E-type - problem - not purring at the moment!

[jagracer]

From memory there is a diaphragm in each carb, make sure there isn't a hole in them.

[lowdrag]

Are you sure about the root cause of your problem? I've toured extensively on my own and with other E-types and never had a vaporisation problem in temperatures up to 42C in the south of France. We toured that year with 35 E-types and not one had a vaporisation problem. Spain, Morocco, Bosnia, Croatia, you name it and never a cough.

[jagracer]

jagracer said:

From memory there is a diaphragm in each carb, make sure there isn't a hole in them.

Just had a look on a spare one and the diaphragm is at the bottom and held in by the four screws that hold the float chamber assy.

Edited by jagracer on Saturday 8th May 17:17

[logiedurno]

If it were the diaphragm - how likely would it be for each to be holed? Also, wouldn't that affect the starting and running from cold?

Just tested it again today - went for a 10 mile run, the car started no trouble from cold and ran great for the 10 miles. Parked up at home (fortunately) and tried starting 10 minutes later - no joy.. flattened the battery trying and hooked up jump leads to range rover so plenty of electric power, still not starting.
Left the e-type for an hour and it started first turn on the (now reduced power) original battery.

I am convinced it is a fuelling issue. The car had a £60k restoration by Hofmann's of Henley 2 years ago and absolutely everything was overhauled on it including the carbs and I reckon everything was working as it should have been following commisioning tests.

I've tried every means of starting it when the engine is hot including depressing accelerator pedal, pumping the accelerator, trying a touch of choke, clutch in, clutch out, no accelerator pedal - everything.

Took one of the plugs out after all this effort today and it was dry, which to my mind, confirms no fuel getting into the engine.

[jagracer]

logiedurno said:

If it were the diaphragm - how likely would it be for each to be holed? Also, wouldn't that affect the starting and running from cold?

Just tested it again today - went for a 10 mile run, the car started no trouble from cold and ran great for the 10 miles. Parked up at home (fortunately) and tried starting 10 minutes later - no joy.. flattened the battery trying and hooked up jump leads to range rover so plenty of electric power, still not starting.
Left the e-type for an hour and it started first turn on the (now reduced power) original battery.

I am convinced it is a fuelling issue. The car had a £60k restoration by Hofmann's of Henley 2 years ago and absolutely everything was overhauled on it including the carbs and I reckon everything was working as it should have been following commisioning tests.

I've tried every means of starting it when the engine is hot including depressing accelerator pedal, pumping the accelerator, trying a touch of choke, clutch in, clutch out, no accelerator pedal - everything.

Took one of the plugs out after all this effort today and it was dry, which to my mind, confirms no fuel getting into the engine.

I had a car (not a Jaguar but the principle is the same)with the same problem and after a lot of faffing with other stuff it was the jet diaphragm. As for a £60K overhaul are you satisfied that they changed every single part, the diaphragms may have been OK but they do get hard and fail. It is probably something completely different but it's another avenue to follow if all else fails.

[logiedurno]

Just looked at the invoices. Carbs fully overhauled by Burlen. The carbs are SU and therefore don't have a diaphragm like the Strombergs.

No doubt it is going to be something relatively simple but I'm still stuck to think what it is!

[jagracer]

logiedurno said:

Just looked at the invoices. Carbs fully overhauled by Burlen. The carbs are SU and therefore don't have a diaphragm like the Strombergs.

No doubt it is going to be something relatively simple but I'm still stuck to think what it is!

Do you know what carbs they are, I thought they were HDs but obviously not. You could try the AED as that may be at fault.

[Gallen]

My father once has a similar thing on his 62 MG Roadster *ok a little different to an E-Type but has the aforementioned SU's.

We unscrewed the top of the carb and checked that there was oil in there... they had become a little dry over the winter and lack of use hadn't helped.

They just needed topping up and it's been fine since. It's now an annual check.

[Hooli]

Gallen said:

My father once has a similar thing on his 62 MG Roadster *ok a little different to an E-Type but has the aforementioned SU's.

We unscrewed the top of the carb and checked that there was oil in there... they had become a little dry over the winter and lack of use hadn't helped.

They just needed topping up and it's been fine since. It's now an annual check.

Good call, empty dashpots on SUs make cars run st.

[lowdrag]

Have you checked the float levels? I'm trying to work through this problem and figure it out with you. Secondly, perhaps when cold the choke aids starting but is the pump providing enough pressure? If some of my ideas you've already addressed sorry, but I'm thinking on my feet here.

[jagracer]

jagracer said:

logiedurno said:

Just looked at the invoices. Carbs fully overhauled by Burlen. The carbs are SU and therefore don't have a diaphragm like the Strombergs.

No doubt it is going to be something relatively simple but I'm still stuck to think what it is!

Do you know what carbs they are, I thought they were HDs but obviously not. You could try the AED as that may be at fault.

