Diesel Doctor Wanted...

[frilaens]

I have just put back in my newly overhauled Penta 2001 (from 1986) and the damn thing won't start.

I have changed the cylinder head gasket, refurbished the cooling water pump and changed the engine mounts because 3 of them had broken. As the gasket was removed I've checked and adjusted the gaps cold (0.3mm) and as the fuel system was removed I've also shifted the two fuel filters. When I turn the motor by hand I can hear the intake, compression and exhaust and when I run the starting motor with and without compression they sound normal. But it refuses to start! A small amount of grey smoke appears at the exaust.

I think the problem is in or after the high pressure pump. The two filters have been bled and I have checked that a fair quantity of diesel is coming out of the inlet to the high pressure pump, but what comes out just before the injector is only a relatively small quantity of diesel. Should there be a copious flow here? I know the injector is self priming but how do I know the high pressure pump is functioning normally?

Regards,

Andy

 

[andy_wilson]

There is less fuel emitted as you move along the fuel system so nothing sounds particularly amiss there.

Grey smoke suggests unburnt, partially atomised fuel.

Did you do anything with the injector?

Is the cold start device working OK?

With a slightly dogey injector you should be able to get it running (like a dog) with some help from a hot air gun down the air inlet.

If that gets it going you could try the MOT station trick to get the old diesel smoker through the test.

Get a decent branded diesel additive (one which claims to clean fuel systems and injectors.

Half fill the final filter with it and stick the rest in the tank.

Bleed, start her up and see if things improve.

If you have to take a stuck injector out you'll probably have to remove the head again to get the copper sleeve replaced (or so I'm told, which is why I give my injectors an annual wash and brush-up as described)!

 

[frilaens]

I didn't mention that the injector was replaced. When I turn the motor over with the injector connector off I get a trickle of diesel coming out. I expected a lot more and at pressure (after the "high" pressure pump). I have cleaned the air filter and checked that the exhaust is emitting water and not blocked.

Andy

 

[vyv_cox]

Too many possibilities for a diagnosis. It's just a matter of going through everything you have done to check if it's correct. It still may be that more bleeding is required, see my posting above.

However, there is a short cut. Try it on Easi-start. This basically eliminates any fuel system problems from the equation. If it won't run on this, there is something seriously amiss, e.g. valve timing, compression. If it runs on Easi-start but not on diesel, there is a problem with the fuel system. Don't ever use the Easi-start again, or your engine will never start without it.

 

[andy_wilson]

The amount of diesel at the injector is miniscule.

If the injector has been changed then I would focus on that. Remove it and connect up the injector out of the block and turn it over the engine. You should see a small puff of finely atomised fuel every other revolution as you turn the engine over. If it is a squirt or dribble then the injector is faulty.

 

[frilaens]

The high pressure pump seems to be normal then, but I wonder now if I'm not getting all the air out of the metal pipe to the injector. I have turned the motor over with the injector disconnected and watched the diesel spurt out for say 30 seconds but was then concerned that the starting motor became a bit warm. As the injector is new I should imagine that it's OK. I will try a longer bleed on the injector tonight after I find another sackfull of rags.....

Thanks for the replies, I appreciate the help.

 

[brianrunyard]

You state, "the fuel system was removed".
Does this include the Injection pump? If so check the injection timing.

Brian
http://homepage.ntlworld.com/brunyard

 

[vyv_cox]

If you are seeing mostly fuel, little air, at the pipe connector to the injector, then it sounds like you have bled it through. It's possible that there is still air in the secondary filter or elsewhwere, but I would expect it to run to some extent.

Injectors have to be really bad for them not to run at all. I once left the needle spring out of an injector on a single cylinder engine, it ran, but not well.

When you turn the engine over by hand, is it very hard work? You should barely be able to get it over TDC.

I would definitely try the Easi-start. if it's an air in fuel problem the engine will run long enough to push it through. If it won't start it will give you some ideas where to look.

 

[aztec]

just a thought, have you adjusted the valve clearances properly? if there too tight you wont get the compresion up enough on starting. also what was wrong with the engine before it was repaired?

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[frilaens]

The valves clearances have been adjusted, and turning the motor by hand is very difficult with compression; I'm not sure I've done it in fact. The reason for the overhaul was the broken engine mounts (the propellor shaft was dropping down on the through hull tube and had lost about 5mm from it's radius!) and the head gasket was leaking oil into the cooling water at high revs (but not the other way). The water pump was leaking through it's drive shaft seal. I had the injector tested while the motor was out and ended up getting a new one. And gave it a lick of Volvo Green!

Andy

 

[Trevethan]

Aha!

I believe the problem is with the paint. By painting Volvo green, you reminded the engine that it is actually a Volvo and should behave accordingly. i.e. not work, cost a fortune to repair and so on.

I suggest a nice coat of blue paint to fix the engine and make it tick over like a Singer sewing machine... *g*

regards,

Nick

 

[aztec]

ok, if you have compression, check injector as suggested, if ok it should fire up. check the operating linkage at the injector pump.

to bleed with the engine turning, slacken off the injector pipe nut, have someone turn the engine over (use decompresion levers if fitted) allow fuel to leak out of pipe untill no bubbles are visible, then tighten pipe and throw decomp levers, it should start, keep engine running briskly to purge any remaining air from system. if this doesn't work. you'll need to go back and check fuel supply lines are the right way round (supply and return) or isolate them by using fuel from a can, if it runs ok from the can it 's the fuel supply.

one more question, did you alter the pump? is it timed, or is it mounted on the block? and adjusted with shims?

