SGOGT4

Good god this is a lot of information!

Thanks guys. My car is wired so that the fuel pumps run all the time. I am relatively certain that this was the sound I heard everytime I turned the key. No such sound now.

I did swap out the fuel pump fuses but didn't have any luck.

A stupid question... when yo uguys talk about grounding a relay or switch, how do you do that?

Thanks

A930Rocket

When you jump a relay, you take a piece of wire, stip each end a 1/2'' or so and place each end in the two holes you need, such as the two the red relays. Look at the male side of the relay and the prongs will be numbered on the plastic. These corespond (sp?) to the two female sockets you need to jump.

Give a slight pull onthe wires above the fuses as well to check for loose wires or just tighten the screws.

Who wired the pumps to run all the time and how? (I guess if you knew this you wouldn't be stranded...)

nathanUK '81 930 G50

Replace the fuses. Me and two mechanics wasted a lot of time by not replacing fuses that seemed to be OK. I also wasted a lot of money paying them too

Ken89911T

Here's more. Don't ask me how I know. The front fuel pump relay runs off the rear pump relay. If the rear pump don't work, neither will the front pump if it's a relay problem. I had a similar problem that turned out to be a bad ground to the rear pump relay - the one closest to the driver. I ran a wire from the grounding pin of the relay to the ground point on the chassis - problem fixed permanently.

Took almost a year of frustrating intermittent failures (sometimes at home and sometimes not) and a 7-cent piece of wire.

Good luck!

InC

Hi guys.. not sure if it is related but I am quite sure it is related to fuel supply. Car started up ok in the morning with some UNUSUAL wining sound(louder than normal fuel pumps) sounds like fuel is choked and fuel pump trying to force the fuel through.. Anyway, idling was about 600rpm, much lower than normal. allowed car to warm up alittle, car started to choke and stalled. Car would only idle for 5 seconds before stalling again. Unable to get the engine to idle. Seems like to me that fuel was there initially when starting but not after.

I have observedthe followings:
1. both fuel pumps are working.
2. Happened to me once but car would be ok after 2 - 3 days, everything else is normal.
3. CDI, ignition systems including spark plugs and distributer are ok.
4. would a faulty fuel accumulator or fuel filter choke up the system causing fuel starvation?
5. Seem very much to me that there isnt much fuel going into the car.
6. always happens when Fuel level is low.
7. could it be the WUR? any symtoms or sound?

Any inputs will be greatly appreciated. Thanks in advance!

sand_man

It could deffinatley be number 4 and 7 on your list. There is also a cold start valve/injector that has also been known to malfunction.

Tell us more about your car - what year, smog equipment, mods, mileage, etc.

To check your WUR, you need the CIS pressure gauge and fuel line fittings as well as the instructions out of the factory wrokshop manual. I can always email you the pages that cover this, if you don't have the manual.

Here is the thread I started regarding my WUR:
https://rennlist.com/forums/911-turbo-930-forum/297546-a-crazy-little-thing-called-a-wur-warm-up-regulator.html

InC

Thanks sand_man.. will work in that area!

SGOGT4

Is there a standard way to know which of the prongs / holes you need to bridge? For instance if I was looking at one of the circular fuses under the front hood, how do I know which prongs would complete the circuit and bypass the fuse?

A930Rocket

Look on the back of the relay. Each prong is numbered and the relay only goes in one way to the socket. Locate the numbers needed and coresponding sockets and place a wire in the two to complete the connection.

You need numbers 30 and 87 on your two red relays. Maybe the same for the yellow relay?

Here's a pic I drew up.

mark '87 930

It is the first two relays closest to the driver. The very first one is for the pump in the back of the car(pump II), and the second is for the one in the front(Pump I).

pin's #87 & 30 is what you want to bridge.

sand_man

BUMP...give us an update. What's going on?

slownrusty

Yup I'm interested to see if you have made any progress troubleshooting?

InC

Tried to start my car again today... after several attempts, it fired up finally but sounded like it was running on half the cylinders for 8 seconds until it finally stalled. Was kinda 'fighting' to fire up. Didn't managed to get it up after that. would simply fire up for a few seconds and stall. Could smell petrol from the exhaust tips. Sets me thinking if i am on the right track! Anybody with similar experience? both my fuel pumps were wining reckon that they were working fine. could it be the WUR, 5 seconds relay, CDI perma tune (heard it clicking when the car fired up for the few seconds)? any way to isolate them one by one?

Thanks again, guys

SGOGT4

As for me I just got back into Michigan where my car ha sbeen stranded... I'll know more this evening after work!

Thanks guys

SGOGT4

Okay so here is the update.

Replaced the Overboost Relay - No Change
Replaced the Ignition Cutoff Relay - No Change
Swapped the Fuel Pump Fuse/Relays Up Front - No Change

A few things I did discover in my travels through the car this evening that I don't understand:

1. There appears to be a female fuse plug adjacent to the fuse panel in the engine bay that is unused in my car. I tried plugging in one of the round red fuses into it. - No Change. What is this fuse plug for?

2. There appears to be a cable in the engine bay that is disconnected. Tracing it down to the bottom of the engine it appears to be attached to an O2 sensor of some sort attached to the exhaust plumbing. I found the matching connector (both on the left side of the engine) and plugged them into one another - No Change. What is this cable for?

3. I believe that I have read that the 930s don't have DME relays under the driver seat like the carrera. What is the large black relay under the seat that we do have? Could this be a potential cause?

4. Where is the overboost switch located on a car that has had a Kokeln long neck I/C installed?

Thanks again guys.