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Fuel pump question....while I'm in there...


Hodgepodge
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I am about to remove a lot of parts from my '75 2002 engine and engine bay in order to eliminate a lot of leaks, refresh the engine. remove the smog controls and, de-gunk and eventually respray the engine compartment.  This 2002 has about 120k miles on it. I have receipts for the car since new and, according to those records, the mechanical fuel pump has never specifically been serviced or replaced. The car has a 32/36 Weber carb with no current fuel delivery issues.   It appears that the fuel pump is still available and not insanely expensive.

 

Here are the questions: 

1. What is the typical duty cycle for a mechanical fuel pump? 

2. Is service or maintenance of the fuel pump included in any of the BMW services prior to 75k miles?  

3. Does it make sense for me to go ahead and rebuild/replace this component since I'm already addressing most other mechanical systems?  

4. Should I screw around with trying to rebuild this thing or just buy a replacement. (The real question here might be do the new ones hold up as well as a rebuilt old one...assuming I do a decent job of rebuilding it?) 

5. When mechanical fuel pumps fail, do they weaken slowly or do they just quit?  

 

My inclination would be to just buy a new one unless the new ones are junk. 

 

Any insight?  

 

Thanks,

 

Scott

 

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I am in the 'if it ain't broke... use it until it is' camp on this one.

 

Could you post a photo of your pump?

There are a few styles that show up on these engines.

 

Ed had success rebuilding one style, using a VW pump kit, while keeping one spring from the original pump, to avoid excessive pressure issues.

 

I bought a new 'stubby' pump, back when I got my car; mostly because I thought it looked cool, with all the little screws keeping the top on.  There are fitment issues with some of the short pumps and it pushed down on the coolant line that runs underneath it.  I have since gone back to the original and it is working just fine.

 

If your engine/pump are still up and running, it might be a good idea to put a pressure gauge on the pump and see what it is giving you.  Weber's like low pressure, like around 2-3 psi, apparently.  My pump puts out just over 4, but the 32-36 does not seem to mind.  I put a regulator inline to dial it down, but could not tell a difference, so I took it back out.

 

On a similar topic, although a tangent, do you still have the original fuel bypass valve installed?  I think it makes sense to have some way to bleed off the pump pressure after the car is shut down.  Those valves often go away during the de-smogging process.  Mine was gone, so I put in a fuel filter, with a second output nipple, which serves a similar function.

 

All that to say, I'd run what you brung.

Tom

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Both early (the kind that have screws holding 'em together so they can be rebuilt) and late (crimped together, can't be rebuilt) pumps seem to be very long-lived.  That is 20+ years.  That's for the OEM Pierburg pumps.  The only problem I've had with a mechanical pump was an after market Italian-made pump (early style).  The pushrod that activates the pump was harder steel than the flange on the pump, and wore a hole in the flange so the pump wouldn't.

 

I replaced that pump with a Pierburg; no problem since.  But I did dismantle the Italian pump and migged up the worn flange, ground it down and have kept it for a spare.

 

+1 on "if it ain't broke, don't fix it."  Just carry a spare pump--5 minutes to change if you ever need to.  And if you carry a spare, according to one of  Murphy's many laws, you'll never need it.

 

mike

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+1 on ordering a replacement. Most places say it is OEM replacement but they send short throat stylr where original was long throat. 

 

I had new shorty and realized the hose routing problem was real. Call Steve at Blunttech and he has NOS long throats. A bit pricier but proper if you are going to replace. 

 

But biggest thing!! The mount holes need two plastic centering grommets that might or might not come with pump. Must have or pump mounts off center and shaft does not engage pump properly. All sadness begins theree

 

 

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One more thing. Another of your best friends is a site called

 

www.realoem.com

 

Type in your VIN and get exploded views of every system on the car with part numbers. Helps you see what previous owner did not do properly!!

 

Also find Maximillian BMW which is expensive but they can get you just about every nut, bolt, grommet, part or piece needed. They are the official US outlet for vintage BMW parts.   But they are expensive....did I mention they are expensive ?????

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Hi Worzella, 

 

Yep, I've been using realoem.com for maybe 10 years now.  I have all my VINS next to my computer monitor. Great reference, but sometimes it can't narrow down between multiple part options.    And here's one back at you if you haven't already seen it.   It is a little piece of software that scans dozens of BMW parts sites for the best price.  Just plug in a part number.  Then it will let you open a page on that site to order the part.  HUGE time and money saver when searching for parts.   I use it to buy parts for all of my BMWs.   It nags for tips on occasion, but has saved me enough to happily send the author a few bucks. 

 

http://www.bmwpnpc.com/

 

Take care!

 

Scott

 

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27 minutes ago, worzella said:

+1 on ordering a replacement. Most places say it is OEM replacement but they send short throat stylr where original was long throat. 

 

I had new shorty and realized the hose routing problem was real. Call Steve at Blunttech and he has NOS long throats. A bit pricier but proper if you are going to replace. 

 

But biggest thing!! The mount holes need two plastic centering grommets that might or might not come with pump. Must have or pump mounts off center and shaft does not engage pump properly. All sadness begins theree

 

 

Good to know.  I was actually going to order the OEM one that is still available from BMW.  

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