Yanmar 2qm15 hard start

[TinkerNZ]

I will start by saying that I am new to diesel motors. I have a new to me Yanmar 2qm15. I have the original manual, a full service manual, and a part list and I learning as fast as I can. I have gone through so many threads to try and find answers but nothing seems to quite fit. I have also just cleaned out the raw water system, done oil, and fuel filters. It has a new starter in the last 6 months, and a new starter battery. So here goes.
The engine is very hard to start. It takes about 4-5 minutes to get it to turn over, with the throttle at half revs or more. Its not cold out (50's). I start with having the raw water cock off so as not to hydrolock. I run the starter for 15 seconds at a time and then give it a break. After a minute or two it will start to catch, but still take a few more minutes to run on its own. Once going its great. I ran the boat for 6 hours the other day with no issues at all. If I shut it down it will start up immediately. If I leave it an hour or two it will start after about 10-15 seconds. The longer I leave it the longer it takes to start up again. By 24hrs its the full 4-5 minutes again.
I have started to think it is fuel related (either air or pump). I opened the secondary fuel bleed screw and pumped the fuel feed pump. No bubbles, clean fuel pushed out. I then backed off the pipes after the fuel pump, that lead to the injectors. Then pumped again, no fuel came out. So I took the pipes off completely. There was fuel at the top of the opening, but when I pumped it did not push out. Is that normal? Out of curiosity (and I have no idea if it was a good idea) I turned on the starter (still at half revs), expecting to see fuel gush out of the fuel pump, nothing. Well maybe not nothing, but very slow, maybe a drip of two. Again is that normal? I put the pipes back on and detached them at the injectors, not surprisingly no fuel came out. So here is my theory (which again is based on nothing but a guess). There is an air leak somewhere in they fuel system and the longer I leave the engine the more air gets in. When starting, the pump is very slowly building pressure, and bleeding the air out whatever hole there is, to the point that there is fuel entering the injectors and then it fires and runs. Plausible? Any other ideas. What should I try next? Thanks so much for any help.

[kayakerChuck]

What is your throttle position when trying to start?

Yanmar calls for "medium speed", about 50% throttle. When it's cold, 100% throttle.

[Wotname]

Welcome aboard CF, TinkerNZ.

The 2QM15 is pretty reliable engine and of course it should start easily when cold. 30 seconds of cranking would be considered a very slow cold start - unacceptable so you do have a real problem.

It will be either electrical (likely) or fuel (likely) or lack of compression (unlikely).

You have replaced the starter motor and battery but are the cables and terminations any good. I would be either replacing the battery cabling (including the negative cable) or at least pulling them off and having a very close look and clean.

Have you tried starting the engine using the decompression levers? Decompress both cylinders, hit the start switch and after say 5 seconds recompress one cylinder (keep the start switch ON). If it fires recompress the other. If this method works, then you most likely have an electrical issue - cables, solenoids, master switch etc.

If the above method makes no difference, then pursue the fuel issue.

[TinkerNZ]

Thanks for the replies. The throttle is at between 50-100%. I move it back and forth between 50-100. I guess thats my old gas engine days of not wanting to flood something. I dont know if that can happen with diesel.
As for the electrical side. Sorry, yes I checked the cables, cleaned the terminals. I did not replace as they seemed fine and the cranking seemed fast. When I watch you tube videos of people starting there 2Qm15's it seems like I am not cranking slow.
That all lead me to the fuel ideas. I really think there must be a pump issue as no fuel seems to be squirting out. Then again if that is the issue how it starts eventually and keeps running is beyond me.

[TinkerNZ]

Oh sorry the decompression lever. I tried both at once, the two are connected by a bar so they cannot be turned off independently. I can remove that and try independently. I did try both off after reading other threads.

[BruceS]

I have no idea on that motor but what sort of stop system is on it? Might be sticky & not releasing with key on? Not adjusted right or spring weak depending?
Doesn't sound like an air problem if no bubbles anywhere you tried.

[TinkerNZ]

Thanks for the idea. The stop system is a pull cable connected to the governor. I will check it but my guess is the is ok as once running it runs fine and I then can use the pull cable to shut the engine down. The reason I think its air or fuel injection pump is that when I go to bleed at the injectors no fuel comes out initially and when it finally does its a dribble. Its not that clean fuel without bubble comes out. There is no fuel or very little. I recently found a video of someone that had taken off the pipe at the injector completely and when they turned over the engine the fuel squirted out at pressure. I get nothing.

[TinkerNZ]

Update on what I tried yesterday and today

Yesterday I went through the full service manual bleed process again

1 - Bled the fuel filter (no bubbles)
2 - Bled the secondary (no bubbles)
3 - Loosen the return line nut on to of injector using the primer pump (clean fuel no bubbles)
4 - Bleed air from the fuel injection pipe by loosening the nipple on the fuel injection valve side. Set half throttle, decompression engaged, and crank engine till fuel is clear and no bubbles. Do one at a time. This took at about 2 minutes of total cranking time to get a very small flow of fuel out of each. Tighten down
5 - Crank engine. It started after about 10 seconds.

