TC still not OK after rebuild

[b-havers]

Gents,
as I guess you all remember (?), my twink went thru a grand rebuild last winter/spring/summer at at 'pro' Lotus garage, but it didn't work properly when returned. As this was rather late in the autumn, I just parked the car in the garage, waiting for summer to come.

Now, the sun is shining, the other cars are on the road, and it's time to check the Elan +2 which sits lonely in the garage.

It starts immediately, but only runs on three cylinders. Black/gray smoke puffs from the exhaust.

When checking the sparkplugs, they all show strong sparks, but the rearmost plug is dripping wet from petrol/oil, whilst the three foremost are completely dry (but very black).

Also, when removing the rearmost plug after having had the engine running for a few seconds, smoke pours out from the plughole. This does not happen to the other plugs.

I've been told that checking spark 'in the air' does not neccessary means the plug has a spark when fitted to the engine, so I will swap plugs just to check.
I will also perform a compression test.

But; if both these seems OK, what else could I check before I contact the garage that did the rebuild?
I'm pretty tired of this engine sh*t now, I haven't had the car on the road for three years

Glad I have the Europa to use in the meantime.

[robertverhey]

First thing to do is a compression test. To fire, a cylinder needs fuel, compression and spark at the right time. You seem to be getting fuel (hence wet plugs) and spark (if you've tested plug out of cylinder)

I suspect you will find #4 compression low or non-existent. Possible causes are burnt /broken valve, holed piston, broken rings, cracked cylinder bore, or maybe a combination of above. Or cracked head

You could also test the cooling system's ability to hold pressure (with a Stant tester or similar). Water may be getting into the cylinder if it's cracked.

Just some initial thoughts

[jimj]

The engine vents, potentially, oily vapour into the airbox adjascent to the rearmost air intake and is inclined to oil up the rearmost spark plug. It shouldn`t be that oily on a newly rebuilt engine, is your sump too full? Try disconnecting the pipe and fit a new plug or dry and clean the old plug with a blow torch. My car sometimes oils this plug starting from cold but then clears as the engine warms. I`ve thought of fitting a slightly hotter plug just in that cylinder (?)
Jim

[rgh0]

I would check

1. compression - same as other cylinders
2. plug lead to no 4 - replace
3. plug in no 4 - replace
4. carb jets in no 4 - swap and see if problem moves with jets
5. O rings sealing and no air leakage around carbs in No4
6. Other differences or blockages in No4 carb throat fuel or air systems (try spare carb if have access to one)

If none of the above gets No 4 firing and no problems apparent then I would scratch my head and seek some help from an expert if i could find one

cheers
Rohan

[b-havers]

Did some small testing during the weekend:

All sparkplugs out, washed them.
Cranked the engine with all sparkplugs out; no oil/petrol/water poured from the plugholes.
Compression test; cyl no 1&3 - 10, cyl no 2&4 - 7.5...
Refitted sparkplugs in random order, fired engine; still runs only on three cylinders (or at least sounds like that)...

Drove ca 2km, among then a 200m sloop hill - big problems getting the car up there

[gordont]

call the garage that did the build, they should take some rsponsibility / interest in getting it sorted.

[mark030358]

Looking at the compression, I pressume units are Bar, then 2.5 Bar is approx is about 30 psi seems a lot on a rebuilt engine. I would have been looking for maybe 10%

cheers

Mark

[rgh0]

Difference in compression between cylinders looks to big and 7.5 bar to low. Even 10 bar on low side on a rebuilt engine if pistons and valves sealing ok.

I dont know what run in procedures you used or details of the rebuild but either rings not sealing or valves not seating properly IMHO. Can you definitely say that ignition and fuel good to all cylinders and problem occuring in same cylinder all the time. New plugs and plug leads should be tried. Checking temperature of exhaust will tell you which cylinders not firing after this.

3 cylinders will get you up most hills , you may be down to 2 cylinders if struggling to drive 2 km and 200 m up an hill.

regards
Rohan

[Higs]

Rohan wrote:

Difference in compression between cylinders looks to big and 7.5 bar to low. Even 10 bar on low side on a rebuilt engine if pistons and valves sealing ok.

The manual says that the compression should be "in excess of 160psi" which is about 11 bar and "each cylinder within 20 psi of each other" (1.5 bar). These numbers would be lower if you were testing well above sea level.

So I think the compression is an issue - a bit low on two and very low on the other two.

If one cylinder is not firing at all then the test would normally be to check the exhaust pipe temperatures (as per Rohan) or to see if removing a spark lead (i.e. disconnecting it from the plug) on the suspect cylinder changes the quality of the running. In either case, if you were not running on one or two cylinders, I would expect quite a bit of back firing.

In general, I am not in favour of wholesale changes of hardware until the disgnosis has been completed.

I also note from your website that your engine was rebuilt by someone else. Any reason why he is not solving the problem for you? Particularly the low compressions....?

Hope this helps

Richard

[andyhodg]

Please forgive me if I am about to say something that you are already well aware of:

Are you using the proper procedure when testing the compression? That is all spark plugs removed and the throttle wide open. I only ask because the first time I tested my compression I did not open the throttle's and a got generally low compressions with fairly large differences.

Good luck

Andy

[pamitchell]

Woujlda leak down test be in order ?

[jimj]

Just a thought, unlikely I know but ...... have you got the correct plug leads going to the right plugs?
Jim

[alaric]

I'm with Jim - what I was about to suggest. Ignoring the compression test it would possibly give you similar symptoms. When I did that I got ignition in the exhaust pipe also. Quite entertaining and certainly wakes up the neighbours. Hope it is as simple as that.

Sean.

[b-havers]

Hi all, thanks for all your concerns

Just a too short answer after a far too long day at work .-(

Comp test was carried out with al lplugs removed, but not on full throttel; will do a new test next weekend.

Plugleads are OK, they are labelled with correct numbers, and are placed the way they were before the engine was rebuild.

IIRC, I did remove the lead from no4 plug earlier in the tests, and that didn't affect the running of the engine.

Yepp, engine was rebuild at a Lotus garage, but I'm not sure I'd like to send it back to them. It was back once, as water poured out from the new waterpump... So I had to pay for another new pump. Not sure if I'll trust my engine to them once more .-(

[billwill]

The plug leads might well be labelled at the plug end, but do they go into the right holes in the distributor.