Pierburg Low Pressure Fuel Pump for Carbs

EWPurdy · 06-04-2005, 12:45 PM

I'd like to replace my original CIS fuel pump (25 years old) with a new low pressure pump since I'm PMO'd now. I've done searches and heard people recommend the Pierburg pump as a good choice.

Pelican sells this pump:

PEL-WP99009-131
http://www.pelicanparts.com/catalog/shopcart/911E/POR_911E_fuelij_pg3.htm

Is this the Pierburg low pressure pump?

Anyone know what size fittings this pump has? My OEM pump has a hose barb fitting on one end (8mm?) and a banjo fitting (M12 x 1.5 ?) on the other. I'd like to find a pump that will fit in with a minimum amount of adapters and whatnot.

RoninLB · 06-04-2005, 12:56 PM

the Bosch stock pump is excellent quality. I also assume you now have the PMO fuel regulator in the engine compartment?

It's understandable that you want a reliable fuel pump. Did you consider getting a new stock fuel pump and pickling the old pump for a back-up?

EWPurdy · 06-04-2005, 01:08 PM

RoninLB,
I'm sure the Bosch part would be great ($$) but I figure since I'm going to replace the pump and I don't need any more than 3.5 psi or so it makes sense to get a low pressure pump. I have a Mallory regulator similar to yours (4309 I think). No sense making the regulator drop 80 psi down to 3.5 when I can get a 7 psi pump. I've read good things about both the Mallory and Pierburg pumps.

RoninLB · 06-04-2005, 01:47 PM

The Mallory and Pierburg pumps are great.. I'd find out how much noise they make before you do the install.

The Mallory 4307 backpressure reg allows a high pressure operating pump that's expected to last at least 75k mi to operate at your low discharge pressure probably forever. The Bosch pump costs a P repair shop about $250.. and it's quiet.

I bet a pelican parts phone call would have all the info you need for a conversion.

velomann · 06-04-2005, 02:13 PM

I have the pierburg.PMO setup in my '6' and am very pleased with it. I have not had any sloshing on corners from the PMO's, and can honestly say it was a good trade out from the high pressure bosch that was OEM in my car. Don at EBS sent me down that road.....good call!

EWPurdy · 06-04-2005, 02:36 PM

velomann,
Where did you buy the pump and what connection fittings does it have?

B D · 06-04-2005, 02:40 PM

Call Pelican and they will get it from PMO for the same price PMO sells it, it's around $80. That is not the Pierburg in the catalog. Not sure about the fittings but they worked fine with the lines my webers already had. I also installed a Moroso y-splitter from summit which is tapped for a pressure gauge to screw right in.

randywebb · 06-04-2005, 02:44 PM

Leave your CIS pump in.

I had the same idea and talked to Richard Parr. He told me not to switch & to just use a pressure regulator. The reason the Bosch pump costs so much -- quality. His pressure regulator costs $45, or $80 for a shiny one...

EWPurdy · 06-04-2005, 02:50 PM

I'd leave the CIS pump in but it's getting pretty loud and I suspect it may fail soon (25 yrs old). When it runs, I can hear what sound like worn bearings and in general the pump output fluctuates.

RoninLB · 06-04-2005, 02:55 PM

Quote:

Originally posted by EWPurdy

and in general the pump output fluctuates.

the fuel pressure ga will fluctuate at low rpm as the needle&seat open&close.

Steve@Rennsport · 06-04-2005, 03:13 PM

Hi Eric:

If your pump is noisy, the first thing I'd do is take a hard look at the rubber mounts that its attached to. When they get hard or sag, the pump will rest against other parts and resonate, making a bit of a racket.

If the pump is not touching anything, I'd kindly suggest that you stick with the Bosch ones as they are FAR more durable than anything else and are very quiet. BTDT, for many many years.

EWPurdy · 06-04-2005, 03:19 PM

Thanks Steve.

Should I replace it with a new Bosch CIS pump or get a Bosch low pressure version to feed my PMOs? I already have a bypass regulator installed so I can do either.

RoninLB · 06-04-2005, 04:21 PM

fwiw, I still have a good 50k '77 pump, then I bought a new 914-6 pump, then I bought a new '77 pump, then I gave the 914-6 pump away. It may have been a good idea to get a carrera or turbo pump.. but I'm low hp so it don't matter.