Today. I tried initially to start the engine up. Nothing. So went through that same process as above. Same thing happened.

This to me suggests two things. Air is getting into the system from somewhere and there is very little fuel pump pressure being generated.

Thoughts and thank you so much for all the ideas.

[Wotname]

Originally Posted by TinkerNZ

Thanks for the replies. The throttle is at between 50-100%. I move it back and forth between 50-100. I guess thats my old gas engine days of not wanting to flood something. I dont know if that can happen with diesel.
As for the electrical side. Sorry, yes I checked the cables, cleaned the terminals. I did not replace as they seemed fine and the cranking seemed fast. When I watch you tube videos of people starting there 2Qm15's it seems like I am not cranking slow.
That all lead me to the fuel ideas. I really think there must be a pump issue as no fuel seems to be squirting out. Then again if that is the issue how it starts eventually and keeps running is beyond me.

OK, then you need to chase down either fuel or lack of enough compression to facilitate a cold start.

This engine has no cold start ancillary devices (glow plugs etc) and relies on a high compression ratio to enable cold starting - something like 23:1 from memory. Once warm, it needs way less compression to start and run. BTW, have you checked the tappet clearance - it should be 0.2mm (8 thou). Another possible way of checking if low compression is the issue is to direct hot air from a electric heat tool directly into the air intake (first remove any air filter if fitted). If it starts quickly, it isn't fuel related.


Back to the fuel issue - while the following has to be done very carefully, it is possible to get fuel into the cylinder by using a small misting spray bottle filled with diesel. Using the finest spray possible, mist a tiny amount of fuel / air into the air intake while cranking. If it catches, stop. You have proved it is a fuel issue.

It is fuel, it sounds like the injector pump or the injectors themselves aren't maintaining pressure in the steel injector lines while the engine is idle. This could be a problem with the check valve in the injector or in the injector pump.

Another thing to try is to rig up a temporary gravity fuel feed going directly into the injector pump. Just some tube and a funnel is all that is necessary.

Or pull an injector, reconnect to the injector line, decompress and turn the engine over until the injector spray is observed. Now let it sit for say 12 hours and and try again. The spray should be observed within a second or two. If not, you have a high pressure side leak or failed check valve.

When the engine is decompressed, you can turn it over for much longer times - at least a minute or two as the starter motor needs very little power to turn the engine over when decompressed. I.E.the starter motor won't get hot but do check by placing your hand (carefully) on the starter motor. If you can hold your hand on the starter motor, it isn't overheating.

[Wotname]

Originally Posted by TinkerNZ

Update on what I tried yesterday and today

..................
4 - Bleed air from the fuel injection pipe by loosening the nipple on the fuel injection valve side. Set half throttle, decompression engaged, and crank engine till fuel is clear and no bubbles. Do one at a time. This took at about 2 minutes of total cranking time to get a very small flow of fuel out of each. Tighten down
5 - Crank engine. It started after about 10 seconds.

Today. I tried initially to start the engine up. Nothing. So went through that same process as above. Same thing happened.

This to me suggests two things. Air is getting into the system from somewhere and there is very little fuel pump pressure being generated.

Thoughts and thank you so much for all the ideas.

I have just seen the post - it really does sound like you are losing pressure on the high side of the pump. This might not be an air leak, it might be a non return valve failure at the injector or injector pump.

In my experience of these engines, very little fuel will be ejected from an open injector line, just a small drop or so. Of course there is no pressure with an open ended line. Refit the injector and making sure any spray pattern is directed away from any part of your body, you should see the spray when you crank.

Earlier Yanmar manuals describe the spray pattern but AFAIK, the 2QM15 manual does not. I can chase up an image from an older manual if you need it.

[TinkerNZ]

Thank you so much for the detailed reply. Not going to lie much of what you said went over my head but I will read through the manual to understand things like tappet clearance. Sounds like the easy things to try are a hot air in the air intake, misting the intake, gravity feed to the fuel pump, and pulling an injector to look at the spray. The manual I have on 3-13 shows different spray patterns (normal, stream, spike, slanted etc). Its good to hear that I should not be expecting to see a huge stream and thanks so much for letting me know about running the starter for longer when decompressed. Oh one last thing. I have not pulled the tank outlet. Say there was crud in the tank that was partially blocking the fuel flow. Could that manifest itself as lower pump pressure? Anyway I will try everything suggested over the next few days and then post an update. Thanks again.

[Wotname]

Originally Posted by TinkerNZ

.......... Oh one last thing. I have not pulled the tank outlet. Say there was crud in the tank that was partially blocking the fuel flow. Could that manifest itself as lower pump pressure? Anyway I will try everything suggested over the next few days and then post an update. Thanks again.

If you mean lower pressure lift pump pressure i.e.the pressure out of the fuel pump going into the injector pump inlet, then yes it would drop the pressure a small amount.

