The Saga Continues… 930 Turbo Problems

I am working on an 85 930 Turbo that’s been giving me trouble for quite some time now.
When the car sits for a day or two it has cold starting problems. Some times the car will start but then idle is very erratic. Generally it will idle below 500 RPM. Pressing on the gas pedal will allow the car to run but the minute you let off the gas, it either wants to stall or stalls. Also it doesn’t sound like all cylinders are firing when the gas is depressed. As if some of the plugs are fouled out.

On a very rare occasion it will start and waiting for the engine to warm up will smooth things out. I am then able to drive the car without problems. The car has no problems starting after it’s warmed up.


Here is a list of what I’ve done:

Tested front and rear fuel pumps -working
Adjusted Air/Fuel mixture using a CO meter (%3 at idle)
Adjusted Idle
Replaced fuel filter
Replaced all 12 spark plugs (twin-plug heads)
Tested spark plug wires
Tested HPV-1 ignition units –getting power and working
Replaced HPV-1 timing sensor
Insured plugs were getting spark –they where
Conducted compression test – all cylinders checked out within 5%
Set timing on HPV-1’s
Starter checked – working

What I haven’t done:

Leak down test (Since the car won’t run it’s hard to warm up the engine to properly perform this test)
Replace Warm-Up Regulator

Any suggestions would be greatly appreciated.

Thanks

Your car still has the CIS injection, right?
The first symptom you described sounds like a bad fuel check valve. If the car sits fuel will bleed off the system and into the cyliders. The fuel pump(s) will have to run prior to startup to regain flow and pressure. This can cause flooding, especially with an enrichment system employed.

Warm up regulator!!!


Ed
'88 930S

Could someone one tell me what hose #20, attached to the WUR, connects to on the following parts diagram? Is this a vacuum line? When I first got the car no hose was attached to this port on the WUR, I later put a cap on it.

http://www.pelicanparts.com/911/911_Parts/1978-83/1-7-5.JPG

it's a vent to the air cleaner, no vacuum, no boost.

If your fuel injectors are 16 years old they may not be as clean as they should be to spray properly; or they could be leaking. Except for the injector under the air pump bracket, they are easy to remove and check. I have found that a fresh can of spray carburator cleaner can be used to test them. The little spray tube fits inside the injector with a good fit. A fresh can will have enough pressure to lift the needle off it's seat. Spray and look for a perfect umbrella pattern out of the injector.
Leaking injectors may be your problem of flooding and eratic running.
Bob W.

Buy a fuel presure gauge and test the fuel injection presures.

My (former) 87 930 went through a period of being difficult to start, although once it started (maybe 2 out of 10 tries) it would idle well and run fine. It turned out to be a bad relay in the engine compartment that was messing with the fuel pump. Grounding one of the fuel pump relays independently allowed the car to start normally until I replaced the big gold relay in the engine compartment. I'm not sure about your nasty idle until warm, though. Sounds like a different problem.

Vic
88 Carrera

Where is the fuel check valve located?

I plan to purchase a CIS test kit on Friday. I am also going to order a new Warm-Up Regulator and Cold Start Injector. How tough is it to install the Cold Start Injector?

What's a good manual for an 85 CIS setup?

I don't have a Gold Relay in the back but I do have a large Red one.

Before you buy any more things and/or make any adjustments you must do the first things first.
1. the fuel pressure must be consistent, correct and reliable. This should consist of uninterupted fuel flow (new filter)and consistent pressure with power on or off. with power off the system pressure is maintained by the check valve, the needle seats in the injectors and the fuel accumulator. (and other areas that must not leak: see your manual) Even if the fuel pump has an internal check valve, put a fresh one on the fuel pump.(it's ok to have two check valves)
2.With power on, the stock sysyem runs both fuel pumps and much of the engine management(warm up regulator etc.) off of one fuse and relay. You must take the load off the relay and fuse. At least run the rear pump with it's own relay and fuse. Better to run both pumps with their own power systems.
3.After the fuel system pressure and flow is reliable then you bring in the guages and test and adjust system pressure.
4.After system pressure is correct then you can test and tweek your system devices.
5. If we haven't said it enough, I'll say it again: buy the fuel injection manuals.
If you are interested, I will show a wiring system that has proven reliable for me. There are other electrical system rewireings that will work too.
Bob W.

On our 1987 930 there are two replays, the rearmost replays on the large panel in the front trunk. You can jumper either/both with the key on to see if the pump(s) run. You can also unplug the sensor connection on the fuel distributor and the pumps will run with the key on but not cranking the engine. In the San Diego area this is done to hot rodded 930s to help them start. If the pumps are original, one or both could be failing and they can both run for a while and then one stop due to heat buildup. The engine will run with one pump, but very badly. I'd recommend checking the fuel pressure and making sure both pumps are in fact running all the time. Good luck.

