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Old 24-06-2019, 15:24   #1
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Leaking valve cover gasket cause hard starting?

Hi,
I have a Nanni 3.21 that is hard to start. There is also a small amount of oily residue at the corner of the valve cover. Would a leaky gasket cause loss of compression and thus hard to start?
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Old 24-06-2019, 15:38   #2
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Re: Leaking valve cover gasket cause hard starting?

The valve cover gasket doesn't have any compression so unlikely related to your hard starting condition.
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Old 24-06-2019, 15:44   #3
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Re: Leaking valve cover gasket cause hard starting?

I'll throw a guess out there and say that most small diesel hard starting problems are about equally divided between slow starting speeds and fuel supply/filtration problems...
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Old 24-06-2019, 15:48   #4
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Re: Leaking valve cover gasket cause hard starting?

As sailah says, the valve cover gasket won't affect starting issues.

Most starting problems are either due to electrical problems or lack of compression.

If you wish to provide more detail of the starting problems, we can narrow down the root cause.
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Old 24-06-2019, 18:04   #5
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Re: Leaking valve cover gasket cause hard starting?

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Originally Posted by Wotname View Post
As sailah says, the valve cover gasket won't affect starting issues.

Most starting problems are either due to electrical problems or lack of compression.

If you wish to provide more detail of the starting problems, we can narrow down the root cause.


The engine takes about 30 seconds of cranking before it will start. Temps are in the 80ís so itís probably not a glow plug issue?
Fuel in the Racor bowl looks clean and itís filter and filter on the engine have less than 10 hours. The tank is also newish, so Iím pretty sure itís not bad fuel or blocked filters.
Battery voltage is also good. The engine turns over quickly.
Where to go from here?
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Old 24-06-2019, 18:14   #6
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Re: Leaking valve cover gasket cause hard starting?

Is this a problem that has existed for a long time or recent events?
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Old 24-06-2019, 18:22   #7
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Re: Leaking valve cover gasket cause hard starting?

Has the problem come on suddenly or has it been slowly getting worse? Engine hours? when were valve clearances & injection timing last checked? Glow plug test? I mean did it start with temp in the 80's without using glow plugs before?
agree with previous posters usually fuel/air or compression problems if cranking speed ok
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Old 24-06-2019, 18:44   #8
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Re: Leaking valve cover gasket cause hard starting?

Quote:
Originally Posted by mrybas View Post
The engine takes about 30 seconds of cranking before it will start. Temps are in the 80’s so it’s probably not a glow plug issue?
Fuel in the Racor bowl looks clean and it’s filter and filter on the engine have less than 10 hours. The tank is also newish, so I’m pretty sure it’s not bad fuel or blocked filters.
Battery voltage is also good. The engine turns over quickly.
Where to go from here?
Engine turns over quickly would usually indicate good electrics (but not always).

30 seconds of cranking is a long time.

If it is only when cold (first start of the day etc) but OK (much quicker) when hot then that would suggest glow plugs (more about that below) or low(ish) compression.

If it is all the time (hot or cold), it would suggest low compression or fuel issues.

Do the easy things first - check valve lash.

I'm not familiar with your Nanni engine but I'm sure others here are.
Does it have glow plugs and if so, how do you normally use them i.e. all the time or only when cold (first start of the day) or only in low ambient temperature?

Some makes / models of engines require glow plugs for every start, others for only first start of a cold engine (in warm ambient air) and some for only in cold ambient air (like say >40F etc). I don't know where your engine (when new) fits in this spectrum but if others, know, please shout out.
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Old 24-06-2019, 19:55   #9
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Re: Leaking valve cover gasket cause hard starting?

It's either compression or fuel. Take a squirt bottle and shoot some fuel into the intake while cranking. If it fires it's a fuel problem, if not, it sucks.
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Old 24-06-2019, 20:19   #10
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Re: Leaking valve cover gasket cause hard starting?

Quote:
Originally Posted by mrybas View Post
.........
Battery voltage is also good. The engine turns over quickly.
Where to go from here?
Before you rule out the electrical side of the question, please consider this cautionary incident.

Recently a friend had a new to him 30 year old 100hp engine that took about 30 seconds of cranking on the first start of the day (ambient temperatures around 20C - 70F). He had been told it had been that way for ages and it had several new starting batteries over the years. Engine was just getting old they said but otherwise good. Cranking speed was "normal".

I just a quick voltage check while he cranked it. OK at the battery but really bad at the starter motor. It took about 10 minutes to isolate the cause to a poor crimp on a bus in the negative lead to the starer motor. Replaced the crimped terminal and now the engine starts in less than 4 secs when cold and turns over way faster. The crimp looked OK on the outside and was properly bolted to the bus but inside was high resistance.

The apparently previously "normal" cranking speed had been decreasing slowly over the years until the slow cracking speed was the new normal.

It pays to confirm any diagnosis with real numbers!

Likewise before ruling out the glow plugs, we need to know exactly how they are meant to work when new.
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Old 24-06-2019, 20:28   #11
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Re: Leaking valve cover gasket cause hard starting?

I will note that when one piston ate its rings on my 3gm30f. The crankcase overpressure would push oil out of any location. If you run the engine, remove the oil fill cap. If you get lots\tons of gray smoke and a pressure relief, then you have bad rings on one or more cylinders.

On mine, one bad cylinder made the engine very hard to start.
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Old 24-06-2019, 20:43   #12
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Re: Leaking valve cover gasket cause hard starting?

Quote:
Originally Posted by mrybas View Post
The engine takes about 30 seconds of cranking before it will start. Temps are in the 80ís so itís probably not a glow plug issue?
Fuel in the Racor bowl looks clean and itís filter and filter on the engine have less than 10 hours. The tank is also newish, so Iím pretty sure itís not bad fuel or blocked filters.
Battery voltage is also good. The engine turns over quickly.
Where to go from here?
After seeing yr engine spec of 23.5 to 1 compression ratio I'd be very surprised if it needs glowplug assistance to start in 80F temp if everything else was normal. So look elsewhere than at glowplugs for the problem
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Old 24-06-2019, 21:23   #13
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Re: Leaking valve cover gasket cause hard starting?

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Originally Posted by Ecos View Post
It's either compression or fuel. Take a squirt bottle and shoot some fuel into the intake while cranking. If it fires it's a fuel problem, if not, it sucks.
Good tip for eliminating potential fuel problem; I must remember it!
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Old 24-06-2019, 21:38   #14
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Re: Leaking valve cover gasket cause hard starting?

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Good tip for eliminating potential fuel problem; I must remember it!
Trouble is, squirting fuel in helps to start when compression is too low as well as possible fuel delivery problems so it's not a foolproof diagnostic tool. OP could have perfect fuel delivery & too low compression.
Good trick if certain compression is ok tho.
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Old 24-06-2019, 22:16   #15
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Re: Leaking valve cover gasket cause hard starting?

30 seconds to start is a very long time, even for old school engines. At 80F 10 seconds would be a long time, if all systems were up to par.

After the engine starts, is everything good? Full power, stumbleless acceleration and deceleration, smooth, mis-free, regular idle and full RPM at wide open throttle?

An improperly adjusted or worn injection pump, governor or linkage, or weak or uneven compression could all result in prolonged starting times, but it's always best to start with simplest first...
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