I have a 1966 Jaguar MK10 with 72k miles, I've had it about 2 months but I still have problems with cold starting. It has 3 HD8 carbs with an auxillary starting carb attached to the front carb. There's a lot of spluttering and un-ignited petrol "back fired" through the auxillary carb.

Also, once started, the engine runs quite well but will not tick over consistantly at 700rpm.

The carbs haven't been rebuilt (not by me anyway) but have new needles floats and have been cleaned.

I also have low oil pressure, about 10psi low and wondered if this could be caused by a weak bypass valve spring....please don't tell me it's the oil pump!!

Thanks in advance.

Neil.

 

Oil pressure is doubtful pump failure--checking the relief valve is a good start--have you changed the oil and filter? On your cold start does the aux carb engage--you would know from the hiss!

 

George - When I test drove the car the oil pressure was OK but I've since wondered if the seller just put new oil in it. I have since flushed the engine and changed the oil and all filters. The aux carb does engage as there is the hiss, I have also changed the 'otter' switch to ensure the aux carb turns off at the correct temperature.

I think I an almost there.....if only I could find the next 'thing' to correct.

I think tomorrow I will remove the aux starter manifold and ensure it's clean and not constricted in some way.

 

Have you ever felt like a complete idiot, I mean a real dummy?
When I bought the car I knew the tanks were rusty inside, I flushed them out, filtered the petrol a few times and fitted a fuel filter which goes inside the glass bowl. Everything was perfect until recently. I kept checking the filter and it was fine, a little rust red colour but nothing to worry about as I'd got rid of the rust.

Last night I was thinking about the way the car tried to start, it would fire and die.....nothing at all. I took the fiel filter off and cut it open....it was clogged solid with rust particles.......the bloody filter filters from the inside out NOT the outside in. I assumed you'd be able to see the filter getting clogged through the glass.

I've now fitted a disposable in line filter....lesson learnt.

 

You have the glass bowl? If so it sounds like someone installed the incorrect element. The correct element filters from the outside in. You must have the V12 filter which worked in reverse--if there was a spring at the bottom it is def. that!

 

I don't know what I have, the glass bowl was already installed when I bought the car. I bought the filter element from Ebay (link below), not sure how the element makes a differance as to how it filters in/out or out/in....do you mean the head of the filter?

https://www.ebay.co.uk/itm/Jaguar-Gl...gAAOSwNSxVShoO

 

The filter element cannot determine the fuel flow, this can only be determine by the filter housings internal porting. As the filter head is bolted to the inner wing it can only be fitted up one way, the fuel line to the filter is steel so the orientation should not change.
Here are photos of the filter bowl that I have just taken off my car and a new one with a cut off screw showing the fuel coming into the bowl enters from the centre and exits from the outer. Also the only filter element was a brass(?) gause disc? Usuals do not list a filter only the disc.

 

Robman - I realise the filter element doesn't have any bearing on the direction of flow but I assumed petrol would flow through from the outside -> in and out throught the centre. I don't know why I thought this.

My filter housing is the one with th 'R' on it. I've removed the filter, replaced the gauze and put a disposable in line filter on so I can see how rusty it gets.

It's a shame you can't buy a cardboard mechanic to whom you have to explain EVERYTHING to, then you'd be forced to think more about things.

 

The filter you have shown is the v 12 filter and is incorrect for your car. the correct filter should have a hole through the middle so the fuel enters the bowl and filters back through. This allows the sediment and crud to be seen as it is captured in the bottom of the glass bowl.

 

I realise the paper filter isn't correct but the gauze filter lets some quite large particles through which will clog the float chambers. For the moment I have removed the incorrect V12 filter (it was labelled as for a MK10 on the Ebay listing), replaced the gauze filter and I will rely on the disposable plastic see through filters until clear petrol comes through all the time. At which point I will re-fit the incorrect V12 filter as I believe this to be superior to the gauze filter. The gauze filter isn't used in conjunction with the V12 filter.

Whilst all this is very frustrating I am learning a lot about a car I knew nothing about. Each time I 'fix' something I move a little closer to a car which runs well.

 

trying to help but you seem to resist fitting the correct filter--they are cheap and correct. refitting the v 12 filter is never going to allow you to see the condition of your fuel. I have a 420G and it works well. The gauze filters were done away with in 1968. As to the E bay listing and the listing of many vendors--they are just wrong! It is a shame you are cutting your fuel lines to install a filter--not needed but your car. Best of luck!

 

George I appreciate your help, I really do. I think the issue is that the car wasn't used very much for 10 years, it's only done 200 miles P.A. for the last 10 years and the tanks are a bit rusty. As I said when I bought it the glass bowl filled up very quickly with crud which, despite the gauze filter, made it's way to the float bowls. I thought fitting a paper filter (appriciate I didin't know the direction of fuel flow) would allow me to gauge the condition of the fuel and prevent crud getting to the carbs.

Fitting the inline filter does allow me to see the condition of the fuel and how quickly the filter is getting clogged. Once I only get clear fuel I will remove the inline filter and revert to standard filters. Do you have a photo of the correct filter? Is it just the gauze filter used on it's own?

I'm faffing about with filters as they're far cheaper than replacement tanks.

Could I ask another question regarding tuning the carbs and slow running? Assuming you're OK with this......I have 3 HD8 carbs which I'm trying to tune for the best economy. The first stage is get them running well and then fine tune for economy, The engine runs well at higher revs but I can't get it to idle consistantly. It will tick over about 700 rpm (I know this is a bit fast for an auto) and after a minute or two drop to 250rpm and eventually stall. Am I missing something obvious?

Please believe I really appreciate your help and you spending time with me.

 

take a look at this Fuel Filters
The comment about the V 12 filter being the only one available is not accurate. The correct filter is very available but more to the point the gauze you have installed works exactly like the correct filter---fuel passes through the center and is filtered on the outside.

 

The bowl you see is a sediment bowl and does not receive a filter element. At the top of the bowl is a filter gauze (part number 7299) which is fitted under the gasket (part number 7298). The actual fuel filters are in each SU-HD8 carb, part number 479. All these parts are readily available at SNG Barrett.

 

Pendliss - Thanks for your comments. I have all new carb filters and the gauze filter has been cleaned. The problem is the fuel tanks contain VERY FINE rust particles which can pass throught the gauze and carb filters. Eventually all the rust particles will have cleared the system and I'll be OK. I realise the correct way to deal with the problem tanks is to replace (VERY expensive), remove and line with some product or other or this way. I have had a look inside the tanks and they are not too bad rustwise so I determined the paper/in line filter is the best way forward as I don't want to waste 300€ of fuel flushing the tanks.

 

Pendliss that was true up to 1968 when Jaguar issued a bulletin that the gauze was no longer supplied and a filter element was introduced. They went further and suggested the filter replace the gauze in earlier models. As this is a 420G it is more than possible it had a filter and not a screen.

 

Why not drain the tanks and filter the fuel back in and drain again until you get the majority of the rust particles out?

 

Robman25 - That's what I did, I filters 20 gallons through coffee filters - twice! There's still the really fine stuff. The other problem is we have a lot of snow here and I can't get the car out of the garage.

 

Does anyone have any thought on my issues with getting a reliable tick-over?

 

When I got my 66 Mark X, the car had been sitting for 12 years. Just like your car, the gas tanks were full of rust and the fuel line was rotting. I removed the tanks and had them resealed with Red-Kote which lines the tanks and prevents them from ever rusting again. I also replaced the fuel line with a new stainless steel line. You may want to consider going this route.