924Board.org

CabooseSA · Joined: 14 Jul 2011 Posts: 18 Location: Virginia

Hello all,

After identifying and fixing my sparking problem, I discovered that my fuel injectors needed cleaning. Before I removed them, the fuel pressure was perfectly fine. The next day after putting the now-clicking fuel injectors in, I discover that I no longer have fuel pressure. The pump doesn't turn on while cranking whereas it did fine only a day ago. My question is: Is it even possible that the pump goes overnight? Or am I missing something obvious?

Also, at some point a week ago the gas gauge stopped giving a reading. I'm not sure if the two are related but I would guess.

Any ideas?

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

DME or fuel pump relay?

Check the wiring/connectors, unplug and reinstall the relays and see if that makes a difference before ordering parts.
_________________
Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

try jumping the appropriate connectors on the relay panel that accepts the fuel pump relay. If it runs, you know it is the relay or possibly the pulse wire that activates the relay when the engine is cranking or running, and the ignition is functioning.
_________________
"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.

CabooseSA · Joined: 14 Jul 2011 Posts: 18 Location: Virginia

Took out the fuel pump relay. Everything checked out when doing the clark's garage checks. I tried manually operating the relay with the cover off while it was connected so as to connect terminals 30 to 87b which supposedly starts the pump. The pump did not start. Do the relay terminals go directly to the fuel pump? I'd like to try putting 12 Volts across the pump to see if it starts.

lolo451 · Joined: 15 Apr 2010 Posts: 24 Location: Toulouse, FRANCE

i think there is a fuse !
_________________
924turbo S2 1981
alfa 75 (milano) twin spark 1989
fiat 126bis 1990

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

On my 924, I had to clean the connections on the pump (discovered by smacking it with my hand from frustration thinking the pump had locked up) and the ground near the taillights to get it to run consistently.
_________________
Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

When you did the Clark's garage checks, did that include jumping the connectors on the fuse/relay block and running the pump? If so, I think that is a fused circuit. Operating the relay manually should, I believe, actuate the circuit (If your fuel pump runs when jumpering the connectors and not when manually operating the relay, you may wish to look at the contacts on the relay - inside the case.) There is an inexpensive replacement for the Turbo relay, that works fine expect for the rev limiter function (so it is about $20 rather than $130. It also works for N/A's with in-tank and external fuel pumps. I don't have the number off the top of my head, but it has '300' in it I believe. You can search for it on the board.

Good idea to always carry a spare relay. At a minimum a jumper cable for the fuse relay block. I carry both a relay, and a jumper wire that is fused and switched.
_________________
"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.

CabooseSA · Joined: 14 Jul 2011 Posts: 18 Location: Virginia

I could not actually do the jumper on the relay socket because the thing was too inaccessible. What I meant by the checks was that the relay was operating as it should. (Relays clicked open when putting 12 volts on the line.) There was a rattling sound inside before I opened the relay up but whatever it was must have fallen out as the sound is not there anymore. Good to know about the cheaper option. Thanks.

So there is no way the fuel gauge not working is related? There's no feature that disables the pump when fuel is gone to keep it from burning out?

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

With diligence you can get in there. It is a bit of a pain but doable. Create a jumper wire by crimiping on two spade connectors on each end of a wire of appropriate length. If you do not have bare male spades, then strip off the plastic covers of those with them. I've also used a paper clip, however I highly recommend a jumper wire.

If you have certain 924 and 931 vehicles...(not 924S 2.5 or 944 engines)...

A thread for the appropriate relay is:

http://www.924board.org/viewtopic.php?t=27710&highlight=fuel+pump+relay+300

OEM Porsche 931 relay w/rev limiter (expensive:) 931.615.113.00

OEM Porsche realy that works for 931 (without rev limiter) but for dual fuel pumps (16amp:) 433 906 059

Aftermarket affordable part (no rev limiter, but 16amp equivalent:) KAE part number 3.300.300 (may also be same part number from other manfuactuers.)
_________________
"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.

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Steve, I think the OP might have a 2.5.
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

Ah, didn't see a reference in his profile, but since it is the 924S discussion board!? Doh.

I think this occurs because I often don't drop in via browsing forums, but rather checking new posts since last visit lists, and often miss the topic name.

Had a similar bad recently.

Better double the Ginkgo biloba.

Thanks Rasta.
_________________
"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.

masterdave · Joined: 10 Dec 2008 Posts: 183 Location: Harrison NY

I had a similar pump problem and found that it was a bad pump ground. I find that the ground wire from the pump is a little flimsy and small. So i ran a new ground from the pump on some heavier gauge wire up in to the trunk to the grounding point in the middle of the trunk where the light array is grounded. Never had an issue since.
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1988 924s
1978 911SC Targa

CabooseSA · Joined: 14 Jul 2011 Posts: 18 Location: Virginia

I pulled out the relay and there was a rattling sound in it. I opened it up and everything seemed fine, and when I put it back together it stopped rattling. I popped it in the car and TA-DA!
Working porsche!
thanks everybody for the help!

Paul · Posted: Thu Aug 04, 2011 11:18 am Post subject:

Buy a new relay already.....
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

No kidding.
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3