Ye 'Ol cold start thread

[8v-of-fury]

Yeah kev, its still a diesel..

If it started right up and ran fine in the cold it wouldn't be an indirect injected compression ignition engine

[RabbitJockey]

yee haw i haven't been following this thread, but this morning my car started up no problem soon as the key was turned with only a single run of the fast glow plugs and the advance knob pulled, i didn't think much of it until i checked the weather and saw it was below 15 degrees this morning. stock 81 rabbit 127k miles with a yellow dot pump at 1.13mm.  no smoking and no missing 15w-40 rotella non synth

[R.O.R-2.0]

my injectors are fine.. they never got over tightened. the only time ive taken them out, is when i swapped heads, and ive had it running darn near perfect with that head/injectors...

this problem arose when i pulled my engine, and subsequently pulled my pump to swap brackets.. i dont have a timing gauge to check with, but im buying one on friday.. its the ONLY tool im missing in my arsenal..

im actually gonna bump my timing up a pencil line width, and see if i can get it to fire up any better.. it was WAY way advanced when i put the pump back on there, soo advanced that retarding the timing made it rev up to where it usually idled..

im still not thinking its injectors, and i KNOW my compression is not stellar, this is the engine i heat seized.. the scoring in the bores was almost un-detectable..

[AudiVWguy]

On the subject of testing compression. I've always been told to do this after the engine is warm, but for our diesels. especially because it's a cold start issue, wouldn't it make sense to test while the engine is cold. Does that seem to make sense?

[R.O.R-2.0]

On the subject of testing compression. I've always been told to do this after the engine is warm, but for our diesels. especially because it's a cold start issue, wouldn't it make sense to test while the engine is cold. Does that seem to make sense?

thats what i would be leaning towards..

i bet my audi ALMOST had acceptable compression when it was warm..

[ORCoaster]

I compression check cold as you say it is the problem area when starting up.  Unless it is hot.  If cold compression is low I like to know that because I know it will come up a bit as soon as it gets warm. 

[8v-of-fury]

So for compression testing.. would i be wise to have all the injectors out of the motor?

[Mark(The Miser)UK]

So for compression testing.. would i be wise to have all the injectors out of the motor?

That's how it's done, but not how your car does it when starting. So doing it with them out gives a figure that corresponds only with a running engine, and decelerating at that. However it is a good figure to make comparison with other's engines who do not have a starting issue.

RE your cold start pullL
The lever is shaped like a wedge on it's internal end, and physically pushes the advance piston the 5 degrees crank. However it is only 5 dgrees of advance whilst cranking.
This is because the pneumatic advance from the pump pressure starts operating around 350rpm, and at idle has used up perhaps 2 to 3 degrees of the advance.
Thus pushing and pulling on the c/s handle should be easier with engine running, and on the earlier pumps, hard to notice the running effect.

If push and pull are same stiffness, then internal pressures may be too high for the pump. If no change in stiffnes of pull fron engine off to engine on then internal pressures may be too low.

There are, naturally, always other possible  other reasons.

Later pumps with some further linkage also raise the engine revs. Not sure if this is to reduce owners concerns of not seeing much or to improve initial running.

[8v-of-fury]

Mark,

From my somehwat limited yet very recent experience with the internals of these pumps, I don't see how the cold start lever could be affected by pump pressures.. It physically turns the ring that the rollers for the cam ride on, and is not attached to anything? Hmm but there is a small port on the front side of the cold start piston.. Which probably pushes back against it eh? Interesting.

Anyway, I have a 91 na pump lid on the 91 or 92 TD pump body and it has the fast idle as well as the advance lever. The lever is slightly easier whilst running, so much that it is smoother if anything. I can hear it physically bumping idle and a little more clack, so its advancing for sure.

Here's an interesting thought I just had, if I start the car cold handle in.. Ill need to be on the peddle a bit to keep it high enough to not stall. It will still smoke and miss, and if I pull the handle it all sort of gets less (smoke and stumble).. But still misses.

[Mark(The Miser)UK]

Mark,

From my somehwat limited yet very recent experience with the internals of these pumps, I don't see how the cold start lever could be affected by pump pressures.. It physically turns the ring that the rollers for the cam ride on, and is not attached to anything? Hmm but there is a small port on the front side of the cold start piston.. Which probably pushes back against it eh? Interesting.

Anyway, I have a 91 na pump lid on the 91 or 92 TD pump body and it has the fast idle as well as the advance lever. The lever is slightly easier whilst running, so much that it is smoother if anything. I can hear it physically bumping idle and a little more clack, so its advancing for sure.
Here's an interesting thought I just had, if I start the car cold handle in.. Ill need to be on the peddle a bit to keep it high enough to not stall. It will still smoke and miss, and if I pull the handle it all sort of gets less (smoke and stumble).. But still misses.

For one moment you  had me worried I was shooting from the hip...
See middle of bottom left paragraph.
Lever should get easier either way as dynamic advance takes over.

As usual the modern improvement makes testing harder for the common man

[8v-of-fury]

Lever does get easier, and it smoothes out as I raise rpms.. meaning more advance.. might I have it set too far retarded?

No i tried at 1.00mm as well, and it clacked like a mofo! but i think i had a fuel leak then.. so maybe i should bump her back to 1.00mm and see whats up??

[rodpaslow]

Not to get off topic -39° this morning (colder if you include wind chill) - two block heaters, one at either end of the block.  Don't even need to use the glow plugs - fires right up on first crank!  (Old 90 1.6 n/a golf) That is after 2 to 2 1/2 hrs being plugged in...

[8v-of-fury]

Not to get off topic -39° this morning (colder if you include wind chill) - two block heaters, one at either end of the block.  Don't even need to use the glow plugs - fires right up on first crank!  (Old 90 1.6 n/a golf) That is after 2 to 2 1/2 hrs being plugged in...

Thats pretty awesome man, I feel confident I could start my car in the same weather with TWO block h eaters! lol!

[burn_your_money]

Anyway, I have a 91 na pump lid on the 91 or 92 TD pump body

That could be your issue. You are missing a stop for the fulcrum lever, but I think it would only effect starting, not running cold.

Can someone explain to me the business of this pintle in the compression tester and it being in different places effecting compression? I'm not getting my head around it.

Also, compression numbers on a cold engine are nearly useless (but not quite) because there is no spec on it so you have no idea what to aim for.

[8v-of-fury]

like imagine an injector, with its flat face with the needle. looking at the end of the compression nozzle, the needle is way up in the "injector" adding like the size of a glow plug to the combustion chamber