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'83 380sec Fuel Pump Relay - 6 pin vs. 7 pin?

5K views 10 replies 4 participants last post by  liammarsh 
#1 ·
So I've been trying to diagnose my hard-start issue and there was a test to check your fuel accumulator by putting the car in D and turning the key to run the fuel pump.

I tried various tests, but in no case could I get the fuel pump to run prior to starting the car. So I went to take a look at my Fuel Pump Relay. Relay in place is clearly a used junkyard part with 6 pins. Pulling it out, I noticed that there are 7 active pins in my fuel pump relay socket.

Ok, so an online search shows both a 7pin and 6pin relay are available, the 7 pin says "with kickdown". Interestingly, my kickdown switch on my pedal doesn't work - not sure if this is related or not.

So two questions - what's the difference between the 6 and 7 pin fuel pump relay.

7 PIN PN# 0015455305
6 PIN PN# 0015450605

Both show in the Mercedes catalog, but RockAuto says the 6-pin is for 380SL/SEL

And question 2 - is there a procedure to get the fuel pump to run prior to starting with the car, or test using jumper leads with the relay?
 
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#2 ·
The "get ya home" method when a relay goes south or to pump the tank dry is to jumper 7 and 8 in the relay socket, don't forget to pull the jumper wire when ya park and shut down
 
#3 · (Edited)
Again, putting a jumper wire in sockets 7 and 8 should get the pumps running but as I said the wire needs to be removed when you get where you are going. If you have a bad FPR you'll need to get a new one, I was told that they are available at the dealer for about 30 bucks (this is what I was told also)

Answering the reply that was deleted here
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Thanks

Just checked. Neither Pin 6 or Pin 7 have power in my application.

Pin 8 has power with the engine off
Pin 10 adds power with the key in the On position.

Interestingly, Pin 6 is the pin that does not get used with the 6-pin relay that is in the car.

Any other suggestions?
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#4 · (Edited)
I deleted my response because my reading comprehension is bad and I jumped 6 <-> 7 instead of 8 <-> 7. :(

I'll try 7-8 next time :)

Does anyone have the actual wiring diagram for each of the pins? Again, in my car, Pin 6 was not used so I'm curious if that is for the trans kickdown since mine isn't working (I'm guessing it is)
 
#5 ·
7 <-> 8 works, and I confirmed with the relay that it also works (for a second) right when I hit the key. So relay works (I assumed it did)

Now I have a new problem - I think my hot-start problem is flooding related. When I left the relay on for a few seconds to "prime" the system (my assumption was the fuel accumulator was not holding pressure hence the hard starts), I now believe the problem is that I'm flooding the car.

New post for a new problem.
 
#6 ·
Ok, normally if everything is working as it should when you turn the key and the ignition lights up the pumps will run for a couple of seconds to charge the lines. The accumulator helps to hold pressure on the line as well, the times I let the SE sit for a couple of weeks or longer I'd have to "prime" it by cycling the pump two or three times then it was an instant start. I have yet to have any problem with Ursula the Coupe, she'll spin over a couple of times and light right off (if that isn't "normal" I'm good with it as I know the oil is pumping through before she fires off.

I have no ideas on your hot start issue, in theory (my understanding) the pumps won't start back til the engine is actually running

If you would, I hate scrolling, edit your profile on "UserCP" and fill in your car, I do good to remember mine
 
#8 ·
Dunno that either, the FPR in the SE went bad suddenly (and something in it controls the A/C compressor as well, this was a 6 cylinder car btw) so, went on a quest to get a replacement and a couple of spares from the yards, problem solved. I have two spares for Ursula as well as the one she's running with. There are several other items that as I find them will be added to my spares box that rides in the boot
 
#10 ·
You're almost certainly right - I'm just curious why. Seems super strange is all.

Does anyone have a wiring diagram for the FPR socket? I'm still curious what each of the pins do, and the result of not having Pin 6 connected in my application.
 
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