(E30 M3) Replacing Fuel Pressure Regulator (Long)

[Penny/Brandon Wood <woody@xxxxxxxxx>]

THE CAR
- - 88 M3, 61k miles, starts great, idles smooth, clean K&N air filter, =
AFM not sticking, new O2 sensor, no known vacuum leaks, Conforti chip

SYMPTOMS
- - When warming up, idling, engine "searches" for correct rpm; e.g. =
begins at 800, climbs to 1800 for 15 seconds, drops to 1200 for a bit, =
then returns to 800.
- - Coast out of driveway, put in first gear, let out clutch then engine =
hesitates, looses power, dash lights flicker.  Must depress clutch =
immediately or engine dies, otherwise it catches itself at 400 rpm for 6 =
seconds and recovers.
- - Same thing could happen at next stop sign or stop light w/in 2 minutes =
of driving off.
- - Occasionally tries to do the same while moving but momentum keeps =
engine rpm up but with no power available
- - Symptoms more pronounced when colder outside
- - Had been slowly getting worse over last year
- - Started noticing black soot in garage & on driveway immediately behind =
exhaust.
- - One day after letting car idle for 5 minutes to warm, noticed 2 ft, =
completely black, splotch on driveway--My car was pissing blood! =20

PROGNOSIS
- - Digest:  Check air flow meter set screw--good advice but for different =
problem
- - Local good-reputation mechanic (had owned E30 M3):  Erratic problems =
are hard to find, don't throw parts at it, live with it until it gets =
worse--same thing said 9 months ago
- - BMW Dealer:  "Started car cold [but during unusually warm weather] =
could not duplicate concern at this time.  Checked fuel pressure with =
gauge, pressure good.  Probable cause for concerned symptom could be =
regulator that would be sticking intermittently causing engine to run =
rich and overload, estimate for replacing regulator...$135 plus tax"  =
Total labor cost--$33.55

PARTS
1 0 280 160 226, Fuel Pressure Regulator; Bav Auto, $59.95 incl S&H =
(original black painted part, 0 280 160 249, was unavailable, replaced =
with above part but now with no paint)
13 53 1 726 960, fuel hose; Dealer, $10.20
51 73 1 470 035, black vacuum hose; Dealer, $4.70 (this was 3 mm inner, =
6 mm outer diameter, not 4/8 mm that I pulled off the car)

PROCEDURE (one beer, easy)
- - What?  The fuel pressure regulator is 1.5 in diameter cylinder about 2 =
in long.  Crankcase pressure is fed into the bottom that modulates a =
value regulating the fuel pressure to the injectors (allows lower fuel =
pressure at lower rpms).  Fuel is fed into and out of it thru a pressure =
connection to the fuel rail and a 2 inch long, 7 mm inner, 14 mm outer =
diameter hose (which has a violent turn!)
- - Where? On the original M3 it sits at the front end of the fuel rail, =
on top of the engine

1) Loosen hose clamps (2) with 5 mm socket
2) Pull out 90 deg fitting at end of 6 in. vacuum hose from engine, use =
pliers--don't scrap your valve cover or fuel rail!
3) Remove 10 mm bolts (2) that hold regulator to rail
4) Put an old rag below regulator to catch fuel
5) Pry off regulator with screwdriver
6) Pull the fuel hose off fuel feed line that parallels fuel rail.  If =
your hoses are like mine, they have aged and are now a permanent part of =
the fuel pressure regulator.  You'll have to replace them (it's a good =
idea anyway)
7) Clean that part of the engine, incl the hose clamps--it's never gunna =
get easier than now!
8) Remove vacuum hose from old unit, separate 90 deg fitting and vacuum =
hose wrapping from 6 in vacuum hose.  (Notice the direction fitting is =
facing)
9) Carefully measure new length of vacuum hose, replace 90 deg fitting =
and wrapping after installing new hose on new fuel pressure regulator
10) Coat o-ring on new fuel pressure regulator with a little oil
11) Install new fuel pressure regulator back on fuel rail.  (I used a =
little loctite on the bolts.)
12) Push 90 deg fitting back into rubber part on engine
13) With hose clamps hanging on fuel feed line, install new fuel hose on =
new fuel pressure regulator and push onto feed line.  Replace & tighten =
hose clamps.  (Don't try to use any old fuel line here!  That bend is =
not possible, you kink the hose, overtax your fuel pump and loose fuel =
pressure...buy the OEM part)

Like I said, VERY EASY, engine now idles consistently at ~800 rpm and I =
haven't seen the hesitation since.

Brandon Wood
BMW CCA #127523

------------------------------

End of bmw-digest V9 #683
*************************