Electric fuel pump rebuild - Injected engine

[vrsmith]

My 250SL has a bad pump. I had no trouble for over a year
and then it failed on me. After knocking it, it started to
work a bit and I could start the car. I replaced it with a
Holley electric for the time being. The car runs well again.
Somewhere I read that the original pump is rebuildable.
I'm going to take it apart and see what I can see.
Has anyone else done this?
On a related note, can an electric pump work if it is installed
higher than the fuel level in the tank? I put mine on a bracket
to lower it, but I wonder if I had to.
Thanks!

[vrsmith]

Based on a recommendation, I got a Holley 12-927 pump which is the
model used in the Pro-jection fuel injection kit. The cost was
about US$135 and the specifications are below. With it in place, the car
is running well and no longer backfires when the throttle is released. I
suspect that the old pump was losing effectiveness for some time. I
went for a 60 mile drive on the weekend and the car never missed a
beat. The new pump is a little quieter.
I never mentioned that my 250SL actually has a 280 engine. The
recommendation said that this pump worked as would a Bosch unit
for the 300E.

[] 43 GPH flow @ 15 PSI (at 13.5 volts)
[] 258 PPH flow @ 15 PSI (at 13.5 volts)
[] 3.5 Amp current draw @ 15 PSI
[] Approx. 400 HP max. - throttle body injection (MB works too)

[psfred]

You can take it apart and check, but I suspect you will find worn rollers of valves, and won't be able to get parts to replace them.

That is a low pressure system, it just kept the IP up to 30 psi or so, and the Holley will work perfectly.

I suspect that you would get vapor lock problems on a hot day with the pump above the tank -- gasoline vaporizes very easily. Factory height should be fine.

Peter

[grimgaunt]

VRSmith,
does this model have an in-tank pump to assist the main pump ?
if so, thats where you need to focus. If that is not the case, then a number of aftermarket pumps that put out the volume needed are available.

please PM me if you need further help

[Arthur Dalton]

>>Somewhere I read that the original pump is rebuildable.
I'm going to take it apart and see what I can see.
Has anyone else done this?
>>

Your problem is brushes.
The Kit comes with two O rings , a seal, and a pair of brushes.
Nothing hard at all.
These pumps are just a vane impeller pump and not much in there to go wrong.. most are just worn brushes or the check valve gets gummed up.
Pay Paul Parts has the kit
I think the last one I did was $14.

[67coupegroup]

Arthur,

Can you provide more info on Pay Paul Parts? I have been looking for this with no luck. Any leads would be greatly appreciated.

[Arthur Dalton]

Ray Paul

http://www.slclassics.com/

It is best to speak with him via phone [ you can get that at the above site]
Most catalogs will list the entire pump, but he has/had the rebuild kits.
He is quite knowing on these parts,,,,,,,

[Arthur Dalton]

Look at

http://www.slclassics.com/230-fuel.shtml

part 30-050K - Fuel pump repair Kit

[driver98]

I'm new to the forum and have read a lot of the posts, let me say that this is an extremely knowledgeable group, and you all seem to be quite passionate about the marque. I've a lot of respect for the thoroughness and professionalism of the authors I've read.
I read with interest your experience with a Holley 12-927 fuel pump as a replacement for the original Bosch unit, saving a lot of money in the process. I have a '70 280SE 6-cyl. that has been stored for about 12 years and I think the old pump is shot; it makes no noise but gets quite hot when the key is on so I suspect it's filled with nearly solidified gas. I'd like to replace the pump with the Holley but I'm wondering what sort of mounting issues I might run into e.g. bolt holes and such. Additionally does the Holley pump have all the correct ins and outs and are they relatively easy to match up to the old pump's?
For the record there are 2 possible pumps for my car, a larger unit and a smaller unit; mine is the smaller unit with the electrical connections closer to the base as opposed to the larger unit which has them higher up on the motor.
The car actually started and ran for about 10 mins the other day when I removed it from the garage where it was kept, then it stumbled, stalled and wouldn't restart. It's getting spark but no fuel which is why I first suspected the fuel pump. The pictures I saw here of an opened pump further my suspicion of it!
I'd appreciate any help any of you can render so I can go about returning the car to the road. I know there are other issues that'll arise but first I've got to get that engine running again.
Thank you all, in advance, for any help!

[Gregg Bambo Jr.]

If the original Bosch $300+ pump produces a Pressure of 30psi and the VR Smith's Holley 12-927 $135 pump has an output of only 15psi, how are these two pumps compatable? Would the Holley be able to meet the pressure and flow demand at high speed? Disassembly of the Bosch is very simple. I replaced the seals in about an hour. If the pump has been overheated and melted the interior varnish winding coating, forget it and replace it.

[Tomguy]

The best thing to do is disassemble it and clean it out, as well as draining the old scuzzy gas from your tank, replacing the filter, and cleaning the strainer. The pump is most likely still good if it gets hot - this means that it hasn't blown out YET, but it's siezed in one position and WILL burn out if power is applied to it too much. If it is siezed, it's probably because of the 12 y/o gas broke down into crud, which settled in the bottom of the tank, and stopped up the fuel pump (and possibly the filter and strainer and injectors). Clean it, bench-test it to make sure it runs (it should, use only 12 volts DC, and make sure you get the polarity right).

[psfred]

Sometimes the plastic internal parts melt in the goo that the gasoline turns into. If you have funny yellow slime inside the pump that appears to be the remains of a pump part, you will have to replace it.

Otherwise, the old gas can become quite viscous and make the pump stick. Use some carb or brake parts cleaner (check to make sure it does not contain methylene chloride, this will melt the internals!) on it when removed, then reverse the polarity back and forth (remote from the pump and carb or brake parts spray, please!) and it may come unstuck and run. If it then produces pressure, it's fine.

The smaller pump was a running change, there is a bracket on it to adapt it to the larger pump mount. Only smaller pumps are available as replacements.

Peter

[Arthur Dalton]

If you can rebuild your original pump, do it . They are the larger pump and are very simple and cheap to fix/maintain.
The later /smaller replacement pump did not have a slide seal between the pump housing and motor armature, so once they get clogged , they are in bad shape.
The original is also very easy to change brushes,the impeller is brass , so they have no plastic inner parts in the pump casing...this is a vane pump- nothing but an impeller, woodruff key and slide seal..simple as it gets.
These are high volume/low pressure pumps and they are the perfect match for the Bosch Injector pump .
You wll know the original pump as the wire terminals are toward the top of the armature casing, and the brush case has access screws. The later pump has the power therminals at the base.
The early ones also have a seal leak hose on the side to warn one if the slide seal is leaking without having to take the pump out..
KISS pump.. keep it if you can...

[driver98]

Thank you all for the prompt replies to my post about the fuel pump, lots of good info there. I do have the smaller pump on my car, and will try to salvage it if I can. However if I do go to the Holley pump, what am I looking at for mounting? Will I have to fabricate something to secure it? And does it have all the same ins and outs as the Bosch? I'll be working on the ground if I can't get a lift to use so minimizing the hassles of mounting is an important issue for me; these old bones don't cotton to the cold ground so well any more!

Thanks again.
TP