Thread: 300tdi running a bit rough after engine rebuild??

sounds like pump timing, have you done a poor mans injector phase/timing check by setting the crank to 90BTDC for number one on compression, cracking the union with the fuel solenoid powered up then quickly turning the crank with a breaker bar while watching the injector union?

Have you checked the delivery phasing for the injection order, it is possible to mix up 2 of the lines and wind up with the timing effectively reversed.

Originally Posted by Defendozer

Hi all,

Well after spending the last two and a half weeks rebuilding the engine (not completely) in my 300tdi it is finally back together and running BUT its not running as well as it should and I'm not completely sure why (obviously I guess cause I'm writing this)!!

Anyway here is a list of all the work that I did:

New crankshaft and con-rod shells fitted
New rings fitted
The bores were honed
New head and gaskets fitted
P gasket replaced
New timing belt, crank pulley, idler pulley and timing belt tensioner fitted
And then there's the new oil, oil filter and coolant etc etc but thats not really important!!

Now the first bad thing was that it was a pain to start, took ages! Finally got it going by putting a fully charged battery in and giving it a few good goes, maybe there was air still in the fuel lines?.. Or something else which is what I'm getting to!....

The next bad symptom is that it is still hard to start, compared to what it used to be like.

The worst thing now though is that it doesn't run smooth, it does seem to idle ok but if you rev it just a little bit it gets "jumpy" and also blows a fair bit of white smoke which is unburnt diesel yes? It seems ok when the engine warms up though but its still not good and I'm not happy.

I'm thinking I have either done something to the rings when I put them in causing low compression or the fuel pump timing is slightly out which I think is the more likely out of the two..

Any ideas at all???? Please tell me its something easy like the pump timing

Cheers, Remo

Is it really noisy/rattly compared to before with pronounced intake pulses?

If so the actual timing could be out a tooth ,But still should start ok

Check your fuel lines/lift pump for damage or leaks & replace sections of line where needed as it could be drawing air & also leaking back to the tank when left standing for a few hours or more, which may explain the hard start issue then getting better as it self bleeds.

Rotate the engine so you can prime the lift pump & leave her overnight, then in the morning crack the bleed screw on the filter head & operate the lift pump. if diesel does not squirt out & it takes a few pumps you know where to start looking

sounds like pump timing, have you done a poor mans injector phase/timing check by setting the crank to 90BTDC for number one on compression, cracking the union with the fuel solenoid powered up then quickly turning the crank with a breaker bar while watching the injector union?

Have you checked the delivery phasing for the injection order, it is possible to mix up 2 of the lines and wind up with the timing effectively reversed.

No I haven't done what you said, does that give an indication of "out" timing?

And all the fuel lines are definitely in the correct places as I didn't completely take them off.

Is it really noisy/rattly compared to before with pronounced intake pulses?

If so the actual timing could be out a tooth ,But still should start ok

Check your fuel lines/lift pump for damage or leaks & replace sections of line where needed as it could be drawing air & also leaking back to the tank when left standing for a few hours or more, which may explain the hard start issue then getting better as it self bleeds.

Rotate the engine so you can prime the lift pump & leave her overnight, then in the morning crack the bleed screw on the filter head & operate the lift pump. if diesel does not squirt out & it takes a few pumps you know where to start looking

Actually thats the other thing, there is a quite bad tapping noise in the top end somewhere, my thoughts were that (A) they are not getting oil or ( the valves are not adjusted properly but I only just did them so don't see how they could be wrong!

I dont' think that it would be a fuel line, its got to be something that I have done as it certainly wasn't doing that before I pulled it apart, thats why I'm thinking it is the timing because its the only thing that I can see being wrong, I really don't know though
Will have a look though for sure.

Mine had simlar issues ruff running and excessive tappet type noise which was the pistons hitting the values turned out to be one tooth out on the timing belt but you also may have 2 separate problems

hey mate id be pulling the little cover plate off infront of the injector pump their 3 bolts their u can loosen to adjust the timing of the pump its quick an easy to do just a small adjustment can make a big difference the how the engine runs, ive timed all my motors by ear I advance them up till they knock then back them off a bit , not the right way to do it but it does work

Mine had simlar issues ruff running and excessive tappet type noise which was the pistons hitting the values turned out to be one tooth out on the timing belt but you also may have 2 separate problems

The crankshaft and camshaft are spot on for timing and I'm 100% sure of that cause the flywheel was locked and the cam pulley was exactly right when I put the new belt in, the fuel pump cog can't be a tooth out either really to be honest because it was locked with a pin the whole time and I loosened the three bolts to get the belt on and to tension it.

How much does the cog have to turn for the engine to run badly anyway? How touchy is it?

hey mate id be pulling the little cover plate off infront of the injector pump their 3 bolts their u can loosen to adjust the timing of the pump its quick an easy to do just a small adjustment can make a big difference the how the engine runs, ive timed all my motors by ear I advance them up till they knock then back them off a bit , not the right way to do it but it does work

Say if the pump timing was somehow out slightly which way would I have to turn the pump to try to fix it?

Ultimately what I would like to know is do the symptoms I mentioned point towards the timing or something else? Just trying to rule out the possibilities here.

I have just completed the same job on my 300 tdi and it went perfectly I think you are out 1 tooth that is why you have a top end rattle. Did you use the correct timing tools to fit the belt? Have a look on YouTube there is a really good video on fitting a timing belt and it also mentions the top end rattle problem.
http://youtu.be/BDokEsr1v-A