'89 911 (930) running poorly. (5mpg)

ewave · 02-14-2004, 10:21 AM

Hi,

After letting my '89 911 Turbo sit for about a year, I replaced the battery and tried to get it started.

It's running now, (the turbo seemed to be not spinning for the first few minutes) and I have driven it for about 200 miles. I've run about two tanks of Techron treated gas through it. Tons of black smoke is coming out of the exhaust, and it's getting about 5 mpg. It runs so-so, and is obviously running very rich. No signs of oil consumption. The boost builds relatively slowly (it was having this slow boost build problem when I parked it a year ago.) It still pulls pretty strong when under full throttle and boost.

My question is, what would you recommend looking into first?

The car has about 55K miles on it, and is close to stock- it has a slightly larger than stock intercooler and the air pump has been removed. It has the original turbo charger. The car has been maintained well (other than being parked for such a long time.)

BURN-BROS · 02-14-2004, 10:32 AM

Here are a few that I can think of

Inspect/clean injectors
check fuel distributor for sticking parts
compression
slow boost could be a number of things but try looking at the pressure relief valve in the intake manifold. If it is slightly open it could cause that symptom.

Keep us informed of your progress and good luck!

beepbeep · 02-14-2004, 11:17 AM

Yepp...bad/leaky seals in relieve-valve will make car boost slowly. As for rich A/F ratio...take of the filter housing and excersize/make sure CIS air-plunger moves freely. They usually get stuck when car sits for long time.

BURN-BROS · 02-14-2004, 12:29 PM

If the plunger was stuck and manually depressed it may leave the plunger in the fully open position(maybe the rich condition you have). Keep in mind the plunger arm would still move freely, yet the plunger(in the fuel distributor itself) would not follow the arm back to rest position.

dean · 02-14-2004, 12:32 PM

I would check your pressures also. The WUR could have gone bad.

ewave · 02-14-2004, 01:08 PM

Thanks for all the suggestions! It's cold and snowing in Dallas right now, so I'll wait for it to warm up a bit before I can check on these things. (My garage isn't heated.)

Is it very difficult to get at the pressure relief valve? I'm a fairly experienced mechanic-- I've had the engine out of the car, and have done my own clutch replacement. I've also got the Porsche workshop manuals for this car, but they are pretty spotty on details like this.

ewave · 02-14-2004, 01:22 PM

Quote:

Originally posted by dean
I would check your pressures also. The WUR could have gone bad.

Dean,

That's a really good idea. I hadn't thought of that. I've been spending too much time with my 3.2L DME based engine that I forgot about WUR. This would make sense. If the engine had a stuck CIS plunger, I would think it wouldn't run at all, as there would be so much fuel that it would get too far out of the ignition burn ratio? (Or maybe it's a combination of both problems...) But a bad WUR would keep a constantly rich condition throughout the whole operating range. That really makes sense. I'll combine looking at the WUR with checking the pressure relief valve and the sticking CIS plunger.

You guys are great!

ewave · 03-20-2004, 12:56 PM

Well YOU WHERE RIGHT!!!

I tested the fuel control pressure, and it reads 0.8 bar at 20deg Celsius (System pressure was 6.75 bar).

I am looking at two Porsche charts, both listed for the 930/68 engine and Porsche PN 930.606.105.06. (Bosch PN 0 438 140 153)

One chart reads a MINIMUM of 2.0 Bar.
The other one reads a Minimum of 2.25Bar.
Both of these values are without any charge pressure.

The Local Porsche dealer wants around $600 for the Warm Up Regulator. :-(

The current WUR in my car has the following Bosch PN 0 438 140 054.

Does anyone know if this is a new Bosche PN and if it is correct for a USA 1989 911 Turbo?

Running with 0.8 bar fuel control pressure obviously would cause the extreme rich running condition I have been experiencing.

I will give you an update when I find a replacement WUR at a reasonable price.

I also took apart the pop off valve assembly. It was in excellent condition, and looked fine. No visable wear or binding.

5axis · 03-20-2004, 01:15 PM

Good to hear you have the turbo figured out.
Nice looking GTS. What is the story? Looks like it recovered nicely. I will have one to go with the 930 someday.

david 89 turbo cab

5axis · 03-20-2004, 01:18 PM

looks like a nice project!

lomotpk · 03-20-2004, 03:17 PM

Very, very interesting. I'm running at about 5mpg as well.

Now, unfortunately I'm more of a mechanical novice. Could someone, ewave perhaps, provide moron simple step-by-step instructions for how to check

[1] The fuel control pressure, and I guess the system pressure as well.

[2] The WUR

[3] The 'stuck plunger' in the CIS system.

I thank you all in advance.

Lomotpk

vash · vash's Garage

lomo, what year is your car?

lomotpk · 03-20-2004, 03:44 PM

Sorry, I thought my sig had all the usual details...

Bastard 84 Euro 930 with an 86 engine, twin-plug, crank-fire.

ewave · 03-20-2004, 07:13 PM

Well I found a WUR for 169.95 exchange.

http://www.specialtauto.com/porsche-parts/index.html

The guy here is local in Dallas so I drove out and picked it up. Just installed it, and put the car back to together... It Runs Great!!!

Turbo's are so much fun!!!

Thanks for all the advice.

Lomo: You need a special gage to hook into the fuel pressure system. I bought mine 12 years ago from Bosch, and it was $400. You can buy the equivalent unit today for around $100.

If you have one of the Porsche Spec Books, there will be a chart showing how pressure should vary with temperature.

HTH.

specialtauto · 03-21-2004, 01:44 AM

Paul, Glad I could help. If there is anything else on the CIS fuel system parts that you may need or I can help you or others with just email me.
John hervey
www.specialtauro.com