Stag behaving badly - need engine help!

[dasadrew]

At long last the day has arrived to get the Stag on the road, but she's letting me down badly and I'm at a loss as to what her problem is .

I'd started her up several weeks ago before I had to go into hospital. Started fine, ran ok, tended to overheat quickly but I found a few leaks which I cured. It wasn't running silky smooth, but didn't seem to be missing a beat - just slightly lumpy. Left it at that and went off for my op.

Got back into the garage a couple of weeks back and decided to give it the full check over and set up. Did the strobe timing (off N°2 lead!), tried to make some sense with the mixture by lifting the carb pistons, looking at Colourtune etc. Seemed to show the symptoms of being rich and the needles were well retracted into the piston. Tried turning out the needles and the Colourtune lost its bright yellow colour. All seemed well so I left the engine and continued to finish off other bits and pieces like windscreen washers etc.

Went to start it today and the bu$$er wouldn't start. After several attempts it did actually turn over but was really lumpy and a couple of times the carbs coughed at me and the engine died. It responded to the accelerator when it actually agreed to fire up, but after 15 seconds or so at higher revs the engine just died.

The only thing which was different to when I fired it up originally was that I'd put oil in the dashpots. I unscrewed the dampers and she really liked that! Started running ok and seemed to even start to get smooth. I put the lumpiness down to oil or whatever in the cylinders from the rebuild etc., and, whilst it was running ok, I got the air filter etc. back into place and screwed in the dashpot dampers again. It seemed more willing to start and it didn't die on me. Still quite lumpy though.

I just decided to drive it a few hundred yards around the block and it was not so good. Quite lumpy, pulled away ok, didn't stall, but sounded somehow like a cylinder or two was missing. Only evened out at higher revs. To cap it all, temperature soared up and even the warning buzzer I'd installed went off (nice to know it works!)

I'm lost - help!

maybe I shouldn't have believed the Colourtune and I've weakened the mixture far too much?

I keep having daytime nightmares about pistons, cylinders etc. and guess I might have to do a compression check, but I can't see how that would have occurred after it having fired up so well the very first time.

Cheers for any pointers!

Drew

[Bandit1200]

Hi Drew
After my engine was rebuilt with reconditioned heads and new timing gear it ran, as you described.
It turned out that the dashpots were over filled and with the wrong oil.
I emptied them and topped up with 3 in1 to just engage the damper pistons and she ran fine.
I hope you find the same simple solution.

Best wishes

Steve

[marshman]

Hi Drew,

If it were my car that had just been rebuilt I would start at the beginning and work through everything - assume nothing!

1. Check TDC mark on front pulley - check by making sure piston is at the top of the cylinder, fairly easy to do through the spark plug hole. If the TDC mark is not right then you are on a hiding to nothing.

2. Check Valve Timing - easy to do once engine is on TDC - do the lines on the ends of the camshafts line up with the marks in the caps?

3. Check valve clearances.

3a. (can't be bothered to renumber everything) Check the cylinder compression are all OK.

4. Check the ignition timing - I have only ever done this static on any car. I have used a strobe when the engine is running but only to check the mechanical and vacuum advance is working. On my MK1 I think I set it to 12 deg BTDC. Once you get the car behaving you can then advance it until it starts to pink. Not sure if you have points or one of them new fangled electronic thingies - all my old cars are points

5. Check plug gaps - Usually I set mine to 25 thou (0.635mm) - again when you get it running if you have electronic ignition you can widen them out a bit if you want.

6. Check throttle and choke linkages are all operating correctly

7. Check the carbs are set for initial running - oil in the dashpots, also check the diaphragms are OK (I know they are "new" but check them anyway.

8. start the car (hopefully!) then play with the carbs to get the mixture right. I find most if not all old cars need full choke to start when stone cold then immediatly push it in around halfway, then gradually push it in all the way to the fast idle position over then next couple of minutes. Balance them first then do the mixture. I have always done the Stag ones "by ear" i.e. a listening tube at each carb intake and balanced to get an even "hiss" and then set the mixture using the piston lift method.

