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Old 10-10-2018, 05:07 PM
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Location: Tucson, AZ
Posts: 5,047
Looking for input regarding electric fuel pump choice

Trying to decide which type of fuel pump to replace the OEM on my '85 500SEL which was converted to MegaSquirt. I'm using 19LB. injectors from a standard Ford 5.0L, a custom fuel rail and an aftermarket fuel regulator.

It was running fine with the original unit but the pump is wearing/worn out. Still puts out the pressure but has developed a bad spot on the armature or worn out brushes. Upon occasion it needs a bit of a "rap" on the pump to get it spinning. Not a problem to me as I keep a small rubber mallet in the trunk but I doubt the Missus would enjoy crawling under the beast for the required action. She's funny that way. I'd imagine if she had to do it then the next place she'd use the mallet would be in my cranial area. She's not a fan of cars which have "quirks".

There seems to be three types available which will fit. The "rolling cam", the "gerotor" and the "turbine".

It's been awhile since I've had one apart but it seems to me the OEM is the "rolling cam" type which has vanes which drive the fuel.

The "gerotor" type seems to deliver the most/highest fuel but requires the highest voltage/amperage. Up to 15 amps depending on manufacturer/model.

The "turbine" is the newest on the market. It has the advantage of the lowest current draw with what seems to be a comparable fuel delivery between the other two types.

They are in the same ball park regarding price and all are Bosch units.

Anybody have any experience with the different types? Opinions regarding their advantages/short comings?

“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
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Last edited by Mike D; 10-10-2018 at 05:25 PM. Reason: clarification
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Old 10-10-2018, 06:41 PM
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Join Date: Jan 2012
Posts: 7,515
You would have to do some fluid pump research to see what type is more efficient then back that info into what fuel pump to use. I'd probably just use another MB pump to eliminate replumbing or would go with a common / universal external pump.

Some pump designs are more noisy that others so take that into account as well. If you FI system has the capability, slow pump speed down at low fuel requirements to reduce noise, save pump wear and alternator load.

I'm not sure what you mean by " rolling cam " and describing it as vane.

There are 3 vane type fluid pumps I know of Roller Vane , Straight Vane and Slipper. Vane. All of these pumps tend to be noisy due to pulsation.

Roller Vane uses a rotating star with rollers in the slots, this was what Bosch / VW used for D jet and probably L jet.

Straight Vane has slots and square vanes, this is common on GM and other power steering pumps.

Slipper is like a straight vane but has wider " vanes " and springs to force the slippers out. This is found on 60's Ford and Chrysler power steering pumps. ( At least one uses this style and the other might not. )

Geo rotor is a gear in gear pump similar to a traditional auto trans pump.

Turbine has actually been around along time for OE applications. Turbine is a centrifugal type pump. Single turbines are used for low pressure , I've seen double for higher pressure.

At least in the mid 90's , MB ( Bosch ) pumps where rotary screw like a industrial air compressor. This is probably the quietest.
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Old 10-10-2018, 07:50 PM
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My vote is for an original replacement. At the lower pressure of EFI it will be loafing along barely breaking a sweat, likely leading to a long trouble free lifespan.

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Old 10-16-2018, 11:58 AM
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I'll throw in my 2 cents for what it's worth. I've owned my MB since 1997. Your '85 is 6 yrs. older than mine. You ask about 3 different types of pumps, but in today's world, I wonder if there are 3 types available? These days, you find yourself left with 3 options:

1. Dealer - outrageous prices

2. Uro - Chinese - near as I can tell, Febi/Meyle may be no better than URO.

3. Salvage yard - for me, ok for specialty metal(nuts/bolts/brackets)

My OEM fuel pump lasted 13 years. It was a single-pump Pierburg. Replaced it with same Pierburg part #. 13 years later pump #2 is dead. Pierburg no longer available.

My options were a new dealer pump or a Bosch pump. I opted for door #2.

Options are drying up.
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
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Old 10-19-2018, 03:02 PM
oldsinner111's Avatar
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Location: bristol,tn
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pierburg is the best,not bosch
make the wealthy, and racist soylent green again
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Old 10-19-2018, 03:21 PM
Mike Murrell's Avatar
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Originally Posted by oldsinner111 View Post
pierburg is the best,not bosch
Good luck finding a Pierburg. That's why I ended up with Bosch.

Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
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