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1986 930 11-22-2014 06:21 AM

No Power to fuel pump
Sp I got the "no power to the fuel pump" issue the other day. The car has been behaving erratically for a while now. You would be going along and the engine would hick up and run rough at around 2k rpm for a minute or so and then it would run normal again. The other day it died and I was able to start it up right away. Went to the garage a few days later and no fuel pump buzzing sound. Bummer!

So I ordered two of the red fuel boost pump relays to start the process. I think that mine were the originals so I figured that it was time and if I really didn't need them, it is always good to have a few spares.

So I got them from Pelican. Paid the $30 for the supposed OEM ones.
(911-615-108-01 )

They got here and made in china ????? The old ones of course were made in Germany and I figured that the $15 ones were the made in china batch. They fit a little loose as well.

So are they all made in china now? What gives??

Of course, they did not change that the car will not fire up. Still no buzzing sound from the pumps. I will have to have it towed next week to my shop. Bummer! It is air cooled Porsche driving weather in Florida now so I am missing out!!

JFairman 11-22-2014 10:03 AM

All consumer electronics is made in China now just like the computer you're looking at right now.
Unless you have a custom made Sagar high end gaming computer from Sager & Clevo Custom Built Gaming Laptops & Notebooks or similer store... but even then the components inside are all made in China. All the mainstream consumer laptop computers are made in the same factory in China... except for Lenovo. They are built in a different factory and they are usually cutting edge as far as consumer laptops. MSI is close.
Thats not a bad thing because these days China has the most advanced technology there is for building consumer electronics and low cost labor doing the actual assembly work. Mostly women because they have smaller hands that can reach into small places with better dexterity than most guys.

Anyway, take a look at the multipin plug connection to the speed relay under the left seat. That's a common place for problems like that and you'll find the infamous white wire from the overboost sensor terminates there.
Also the inside of the yellow relay if your car has one. It snaps apart so you can see and clean the two relay contacts inside it.
And check it's plug connection on the engine compartment relay panel and the relay plugs on the front relay panel.
The male pins on Porsche relays have a split in them and spreading them a little with a small flat blade screwdriver will make them fit snugger and make a better connection.
Some dielectric grease on any spade terminal or plug connection in the entire car will help keep corrosion from spoiling them.

T77911S 11-24-2014 05:12 AM

take a look at the sticky at the top of the page. go enar the end were i added info on the fuel pump circuit.

1986 930 11-25-2014 08:27 AM

Thanks for the pointers.

I looked at my "yellow" relay in the engine compartment today. It is actually more like lime green. It has a brown wire going into the relay. What is that? I pulled it and it looks clean. I cannot disconnect the wire from the relay and the other end disappears into the wire bundle leading away from the area.

Thanks again,


T77911S 11-25-2014 11:06 AM

here, read this:

look at the fuel circuit as 2 seperate circuits. one is the 2 FP relays, the yellow relay(contacts), the rev limiter, and the pressure switch. the other circuit is the yellow relay(coil) and the AFM switch.
the AFM switch removes ground from the yellow relay, de-energizing it when the engine is running.
the FP circuit gets its ground through the contacts of the yellow, then the rev limiter then to the pressure switch.
all the yellow relay is doing is energizing the 2 FP relays. the yellow relay is also (?) what gives the 1-2 sec FP run before starting.

short description:
the yellow relay is controled or energized by the AFM switch. with the key on and engine off, the AFM energizes the yellow relay, removing the ground to the 2 FP relays. that ground is of course the boost pressure switch.

the drawing i have for an 86 shows the speed relay or rev limiter side cuts out at 7k, and the other side is for the O2 sensor. it shows it cutting out at 3k.

tim's relay had several broken solder joints. one was on the coil for the FP's. the others where on some of the major pin joints. some even for the O2 side. so for those that have bad relays' pull them apart and just resolder the points i mentioned.
you can apply 12v to pin 7 and ground to pin 5 to test the relay. both relays should pull in.
(i actually used a 9v battery)

here is how i would go about TSing this system: based on whats esiest to do first and each step does not fix it.
(if one pump runs and one does not, then the FP or the relay.)
the letters in () are to go along with the diagram above.

both pumps not running:
i would reach around and pull the connector off the AFM. as soon as the key is ON, no start needed, the FP's should run. (F)
then i would check to see if the boost pressure switch is grounded. with connector off AFM, ground the wire on the boost switch. (A1)
jumper 30 and 87a on yellow relay. (G5)
jumper pins 1 and 2 on the speed relay. (B3)
IF 1 and 2 run the pumps, check for 12v to speed relay. (M pin 7)
if 12v present, speed realy bad. bad solder joints is a problem on this relay.
jumping the FP relays really only lets you know the FP's work.
grounding (D4) just cuts the circuit in half. if the pumps run, then it is something on the left side. if they do not, then it is on the right side.

a note for the yellow relay:
unlike most realys, the yellow relay runs the pump in the de-energized mode. so the coil can be bad and the pumps can run. you might consider popping the cover off and cleaning the contacts with fine sandpaper. i bet there are a LOT of good/repairable yellow relays that have been replaced.
the yellow relay and speed relay are known for bad solder joints.

the FP circuit was different for the years on the 930 from what i am told. the 87 has a fuse in the wire bundle itself that feeds power to the speed relay. it is a pain to get to....from what i am told.

Bruce Eyring 11-25-2014 12:16 PM

the conditions you describe.....hick-up...then will not start....let it sit a while and it is almost always the yellow relay in the engine compartment....after 317,000 miles on my '88 930...I know to carry a spare. PS. I have never had a red or black relay go bad.. only the original equipment relay...the aftermarket ones are junk. In my case...on a 1988 930...the manufacturer is Wittrin... and the part number is 91161511801 Wittrin is a German Co. and is the original equipment manufacturer for Porsche. Buy it on line...cheaper

1986 930 11-25-2014 01:24 PM

Thanks for the info.

I have an '86 so it looks like 91161511801 is not quite right. With the wire into the relay, I can't get it out to clean the insides without cutting the wire. This wire literally disappears into the depths of the engine bay inside a large wire bundle.

My '86 is an Ultra-Smith RUF conversion so it has a lot of electrical things that were probably pretty cool in 1986 but not so much almost 30 years later while troubleshooting electrical problems.

I will keep pressing ahead.

1986 930 11-25-2014 01:58 PM


Found the correct relay. 911-615-118-00 M504. So the wire appears to be a ground?

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