I have voltage (with the jumper) through the fuse for the fuel pump, and the fuel pump is not getting 12VDC. None of that wiring harness has changed since I drove the car in a couple of weeks ago. The problem almost has to be at the bottom of the fuse box. My plan is to disconnect the fuse box again, clean all the connections, and rehook them.

I was going to do that this morning, but it was single digit degrees outside, and only slightly warmer in my garage. I walked in there, and promptly gave up for the day. Tomorrow and Saturday is supposed to be warmer.

 

If memory serves me correctly, the fuel pump fuse also supplies power to the O2 sensor heater and the middle terminal of the idle controller. Might be easier to test voltage at those points.

 

yes your right it does supply terminal 2 on the O2 sensor but that will not help here unfortunately as the wiring is in a different part of the loom and frankly the fuel pump is probably more accessable

if Stogie has 12v+ at Fuse 34 (fuel pump) and zero volts at the fuel pump then he will need to run a new wire feed to the fuel pump from the fuse. its simply not worth ripping out all the carpets and undoing the loom to find and fix a break in the wiring.

i assume that the earth connection for the fuel pump has been checked ?

the next step should be to run a piece of wire from any 12v+ source (ie battery) to the fuel pump and then test it with the 3xwire bypass in place . Lighting cable from a table lamp or similar will do for a test .

Wrap up well Stogie and get out there .......are you a man or a mouse ?

 

All these connections merge at a single point at the plug that goes into the fuse box. If power is not on the O2 connector, it points to a wiring problem to the pump. If no power is at the O2 connector, that points to the fuse box. I was thinking the wiring harness to the pump was not touched since the car was running.

The O2 connector is easy to get at, snapped into a holder at the firewall. The fuel pump is behind a cover under the car.

 

the op has already stated that he has tested for 12v+ at the fuel pump fuse and says that there is 12v there .

What is the point of checking the voltage at the O2 plug when we have already established that there is a voltage at the fuel pump fuse ??? That doesn't help us does it. We are interested in the feed to the fuel pump from the fuse

I appreciate that you are trying to help Adker but I have already troubleshooted this fault through a logical systematic check of the Bosch fuel injection and engine management system .

All you are doing is reiterating what I have already established ? and confusing the issue.

 

Voltage at a fuse does not mean that that voltage get through the fuse panel connector plug.

 

Exactly!!! That is why I tore the fuse box back apart this morning. I cleaned all the contacts on the panel, and all of the contacts in the connectors. Tomrrow I will put it back together and see what happens.


Now I have to shower, go to the gym and work. This shift is a car tinkerers pain in the butt. Only three more weeks and I am back to normal, and will have more then an hour at a time on weekdays to play with the car.

 

wow that picture is enough to make most owners shudder

Anyone capable and willing to rip that lot out knows what they are doing

Look forward to hearing how you get on. Well done, nearly there

 

Actually they are all keyed to their own slot and direction. It is tight, but not really as complicated as it looks. I am hoping one was not seated well, or my used harness had dirt in the connector.

 

Got the snow off and took a look, that last fuse plug slot is indeed empty on my 86 parts car.

 

Make sure that you check continuity carefully between the fuse holder on the top and the fuel pump feed wire in the connector beneath .

There are only four possibilities now regarding the non working fuel pump.

1 . there is a break between the fuel pump fuseholder and its connector
2. the fuel pump supply wire from the connector to pump is broken somewhere.
3. the fuel pump earth is defective
4. the fuel pump is defective

One of the favourite places for aftermarket immobilisers is to break into the fuel pump feed wire . Your replacement loom may well have a break somewhere for a previous immobiliser/alarm system . You may find it easier to run a new feed wire

 

I concur. Since the car drove in to the garage with only the marker lights not working I doubt it is the fuel pump. One of the other possibilities has to be the culprit. I will go out in an hour after it warms up a little and find out which one.

 

Thanks. One less thing to wonder about during reassembly.

 

ITS ALIVE IGOR!!!!!!!!!!!!!!!!!!

I reassembled the fuse panel, and the car starts both with the jumper and the DME relay. Now all I have to do is put the rest of the car back together. I should be driving my 944 to dinner tomorrow weather permitting!!!

Thank you everybody for your help. I will post a reassembled picture on this thread soon.

 

fantastic news !

Thats a great Christmas present to yourself , well done .

Have a great inaugural drive .