Mechanical v Electric fuel pump?

[dwomby]

My car was fitted with an electric pump many years ago by a previous owner when the engine was replaced with a 1978 Dodge 360. I need to replace it. It had been VERY noisy and now it's failed. I had planned just buying a new electric pump and have just redone the wiring and fuel lines with that in mind. There are a bewildering array of electric pumps available and I have been trying to find the quietest that will do the job.

However, it seems that the quietest option could well be to ditch the electric and revert to mechanical pump which is, of course, how the car would have left the factory anyway.

So I am curious, why do owners fit electric pumps to replace the mechanical ones unless they have greatly uprated the power of the engine and need higher fuel flows or PSI? Is there some other benefit that I am not aware of?

David

[David C]

The main advantage of an electric fuel pump is that you don't need to churn the engine over to fill the carb when the car hasn't been used for a while.

[dwomby]

Originally Posted by David C

The main advantage of an electric fuel pump is that you don't need to churn the engine over to fill the carb when the car hasn't been used for a while.

Ah, yes. I hadn't thought of that.

David

[dwomby]

Originally Posted by David C

The main advantage of an electric fuel pump is that you don't need to churn the engine over to fill the carb when the car hasn't been used for a while.

I am away from the 3-4 months of the year. So this may be an issue but I suppose I can just disconnect the coil HT lead and turn the engine over on the starter to fill the carb float chambers then reattach the coil.

David

[John Simmons]

Originally Posted by dwomby

I am away from the 3-4 months of the year. So this may be an issue but I suppose I can just disconnect the coil HT lead and turn the engine over on the starter to fill the carb float chambers then reattach the coil.

David

I don't think that would really help anything. The main problems with turning the engine over cold until fuel gets to the carb is wear on the starter and possible minimal cylinder lubrication.

[David C]

On further reflection it isn't just after long periods of standing. It gets fairly hot under the hood and fuel evaporates when the engine is shut down. An electric pump will also help with hot starts. I think the Filton engineers must have had good reason to replace the mechanical pump with the SU.

There are many opinions on the electric pumps. Several have become infuriated with the SU and gone to Holley, Mallory etc. The latter have good output and are reliable but have been criticised for being noisy and may generate more pressure than you need, lifting the needle valve and causing a rich mixture.

The main problem with the SU was its mechanical points. The AUF404 was double ended and had twice as much to go wrong. The later, solid state, switching seemed much better and was a fairly easy retro-fit. I modified my pumps in this way and was very happy with the result. New pumps with this type of switching are available in the UK for about £300.

If you do go for a racing style pump you need to make sure it is mounted on a suitably compliant base with flexible hoses so vibration isn't transferred to the car.

[Nick Challacombe]

I fitted a red top Facet to my 407 20 years ago, it failed this year after 56,000 miles. I fitted a one immediately.
The Facet came with a pressure regulator which I soon found the most suitable pressure for my 313 engine. I mounted the pump under the off side wing near the servo. It is mounted rubber insulation bolts so the tap, tap tap noise is hardly heard on tick over. My car is still positive earth, Facet used to do both positive and negative pumps. They now only offer negative but it is a simple job to wire it up for positive earth.
It is an almost instant start as mentioned not turning over the starter motor.
I can see no reason not to fit, just makes life simple.

[dwomby]

Originally Posted by John Simmons

I don't think that would really help anything. The main problems with turning the engine over cold until fuel gets to the carb is wear on the starter and possible minimal cylinder lubrication.

Good point, John. Thanks.

Originally Posted by David C

On further reflection it isn't just after long periods of standing. It gets fairly hot under the hood and fuel evaporates when the engine is shut down. An electric pump will also help with hot starts. I think the Filton engineers must have had good reason to replace the mechanical pump with the SU.

There are many opinions on the electric pumps. Several have become infuriated with the SU and gone to Holley, Mallory etc. The latter have good output and are reliable but have been criticised for being noisy and may generate more pressure than you need, lifting the needle valve and causing a rich mixture.

The main problem with the SU was its mechanical points. The AUF404 was double ended and had twice as much to go wrong. The later, solid state, switching seemed much better and was a fairly easy retro-fit. I modified my pumps in this way and was very happy with the result. New pumps with this type of switching are available in the UK for about £300.

If you do go for a racing style pump you need to make sure it is mounted on a suitably compliant base with flexible hoses so vibration isn't transferred to the car.

Thanks, David. FWIW attached is a pic of what was in the boot until I took it apart to set it the right way up! It's a Mallory 140 and supposedly very quiet. Since being turned the right way up, it's only managing 2.5PSI !!!!! I'd just put in another except it's rather expensive and overkill for this engine anyway.

I have been looking to see if I could fit a mechanical and it seems unlikely anyway. My car has its alternator sat on that side of the engine and there's less than 3" clearance between it and the blanking plate over the mechanical pump location.

Originally Posted by Nick Challacombe

I fitted a red top Facet to my 407 20 years ago, it failed this year after 56,000 miles. I fitted a one immediately.
The Facet came with a pressure regulator which I soon found the most suitable pressure for my 313 engine. I mounted the pump under the off side wing near the servo. It is mounted rubber insulation bolts so the tap, tap tap noise is hardly heard on tick over. My car is still positive earth, Facet used to do both positive and negative pumps. They now only offer negative but it is a simple job to wire it up for positive earth.
It is an almost instant start as mentioned not turning over the starter motor.
I can see no reason not to fit, just makes life simple.

Thank you, Nick. Facet are a strong candidate but my car is all wired and plumbed for the pump to go in the boot sitting marginally below the level of the fuel tank bottom. I think I'll have to stick to that setup for now (mostly because of the wiring changes I'd need to make) and will let you know what pump I install and how it sounds!

David

[dwomby]

I have ordered a Mallory Comp 70 for the car.. I'll update after I fit it.

David

[Nick Challacombe]

David,
I do not see a pressure regulator on your Mallory which appears to be upside down. The Facet regulator is not their own I think it is a Purolator and could be fitted to increase / decrease your pressure.
Good luck and would like to hear how you get on.

Nick

[dwomby]

Originally Posted by Nick Challacombe

David,
I do not see a pressure regulator on your Mallory which appears to be upside down. The Facet regulator is not their own I think it is a Purolator and could be fitted to increase / decrease your pressure.
Good luck and would like to hear how you get on.

Nick

LOL - yes, Nick, it WAS upside down. That's the way it was when I got the car and it was noisy, so I re-installed right-side up it after taking that pic. There is an external pressure regulator - it's the smaller canister you see in that picture - but with or without it, that pump is now only giving 2.5PSI and some occasional pulses of more.

David