SGOGT4

Hey guys... trying to identify possible problems with my car. Ended up stranded last night out in the middle of no where ohio and had to have my 930 flat bedded to Kzoo Michigan where I needed to be on business. Car was running seemingly fine when I pulled into a rest stop to make a pit stop. When I got back to the car it would crank over fine but wouldn't catch. I noticed that the fuel pump(s) aren't running as I normally can hear them when I turn the key in the ignition.

To make a long story short. The car is going to be vacationing at the hotel until Monday when I will be back in town. I have the DME relay that sits next to the brain under the seat on order for delivery monday. I also have an ignition cut-off relay and overboost relay on order to be delivered tomorrow.

Are there any other suggested components that could be causing this? I checked the fuses / relays under the hood related to the fuel pumps and they don't seem to make a difference when I swap them out.

Thanks in advance guys!

sand_man

Honestly, I didn't think the 930 (any year) used the DME relay.

sand_man

So when you normally turn the key, you hear the fuel pumps run, does that mean that your electrical connection on the CIS fuel metering housing has been disconnected? This is something that owners often disconnect. Mine is still connected and I don't hear the fuel pumps run when my key is switched over. I'm curious because, if this is still connected, you should be able to pull the connection, turn the ignition on and be able to hear the pumps run.

sand_man

I once had the plug that connects to the bottom of the CDI box come loose and that kept things from starting until I noticed it.

Also, I've heard that a disconnected Thermo-time switch on the driver side chain housing can keep the car from starting.

bogey1

I have a 3.6T, so I am not 100% sure on the parts list for your car but.... I had a similar problem, and it ended up being the stock car security system, which is located under the drivers seat. When its triggered (or shrted), it cuts ignition AND fuel pumps. Felt like it would start, but nothing. We swapped out the DME, relays etc (from another car)trying to figure it out. The dang thing cost like $400, but fixed it.

sand_man

The ignition "run-on" relay has also been known to be troublesome:
https://rennlist.com/forums/911-turbo-930-forum/288234-engine-runs-on-as-a-safety-feature.html
And don't forget, there's always the simple disconnected primary wire from the coil to the center of the dizzy.

A930Rocket

Before you replace all kinds of parts:

Do you hear the CDI box whinning? If not, check the connections

Pull the plug wire off the coil and see if you get a spark.

I would turn the ignition on and then press down on the A/F metering adj screw. This will push the metering plate down and make the metering switch connect. You should hear the yellow relay click and a buzzing sound because the fuel pumps are kicking in. If not, check and tap the yellow relay. Pull it in and out several times. Jump the yellow relay and the red relays to see if the pumps work. Numbers 30 and 87 for the red relays.

What else guys?

mark '87 930

As an alternative, you can jumper your relay so you can make it home! And then do all the troubleshooting you need to! Are both your pumps not coming on? It sounds like your connector to the air metering plate is disconnected, which is why you used to hear the pumps as soon as you turn your key. Mine was like that as well, and I have recently reconnected it. The pumps now only come on when the car is being started. Don't worry so much about that, I'd be more concerned about the pumps not working at all.

Very important as well, is CHECK YOUR FUSE carefully (I think it's the 8th from the back) and also the wire going to the top of the fuse connection. If you look closely, you may find that the wire is black or has a melted insulation section.. I was victim of that as well.

The overboost relay can be bypassed by grounding the overboost switch which you find under the intercooler, section closest to the driver (Front of the intercooler). It is one wire and it is white.

A930Rocket

I don't think the pumps will work at all w/o the metering plate switch connected or jumped?

Also, I think it's number 6. Good idea on the loose wire. BTDT...

mark '87 930

I'm not sure what BTDT means...

The pumps do work if the connector is unplugged.. mine has been all this time. It just means that they run all of the time. The main reason for the connection is safety. If ever you're in a collision of sorts and your engine stops, the fuel pumps stop..mainly so it doesn't keep feeding fuel to a fire or some other near incident. They only turn on when there is airflow at the metering plate.

sand_man

Yes this is true. With this wiring disconnected from the metering housing, the pumps will run all the time (ignition switched on). I think it's better to leave it connected. But it's a good way to test your fuel pumps...disconnect the electrical plug from the housing and turn the ignition on...the pumps should run. Just don't let them run for long without the engine running!

sand_man

930LDR, you need to confirm if the sound you've been hearing (ignition switched on, car not running) is the CDI box or the fuel pumps. In other words, unless you've got the wiring disconnected from the back of the air/fuel meter, you WON'T hear the fuel pumps...even if all the relays are good. It's a safety feature designed to keep the pumps from running (and flooding the cumbustion chamber with raw gas) if the engine isn't running.

Another thing it could be is a faulty fuel accumulator. It's the tank located next to the fuel filter. I think it's designed to help hold your fuel pressures.

A930Rocket

BTDT=Been there, done that.

I knew the pumps only worked when the engine was running and that switch controlled it, but didn't know it would run with it unplugged...

sand_man

This is a lot to take in 930LDR, but also check the connection on the overboost switch...on the BOV housing. It's a single *I THINK* white wire with a brown stripe.

Last930

Easiest thing first - check the fuse for the fuel pumps - the diagram for which fuse runs which circuit is on the inside of the fuse block cover. There are numerous articles (ex.Pelican Parts) on the overheating/resulting corrosion/poor contacts of the circuit that powers the fuel pumps. With the key on, wiggle the fuse and holders around and see if the pumps come on.