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malpaslane
Joined: 23 Mar 2008 Posts: 78 Location: wales, uk
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Posted: Wed May 07, 2008 4:58 am Post subject: 931 FUEL PUMP RELAY |
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Hi All, can anyone tell me if the turbo had an uprated fuel pump relay, i bought a new one when i was trying to get the car going, but after only the second short trip out the relay burned out and wouldn,t start the car after i had stopped, all earths have been cleaned and all new fuses fitted,but the relay i have bought is the same as a vw golf gti or standard 924. Are they the same or should the turbo relay be stronger. many thanks Rik.... _________________ 931 1982, PAIN IN THE ARSE,BUT GETTING THERE. 911 1976 2.7. 931 1981 S2(NON RUNNER) ALFA 156 SPORTSWAGON. |
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Smoothie
Joined: 01 Jan 2003 Posts: 8032 Location: DE (the one near MD, PA, NJ)
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Posted: Wed May 07, 2008 11:05 am Post subject: |
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The thing to look at is the relays' amp rating. The earlier 924s up to '78 that got only one fuel pump, also got a lower rated 12A relay. Later cars with 2 fuel pumps (both 924NA and 931) got a higher rated 16A relay. _________________ "..it's made in Germany. You know the Germans always make good stuff."
'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox |
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malpaslane
Joined: 23 Mar 2008 Posts: 78 Location: wales, uk
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Posted: Thu May 08, 2008 5:07 pm Post subject: |
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Hi Smoothie, my relay seems to be the right one, i,ve rang the local dealer and they only came up with one part number for my car (which is the one fitted),but i,ve found a different part number in a part number listing book i,ve got , the one i,ve got fitted is 433 906 059 which dealer lists and the other number i,ve found is 931 615 113 00. Another question i,ve got is about the fuel filter, i,ve put a new one on which is the same one listed for a 944, is this right or not , as again i,ve got a different number listed in a part number listing book and on a porsche mirco cat i have and could the wrong filter cause the relay to blow if the flow isn,t right?. many thanks Rik..... _________________ 931 1982, PAIN IN THE ARSE,BUT GETTING THERE. 911 1976 2.7. 931 1981 S2(NON RUNNER) ALFA 156 SPORTSWAGON. |
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malpaslane
Joined: 23 Mar 2008 Posts: 78 Location: wales, uk
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Posted: Sat May 10, 2008 12:43 am Post subject: |
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This is getting confusing, i,ve had another long telephone call with the dealers today and the garage that are trying to tune my car, first the call to the dealers about the relay, they first said that that relay number for uk turbo models was 433 906 059, then i found the 931 615 113 00 number and rang them again, they then said yes that was the number for the turbo model and now today i,ve rang back to order it ,they,re now saying that 931 615 113 00 is only for the USA and the 059 number is right. Second the garage are saying that the new 059 relay in the car is getting warm and is drawing about 13amps, plus i,ve another post on the board about the fuel pressure that the garage are saying is causing a problem with the tuning, where can i go from here, a bar is best i think... _________________ 931 1982, PAIN IN THE ARSE,BUT GETTING THERE. 911 1976 2.7. 931 1981 S2(NON RUNNER) ALFA 156 SPORTSWAGON. |
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emoore924
Joined: 13 Apr 2004 Posts: 2815
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Posted: Sat May 10, 2008 9:23 am Post subject: |
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This is probably a dumb question but do you have the new fuel filter oriented properly? A lot of folks get it backwards. I wonder if you've got it in 180 from the way it should be and it is somehow blocking the fuel flow thereby overheating the pump...
I can't say that I've heard of someone using a 44 filter on a 24 but I'm no expert on something like that...I'd want to use the factory part. |
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Smoothie
Joined: 01 Jan 2003 Posts: 8032 Location: DE (the one near MD, PA, NJ)
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Posted: Sat May 10, 2008 9:44 am Post subject: |
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The 931.___ relay has a built-in rev limiter and costs >$90. It cuts fuel rather than spark for cars that got catalytic converters (unburnt fuel is not good for cats). UK and other RoW cars got their rev-limiting built into the distributor rotor - that arrangement cuts spark and allows unburnt fuel through the exhaust. _________________ "..it's made in Germany. You know the Germans always make good stuff."
'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox |
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malpaslane
Joined: 23 Mar 2008 Posts: 78 Location: wales, uk
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Posted: Sat May 10, 2008 9:53 pm Post subject: |
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Hi emoore924, filter is on the right way, some parts shops over here list the 931 and 944 fuel filter as the same one so i went with it ,but looking at some part number books i have ,i found that there was a different number for the 931 . The rotor i have in the car isn,t a rev limiter one, i,ve never seen one a uk car before, i,ve only ever seen standard ones. my relay seems to be drawing about 13.5 amps ,so won,t last long ,the last new one lasted about 30 miles and burnt out, so i don,t know what to do about it. many thanks for your help. Rik.... _________________ 931 1982, PAIN IN THE ARSE,BUT GETTING THERE. 911 1976 2.7. 931 1981 S2(NON RUNNER) ALFA 156 SPORTSWAGON. |
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Smoothie
Joined: 01 Jan 2003 Posts: 8032 Location: DE (the one near MD, PA, NJ)
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Posted: Sat May 10, 2008 10:59 pm Post subject: |
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Well, rumour has it that some markets' DITC boxes have built-in rev-limiting, so either that's true and yours is there, or you'd also use the 931.___ relay.
