300TDI missing on one cylinder

AJofShabby · Mar 21, 2020

Hi all

I have a misfiring 300tdi. I went laning a couple of weeks ago, spending 12 hours in my 90. Some of the driving was quite harsh on the car and me! The car temp went slightly over normal but the electric fan didn't have to kick in. Water lever seems fine. There is no residue on the oil cap, oil level seems fine.
On the return trip the car started to lose power and was maxing out at about 50. The car runs sort of OK at speed but on idle there is a lot of vibration and the exhaust noise is a putt-putt. I have tried the following:
New fuel filter - old had some sediment but not too much
Cracked off each injector and the engine died for each apart from the one nearest bulkhead. I swapped that injector with its adjacent one but the bulkhead cylinder still didn't die when cracked whereas the injector did when in the next cylinder.
Fuel supply seems OK as it sprayed me when I cracked the injectors (new to this spannering) but I don't know if the fuel flow is the same across all four injectors.
Lift pump handle always seems loose so it may be that every time I stop the engine it happens to be in the "wrong" spot to enable the handle to prime or it could be that the pump in broken.
Does anyone have any ideas, pls? I have plenty of time on my hands right now.
Thanks.

steve2286w · Mar 21, 2020

So,you have proved, you have a misfire on number 4, can you run it with rocker cover off and check all valve gear working , I would then check tappet gaps, ensure not missing a valve cap on no 4 valves
Also Ensure the fuel pipes to no 4 and tight at the pump end

AJofShabby · Mar 21, 2020

Thanks Steve, I will give that a go.

steve2286w · Mar 21, 2020

Next step would be check compression pressure and compare it with the others

Perhaps with cover off check the valve lock nuts not worked loose allowing too large a gap

Blackburn · Mar 21, 2020

Check around the back of the head for signs of blown head gasket no 4 cylinder area.

kevstar · Mar 21, 2020

Blackburn said:
Check around the back of the head for signs of blown head gasket no 4 cylinder area.

2nd that quite common.

AJofShabby · Mar 21, 2020

I think we hit the limit of my ability after the first post!

Blackburn said:
Check around the back of the head for signs of blown head gasket no 4 cylinder area.

What are the signs to look for? The oil breather pipe looked a little wet this PM but v difficult to look behind the engine.

steve2286w · Mar 21, 2020

http://www.glencoyne.co.uk/tdipage2.htm#b

AJofShabby · Mar 22, 2020

Afternoon all . I hope you are all safe and well. I took the rocker cover off and stated the engine - lots of oil everywhere! It transpires that one of the valves is sticking. it is the second one down from the bulkhead, over the misfiring cylinder. Shd anyone have any ideas pls let me know; I am off to the tinternet to have a look . Hope fully this is the issue!

steve2286w · Mar 22, 2020

I think you found the problem
Oil everywhere a good thing
We’re the rockers going up and down on no 7 and 8
When you mean sticking what did you see
Are the valve caps on top of valves
Have you tried adjusting valve tappet gaps 0.2mm or .008” depending on how old you are using the rule of 9
Have a search on here
Next is to see if the pushrod is fully engaged at the bottom end and is straight
See if you can adjust the tappet to withdraw the pushrod and check it’s straight
If so put it back in engaging the half round hole in the brass tappet slide in pic below

AJofShabby · Mar 22, 2020

Hi again. So with a but of investigation all is revealed. One of the rocker arms has snapped....

steve2286w said:
I think you found the problem
Oil everywhere a good thing
We’re the rockers going up and down on no 7 and 8
When you mean sticking what did you see
Are the valve caps on top of valves
Have you tried adjusting valve tappet gaps 0.2mm or .008” depending on how old you are using the rule of 9
Have a search on here
Next is to see if the pushrod is fully engaged at the bottom end and is straight
See if you can adjust the tappet to withdraw the pushrod and check it’s straight
If so put it back in engaging the half round hole in the brass tappet slide in pic belowView attachment 203490

Hi

Things have moved on - snapped rocker valve! Pic in separate post. Just the rocker in No 7 (guessing as it was second from the bulkhead) was broken (would show video but I can't upload one). Need to buy either a new rocker arm and rebuild existing one or buy used shaft and set. Pushrod is fine.

steve2286w · Mar 22, 2020

Good, simple fix I replaced a worn one from turner engineering, I also got a pack of the valve caps as they can punch through , make sure you order correct one my 200tdi had the number stamped on

steve2286w · Mar 22, 2020

Have a read or search how to do remove and refurb shaft
Basically undo all the bolts a few turns at a time to unload evenly leave the end ones in until you’re on a clean bench
And keep all springs and washers etc in order take pics , these are from my rebuild thread on the 200tdi forum I did last year
Inspect and clean each part
Last is the valve caps with the worn rocker that I replaced the marks were from the valve itself as the cap had punched through

Stanleysteamer · Mar 22, 2020

Glad you found it mate! Just do make sure that the valve that the rocker operated is not jammed. If it IS jammed, the same could happen again.

AJofShabby · Mar 22, 2020

Stanleysteamer said:
Glad you found it mate! Just do make sure that the valve that the rocker operated is not jammed. If it IS jammed, the same could happen again.

How would I do that?

Blackburn · Mar 22, 2020

If you turn the engine so No two cylinder has both valves closed No 4 cylinder should be well below TDC, you should be able to push the valve down with a small lever to see if stuck try the other valve on that cylinder for comparison.
When you take the rocker shaft off to fit new rocker arm put a straight edge across the top of all valves , they should all touch the straight edge , ie all the same height.

Stanleysteamer · Mar 22, 2020

The simplest way is to hit the top of the valve gently with a hammer. If the valve is seized it won't move, if it isn't the valve will move a bit and then come back under the power of the spring.

AJofShabby · Mar 22, 2020

Thanks both. I’ll try the hammer approach first; it’s my go to tool of choice.

steve2286w · Mar 22, 2020

Don’t knock the collets out though

Henry_b · Mar 22, 2020

don't use a standard hammer either.

Nylon or rubber i'd use..

300TDI missing on one cylinder

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