Lacking in pulling power

[alexander]

Hi All help and suggestions please

The Javelin is lacking in power, pull out coke and it improves .
Looked for air being sucked in using first propane and then carb cleaner, no leaks found.
Compression check 150 on all cylinders.
Checked timing. Checked tappet setting. All seemed correct
Connected vacuum gauge and got a reading of 15 on tickover on revving the engine reading drops back then returns to 15. ( should I see a higher reading)
I suspect that the cam timing may be out , am I on the right track or should I check any thing else
Thanks in advance
Alexander

[JUP]

I would start with the basics
Change the plugs and check the plug leads and check the quality of the spark
Also is the petrol ''old petrol'' that has sat around all winter ?

I am assuming it was running ok but has just developed this fault ?

[alexander]

Had problem before winter storage, fresh petrol and new plugs but thanks for suggestion

[alexander]

Today I checked the cam timing using information provided on the forum by Keith and David, seems cam timing is correct.

I had at first thought it was an air leak in the fuel lines as I can improve power by pulling out the choke, but today with clean plugs the signs are it’s over rich with black plugs and exhaust . On Saturday I will use colour tune plugs to see what’s going on and check air intake. I’ve also used an airline on the jets in the float chamber and checked the jets for correct size.

Again any suggestion’s welcome

Alexander

[Forumadmin]

Probably the valves in the fuel float.
Carefully take off float chamber and check level or look down throat and see if dripping when pump manually activated.
Maybe holed float, just shake.
Or maybe fuel pressure too high.

[PJGD]

How bad is the problem, i.e. how down on power is it?

When I got my first Javelin in 1965, at some point I checked the plugs for some forgotten reason and inadvertently put the plug leads back on the wrong plugs because I assumed that the distributer rotated clockwise. It does not, and so I ran around on only two firing cylinders for a couple of days until I eventually worked out the problem!

[David Morris]

Hi Alexander,

Well done! You have done a lot of diagnostics and shown that the valve timing is correct, that the valves are seating correctly, so the pistons are good on compression. Using a spray, you have checked for induction leaks and found nothing amiss. I think you mentioned that you now plan to use a Colourtune, to check for correct mixture. I hope this shows up the problem, but my suggestion is to go back to the electrics.

Basically, the Javelins are pretty simple engines, but for some reason they are susceptical to spark problems. So, let's have a look at the electric side of things. Have you got a good spark going to all cylinders? My suggestion for checking this is to obtain an in-line spark tester. I think Sparkrite do one on Amazon at £3.95. This flashes whenever it sees a spark and needs to be swapped around the foir plugs in turn. That should check the points, coil and condenser. I always trusted NGK plugs and the only time I was stranded by the roadside was with a dodgy set of plugs, probably purchased from a stand at a Car Rally? Don't trust so-called NGK's that look nice and cheap on the internet websites. They might be 'knock-off' copies and if they look cheap, that's probably a good reason to avoid.

Another area to check is the distributor. Are there any signs of arching inside the cap? What about the rotor arm? Is it a black one? For some reason, I have had problems with the black ones, as there are too many duff ones on the websites. I always used red ones from a reputabe UK supplier.

Finally, have the bonnet open on a dark night and the engine running. Are there any signs of arcing from the leads to metal in the engine bay?

Anyway, best of luck and have a Happy Easter!

David

[David Morris]

Hi Alexander,

Just had a look on the internet for any one with problems with the black rotor arms. Seems folks have had symptoms of fuel starvation and rough running/loss of power with the black ones, and attributed it to high levels of carbon loading in the black ones?

Doesn't prove much, but it might be worth checking if yours is a black one? I have certainly experienced problems with the black ones, which were cured when I fitted a red one.

All the best,

David

[alexander]

Away on holiday last week so today I used two colour tune plugs and a balancer . The car was so rich that the colour tune plugs blackened so bad that I could not read them. Fitted two new needle seats and adjusted spacers to get a cleaner burn. Balancing not so easy , left hand carb looking from front of car with adjuster not touching give higher reading than right hand carb that’s adjusted with a 0.030 gap.
Tick-over too high also but certain sorting of left hand carb will also solve tick-over.
Balance and tick-over finally sorted after resetting coke and adjusting carb connecting rod .
Found a red rotor arm and will fit once car road tested.
I really over thought this one but as the car improved with choke I discounted rich mixture and thought first that as I had changed the cam some months back that I had made a mistake and the problem was cam timing.
Still far worse ways to spend your time and all part of the fun.
.
Thanks again for help and comments
Alexander

[Keith Clements]

Common problem. On Jupiter's the diagnosis is quicker because the electric fuel pump keeps ticking.

On the Jav you might detect by not getting the pressure release valve operating when manually priming

But you should be suspicious if when priming petrol oozes out around the outside of the carb body or down the throat.

[David Morris]

Hi Alexander,

I don't know why your original thread seems to have been taken over by Keith posting a new thread on Float Valves, but hopefully going back to your original thread on the lack of pulling power... I am glad you are getting some good diagnostics with the colour tune.

Are all four cylinders now showing the same colour? You mentioned using a balancer. Is this a Syncrometer? I have found this very handy for Javelins, since it just plugs into the carb inlet tubes, once you have removed the rubber bellows. My Javelin gave a gauge reading of about 6 in the scale, when the carbs were in balance. They are available on eBay.

I found the carb link rod difficult to adjust easily, the danger from your hands being sliced by the fan! Fortunately, a previous owner had devised a beautifully-crafted micro click adjuster in brass, that gave you precision adjustment on the length of the rod. I should hve had drawings made for this before the car had a new owner, as it would have been a hot seller as a Christmas present! Maybe JCS should have sold them?

Anyway, it looks like you are well on the way to finding the answer. I had an electric pump fitted to my Javelin and found that around 2lb/sq.inch was enough fuel pressure before the carb. valves started to be overcome. I had fitted a pressure limiting valve to achieve this pressure. I hope the red rotor arm helps too?

All the best,

David

[Forumadmin]

David, I have merged your topic with the original by Alexander. Note the the Reply subject can be different to the Topic subject but is still under the Topic subject.