924Board.org

[stevekat]

Paul, thanks for those photos of the fuse box connectors.

[stevekat]

Regarding the fuel pump running momentarily when the car is off and the ignition switch is turned to run, using the KAE 433 906 059 fuel pump relay, with the KAE number 3.300.300 on a 1981 931, the pump does seem to run momentarily when the car has been off for a while, but if one shuts the car off, and then turns the ignition switch back to run, the pump does not run momentarily. Might have to do with a capacitor in the relay having to drain off before that cycle runs, or something along those lines.

[Maybe924]

I've got a different relay and it definitely does not prime the pump before starting.

I purchased it from Performance Products:

On the box it shows this part number:

931.615.113.00

On top of the relay itself it shows:

896481
SHO
W-Germany

Where did you get your relay? Is it 931 specific?
_________________
1981 931 GT (CGT Intercooled)
1985 911 Targa Carrera (Sold)

[Paul]

[Maybe924]

OK I found the relay part number you have on Pelican parts but it doesn't show that its for a 931. Also it doesn't show that its 16A. Are you sure its the right relay?

I'd like to get a relay that primes my pump again, since it takes a good 3 extra cranks to get the car started without the priming function.
_________________
1981 931 GT (CGT Intercooled)
1985 911 Targa Carrera (Sold)

[stevekat]

The relay you have is the factory spec relay with the rpm over-limit protection. The rev-limiter is built into the fuel pump relay on these cars, at least the 1981 and on, DITC ignition equipped vehicles.

Your 931.615.113.00 relay is rather expensive, something like $110 - $160, and hard to find. From the posts on the board, and other sources, the 433 906 059 relay is too, a 16A relay, made for two fuel pumps (one primary and one in tank.) So it can handle the current. It does not include the over-limit feature. These relays cost about $18 to $22, at least the generic ones from KAE, their part number 3.300.300, a big difference.

In installing mine and getting my system back to normal, I tested the relay and it works as advertised. It requires the pulse from the ignition and shuts down if the pulse is absent. It doesn't always prime the fuel pump, but seems to usually do so after the car has been off a while, I assume something in the relay itself, related to a capacitor discharging or something along those lines. I'll report back on this if I can discern why it does not always run the pump momentarily.

Did your old relay prime the pump? If so, maybe the replacement you ordered from Pelican is not an exact factory equivalent part, and behaves slightly differently, though it functions reasonably well.

Might as well order the 433 906 059 and see how it works. The cost is reasonable enough. And this way you'll have a spare with you in case your OEM relay gives up. If the newer relay works like you want (runs the pump momentariy,) you can keep your OEM relay as the spare. Either way you are in good shape.

Pelican doesn't list them for the 931 because it is not made for this car, though many owners use them.

It is a good idea to keep a spare relay. Even this rather generic relay was not in stock at any stores in my area. Probably a next day order. Easy to get stuck somewhere without one, thought you could jumper the terminals in the relay block in an emergency, at your own risk.

One item, make sure you turn the key to run, all the way, to make sure the circuit that powers the relay is on...if you stop a bit short, the circuit might not activate.

[Maybe924]

I'll certainly give it a try.
_________________
1981 931 GT (CGT Intercooled)
1985 911 Targa Carrera (Sold)

[Maybe924]

IMPORTANT UPDATE:

I received the alternative Fuel Pump Relay (433 906 059) in the mail today. I popped it in and low and behold it fixed my hard start problem AND my dipping idle problem!

This is a fairly big deal in that I've been spending months trying in vain to diagnose and fix these two issues. I actually had purchased a new fuel pump relay this past summer from Performance Products. It was part no. 931.615.113.00. I was replacing my original fuel pump relay which had finally kicked the bucket. The replacement relay did manage to get the car started but it didn't prime the fuel pump with the key in the on position, it now took 5 cranks to start the engine and then I had a problem with the idle dipping. Thinking the first one might be faulty I purchased another but after receiving and installing another of the 931.615.113.00 relays I was still experiencing the same problems.

What confused the diagnosis is that at the time when the original fuel pump relay bit the dust I was in the process of fixing some vacuum leaks, and a fuel pump issue. I just couldn't tell which came first, or what caused what.

Over the past few months I've checked the cold start valve, the thermo-time switch and the AAV. I've checked and double checked for vacuum leaks. I've tested voltages and replaced my upper charge tube in place of the CGT intercooler... just in case it wasn't getting a good seal.

And then BAM... I pop in this alternative fuel pump relay part no. 433 906 059, and my problems go away. It started before the second turn and my dipping idle is history.

On top of that this fuel pump is only $18 at Pelican Parts.

I wonder how many 931s are running like crap because of their $104 "OEM" fuel pump relay 931.615.113.00???
_________________
1981 931 GT (CGT Intercooled)
1985 911 Targa Carrera (Sold)

[Buwani 931]

Cool, so the(433 906 059) does prime first?

Shawn
_________________
1980 931
That's thirty minutes away. I'll be there in ten.

[stevekat]

Glad this worked out so well for you. My 433 906 059 does not prime every time - would be interested in your experience...mine usually primes if the car has been off a while. I am getting in a spare and shall see if that unit behaves differently in this regard.

Interesting how chasing these problems is a black art.

BTW, can you elaborate on dipping idle? Does it fluctuate up and down, etc. What symptoms?

[Maybe924]

[stevekat]

Does your relay prime every time, ie: if you turn off the car, and then within a few seconds turn the key back to the run position before starting, does it prime again? My car does not prime every single time the key is turned from off to run - my system seems to be contingent on how long the car is off, or some other variable. Would like to get some baseline.

[McGyver]

Regarding to this scheme:

elements:
capacitor on 5 - 1.5uF - in KAE you got 1nF
resistor between 6,7 and 4 - 620k on scheme and 0,6M in KAE

If you know how NE555 work that elements in KAE gives power to fuel pump just for 0,6s. So I think changing this two elements will change time which powers fuel pumps...


So...
Original relay powers fuel pumps about 1sec
KAE makes it for about 0,6sec

I don't know what is original time in 931 relay (I'm not sure that on scheme is correct) but I think we can change it to ~3 to 4 seconds and that will be enough to make good fuel pressure to start.

Does anyone try this way to solve that problem?
_________________
931 82' - 5000km after full engine rebuild

SOLD: 924 81' N/A- with turbo gearbox "dogleg" - great but mysterious car
www.mauser98k.internetdsl.pl - if someone like german rifles (English version avalible)

[morghen]

i knew that ß555 can provide different temporizator intervals ?
_________________
Supercharger and EFI kits
https://www.the924.com

[stevekat]

I think it would be nice to be able to set a custom time for the fuel pump relay to prime the system.

Mine does not prime each time however.
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.