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Please help. Not running right


PeaTear
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Please help me. Shortly after I bought my Spitfire I started to have poor running issues, difficult to start, misfiring and engine cutting out and got to the stage where it wouldn't start at all. 

To try and eliminate everything that could be at fault I have so far

1 drained the petrol and refilled with super unleaded with miller's vspe additive so technically it should have 99ron

2 replaced distributor components, cap rotor, condenser, points and set points gap

3 changed HT leads and spark plugs

4 reset timing back to 8degree btdc

5 cleaned and reoiled air filters

After all this it started but would die after about a minute so I then tuned the carburettors as per instructions in the Haynes manual 

I can't say I've tuned the carburettors correctly as this is the first time I have done anything like this but it did start and run much better. 

Although it's running better there is absolutely no power from the engine. A cyclist overtook me on a hill as I couldn't accelerate past 15mph in second gear

There is also some backfiring going on. I only noticed it in 1st and second gears at about 3500 rpm. 

What else can I do to try and resolve this

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Are you sure your timing is set-up correctly and not 180 degree out ??

If all good, it appears to be a fuel related issue in so much limited supply when full demand is required - taking in to account your induction side updates...……….what is the condition of the fuel pump ??

Despite your ignition part changes, quite often some of those parts may still be poor quality - specifically rotor arm.

My only other observation is perhaps the coil.

Regards.

Richard.

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Its very hard to diagnose from anyone description as its all in the feel!

But I would look at the dizzy for a start - make sure the vacuum advance is working as well as the weights doing their job - easiest way is with a timing light as you can watch the timing mark move as you rev it.

I know you have said you have checked points, but when mine was as you describe, I found the points to be closed pretty much. 

But as tuning the carbs has improved things, it would be worth checking the float level in the bowls as that makes a difference - and that the linkages are all working properly.

 

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PT,

There's a similar story towards the end of the "Twiddle day 2 thread". That looks like it's the manifold gasket and this may also be your problem. I've had it and it can easily be overlooked. As Richard says new parts can be poor quality and add to the problem.

Doug

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9 minutes ago, classiclife said:

Are you sure your timing is set-up correctly and not 180 degree out ??

If all good, it appears to be a fuel related issue in so much limited supply when full demand is required - taking in to account your induction side updates...……….what is the condition of the fuel pump ??

Despite your ignition part changes, quite often some of those parts may still be poor quality - specifically rotor arm.

My only other observation is perhaps the coil.

Regards.

Richard.

How do I check if the timing is out 180degrees?

Forgot to say I did also clean the crap that had got stuck in filter of the fuel pump.  I can only assume the pump is working well as it took nearly no time for it to refill the float chambers

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4 hours ago, PeaTear said:

How do I check if the timing is out 180degrees

 

2 hours ago, PeaTear said:

When I reved it, the engine was quite slow to return to normal idle speed. 

Timing - your WSM will give you a very detailed account how to set TDC by ensuring that the rotor arm is positioned correctly for No 1 cylinder.

However, more interestingly is your quote about slow return to idle speed, this may suggest the carb dashpots are catching on the housing as they should slide down progressively if they are located correctly - you can test this by removing the cover and turning the dashpot about 90 degrees each time, you will be looking for a smooth progressive slide. Additionally you need to ensure the dashpot has the correct level of oil - preferably 20/50.

Failing that you may have a needle or both that are out of alignment - either inserted incorrectly or actually out of shape / bent.

I see Pete has added whilst typing this so he may be explaining the above as well.

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I’m no expert but I’ll add my 2 peneth worth. If cylinder no1 is close to the top (stick a screwdriver in spark plug hole carefully to check or better still shine a torch in to observe the movement of the piston) and the valves are closed this should be the correct firing position so distributor should be on no1 firing position. There has been a thread on here about movement of the vibration damper causing timing marks to miss align could this have contributed, did you use a strobe. The lack of power suggests to me possible timing so just double check the facts first before eliminating timing.

good luck and let us know the outcome

Adrian

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2 hours ago, Pete Lewis said:

Check the choke is fully returned and the jets have acctually returned up the the adjusting nut afer you have used the choke

SU are notorious for the nasty linkage to be strained bent and stiff  you poke the choke back and the jet stays dropped 

Pete

That was my initial thought but cleaning all the crap off it allowed it to return back to normal position when pushing the choke back in.

 

Another thought. Could I still have the mixture too rich. I was able to start the car without any choke after leaving it for a couple of hours (I fell asleep) . Idle was a tad low but there was no issue with the engine running.  

I'll retry the baseline set up tomorrow and adjusting the timing again

 

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Quick update. Checked the timing was at 8degree BTDC. Set the idle screws 1.5 turns in from the point it touches the levers. Screwed the jets up level with the bridge and unscrewed 2 turns.  Restarted the engine and dropped the idle speed to 900 rpm.  When I went to adjust the jets to get a fast idle, scrrwing them up or down drops the engine rpm, this is a new one as any previous attempts would increase the rpm when leaning the mixture. I'm afraid to take it out on the road as it barely made it up the hill to my house. 

I think I may need to find someone that can set this right 

Any members here from Northern Ireland that could recommend somewhere?

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Have you balanced the carbs? As well as making sure both carbs are in sync (So both butterflies open at the same time) 

It does sound like you have got it almost there though - idling at 900rpm is about right - well the upper end of right. Spec I think is 700-900rpm?

If its not pulling up hills, then it could be dizzy - have you a timing light to see if it advances when you rev the engine?

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Can only balance them by ear, I don't have a vacuum gauge and both butterflies opening in sync

Unfortunately I don't have a timing light. Is it a worthwhile tool to have?  

That's probably a silly question. Every tool is worthwihile

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Timing light is useful, but not essential - most here will tune by ear - peak revs then back off a tad - take it for a run, if it pinks under load, back off a bit more etc.

But they are also useful for proving things like the dizzy is working correctly.

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Progress report. ITS WORKING. :D:D

I retarded the timing to 6degrees and, with the long haired general on standby with a tow rope, went for a 20 mile spin. 

She didn't miss a beat and no loss of power.  I'm so happy. Now I'm confident enough to take it somewhere to get the exhaust leak sorted. 

 

Thanks you everyone for your patience and all the help to try and get this going again

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