Reconditioned engine first start, running rough

[coconup]

Hi forum, I had a bit of an anticlimatic day yesterday when I attempted a first start of this D24TIC engine I have been reconditioning for over a year.

See this video as a reference: https://www.youtube.com/watch?v=qvTZkiHrkUc

Everything on the engine is new or freshly refurbished: block, head (and its gasket), pump, injectors, glow plugs, pistons, piston rings.. everything.

I have timed the pump following the usual procedure I have already used in another engine I have and I am sure it's correct, although I will double check it first thing. I also primed the pump and bled the fuel lines by leaving them disconnected during the initial cranking, until diesel would start spilling from the injector caps. Finally, I have primed the engine with oil before even attempting to crank it.

It seems to me the engine is running uneven and occasionally misfiring. Giving a bit of gas seems to improve the way it runs (so low idle might be one issue), but even at higher RPMs I feel it's not running right.

Symptoms point me to these possible sources of the issue:
- Wrong pump timing, although just done
- Defective glow plug(s), although all new
- Defective injector(s), although all freshly refurbished
- Defective pump, although freshly refurbished
- Lack of compression in one or more cylinder

My plan now is to check the following, in this order:
- Pump timing
- Glow plugs voltage
- Compression test on all cylinders (sigh)
- Testing injectors

Anything else comes to mind that could cause the engine to run as it does? Any tip is appreciated, I will post results here once I have them

[ngoma]

Originally Posted by coconup

My plan now is to check the following, in this order:
- Pump timing
- Glow plugs voltage
- Compression test on all cylinders (sigh)
- Testing injectors

Good game plan, except I don't understand your suspicion of GPs, as you did not describe anything about hard starting, and GPs would have little effect on the uneven running and misfiring you describe.

What method was used to rebuild/test the injectors?

What method was used to rebuild/test the IP?

What method was used to set/test the IP timing?

What method was used to set the camshaft timing?

Can you track the misfire to a particular cylinder?

After checking IP timing you could perform the procedure: Loosen the injector feed line at each injector successively to see if one or more do not produce a change in idle quality.

[coconup]

Originally Posted by ngoma

Good game plan, except I don't understand your suspicion of GPs, as you did not describe anything about hard starting, and GPs would have little effect on the uneven running and misfiring you describe.

What method was used to rebuild/test the injectors?

What method was used to rebuild/test the IP?

What method was used to set/test the IP timing?

What method was used to set the camshaft timing?

Can you track the misfire to a particular cylinder?

After checking IP timing you could perform the procedure: Loosen the injector feed line at each injector successively to see if one or more do not produce a change in idle quality.

Thanks @ngoma for the answer. You might be right about glow plugs, although I haven't mentioned the engine also has a hard time starting when cold. It was the first start ever though, so I am not sure if it would be better on a second attempt (going to do that today).

To your questions:

I bought reconditioned pump and injectors, hence I am not sure what the exact method for reconditioning those was, but both came from reputable sellers.

Camshaft and IP timing were done according to the book and as described in Sticky posts in here too (by yourself it seems! ): https://d24t.com/showthread.php?t=1684

I couldn't yet locate misfires to a specific cylinder, that would be my goal today in case I find timing is not the issue. With regards to this, thanks a lot for the tip regarding disconnecting one injector at a time and seeing if it makes a difference, I had not thought about that

[coconup]

Back from the man cave:

- Timing is perfect at 0.9mm (1.10mm with cold start device connected)
- Glow plugs do glow , but the engine does have a very hard time starting up when cold. Today's first start was no better than the very first one, unfortunately
- I tried running the engine and disconnecting fuel lines one at a time as suggested (thanks again @ngoma). Performance degraded when doing so at all injectors except maybe with nr. 3. I say maybe because the engine runs rough already, so it was sometimes hard to tell what impact a single injector would have. But I'd say disconnecting nr. 3 resulted in a less noticeable difference than disconnecting the others.
- I then ran a compression test on all cylinders and I got consistently low results at around 380-400psi for all of them. This cannot be right and I believe (/hope) it might be because of a cheap tester + a tired battery that I had used to crank the engine the whole day. I will try again with a better set and with a charged battery, expecting to see at least 450psi. On the other hand, no cylinder falls out of the range, so for now I tend to think compression is not the issue.

I guess this leaves me with injectors or IP as the main suspects. I will test injectors tomorrow one by one. Not sure what I can try on the pump in order to diagnose potential issues.. any idea?

Two other things I noticed:
1. All injectors nozzles were dry except nr. 1, which was wet with what looks like oil. Not sure how worrying of a sign this is, if at all. Any opinion? Remember all of these are brand new with a mileage of zero, as is the rest of the engine. I'm attaching a couple of pics (one of the dry injector and one of the wet nr. 1 injector)
2. Touching the exhaust manifold after the engine ran for a while, I could notice a substantial difference in temperature between cylinder 1 and 2 (which were hot) and 3,4,5,6 (which were relatively colder, sometimes much colder).