OK, I've just checked my SU service book and they are HD carbs and they do have a diaphragm which is part of the jet assy. Another possibility is an air leak in the AED pipe or again the jet diaphragm in the AED. Maybe you should take it back to the people who did the £60K restoration or phone Burlen Fuel Systems and ask them.

[logiedurno]

Thanks for all the replies folks.

The carbs are HD8 and do have the small diaphragm in their base. There isn't an AED as such - the manual choke lifts and opens an auxiliary jet to enrich the mixture.

I have topped up all the dampers to correct level with correct SAE 20 oil - problem still present. Also checked fuel cap is ok and venting the fuel tank (tried leaving it off whilst starting from hot - again no joy)

I am loathe to start dismantling the carbs as I know they were fully overhauled by Burlen and I know they replaced all "wear & tear" items with a kit of parts for each carb including new needles and jets. The carbs were set up by Hofmann's and still perform very well when the car is actually running!

I can't take it back to Hofmann's to sort as I now live 500 miles from them!

I may phone Burlen's and Hofmann's to ask their advice this week.

The SU fuel pump is not brand new and it might be worth replacing it if it were a question of getting some extra pressure into the fuel line.

I felt the carbs, float chambers and metal fuel splitter line to each carb unit after the engine was fully warmed up and while the car would not start and none felt particularly hot - just warm - so I can't think it would have been hot enough to vapourise the fuel..

[Gallen]

I know its ever so simple but have you also checked the fuel filters? Especially if you have additional in-line filters somewhere along the system.

Just be careful whatever your next move is... Someone told me Petrol's flammable ;-)

[SlipStream77]

You've said the problem sounds like vapour lock. Have you checked the cooling system; rad, thermostat etc.? If the temp's look ok, it may be that you need some insulation somewhere.

[lowdrag]

Well, based on your reply it seems to me that you have a float level problem. Simply take off the cover of a float chamber when the problem occurs and see if there is enough petrol in the float chamber. I can't see it being a radiator or thermostat problem because you'd have a big puddle of water under the car when you stop from the overflow pipe (I assume you are running at least a 7lb pressure cap anyway - I run a 13lb one with modern hoses instead of the original 4lb cap) and similarly if it was the thermostat you'd either be overheating and boiling or the engine would be running too cold and this would show on the gauge. To check the fuel pressure either loosen the pipe at the fuel filter outlet or better one of the unions on a float chamber. It can't be a carburettor lacquering up with old petrol (a well known problem) since the carbs have been rebuilt recently. I'm now betting on float chambers since with choke it starts when cold. Famous last words perhaps.

Edit: While this doesn't apply to a 4.2 those with a 3.8 might like to note that the original style thermostat is far better than the modern ones. Look at this:-



This is the old style Smiths thermostat with the copper shield and you'll note this one is open. It failed in my E-type a few weeks back and these fail open. The modern ones without the shield fail shut causing overheating. They turn up on Ebay from time to time and are well worth buying. Martin Robey sell them at £25 I believe but my ones cost normally around £2!

Edited by lowdrag on Sunday 9th May 21:03

[jagracer]

Have you checked the valve clearances or done a compression test when it's hot?

Edited by jagracer on Sunday 9th May 21:12

[logiedurno]

Thanks very much for the advice Lowdrag. I will do as you suggest tomorrow and check the float level heights as per recommended in the Haynes manual. If they are set according to the correct spec (I think a 7/16 inch bar is recommended) would there be any advantage or improvement in altering this setting to allow a little more fuel into the chamber without overflowing it?

[logiedurno]

Should have also said.. New radiator - new thermostat - new 7lb radiator cap - new hoses all round - thermostatic controlled fans working well - no overheating problems. Temp gauge generally sits just into "normal" section when fully warmed up.
When refused to start while hot I cracked open the fuel connection unions to all float chambers and fuel is certainly flowing to the carbs.

Valve clearances are fine and cylinder pressures are all within 20-30 psi of each other and in normal range.

[jith]

Dear me, misconceptions abounding!!

Logie, let's get some reality in here. Your E has a manual choke setup. It has no AED unit to enrich the mixture. When you pull the choke cable it activates a spindle which lifts the mixture adjusting levers on the bottom of the carbs; i.e. it simulates turning the mixture screws rich. This in turn pulls the jets down inside the carbs enrichening the mixture.

Most Jaguars of this type have the same design of jet which is brass with a small vulcanised rubber diaphragm. This diaphragm is vacuum sensitive and must be perfect or you will get all sorts of problems.
The E is the only one with a manual choke therefore it puts much more wear potential on the diaphragms as they are stretched every time the choke is used. On the AED versions they are only moved slightly when effecting adjustment for mixture.

Some of the jet assemblies I have seen recently are of dubious quality, (probably from China!) and are prone to failure. You must check the diaphragms for pinholes or tearing. If you have fuel at the float chambers, the dashpots are not seized and the plugs are coming out dry there MUST be a problem with the diaphragms.

Let us know.

[jagracer]

Have you tried another coil yet?