My fuel pump has packed in on my '79 carb fed 1500. Currently it has the (I assume) original 30 year old mechanical pump.
I guess I have 2 options. First is to replace like for like (another mechanical pump) the second is to fit an electric pump instead of the mechanical one.

If I go for the 2nd option, I know I need a low pressure (4.5-5psi???) pump but my question is;- Do I need to vary the pressure at all. i.e. on a mechanical pump, the faster the engine is turning, the more fuel is delivered, on an electric pump, I assume the pressure and flow is constant. Is this an issue or will the fuel just return to the tank when the float level is at the top?

Also, if I do fit an electric pump, do I remove the mechanical one and fit some kind of cover plate where it used to be or simply cap the output pipe?


Thanks in advance,

Mike

Any electric pump is going to outpace the mechanical pump for pressure and flow, the important bit is that the supplied pressure does not exceed the limits of the needle valve in the float chamber. Thankfully because the X1/9 carb has a return circuit for fuel the results of a little excess pressure are very small as it is constantly bled off.

If it was an injection system the varying fuel pressure would be a useful bonus and allows for a little extra tuning but on a carb system it serves no purpose at all really.

Thanks jimbro1000 - appreciated!
What would you suggest in terms if pump size? Is 3.5-4.0psi enough for all conditions or should I get a bigger pump (6psi) and add a regulator? Also, any thoughts on my second question? Remove the old pump and try to blank it or just cap pipes (or do nothing!!!)

Mike

Hi mate, unless you have your heart set on one, there are no real gains worth the hassle of converting to an electric pump from a mechanical one..
We came upon this question recently on our X and after weighing up the pros and cons we opted for the mechanical one.
Ease of fitting and cost were the biggest factors in our decision as our old pump was noisy and clearly was not performing well..
We got our replacement pump from Eurosport for around 40 euro and the cheapest electric pump was double that..
Its your car but I'd stay with a new original pump.

Thanks for that. I appreciate your response. I did fancy an electric pump (neater fuel line location, more controllable etc) but ultimately, I want a reliable fuel delivery and will take your advice and buy another mechanical pump. I suppose if the original pump lasted 30 odd years, it's not a bad 40 euro investment!!!!

Mike

The advice on sticking with the mechanical pump is good - other than simple availability (which isn't an issue yet), there are only two good reasons for adopting an electric pump:

1) You are upgrading the power of the engine and need more fuel to do it

2) You have a hot start/fuel vaporisation problem

Very few people swap to an electric pump for anything else. It isn't just the cost of the pump but also the safety features of a mechanical pump that automatically stops working if the engine stops. An electric pump ideally requires some form of cutout control otherwise it will just keep pumping fuel. With low pressure pumps this isn't so much an issue unless the car rolls over but higher pressure pumps can cause the engine to flood (and I don't just mean a little hard to start) and can constitute a substantial fire hazard.

To answer the other question though - you only need a basic low pressure pump - they easily supply enough fuel for up to roughly 100bhp. If you were to go with an electric pump steer clear of the cheaper (square) pumps - such as sold by Facet and go for the larger tube shaped pumps, they cost a bit more but are fully servicable and a lot more reliable.

Hello

I have the same issue, I suspect my mechanical fuel pump is worn out.
I also have starting problems when the engine is hot (fuel vaporisation), therefore an electrical pump seems to be the solution. Can this be mounted high in the engine bay, or does it need to be placed as deep as the mechanical pump?

Hi guys, I do have a tubular shaped facet fuel pump on my x, no inline fuel control device is fitted,but I do have loads of engine mods and twin 40 dcnf carbs.
No hot start problems and it never floods. Been on the car for 4 years and never let me down.
Mounted it where the carb cooling fan used to be..what a waste of space that was...IMHO