[BogfordGarage]

Prehaps there's some issues with the injectors on 1,2 and 3 which maybe why it is hard to pinpoint which cylinder is the real problem. Hopefully the injector is wet with diesel and not oil if so it could be there is some crap in the nozzle causing it to leak or dribble. With any luck pop testing the injectors will give you some idea of what's going on.

[ngoma]

Agreed that compression test results that show consistent readings balanced across all cylinders is more important that the actual numbers, given that at this stage we can consider the engine not even broken in yet (you did replace the rings and rehone?) and the actual compression should rise during complete break in.

As far as troubleshooting the IP, this is where you start swapping injectors to see if the problem follows the injector or not. One recent poster successfully used that method to find the issue to be one IP delivery valve missing its spring. But in your case the previous test (removing fuel to each injector sequentially) results were rather nebulous so we might start looking at more esoteric causes.

It is possible to reassemble the IP with the internals 180deg. out, but you said the IP was rebuilt by a reputable shop?

Possible that the throttle lever could have been removed and replaced in a different position on the splined shaft? Known to cause idle and off-idle issues.

More troubleshooting perception aids:

No-contact IR thermometer to measure temperatures at exhaust ports (better than your fingers!).

Mechanic's stethoscope (or hose, or long screwdriver, etc.) held at each exhaust port, and each injector boss, to help discern any audible differences between cylinders.

[coconup]

Good new first: testing the injectors was the right thing to do and it turns out cylinder 1 injector (the one that was wet when removed) has a "taking a leak" spray pattern: https://www.youtube.com/watch?v=MYt06n9Qv24

What are the odds with a freshly reconditioned injector?

I was pretty confident swapping this one out with a known working injector from the original batch would finally solve the issue, but of course it didn't. After reinstalling all injectors and fuel lines, hard start continued and I now can see air bubbles going through the transparent IP intake hose. They might have been there all along, but I honestly did not notice them till today.

I then went ahead to replace all leak-off pipes (again, since I originally reused the ones I had mounted earlier), followed by all copper o-rings on the injection pump (intake + out screw), followed by retightening all hoses on the filter and replacing (again) the plastic return valve. Nothing made a difference, bubbles are still showing up.

The engine is off the car, so the fuel lines are as simple as canister -> filter -> IP -> filter -> canister.. it should be an easy one to figure out, right?

Is there any trick to more easily locate the source of the leak? I know the back of the pump might also be a source, but the damn thing is like new.. at the very least it should be sealed. I cannot see any place where diesel is obviously leaking. I gave up for today, too exhausted..

@ngoma to your questions: yes the block was rehoned and all pistons (+ their rings) are new. Regarding IP, I got it off of eBay and the seller has nearly 100% positive feedback. I already had trouble with them though, since clearly they did not know how to properly set the cold start device. But I tend to believe the rest should be in order. Regarding the throttle lever, they would have done that too, so hard for me to tell whether that is a possibility.

[coconup]

Originally Posted by ngoma

Agreed that compression test results that show consistent readings balanced across all cylinders is more important that the actual numbers, given that at this stage we can consider the engine not even broken in yet (you did replace the rings and rehone?) and the actual compression should rise during complete break in.

PS I did not know that breaking in is a thing when rehoning and replacing pistons, thanks a lot for the hint. Do you have a rough idea of what to expect from a compression test now, and of how long it should take for figures to improve? I was planning another compression test this weekend with a better set than the chinese one I used so far.

[BogfordGarage]

Are you able to pinpoint when the bubbles appear in the clear fuel line? This might seem like a silly question but when trying to get our 760 running for the first time we had this problem.
It would start okay, throttle up but as soon as you let off the throttle bubbles would appear while idling, then stall. This turned out to be the axial seal on the pump drive shaft, but like you say yours should be fine as it's new. The way we found the leak may help you.
Take a priming bulb attach it directly to the pump inlet and create a vaccum with it, after doing this a hissing noise could be heard and it was traced to the seal. Pressurising the pump didn't reveal anything so it was air getting in rather than fuel getting out that was the problem. I hope this helps.

[coconup]

Originally Posted by BogfordGarage

Take a priming bulb attach it directly to the pump inlet and create a vaccum with it, after doing this a hissing noise could be heard and it was traced to the seal. Pressurising the pump didn't reveal anything so it was air getting in rather than fuel getting out that was the problem. I hope this helps.

Great tip, thank you. I will try this on Saturday and see if I get anywhere. I have the feeling I have a similar problem since I cannot see any fuel leaking. My main suspect at the moment is the transparent hose itself, since I already replaced everything else (except the IP seal of course) without success.