1.6d shudder after cold start, goes away

[NWVintage]

I'm having a problem that seems strange and I can't figure out what I might even try...

1.6d
I get a severe shudder and it almost dies a short time after a start when it's been sitting for a few hours. It starts right up (been about 45f here in the mornings) and it runs great after it gets passed the shudder. The thing that I find hard to wrap my head around is the fact that I can't find any sort of fuel leak anywhere. It seems to me that the most likely cause is air intrusion but I can't find anywhere that this appears to be happening. Also, it happens a bit after startup - I can start it, idle it for a minute or so, drive for a half mile or so, and then it happens. I replaced the fuel filter/separator the other day, to rule that out - it did turn out to be a bit dirty and did help the overall running condition of the engine but the shudder still shows up shortly after starting. I'm going to replace my clear line between the filter and the pump today - it's a bit stained - but I don't see any bubbles coming through there.
Thoughts?

[vanbcguy]

Do you have a clear return line?

A bad mainshaft seal on the injection pump can cause this.  It doesn't usually leak since that part of the pump is where the vane pump lives and it is not pressurized, but the pump will happily pull air in to the vane pump there.

If it is the mainshaft seal you would see air bubbles in the return line but not the supply line. 

[ORCoaster]

Are all the mounting bolts tight?

[TylerDurden]

Agree with both above posts: clear lines in and out, bolts tight.

A test with clear lines & bottle-feeding would be my next step.

[NWVintage]

Ok. I'll do clear lines both ways and check the bolts. See where that takes me.

Today, it took two tries to get it started but then it was fine...?

[NWVintage]

So, I put clear lines on both supply and return. Getting some air in the return but non in the supply except after sitting over night, so it looks like the rear seal is the most likely culprit. I also resistance checked the gp's and they're no looking so hot. Going to start in on both today. Any tips/tricks I should be aware of? Plan is to just remove the pump, replace seal, put everything back. The t-belt has like 10k miles on it, so I won't bother with that and I'll follow the Bentley to a "T". Anything else I should be thinking of?

[vanbcguy]

Definitely replace the GPs while the pump is off - it is about 4 gazillion times easier than when the pump is installed.  Even if they check out ok, the hassle of doing them later outweighs the few $$s you'd save.  Bosch Duraterms are the only plug to use.

If it is running ok now, it'd be a good idea to practice using your timing tools and take a measurement of where it is set currently.  Then when you reinstall the pump you can make sure it is set to the same spot, saving you some tuning time.

[NWVintage]

Definitely replace the GPs while the pump is off - it is about 4 gazillion times easier than when the pump is installed.  Even if they check out ok, the hassle of doing them later outweighs the few $$s you'd save.  Bosch Duraterms are the only plug to use.

If it is running ok now, it'd be a good idea to practice using your timing tools and take a measurement of where it is set currently.  Then when you reinstall the pump you can make sure it is set to the same spot, saving you some tuning time.

Thanks, I will check the timing before I pull it. I actually would like to retard it just a little more - there are two ranges that different sources recommend for timing this engine and I went in the overlapping area but now that the rings are seated, I can probably run a little less advance to get better mileage and still be able to get her started when it's cold.

I started yesterday but probably won't get back to it until at least monday. Does anyone have any recommendations for getting the pump pulley off without buying the special puller? Mostly because I don't want to order and wait for the puller. It looks too tight to get a standard puller in there. Loaner tools from big parts stores would be ideal...

[air-cooled or diesel]

Getting some air in the return but non in the supply except after sitting over night, so it looks like the rear seal

that's the front seal, front of the engine, technically. although you ll find often front of engine is referred as front of car, ie radiator 'side'. for instance on a type I bug and air cooled engines the front of the engine is pointing out the rear, but often misstated as rear of motor. its the rear of car, but front of motor.
i'd consider re-sealing whole pump, and using Viton seals. theres a thread on re-sealing on web site. with the Viton seals you can run bio-diesel over 5% safely.

[745 turbogreasel]

I've changed that seal on the motor using clothes pins to keep the timing belt engaged.
Best practice would be to reseal the whole thing though.

I  welded up a fake puller in just a few minutes, but i mostly use  2 chisels or scredrivers prying lightly form opposite sides, and a little tap from the brass hammer.
trying to pry it off from one side will  easily bend the pulley, so don't do that.

[NWVintage]

Getting some air in the return but non in the supply except after sitting over night, so it looks like the rear seal

that's the front seal, front of the engine, technically. although you ll find often front of engine is referred as front of car, ie radiator 'side'. for instance on a type I bug and air cooled engines the front of the engine is pointing out the rear, but often misstated as rear of motor. its the rear of car, but front of motor.
i'd consider re-sealing whole pump, and using Viton seals. theres a thread on re-sealing on web site. with the Viton seals you can run bio-diesel over 5% safely.

I misstated the name - I was speaking nonsense essentially, so never mind that.

I thought that air in the return but not the supply was indicative of the input shaft seal?

I'm not going to reseal the whole pump because I simply don't have the time right now. Biodiesel is a great thing for many reasons but I simply don't have the time right now. It's an easy thing to get at if I need to do it later, so I'm not that concerned about it.

[TylerDurden]

No worries... we got the picture.

Yes, air in just the return will 99% be a bad input shaft seal.

FWIW, the shop where I get my kits said the seals are viton or as good.

[745 turbogreasel]

I don't think he was pointing to a non front seal diagnosis so much as  the tendency for all of the seals to start leaking around the same age.

[fatmobile]

 Any air in the lines after sitting over night?
 How much air is exiting the pump?
 Sooo, when you shut it off; do a few small bubbles come out of the front of the pump?

 Do you have clear lines between the injectors? or at last the tubing from the injectors to the pump. I had an injector that pumped air out the small lines once. Looked like it was coming out of the pump.

[NWVintage]

Any air in the lines after sitting over night?
 How much air is exiting the pump?
 Sooo, when you shut it off; do a few small bubbles come out of the front of the pump?

 Do you have clear lines between the injectors? or at last the tubing from the injectors to the pump. I had an injector that pumped air out the small lines once. Looked like it was coming out of the pump.

Yes, there was air in the lines after sitting over night. There is no fuel exiting the system anywhere; only air entering. The air in the return line was a stream of small bubbles which increased in number with rpm. No clear lines between injectors - I suppose I'll check that if this doesn't work.

At this point, I have replaced the input shaft seal and glow plugs, and have gotten as far as setting the timing. I just have to put the periphery pieces (valve cover, t-belt cover, air cleaner, etc) back and I will be ready to try it out. I was hoping to finish today but it's pouring rain, I don't have a covered space to work on it, and I have another vehicle. The weather isn't looking too horrible tomorrow, so hopefully, I'll get an hour or two without rain to finish up.

I don't think he was pointing to a non front seal diagnosis so much as  the tendency for all of the seals to start leaking around the same age.

Yeah, I understood that but like I said, I simply don't have time to dive into that project at the moment. In this context, you are using "front seal" to refer to the input shaft seal, correct?