Nanni 3.90 HE crank no start

[Alapa1964]

Hi Guys
My problem is Ive got a Nanni diesel 3 cylinder 3.90 HE that cranks but will not start. Ive replaced all fuel filters, bleed the lines systematically from tank to top of injectors, fuel is coming out no bubbles. Then checked new glow plugs with 12volt and replaced old ones. Then checked glow plugs while in the engine all good. Engine was running the day before but was getting harder to start over the last few months. I never had to prime with a hand pump, which is located just after the tank but lately, I have. Not sure if this helps or is a problem..Checked lift pump seems ok, replaced injector pump. Any help would be appreciated. Thanks

[Wotname]

Good to see your first post!

Sounds like you have fuel to the injectors so that only leaves Air or Compression.

Lack of air can be induced by clogged exhaust / mixing elbow so check the exhaust system for restriction, especially at the water injection point.

Lack of effective compression can be caused low starting rpm so check battery, leads, connections for corrosion etc (including the negative return cable).

[Pandor]

Agree. Sounds like fuel ok, so how old is your starter battery? That was my issue last time I had crank but no start.

[Alapa1964]

Thanks for reply guys,, Ill check both suggestions when I visit boat next,, which is 4 hours away from where I live..I will tell you how I go..

[skipperpete]

I’ve no firm idea why she won’t start after reading the list of things you already tried without success, but with so much dead cranking it might be wise to turn off the raw water seacock to avoid filling the exhaust. Actually, it might help if you drained the aqua-lock, if its already full it qualifies as a blocked exhaust.
A blown head gasket could be a prime suspect, especially if its blown between two cylinders.

[MIRELOS]

what about your batteries; diesels need cranking power, even though the engine is turning if the battery is old it might not have the cranking power to start the motor

[Madehn]

So on my perkins6354 I can get fuel out of the injector tops while cranking while the go pump still has some air in it. It will look like everything is bled but won’t start. Does your hp pump have a separate bleed fitting. If so then bleed the go pump and she will probably start up. If the engine is worn then you may have an issue with not spinning it fast enough to generate enough compression to fire. Might try squirting some wd40 down the intake, this will help get more of a seal around worn rings as well as putting a fuel into the piston. Still putting my money on air still in system. Best of luck

[capt jgw]

Since this seems to have developed over time I'd bet on low compression or a blocked intake or exhaust. Most likely is probably exhaust, mixing elbows do clog up and it's a common question on all the forums. Easiest to check would be the intake, just pull the air cleaner off. If that doesn't work I'd pull the elbow and check for clogging. Just for fun try to start with the exhaust disconnected, wear hearing protection because it will be loud as hell. If it starts with either of those tests you'll know where the problem is. If no go the next step is a compression test.

[Madehn]

That blocked exhaust makes a lot of sense as well

[skipperpete]

Beware the mixer elbow on Nanni engines, they actually form part of the end of the heat exchanger and were bronze up until the 3.90? I think now its cast iron or aluminium and if you take it off you’ll need the Nanni gasket and a coolant change unless you catch it in a bucket.

[Alapa1964]

Wow I'm so impressed with the support this forum has provided. Thank you to every one who makes this site work.. It can feel isolated and demoralizing owning a sailing boat and not knowing anyone ,,,learning about the whole sailing process as a newcomer.. Thank you..Its got four house batteries and one spare- three new, two 4years old..Ill start there and check voltage..Intake is clear ,so Ill check exhaust next,, Then Ill do a compression test..Ill also turn off raw water intake which I didnt do previously..Thanks a lot ''''''Ill let you know how it goes next week.

[Alapa1964]

Hi Guys
Well I've been to boat and tried to start the motor with a full charged battery 14.3volts,turned off salt water sea cock, cranked but wont start.
Pulled the heat exchange off and apart no blockages.
Check intake manifold and its clear.
Bought a diesel compression test and checked all pistons through injectors showing zero compression on all cylinders,, thought this was a bit strange as I would have thought it would show some low reading , nothing. So I tested through glow plugs same as before needle twitched but did not rise..
Did a valve adjustment and tried again, ,same results.
Noticed voltage dropped to 12.5volts after test ,not sure if this is a problem.
I guess I need a recondition engine $3500 and hand over of this engine. It has a New Heat exchange which was $3000, so this is not so bad. Weather has been blowing all summer and rain showers every day so this makes me feel better.

[skipperpete]

Well, that narrows it down a bit, I’m not sure I’d be making the leap into buying a recon though ...until I’d ....#1,adjusted the valve clearances again but this time , after you tap the rocker arm lightly with a hammer to see if they all pop back up immediately...#2 checked where the loss of compression actually occurs (leakage test) and #3 .... removing the head after these simple checks to view the condition of the cylinders and head gasket if the leakage test indicates a problem in either of these areas. I’d suggest that you might have a couple of stuck exhaust valves caused by the humidity created by the wet exhaust, a fairly common event.

[Alapa1964]

Thanks for your reply
I did take the head off when I was last down at the boat everything looked fine the cylinder walls were very smooth, tops of pistons looked fine. I will adjust the valves again as you say, before buying the reco engine..Can I use this tester for the job:
Combustion Leakage Tester Petrol Diesel Gas Engine Cylinder Leak Down Tester Kit which is used through radiator cap.

[skipperpete]

Originally Posted by Alapa1964

Thanks for your reply
I did take the head off when I was last down at the boat everything looked fine the cylinder walls were very smooth, tops of pistons looked fine. I will adjust the valves again as you say, before buying the reco engine..Can I use this tester for the job:
Combustion Leakage Tester Petrol Diesel Gas Engine Cylinder Leak Down Tester Kit which is used through radiator cap.

No!......
You only need the glowplug fitting that you got with the compression tester, a length of hose..... and a supply of compressed air. Roll the engine over to bdc and loosen the adjuster on the open valve then allow the air into the cylinder and listen closely to where it leaks out.
If it hisses into the inlet manifold, thats a leaking intake valve.
If it bubbles in the aqualock (or hisses) thats a dodgy exhaust valve or seat
If it hisses at the oil filler cap its either the rings or possibly a headgasket blown to the pushrod gallery
If it bubbles in the header tank ..... blown head gasket to waterways.
There is a scenario where the head gasket blows between cylinders that gives a confusing reading but since you had the head off, probably not worth considering .
Don’t worry about getting a percentage reading, all you need to know is how loud the hissing or bubbling is.
There’s still a chance that the schraeder valve or non return valve in your new compression gauge is leaking, that’ll give a low or zero reading on the gauge.