Hot fuel pump relay
07-22-2004, 01:47 PM
#2
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Heat indicates resistance, resistance isn't a good thing for relays .... they are essentially a low current controlled "on-off" switch. As relays age, carbon builds up on the contact points.
I suggest that Porsche owners replace relays as an "age" related item rather than waiting for them to stop working. The most important relays to replace are the LH, EZK and fuel pump relays. I haven't heard much about headlamp relays causing problems, but you could "see" problems with those relays too!
I suggest that Porsche owners replace relays as an "age" related item rather than waiting for them to stop working. The most important relays to replace are the LH, EZK and fuel pump relays. I haven't heard much about headlamp relays causing problems, but you could "see" problems with those relays too!
07-22-2004, 06:18 PM
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I replaced my fuel pump relay a month or so ago and stopped having intermittent stalling and hot starting problems. Get a six-pack of them and put them in the glove box.
07-23-2004, 04:30 PM
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Although I'm not sure about the specific parameters of these 2 particular 928 relays, you should check and see whether the horn relay and the fuel-pump relay are actually the same part number. There is generally a substantial difference in the construction and current draw, between intermittent-duty cycle relays and continuous-duty cycle relays. The former are NOT designed to have their coils energized for prolonged periods, and will seriously overheat and soon fail. It would be my assertion that, although the pin-outs are the same, and therefore swapping-to-test, or emergency replacement, would be appropriate, I doubt that the horn relay is suitable for permanent exchange of the fuel-pump relay.
It will come as little surprize that the continuous-duty relay is substantially more expensive than the intermittent-duty unit.
It will come as little surprize that the continuous-duty relay is substantially more expensive than the intermittent-duty unit.
07-23-2004, 04:57 PM
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Originally Posted by BrianG
Although I'm not sure about the specific parameters of these 2 particular 928 relays, you should check and see whether the horn relay and the fuel-pump relay are actually the same part number. There is generally a substantial difference in the construction and current draw, between intermittent-duty cycle relays and continuous-duty cycle relays. The former are NOT designed to have their coils energized for prolonged periods, and will seriously overheat and soon fail. It would be my assertion that, although the pin-outs are the same, and therefore swapping-to-test, or emergency replacement, would be appropriate, I doubt that the horn relay is suitable for permanent exchange of the fuel-pump relay.
It will come as little surprize that the continuous-duty relay is substantially more expensive than the intermittent-duty unit.
It will come as little surprize that the continuous-duty relay is substantially more expensive than the intermittent-duty unit.
- only missing the one critical caveat of Porsche design mentality -" Ve uber design alles!!" 
.The same relay part number 141.951.253.B is specified for the ignition X relay, the defrost, fresh air blower, horns, auto starter relay, fuel pump, back-up lights, and finally, the LH jetronic.
No - a "six - pak" is not enough, got to carry a dozen!
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07-25-2004, 11:17 AM
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I see you guys are talking about the S4 or at least the poster's car is... it may be the case there, but BrianG is correct concerning the earlier cars at least. The fuel pump and horn/foglight type relays have different part numbers. My fuel pump relay was giving me trouble the other day so I replaced it with the horn relay like I had read so many times on this forum... it was great for the first 5 minutes.. car started right up and was driving normal, then after that 5 minutes, the relay started to fail... I pulled it out and noticed it was very hot. I then attempted the foglight relay, and it did the exact same thing (in even a shorter amount of time)... luckily when I put the original fuel pump relay back in, it was done giving me trouble and let me drive home without problems (about a 30 minute drive).
Also for what it's worth, the fuel pump relay is bigger than the others.
Also for what it's worth, the fuel pump relay is bigger than the others.