If you mean the pressure on the high pressure side of the injector pump, then no, it would no effect.

The fuel lift pump draws fuel from the tank and delivers to the injector pump. The pressure from the fuel lift pump is only a few psi (less than 10 psi).

The injector pump delivers fuel to the injectors at around 2,500 psi. A small change of a few psi going into the injector pump makes zero difference to the output side of the injector pump. It will always be around 2,500 psi.

[TinkerNZ]

Thank you for the clarification. One less thing to worry about. I did not fully understand when you said that it could be the injector pump check valve so did some research (

https://www.youtube.com/watch?v=5YLRtA_QHa8

) and the symptoms that a failing check value would produce sound very similar to what I am seeing. I think I should start with you recommendation of pulling the injector, looking at the spray, then leaving it for 12hrs and see if there is still pressure in the system. I will also wrap all the high pressure side connections with paper towels to see if there is any evidence of leaks over that time, but there is nothing obvious at first glance. Thanks

[TinkerNZ]

Sorry it took an extra day. Here are the results.
1. hot air in the air intake - No change, did not fire
2. misting the intake - fired immediately, then died
3. Pulling an injector to look at the spray - Injector looked clean, it did not spray. So I put it back in, went through the full bleed process on then pulled it again. Then it took about 10 seconds to start spraying using half throttle and decompression level on. The spray looked like the normal picture in the manual to me. I pulled the second injector and same, normal.
4. I left the injector out overnight. Using half throttle and decompression level on I cranked and it took about 30 seconds to see any spray and about 1 minute to get consistent spray.
5. Oh there were also no obvious full leaks. I had cleaned the motor the day before and put show towels around the joints. So evidence of leaks.

This all points towards check valve in fuel pump, right? So is there a next step. The manual goes through how to pull, test, clean the high pressure pump, but does not specifically reference a check valve. Not to mention I suggests never to pull unless you have experience. I dont. I thin something I need a shop for. There was another forum post of someone asking for advice on best place to take a pump for service and the most recommended is local. Is that the best idea? There is also a new pump (non OEM) listed online for $390 plus shipping. Which sounds like a lot but I am guessing to service the existing one is not cheap. Then there is all the videos and posts about people miss aligning the the pump when reinstalling and getting a run away. Its all a little daunting. Thanks for any advice.

[Wotname]

Originally Posted by TinkerNZ

Sorry it took an extra day. Here are the results.
...................
4. I left the injector out overnight. Using half throttle and decompression level on I cranked and it took about 30 seconds to see any spray and about 1 minute to get consistent spray.
5. Oh there were also no obvious full leaks. I had cleaned the motor the day before and put show towels around the joints. So evidence of leaks.

This all points towards check valve in fuel pump, right? So is there a next step. The manual goes through how to pull, test, clean the high pressure pump, but does not specifically reference a check valve. Not to mention I suggests never to pull unless you have experience. I dont. I thin something I need a shop for. There was another forum post of someone asking for advice on best place to take a pump for service and the most recommended is local. Is that the best idea? There is also a new pump (non OEM) listed online for $390 plus shipping. Which sounds like a lot but I am guessing to service the existing one is not cheap. Then there is all the videos and posts about people miss aligning the the pump when reinstalling and getting a run away. Its all a little daunting. Thanks for any advice.

What it points to is a loss of pressure in the steel injector line as it sits over night. As there is no external evidence of fuel leaking out, then the loss of pressure must be occurring at one end of the injector line or at the other end of the injector line. That is to say, the injector end is leaking into the cylinder head or the pump end is leaking back into pump body or crankcase. When I say leaking, I mean a couple of drops only which releases the stored pressure in the steel line.

When you next start, the injector pump has to build under the pressure again until it gets to the 'pop' pressure of the injector, that is the point when you observe the spray.

So which end is it or is it both ends?

I forgot to say earlier you should look at the injector after it has 'popped' and watch for any small dribble of fuel from the nozzle. This would indicate a leaking injector which would cause the loss of pressure as it sits. Also you should do these tests at full throttle (WOT - wide open throttle) as this gives the maximum fuel delivery and thus easier to spot problems.

If the injector is leaking, you need to take it to the injector shop for repair - it is a common thing. You could also take both injectors into the shop and ask for a quick go/no go test. They measure the pop pressure and check for a dribbling nozzle. The shop here in Tassie usually does it for free - it only takes 5 minute to do both injectors.

The other end (injector pump) is way harder to DIY test. The pump needs to be removed and taken to the shop. Even removing the pump is not straightforward to the beginner mechanic but it is possible if you are mechanically literate and can understand the service manual.

My humble advice is to take both injectors to the shop and have them tested / repaired as required. This might fix the issue or at least gives you some confidence the problem is with the injector pump. If so, decide if you are willing to pull it or get a mechanic in the loop.

The attached picture is from the service manual and the circled part is the "check valve", Yanmar calls it the delivery valve. I use the term 'check valve' for any type of non-return valve. Note there is one for each cylinder.