V12 fuel pump options

[SESH]

Hi all,
Can anyone give me other good options for a series 3 V12 fuel pump, other than the standard SU twin pump.
Thanks
Mike

[MarekH]

It's actually a very good setup.

Firstly, it's a low pressure pump so the carburettors won't get flooded.
Secondly, even if one pump fails, the remaining pump is enough to refill the float bowls at low to medium rpm.

If you think the points are unreliable, there are electronic options, not all of which are expensive.

What exactly is the problem that needs fixing?

kind regards
Marek

[SESH]

Hi Marek
The current pump was fitted about 20 years ago. It's a single non oem pump. I am experiencing some running problems when hot at low speed and rpm when you pull away. At speed it seems to run ok but it feels like fuel starvation at low rpm.The pump has been making some different noises (unless it's my imagination). Thought it was worth changing the pump although the double SU is quite expensive and wondered if there was a good cheaper alternative.
Mike.

[mgcjag]

Red top Facet pumps are i believe cheaper..you will need a pressure regulator to ensure correct delivery....you will need to check specifications...flow rate etc....think they will make more noise.....Steve

[MarekH]

You'll have to explain how you have fuel starvation at low rpm and not high rpm.

The fuel pump only refills the float bowls and any excess fuel returns to the tank via the return on the left hand side of the engine. The only logical pump related reason I can think of is that you have low voltage at low revs and the pump doesn't run. Or you need another explanation.

Inline (i.e. not lift pumps) are cooled by fuel flow and break down (permanently) if overheated.

kind regards
Marek

[SESH]

Hi Marek,
Wondered if I was getting fuel evaporation at high temp, but as you say the pump runs constantly because of the return fuel system, so fuel should be cooling the pump on a constant basis. I have been suffering erratic running for some time and have suffered rich mixture which could be a vacuum leak. I have spent a fortune on tune ups and carbutettor parts in recent months but still cant get to the bottom of it. Really need to find a Jaguar V12 expert in my neck of the woods!
Thanks
Mike

[MarekH]

Dear Mike,

A vacuum leak most likely causes lean running and would be most apparent at idle, when other airflow (through the butterfly) is at a minimum. You can check for vacuum leaks with a can of propane - sprayed at the source of the leak at idle, it would richen up the mixture.

I run four lambda sensors on my downpipes. I have considered offering that as a service but people rarely want to pay for advice.

If you are anywhere near Guildford, you are welcome to come over and discuss.

kind regards
Marek

[SESH]

Hi Marek,
Unfortunately I'm quite a way away from Guildford. I'm in Southend. Otherwise i would have taken you up on your kind offer. Interestingly I bought the car from Hindhead not too far from Guildford about 11 years ago.
I have replaced a lot of vacuum parts on the carbs in the recent past including the spindle seals. But I still have issues that i need to resolve.
Do you know any v12 experts near me?
Thanks
Mike.

[MarekH]

Sadly, I don't know Essex well at all.

Beacon Hill Garage in Hindhead seemed quite nice when I chatted to them last year. They purchased clear front and rear lenses for a v12 that they were working on at the time.

kind regards
Marek

[71 V12]

Mike,

You need to check all the rubber connections on the engine breathing system including the big grommet at the top/ front of the left bank and the timing chain tensioner inspection grommet on the front face of the right bank.

Are all of the vacuum ports in the manifold blanked? There are 2 or 3 of them, mostly used to control the cold start flaps in the inlet manifolds which for sure no will longer be working.

[Bob.]

Hi Mike,
A couple of thoughts.
Do you still have the original OPUS ignition system and if so is the amplifier still mounted on top of the engine?
The amplifier is well known for problems resulting from high temperature. These can cause partial or total loss of sparks although apparently after cooling they often work normally again until the next time they see a high temperature. (After the end of S3 production Jaguar finally issued a Technical Note to relocate the amplifier away from the engine to the front of the top tube of the picture frame).

If the fuel recirculation pipework is restricted in any way or the fuel pump is producing less than 1.5psi, a vapour lock could occur in the fuel line which crosses the top of the engine when under bonnet temperature is high. The LH carbs may still be fed fuel but not the RH ones. 1.5psi is significant because that is the system pressure set by the non return valve (NRV) located in the return line by the LH front carb. If the pump supply pressure is too low no recirculation will occur. The NRV could be sticking but is easily dismantled to check - if working normally it "sizzles".
Hope this helps,
Bob

[SESH]

Thanks all for your thoughts.
I will investigate all suggestions made.
The ignition system is a new Barratt distributor and module and the module is located onto the front picture frame.
Marek, Beacon Hill Garage was the garage that maintained the car before I bought it. In fact they carried out a full engine rebuild in the early 2000's
Kind regards
Mike

[Heuer]

Red top Facet pumps are i believe cheaper..you will need a pressure regulator to ensure correct delivery....you will need to check specifications...flow rate etc....think they will make more noise.....Steve

The noise the Facet makes is intolerable IMHO, especially in a FHC.