A CIS does not have electronic injectors so no Fuel Injection relay. Since no FI relay, no three lead bridge/jumper will be used.

The comments about jumping the FP relay means to bridge the relay pin connections in the CEP; this takes the relay out of the circuit and provides direct voltage through the path previously discussed. The Pin numbers on the relay should give you the corresponding orientation to the pin socket/slot. Only need to use a two lead (male) bridge 15 or 30 to 87 if you have FP spin with 30 but not 15 you have an issue from Ig switch to CEP FP relay.

Get the Wiring/Current flow diagram for a CIS and it will be consistent for the euro and a relay map to show you the plug configuration Manuals the '79 is CIS the '80 is not. These diagrams do not show the CEP configuration...Configuration diagram Key but the plugs are not labeled...as suggested look close with good light...A-Z left to right is a general rule but it goes out of sequence at the middle where the single red leads from the jump post plug in.

Jon

I hooked a wire directly from the fuel pump fuse ( it had power ) and then to my fuel pump positive side connection. The pump didn't turn over continuously when I did this. When I intermittenly put the hot wire on it, it seems to bump over but then stopped. With continuous hot voltage, shouldn't the pump continuously run? The pump is new.

Clogged with debris?
Remove (no sparks!)
Take it away from the car, reverse terminals on a 12 v battery to attempt to clear its throat.

Actuation should be properly installed, then jumper 30 to 87 at panel (its in the WSM, too).
Running other wires up in that tight space by the pump risks spark.


Oops on injection relay, sorry, wrong 80.

The smaller diameter connector on the pump is the positive. Did you connect the lead to the wrong connector? Also, have you checked to make sure the negative lead has a good ground connection to the body?

+1 on possible clog if it does not run consistently it should just spin until no voltage...as suggested pull the FP (it is not very hard) and put 12 v to the pin and ground the other pin then reverse the leads so it goes in the opposite direction. The FP is just a motor that can be energized in either direction based upon which side gets the 12 v. When you energize the pump fuel will pump out one side so have a tub to catch the fuel. One note when you pull it...do not bend/crimp the Fuel lines.

If it was clogged replace the filter and possibly pull and clean the tank...

I believe now my new fuel pump is junk. I grounded it and put continuously current to it and it virtually does nothing.

Does anyone know what the Porsche part number is for the correct fuel pump for this K Jet 1980 928S Euro? The 1980 US version L jet fuel pump doesn't interchange with the K Jet, I don't believe.

Also, what should be the fuel pressure for the K Jet pump?

thanks everyone for your help!

Here's the one I bought for my K-Jet almost 2 years ago. Still runs strong.

Google A U T O H A U S AZ and check this part number ( 69513 )

around $200

The CIS fuel system needs more pressure/volume than an L jet pump provides. A minimum is 5.5 bar with 1100 ml/30 second volume is required. Pierburg makes a 6.5 bar pump than has worked for 5+ years on my 931. It comes with an assortment of fittings for adapting to multiple CIS pump configurations. Mine came with an external check valve, but I have heard the new ones don't, so that may require using the one from your existing pump.

If you have run your existing pump for more than a few seconds without fuel it has probably seized.

Or fried.

They can get jammed with little bits of debris.

I had a new one jam and cleaned it by switching polarity back and forth while spraying WD 40 into the inlet.
Actually I installed leads on the pump so I could do this in-situ, but it's dangerous as can-be.

If you put your ear to it, or hand on it, and energize, you can sense whether its salvageable or not by the hum. Or lack of it.


Good info on CIS pump difference and source!

Yes, the one I referenced is specifically for a 928 CIS (like mine). It has the long neck which is the check valve. Also, provides the required volume for CIS (K-Jets). No adapters or external check valves on this one.

Will this one work for my K JET? :

FUEL PUMP 80 PORSCHE 928 S 8 CYL 4.7L WALBRO GSL392: eBay Motors (item 320503217204 end time Nov-11-10 16:17:34 PST)

I called Arizona ******** and he said he didn't carry any pumps for the Euros. I then gave him the part number you said and he couldn't guarantee it was for the S Euro. I trust your knowledge and everyone else's on here implicitly so I ordered that same pump that you did. Thanks! :)

Yeah, they are good to work with. Euro or US CIS is the same volume I assume. Either way, been almost 2 years with no issues at all on my Euro. How is your internal pump?

I believe the internal pump has been removed. Is it absolutely necessary to have both running? I drained the tank - maybe I should drop it down and look inside. Any hints on the best way to drop the tank and possibly change the internal pump? I bet its a toughie to reach.

Not really hard to do. Put a jack under the tank. Remove the 2 bolts holding the strap at the bumper side. Slowly lower the tank about 4 inches or so, then you'll have ample leverage space to remove the In-tank pump. I used a large Crescent Wrench. Also, make sure you douse the threads with PB Blaster or equivalent.

FYI, I ran with only 1 pump for almost a year with no issues, but decided if Porsche put it there, it probably needs to be there. I believe it is there to prevent hydro-locking.

a few things on dropping the tank ,
first there is a hose thats connected to the main body of the tank and it passes through the chassis and connects to the fill spout area,
this hose must be disconnected,
first at the fill spout its a hose about 1 1/2 in in diameter.
Then the top tanks securing bolt at the top of the tank behind the filler cap has to be unscrewed,
remove the rubber bellows to find it.

Then the vent tube inside the fenderwell,
then the fuel return line next to the sending unit disconnected.
Once all of these are taken apart then you can lower the tank and feed the 1 1/2 vent line out from the chassis go slow so you dont damage the vent connctor on the tank body its plastic and can crack.

For your situation I would not drop the tank but instead prop the tank up then remove the 2 bolts on the rearside of the cradle let the cradle drop down enough to get a socket on the tank pump if you have one,
( this can be verified by seeing wires plugged into the base are of the fuel outlet on the tank)
If you dont see wires plugged into the base area then you dont have a inner tank pump.
If want to remove the pump or in its place a fuel tank strainer only use correct sized deep socket 19Mm IIRC .
Warning there is a strong chance you will damage the outer collar of the tank and thus the tank will leak and a new tank will need to be fitted ,
so working on this part can cause other damage.
you can remove the tank sender from the top and look inside to see inner pump/strainer.
NOTE heat the sender nut in very hot water prior to installing it this will let it be bigger and then cinch down as it cools resulting in a tighter seal

Dang! That 3 paragraph super duper explanation makes my 2 sentence answer pale in comparison. MrMerlin got all the details in his answer, go with his.

One other question about hooking up the external fuel pump:

I have 2 positive wires and 2 negative wires for the fuel pump. Why is this? They both need to be put on the positive and negative terminals? I tested both positive wires and only one had power when i jumped the fuel relay.

thanks for all the information :)

where are these wires??
If you have 2 sets of wires then you should have 2 pumps if your only running one pump the make sure the other wires are secure.