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[frilaens]

Last night I bled the fuel system as recommended and tried again; the engine turns over "normally" on the starter and small puffs (and some impressive rings) of grey-white smoke appear at the exhaust along with cooling water. But no start....

Some observations, comments:

The fine filter (which has just been replaced) seems to need bleeding again and again without an apparent source of air (or maybe the return from the injector when the injector is not conected)).

When I operate the lift pump manually and vigourously I can hear that the fuel flow is disrupted and possibly air?? Maybe the return valve is not working....

When the motor was out I removed all of the fuel system apart from the high pressure pump which sits in the engine block. However, when tightening the pipe nut once I noticed the central pump was also rotating and just tightened it up. I don't know how the timing is adjusted (what are shims?)

Andy

 

[frilaens]

Thanks for reminding me

I bought 4 engine mounts which I reckon are made of rubber impregnated with gold.....

Unfortunately given my location (I live in Trondheim, Norway) and it's proximity to the Vovlo homeland there isn't too much choice!

Andy

 

[Trevethan]

Hva driver du med i Trondhjem?

 

[aztec]

check injector again by fitting it to the injector pipe and turning over the engine, as mentioned in an earlier post there should be a fine spray. it's possible that the needle in sticking, maybe due to water withing the injector during storage, (we had simmilar problems when using poor quality fuels in MAN diesels), what this does is allow compression pressure to overcome the injection pressure and air lock the injector pipe. the outlet connection on the pump should be locked with a clamp so as not to turn, but i recently replaced one on a slanzi/lombardini pump, and it did'nt need caliberating. if you've not had the pump out forget that bit. i would bypass the fuel supply by using a remote (gravity fed) tank, to isolate the fuel delivery system, bleed and try again. it sounds like an air problem as it's trying to fire. also check max fuel/cold start (if external , but probably not) make sure you have full throttle and the stop lever is adjusted correctly i.e. on the right stop.

if the thing runs ok with an indepentant fuel supply, i'm afraid it's a long process of rechecking all connections. and unions especially ones that have been under tension. also one thing that comes to mind is a boob i made once, i put a small piece of wood into a diesel line to stop it leaking into the bilge, then forgot about it, needless to say it took bloody ages to find, and acute embarressment was caused!



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[vyv_cox]

If you have bled the engine using the full procedure, working from the tank (assume this has plenty of fuel in it?) the system will be essentially full of fuel with only minimal amounts of air at some high points. These are not important.

You say that the secondary filter keeps filling with air. The possibilities are either:
1. You have not bled right through the primary filter and some air remains there, or
2. Air is being drawn into the system. The two possibilities here are either that there is a leak on the suction side of the lift pump, or that the diaphragm in the lift pump has a hole in it.

Your final sentence is a little worrying but I don't know the engine you are working on. Usually the metering pump rotational position is highly critical to the timing of fuel injection and if you have moved it the engine has no chance of running. Check that a squirt of fuel comes out of the injector at just before TDC - if it comes out at another point of revolution there is a timing problem. You will need at least the workshop manual to set this up. Don't just guess where it was previously, a few degrees out can cause serious damage.

Shims are thin pieces of metal sheet, with very precise thickness, used to set up metering pump timing in some designs. With these it is not possible to change the timing unless you remove shims or put some more in.

I repeat for the second time - try it on Easistart.

 

[johnt]

Hi Andy
1/ from what you say it seem that the high pressure pump hasnt been disturbed ..? if that is so it wont be the timing and it wont need reshimming.

2/ every thing else in the fuel system did get disturbed ?

If so...... start with the fuel lift pump..thats the one you can prime by hand ... take it off, take it apart and check that the valves in it and the diaghram are clean and sound, on reassembly blow through it ..you should only be able to push air through it one way ....the direction of flow (double check it !)
Refit.. check the flow by pumping with the outlet disconnected, put a finger over the outlet and try to hold the fuel back
then check all the pipes from there on , are the olives ok ..have they been overtightened and squashed.. work through the system checking each item as you go ..if it still wont start ..take the injector back and get another one !


John T ..a.k.a 'The Diesel Doctor' (can I kill someone at Practical Boat Owner for that nickname?)

 

[frilaens]

Jeg jobber i olje industrien... jeg er geofisiker i et lite selsap som heter Seabed Geophysical. Vi samler seismikk på havbunnen....

 

[frilaens]

I've just re-read my RYA Deisel Engines book and found a couple of things to check (in addition to taking out the injector and the Easistart). One was that I didn't check a gap when other valve was fully depressed. I re-adjusted them and at the same time (worst mistake... change two things) noticed the oil I was using was not the recommended SAE 20/W30 so I drained it but didn't have a replacement so will try to start it again tonight. I'm not sure how importand it is; I think from memory the one in there was 15/W40. I will try and find Easistart or it's equivalent in Norway, as well, although I don't like the idea of opening up the fuel system again...... she is beginning to smell like a tractor

About the "loose" high pressure pump; I think I had overtightened the locking nut on the outlet pipe and so when removing it the pump started turning also. It's a Bosch if that help. All I could do is re-tighten it and hope it's just a locking nut (underneath the nut on the tube there are grips which might be something to do with adjusting).

Andy