With regard to the cooling problem - check you have the right thermostat with a "jiggle" pin in the bleed hole and that it is at the top. Check you have no air locks. See if you can pressurise the system (I use a bike track pump and pump it to about 15psi and make sure it holds). If it won't you have a leak somewhere, usually at one of the hose joints - go round and tighten them up. Top up the system and it should be OK.

Wouldn't worry too much about valves and pistons remember it's just a internal combustion engine that works on the same principles as every other ICE.

Roger

[edd]

When ever I had problems I just go over the whole arrangement again starting from timing. When I first tried mine I had the distributar leads running the wrong way. Some leads are also so rubbish and don't conect either at the spark plug or in the dizzy. Once it's running you can remove each plug temporally to see if the note changes to indicate what cylinders or bank are not firing also.
It's a real shame no members are close to just swap carbs etc
Good luck Drew.

[dasadrew]

It's so heartening on the forum that, when it comes down to the real things that matter (Stags!) people are on hand 24/7 to offer advice and help.

I'll be going through the checks tomozz - I've already checked the plug wires tonight!

Could me having weakened the mixture made such a difference? At least it's a quick check just to wind out the needles again to see what happens I guess.

I'll feed back bit by bit but, if anyone has a gold-plated solution for minimum effort let's hear it now!

Drew

[mike@thenook]

Hi Drew,

My guess and only a guess is timing, it sounds to me as though you may have a tooth out on one sprocket which is causing the unevenness. Putting more fuel in may mask the problem.
Sometimes after an engine re-build because everything is a bit tight it will produce more heat but not so much that the needle is hitting the red or getting near.
Hope anyway the checks go well and you find the problem quickly, so annoying after so much effort completing a re-build, I know from experience!

Cheers!

[DJT]

Drew, check the distributor isn't 180 degrees out. It is easy to get this wrong and the engine will sometimes run, but roughly.

[dasadrew]

Thanks guys - I'm glad no-one has mentioned HGF yet!

[flying farmer]

Sounds like a stuck thermostat regarding the overheating. Many thermostats seem to lack any form of jiggle pin and I often resort to drilling a very small hole to assist air bleeding.
When you said it refused to turn over, was the starter trying to turn the engine?

If it was then you may have a cylinder full of water, usually leaky inlet manifold gaskets, which would explain the lumpy running once it did start.

Neil

[Guest]

Hello, first check the ignition rotor arm! Change it, normally you can not see any defects but it's still there...,. Then check ignition-timing advance and the vacuum unit.

Claus

[dasadrew]

OK, the tests have started..

Cooling:
a) Thermostat removed. Jiggle pin was free and at the top. Tested the thermostat in boiling water, starts to open at around 78°C and is plunger is fully out at around 83°C

In an Armageddon scenario, considering the engine has only been ticking over in the garage for a few minutes and the temp gauge was at the "H" borderline, then went off the scale in a few hundred yards of driving, could this mean that the water pump itself isn't doing anything?


Lumpy Engine:
1) Rotor arm is a super-duper one from the Distributor Doctor

Cheers

Drew

[dasadrew]

Next steps:

Cooling:
a) Thermostat removed. Jiggle pin was free and at the top. Tested the thermostat in boiling water, starts to open at around 78°C and is plunger is fully out at around 83°C

In an Armageddon scenario, considering the engine has only been ticking over in the garage for a few minutes and the temp gauge was at the "H" borderline, then went off the scale in a few hundred yards of driving, could this mean that the water pump itself isn't doing anything?


Lumpy Engine:
1) Rotor arm is a super-duper one from the Distributor Doctor
2) Vacuum advance is working fine
3) went to check each of the spark plugs. Pulled off the leads and 7 were really tough to get off. One was easier. Did a couple of simulations and found that one could be pushed on firmly without the metal sleeve 'clicking' onto the spark plug!!! I'd pulled off two HT cables to take out two plugs for the colourtune and this would explain why it runs lumpier now (I hope) although it was never silky smooth. can't check now as thermostat is removed.