I’ve unplugged the sensor on the fuel distributor and both pumps are running. I’ve also installed a new fuel filter into the system.

I did order up the Bosch Fuel Injection book today.

What I am trying to stress is that you need more than just "both pumps are running". The real concern is reliability under all conditions. As other turbo owners have mentioned and already know or will find out, the fuel pump electrical system on a turbo in stock form is overloaded. The electrical system (hence the fuel system)in stock form on my '82 needed to be upgraded before the car was reliable.
The relay will get hot and introduce resistance to the supply voltage to the fuel pumps (especially the rear pump)and the engine management system. Heater elements (warm up regulator)will not be consistent in their heating curves. Fuses will blow or fry their contacts. All signs of electrical over load. If you have a single relay and fuse supplying the current for both fuel pumps and engine management taking its power from the rear fuel pump(which is the stock system) then the electrical requirements for an aging fuel pump system are too much for the stock system.
Is your fuel pump relay hot to touch when the car is running? Have you blown fuel pump fuses? Have you already put in a larger fuse? Is the spring clip fuse holder to the fuel pump fuse dis-colored from heat? If yes to any of these you need to upgrade.
After upgrading the fuel pump electrical system my starts instantly. In the morning I just reach in the car, turn the key a tick. Not even a full crank. The car has never hiccuped-not even once.
I din't mean to lecture, only trying to keep you from over looking I what I believe is an inportant problem with a turbo.

I'm curious about what that advantage is to disconnecting the airflow sensor. I understand this will cause the fuel pumps to come on a little earlier, and may shorten the cranking time a second or two, but is that worth defeating the safety circuit that shuts your pumps off if the engine dies? I'm not preaching, I'm just wondering if the only advantage is that your engine starts just a little sooner.

------------------
Bill Krause
'79 911SC Euro

As we have communicated before, on shut down the fuel system maintains pressure; so that on next start up the injectors have enough pressure to inject. If your fuel injection system is old and leaking a little from normal old age, then having the pumps come on with the ignition on before they come on with cranking the engine, may rebuild system pressure slightly sooner. In my opinion not a good reason to defeat the air flow switch.
Bob W.

Bob W.,

The fuel pump relay doesn't get hot to the touch. I haven't blown any fuel pump fuses or had any bad relay's. I haven't put in a larger fuse. The fuse clip does not look discolored from heat.

I am running dual HPV-1's for ignition but they are on their own circuit.

I always appreciate everyone’s help and advice. This problem has me stumped along with a lot of other people. I plan on testing fuel pressure next week.

OK, If you are confident that the fuel supply is reliable then I would start checking the things that you can do your self.
When the throttle is opened, the sensor plate will deflect in relation to the amount of air flowing through the air horn past the plate; this in turn moves the metering piston to meter fuel for injection. It is not hard to take the top of the air box off which has the metering system in it and clean and make sure the metering piston is following the deflections of the metering plate. The piston must be completely free moving in it's bore. Use spray carb cleaner on the piston and bore to clean. Make sure the metering plate is centered. Both procedures are in the book. This requires a new gasket. Also the warm up regulator can be taken apart and cleaned. I'm assuming your high tension system is ok. Your hpv-1's either work or they don't, I don't know what you can check.
Bob W.

Bob,

I don't currently have an Air Box installed. The HPV-1's are mounted on a custom bracket behind the air conditioning compressor so you can’t fit a factory or aftermarket air-box. The CIS has an Edelbrock Triangle type filter on it (not the best solution but it seems to work). This makes access to the CIS real easy.

The sensor plate looks clean and correctly aligned. If I slightly depress the plate I can hear fuel being injected. When I start the car you can see the plate slightly lower.

Next week I plan on going through the entire fuel system. I’ll keep you posted on what happens. What type of readings should I look for when testing the fuel pressure, etc.? Can I pull the injector's out by hand or do I need a special tool? I thought I would put each one in a glass bottle and check the spray pattern.

Take care


[This message has been edited by AMG Hammer (edited 04-05-2001).]

The injectors for the turbo are threaded in. Just disconnect the fuel line and unscrew the injector. The SC's are pushed into an o-ring and may be hard to remove when the o-ring gets old and hard. The turbo's are threaded and use a flat sealing washer and are very easy to remove. CAUTION-the threads are very fine, be careful not to cross thread them when reinstalling.
Bob W.