Oh yeah.. I told my brother to change his '88 pump about 9mo ago because his very nice lala land 911 had 80k mi on it. No biggie, it's a routine we do. Anyway he sent me his '88 pump and I ordered a M12x1.5 - M10x1.25 /pn 911 608 211 00 pump adaptor. It's the wrong part to replace, but, It's the correct replacement..

i'm pickled tired mixing my pickling formula of 10w non detergent and Marvel.

Steve@Rennsport · 06-04-2005, 04:51 PM

Quote:

Originally posted by EWPurdy
Thanks Steve.

Should I replace it with a new Bosch CIS pump or get a Bosch low pressure version to feed my PMOs? I already have a bypass regulator installed so I can do either.

Hi Eric:

Since you already have the pressure regulator, I would get the CIS pump.

Plus, its less expensive than the Bosch low pressure pump used in the 911T & 914/6 cars.

EWPurdy · 06-04-2005, 05:04 PM

My only concern with a high pressure pump is that the Mallory bypass regulator is almost adjusted to the stop to get the pressure down to 3.5 psi. I figured a lower pressure system would allow the reg. to operate in the heart of its adjustability range.....I guess 3.5 psi is 3.5 psi regardless.

Steve@Rennsport · 06-04-2005, 05:33 PM

I understand. I was trying to save you some money,....

Around here, the only pump I use for carbureted cars is the Bosch low pressure pumps (with a low-pressure regulator set at 3.5 psi), even though they are not cheap.

RoninLB · 06-04-2005, 06:53 PM

Quote:

Originally posted by EWPurdy

My only concern with a high pressure pump is that the Mallory bypass regulator is almost adjusted to the stop to get the pressure down to 3.5 psi.

full cc means no spring psi on the diaphram. No spring pressure means the feed and return is almost an unrestricted loop. Actually if you Only connected the feed to the return, without the 4307&carbs, you'll be able to see if you have any return friction. The reg is about .5psi in friction.

So what is your gauge psi if you turned the reg full cc? I hope it's less than the 3.5psi. My routine is to allow at least some spring on the diaphram to prevent it from slaming at start up. Some spring only at 4 or 4.5 isn't a bad idea either. If you have some spring at 3.5 then that diaphram will last a very long time. The 4307 has a great diaphram to begin with.

Let's say you have minor spring at 3.5 and for some reason the psi slowly falls lower at the same setting. So the pump is wearing, filter is dirty, or you're getting a clog and you add some spring to restrict the return and increase the carb psi back to 3.5.

what's psi at full counterclockwise ?

velomann · 06-04-2005, 07:52 PM

Hey Eric,
Sorry to not get back to you sooner. I bought the pierburg from EBS in Sparks Nevada (engine builders supply, they advertise every month in Excellence) from Don there......excellent people to work with, and I have always been very satisfied with their timeliness, service, and competittive pricing. I went with the lower pressure for the exact same reason you are concerned about, having a system operating within standards and not being forced backwards to much. I have the dual PMO's as I mentioned, and this pump feeds them plenty, with an 's' cam engine. For the most part, you have had several very skilled P-car people weigh in on opinions, it comes down to which one matters to you at this point!

EWPurdy · 06-05-2005, 07:37 AM

Quote:

Originally posted by RoninLB

So what is your gauge psi if you turned the reg full cc?

With the adjustment full cc I have 3.1 psi or so. I say or so because when my pump fluctuates it goes up by about .2 psi. When the pump does fluctuate it's as if someone just gave it more voltage across the terminals - the pitch of the hum is notably higher for a few seconds or so until it goes back down. Perhaps I should replace the fuel pump relay...

73911guy · 06-05-2005, 09:33 AM

Since no one else has brought it up in this thread and I know SOMEONE will take offense (I like to take the antagonist's view every now and then), I'll suggest using a Holley "Red" fuel pump and a Holley fuel pressure regulator for cars with carbs. Fuel pump is $95 and regulator is $25. Pump is a rotary vane type and makes a lot of noise when it is on and the engine is off but can't be heard once the engine is running. Can be bought either mail order from Jeg's or Summit, also your local speed shop so if it fails its easier to get a replacement than the others. Also, with the regulator you get two outlets so its easy to run a separate line to each carb. Rebuild kits are available for both.

Choking down an 80 PSI CIS fuel pump with a regulator to the 3.5 PSI you want for carbs makes NO sense to me. Seems like you're really making the pump work hard and thus prone to failure sooner than one designed to run at a lower pressure.

But all I know is that the Holley parts work very well for me and I'm not concerned about retaining the stock look. In fact, I've got a Racor 110A fuel filter waiting to go in based on a recent thread on the Early 911S board about how well it works.

Jim