next to the rear sliding door. Otherwise a brand new boat. An 18 year project.
No spin-on filters? Why? Makes no sense, no sense at all. Same with electric fuel pumps. Brian is the same guy who has said that spin-on adapters will not fit on Lehman 135s. They do, with room to spare. American Diesel is a terrific resource and supplier but sometimes that guy leaves me scratching my head.
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Old 03-21-2020, 02:57 PM   #18
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I think that AD has seen a lot of issues with the spin on adapters so they donít like them. We have the 225 version and are currently derating them to 180. We still have the original PITA filters and will probably stay with them. The real problem is bleeding the filters after changing them. I am replacing my 900FG Racors with 900MAs. I did one this year and also put in Racors fuel priming pump into the new Racor so I should not have the priming issues since I will be able to just push the button for the priming pump.
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Old 03-21-2020, 03:05 PM   #19
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I think the problems are with the quality of the spin-on adapters out there. I ordered 4, broke 2. Luckily they were replaced for free.
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Old 03-21-2020, 03:59 PM   #20
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I installed the Racor CAV Spin on adapters and Baldwin spin on filters on my single FL 120 20 years ago. I have not had any issues at all during the last 20 years.

The spin on allow prefilling of the spin on elements to make bleeding easier, faster and no spills. I do have an electric fuel pump to pressurize and bleed air.

I replaced the Baldwin fuel filters this year after 20 years and 3,000 hours in service. I cut them open and they were clean inside. The filter media pleats were discolored from the dyed diesel but the pleats themselves were in great shape.

I have 2 micron Racors upstream of the on engine filters.
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