The 433.___ and 931.___ relays are 16A. The single-pump 12A one for the older cars starts with 477.___ - http://www.924board.org/viewtopic.php?t=10360
Possibly a fuel pump problem overheating the relay? A few other items are powered through the relay - the AAV, WUR, (and the thermo-time switch?).
Does the fuel pump get too hot to touch?
I've also heard of FP relays that have the built-in fuse, overheating to the point of melting.. _________________ "..it's made in Germany. You know the Germans always make good stuff."
'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox |
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malpaslane
Joined: 23 Mar 2008 Posts: 78 Location: wales, uk
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Posted: Sun May 11, 2008 4:46 pm Post subject: |
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Thanks Smoothie, you might be right about the fuel pump as at the moment the car also has a pressure problem, where when the gauges are on it the pressure goes up and down so the garage can,t set my mixture. maybe the two problems are related, i must admit i did buy the cheaper larger pump you can buy,instead of the smaller bosch one which is fitted to the turbos when i first got the car up and running. Do you think this could be causing both my problems. many thanks Rik... _________________ 931 1982, PAIN IN THE ARSE,BUT GETTING THERE. 911 1976 2.7. 931 1981 S2(NON RUNNER) ALFA 156 SPORTSWAGON. |
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Smoothie
Joined: 01 Jan 2003 Posts: 8032 Location: DE (the one near MD, PA, NJ)
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Posted: Mon May 12, 2008 12:06 am Post subject: |
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Yes.
Varying system pressure is a sign of a pump problem (, but of course it's a problem that could also be caused by weak-wiring/flakey-connections to/from either the pump or the relay as well).
How's the charging system? - steady voltage being produced? _________________ "..it's made in Germany. You know the Germans always make good stuff."
'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox |
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malpaslane
Joined: 23 Mar 2008 Posts: 78 Location: wales, uk
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Posted: Mon May 12, 2008 3:13 am Post subject: |
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The charging system has been playing up since i got the car going, at first it was fine ,but once i,d had it running for awhile the volts went down below 12 volts , i had fitted a new belt ,so checked to see if it was the right tension and it wasn,t far away, so i left it as it was. The next day i started the car and the volts were back up to what they should be,but the next time they were back down, so i retensioned the belt and the volts stayed at just over 12v on the gauge, so the charging system has been moving around abit , could this be the problem? _________________ 931 1982, PAIN IN THE ARSE,BUT GETTING THERE. 911 1976 2.7. 931 1981 S2(NON RUNNER) ALFA 156 SPORTSWAGON. |
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Rasta Monsta
Joined: 12 Jul 2006 Posts: 11723 Location: PacNW
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Posted: Mon May 12, 2008 4:20 am Post subject: |
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Check it with a separate volt meter across the battery and verify the reading on your cockpit gauge. . .but just over 12 is no good. _________________ Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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malpaslane
Joined: 23 Mar 2008 Posts: 78 Location: wales, uk
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Posted: Mon May 12, 2008 5:14 am Post subject: |
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so if the alternator isn,t charging as it should ,this would cause a pressure problem because the pump isn,t getting a steady supply of volts. _________________ 931 1982, PAIN IN THE ARSE,BUT GETTING THERE. 911 1976 2.7. 931 1981 S2(NON RUNNER) ALFA 156 SPORTSWAGON. |
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Paul
Joined: 02 Nov 2002 Posts: 9491 Location: Southeast Wisconsin
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Posted: Mon May 12, 2008 6:23 am Post subject: |
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It's as simple as Ohm's Law. For a steady load (the fuel pumps) as the voltage goes down the current (amps) goes up. So yes low voltage can toast wiring, relays, and even the pumps. _________________ 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. |
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RC
Joined: 25 Mar 2007 Posts: 2636 Location: Australia
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Posted: Mon May 12, 2008 9:37 am Post subject: |
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Paul wrote: | It's as simple as Ohm's Law. For a steady load (the fuel pumps) as the voltage goes down the current (amps) goes up. So yes low voltage can toast wiring, relays, and even the pumps. |
Sorry Paul but that is only true if the power (wattage) is constant, since W=V x A.
For a given voltage the current (A) drawn depends on the resistance of the load. Although the fuel pump has an inductive component the DC is calculated using ohm`s law. Generally the alternator output is 13.8 - 14.2 V. Say 14V for this example. If the pump draws 8 A (IIRC), the resistance = 1.75 ohm. (R=V/A, 1.75= 14/8 ) The power is 14V x 8A = 112W.
Now if the supply voltage is 12V, the resistance remains 1.75 ohm, the current drawn is A = V/R or 12/1.75 = 6.86 A. Power is now 82W. See the difference, only 73% of the power at 14V.
Possibly why the pump may be under performing, however the Bosch rating may be at 12V anyway and the pump must obviously work at battery voltage or the engine would never start. IMO if the pump is OK it shouldn`t be a problem though.
Roger |
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