[Mgb-v8] Fuel Pump Woes

[Dodd, Kelvin]

Carl:

It is possible your SU pump was on the way out as a tired SU can have
problems delivering fuel under heavy engine load. There may also be some
issues with the rubber lines used on the late, in-trunk installation
that aggravate starvation problems. The earlier cars with braided 3/8"
hoses and rigid lines tend to have fewer problems with flow. Usually,
they either work or quit.

MGB road racers are no different than any other speed fiend, with a
penchant to replace anything that even seems could be a problem with
over kill devices. On the race track a noisy fuel pump isn't an issue,
but for the street it can be a real pain. Especially if the pump whines
in time to the turnsignals when stopped at an intersection. BTDT. The
factory used SU pumps in all of their endurance racers and rally cars,
albeit ones with twin coils.

I'm all in favor of modifications, but I gotta stick up for the good ole
SU pump. They really do a good job and have gotten a bad rep. for no
good reason other than the fact that most people only experience them
when the pumps are pretty tired out.

I've done my part to replace SU pumps with all manner of after market
types and have finally come back to using the original pumps. Even in my
'65 MGB vintage race car.
I really got the point made to me when the two different aftermarket
fuel pumps installed by a PO in my Jaguar 3.8S both took a dump. Oh,
that also gives an idea of demand. The 4.2 Liter E-Type uses just one
standard SU pump to supply the very thirsty straight six.

One thing to add is that the oxygenated fuels now being served up are
playing havok with a lot of after market pumps that previously gave good
service. Also many of the US manufactured pumps that had good
reputations are being out sourced. We have had a rash of problems with
after market pumps used for our supercharged applications and the Dupree
type intermittant pump from a major manufacturer has been pulled from
the market as not being compatible with modern fuels.

With the change in fuels, anything using a rubber seal needs to be
carefully evaluated.



Kelvin Dodd



> -----Original Message-----
> From: Carl Floyd [mailto:cmfloyd at chartertn.net]
> Sent: Saturday, October 18, 2008 6:46 AM
> To: Dodd, Kelvin; mgb-v8 at autox.team.net
> Subject: Re: [Mgb-v8] Fuel Pump Woes
>
> Kelvin,
>
> Interesting.
>
> I tried sticking with my stock '79 B SU pump. I found when
> driven hard in the turns )like 5K+ RPM in 3rd gear around a
> curve) it would lay down like I had run out of fuel. It was
> as though the SU couldn't fill the float bowl fast enough. I
> tried raising the the floats with no change. Switched to a
> noisy Carter, & 5 or 6 track days & same number of
> autocrosses later, problem seems gone for good.
>
> The 4 banger MGB road racers swear by the Holley fuel pump
> that flows a gazillion GPH.
>
> Carl Floyd