Replace Fuel Pump or Entire Assembly?

[CDAG]

Hello,

1998 Z3 1.9 Auto - 227,000.

This is a great forum, thanks for all the help. With it, I've replaced H20 pipes, radiator, Head gasket, CCV, auto trans, flex joint (not doing it led to problem with trans - which I found 55K for $250!), struts, shocks, control arms and a few more odds and ends. Got the car @ 160K for $1,700

Current issues are: Fuel pressure is at 34, per manual should be 44...hesitation at highway speed (70), and while headed up hills from a start (i.e. low speed), I have lean P1074 code, also an 02 code. Also, Knock sensors show needing replacement - I can't remember the # right now.

Found A few small exhaust leaks at manifold (checked with blower & soapy water), no vacuum leaks detected (used self-made smoke machine - Paint can, Soldering iron, mineral oil, rag. compressor).

Regarding the pump, I alternately pinched off sending side then Solenoid side when stopping engine... with solenoid side pinched (sending side open)...pressure drops quickly to 20...then slowly lower. Sending side pinched (solenoid side open) and stays at 34, so I think the solenoid is fine.

My questions:

1) Recommendations on fixing the fuel pressure issue - I see a lot of options regarding the pump and am wondering if I should replace the entire thing (assembly, pump, sending unit, pre-filter, etc with OEM (FCPEuro has it @$350)or just the pump (@$100 on FCPEuro) or Pump and sending unit (about $100 on carparts "spectra premium)- . I already replaced the fuel filter.

2) Are there other gaskets, seals, etc recommended?


3) On the exhaust leaks (soapy water bubbling where pipes connect to the exhaust manifold), I'm thinking of using some cold weld quick steel (rated for exhaust manifolds + 2,400degrees) per a youtube video - has anyone done this successfully? Thoughts?

Once done, hopefully the lean code will be gone and I'll look take care of Knock sensors, and check 02, etc

Thanks!

[jclausen]

I replace the complete unit in my car with the factory pump as a preventive measure as it had never been replaced. But I work in the business so I got a good price on it. You would have to weld the manifold nothing is going to seal that gets to hot

[BimmerBreaker]

On that car I would probably replace just the pump. Ive not seen issues with housings on those like I have with s54 housings for instance

Inspect the housing before replacing though. Make sure its good. If through FCP you could buy both and return the full housing unit if not needed. $20 or so for return shipping

[CDAG]

Thanks all! Job is completed.
I ordered the whole assembly and pump-glad I did. My thought was the plastic more got be brittle (Car has 227K), and I hadn’t found instructions on pump only. When removing the old assembly/pump I broke one of the outlet nipples. Once the pump was removed, I could not see how to separate the pump from the assembly and install a new prefilter- on my old pump the prefilter seems to be part of the assembly, and connecting new pump to old assembly seemed dicey. I’ll try and get pics up for the next person.

Interestingly, I’ve driven about 60 miles- no P0174, O2, or knock sensor codes. Looks like a case of slowly fading fuel pump.

[Cremaster]

Could you please explain the home made smoke machine?

[solimans]

I noted this smoker at one point...

https://www.ebay.com/itm/Autool-SDT-...pid=2244198529


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[Randy Forbes]

I noted this smoker at one point...

https://www.ebay.com/itm/Autool-SDT-...pid=2244198529


Sent from my iPhone using Tapatalk

While not a tool you'd be reaching for every weekend, practically indispensable for diagnosing an assortment of problems; at least this one won't break the bank!

This is a good tip.

[CDAG]

DIY smoke machine- There are several examples on YouTube. Here is what I did:
1) Empty, clean paint can ($5)
2) drill hole in Lid to fit soldering iron ($30 from Lowes)
3) drill 2 other holes in lid (opposite sides) for empty pen shafts to be inserted. Epoxy pen shafts in place.
4) Run 8 foot clear tubing from can to engine (size tubing and pen to match
5) put 6 inch tubing over other pen- attach compressor hose to tube (at low psi, or use tire pump, etc)
6) old t-shirt soaked in mineral spirits/baby oil - place in tin can
7) turn on soldering iron/put through lid against oil soaked rag to start smoke(I lit my rag with a lighter to get it started.
8) With 8 foot hose attached to engine area (I pulled a vacuum line and ran it there ) run compressor to drive smoke into car.
you can permanently attach soldering iron to lid. I used gorilla tape so I could use iron for other purposes.