380SL Help...runs barely

[jim blanton]

Good all,

We bought a Nov 80 380SL a few months ago and have been
working on it ....first it was one lifter...replaced that...then plug wires,
roter and cap...new plugs....new vaccum lines and connectors...new
fuel pump...new filter...fuel resv...and lines that hook the fuel systen
together..and the filter in the tank...

At that point it ran but had the high idle pb...new control unit and
now the idle is 750 more or less...

Now the real pb....the thing starts fine...idles fine...until you
get up 1300/1400 rpm...starts missing....vaccum gauge starts
to the left...if you let it drop back it runs...if you try to give it more
gas it dies.

Checked the fuel press and its abt 5 bar...steady...

Anyone know what is going on with this car....

Jim in Texas

[jim blanton]

Correction....I had the fuel pressure numbers wrong....with
the engine at 750 rpm the gauge shows 85 psi steady and
50psi with the engine stopped.

[meltedpanda]

off the top that pressure sounds off, I will check tonight when I get home to my manuals. vacuum leak comes to mind as well, sticking throtle plate?

[jim blanton]

Evening Ron...thanks...the plate moves free both and down...and
with a can of starter fluid checked everything I could spray...also
checked the small screen in the wur and its is clean...also have
new vaccum lines and connectors..

[meltedpanda]

pressures - cold pressure, engine cold, pump energized - 18-34
system pressure - 75-84
warm control pressure -49-55
rest pressure 22-25
your pressure seems high and could be your issue. recheck cold and warm control pressures
When control pressures are high the travel of the control plunger is limited, which limits fuel , which causes poor function under load

missing under load can also be indicative of ignition issues - timming - been checked?
Coil - ?
next would be low injector fuel flow ( too lean) or absent - check to make sure they are firing.
good luck

[jim blanton]

Ron...with gauge hooked between the fuel dist (on the top) and the
wur with the cut off lever on the wur side the readings are as follows with
warm engine....

5.5 bar /80psi with valve open

5.5 bar /80psi with valve closed

3.0 bar /45psi with engine shut off

I see that when I moved the shut lever from open to closed with the engine running it would drop abt 60 psi in a second then back to the
5.5 reading.

Timing checked...ordered new coil...

Going to re check vaccum for leaks...

[meltedpanda]

what do you have your timing set at , these love to be advanced a bit

[jim blanton]

Ron....timing set per manaul...also check output or return line that goes from
FD back to tank..will check in again but at there its a pretty flow...and hooked
vaccum gauge ...15 and up to 20 before the thing starts gagging...my words ..
one thing i noticed is the plate does not move much...the work goes on

[ctaylor738]

With a warm engine, you need to have 3.4 - 3.8 bar control pressure (valve open). If you have 5.5, check the filter in the WUR inlet, it's probably plugged. A Search will bring up several posts on how fish it out and clean it.

If it's clean then your WUR is hosed or a long shot is that the small line back to the FD is plugged.

And, are you sure that the return line to the tank is clear?

[jim blanton]

Afternoon ....going to check both the return line back to the gas tank and read
up on the WUR...the car's fuel filter was pretty bad but the tank filter was not as
bad...I ordered the book on the FI systems ...be good to have hi...the WX in TX
is good for SL work...Jim

[jim blanton]

Evening Ron.....sent off the WUR for rebuild.....should have it back soon
and will report....still waiting for the book...Jim

[meltedpanda]

hope it ends up well for you !

[jim blanton]

After Ron.....well had some time and installed the rebuild WUR...and not a lot of change..
still idles fine abt 750 rpm...and now the max rpm before gagging is abt 2K...one pb was
wires going to the WUR had been repaired but one wire was apart hi...so repaired...12v
going to it now...one thing I saw was when I wiggle the rubber connector that goes
on the end of the slider into the manifold the vaccum changes ...need to check the numbers...and the rubber fitting is new. Also checked the return line at the cooler and
its pretty good..ie...fills a coffe can in 15 secs...so the work goes on. Also going to
hook up the gauge and check the fuel p with the new WUR and the power feed repaired.

[jim blanton]

Afternoon Ron.....test on the WUR...3.5 bar (closed) or 50psi and 5.75 bar or 85psi open...and 16 on vaccum...falls off as the rpm comes up and the gagging starts...
and I am wondering if the new rubber connectors such as the ones I put on the
slider are sealing...if one moves the slider around you can hear a hiss and the
vaccum gauge moves around...something to check

[have mercy]

I have ran into the rubber blader under fuel dist. where the rubber hose come off toward engine (pvc) where that hose tie's in to blader to lose Vac ,when you give it gas it loses vack., causing the car to fall on it's face. Check out blader.