Cheers

Drew[/QUOTE]

[dasadrew]

Update

Cooling:
a) Thermostat removed. Jiggle pin was free and at the top. Tested the thermostat in boiling water, starts to open at around 78°C and is plunger is fully out at around 83°C

In an Armageddon scenario, considering the engine has only been ticking over in the garage for a few minutes and the temp gauge was at the "H" borderline, then went off the scale in a few hundred yards of driving, could this mean that the water pump itself isn't doing anything?


Lumpy Engine:
1) Rotor arm is a super-duper one from the Distributor Doctor
2) Vacuum advance is working fine
3) went to check each of the spark plugs. Pulled off the leads and 7 were really tough to get off. One was easier. Did a couple of simulations and found that one could be pushed on firmly without the metal sleeve 'clicking' onto the spark plug!!! I'd pulled off two HT cables to take out two plugs for the colourtune and this would explain why it runs lumpier now (I hope) although it was never silky smooth. can't check now as thermostat is removed.
4) Just removed all spark plugs. All are expectedly sooty as the car has only ever idled in the garage up to now, but ...... only 6 plugs have signs of a spark having ever taken place. Interestingly, the one with the loose plug lead shows signs of having sparked well at some point in its life.

RH:
Plug 1: sooty with evidence that a good spark has been taking place (Pic 1)
Plug 3: sooty with evidence that a good spark has been taking place (Pic 1)
Plug 5: sooty with evidence that a good spark has been taking place (Pic 1)
Plug 7: sooty with evidence that a good spark has been taking place (Pic 1)
LH:
Plug 2: sooty with evidence that a good spark has been taking place (Pic 1)
Plug 4: sooty with no evidence that a good spark has been taking place (Pic 2)
Plug 6: sooty with evidence that a good spark has been taking place (Pic 1) had loose plug lead
Plug 8: sooty with no evidence that a good spark has been taking place (Pic 2)

Is there anything carb-wise or dizzie-wise that could only affect cyls. 4 & 8 ??

In summary, it seems at the moment that the lack of a silky smooth engine from the beginning is down to 2 plugs which are not sparking well, the really lumpy engine was a loose plug lead.

Pic 1 bright metal where an energetic spark has been taking place
DSC01081 (Custom).JPG































Pic 2 just sooty but it seems that combustion of some sort has been happening
DSC01080 (Custom).JPG


































Cheers

Drew

[dasadrew]

Just checked contact gaps in the dizzie - not good. Of course, they'd only been set at the start by turning the engine by hand one or two turns. I guess things have seated a bit now that the engine has been run. Looks like I might get to a smooth running engine yet!

Cooling is still a problem though

[marshman]

Just checked contact gaps in the dizzie - not good. Of course, they'd only been set at the start by turning the engine by hand one or two turns. I guess things have seated a bit now that the engine has been run. Looks like I might get to a smooth running engine yet!

Cooling is still a problem though

Can't help with the cooling, though if it was all full of water I can't think you have done any real damage just running for a short period.

With regard to cylinders 4 & 8, I think they are in order in the firing sequence, so if your points gaps re a bit iffy and there is some play in the distributor shaft it could just be that the points gap was just too small as 4 & 8 came up to fire. Whilst you have it all apart I would check continuity from the contact in the distributor cap through to the contact in the plug cap just to make sure you don't have any duff leads.

I'm sure you will get there but it is always harder on a rebuild as so much has been changed/rebuilt etc. that you are not in the position of a simple breakdown where it was working and now its not. This is why I said go back to the beginning and methodically check everything - which you are doing.

I should be going for a restart on my VW Passat 1.9tdi engine this afternoon after a total rebuild, (new cam, cam buckets, cam belt, oil pump, turbo, clutch, DMF, head off, cleaned EGR valve etc.) - so much to remember to do - run in the hydraulic tappets, prime the oil feed to the turbo, clear fault codes on the ECU, hope everything is plugged back in, cross fingers etc. Give me an old classic car any day - the simplicity!

Roger