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Mike80911's Avatar
 
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Fuses in place of FP relay is this OK?

I was going over everything on my 86 for the first time this weekend as I have only had the car for about a week. I noticed a wire running from the fuse box to the negative terminal on the battery. The wire was simply stripped and stuck between the post and clamp on the battery so I removed the fuse cover to trace it back and what I found surprised me and I am not sure if it is a good thing or not. The relays for the fuel pumps were removed and replaced with 30 amp blade fuses. I am not really an expert in auto electrical but I did not think replacing a relay with a fuse is acceptable am I right? Do I need to get the relay fittings and replace this mess? Will this cause a problem in the future? I do not understand why someone would go to all of this trouble to do this I know the relays are sometimes unreliable but I usually just keep spares in the glove box. I have included a pic so you can get an idea of what was done. The brown wire taped to the green wire is the one that was connceted to the battery. Also if you notice the wire connectors in the rear of the fuse panel. This would lead me to believe this was not done by a qualified person.
Thanks

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Old 04-15-2013, 05:09 AM
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If you're not comfortable doing electrical work i would take it to a shop.
Some serious hacking there. They fused the fuses WTF.
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Old 04-15-2013, 06:30 AM
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One of the joys of buying and driving old cars is undoing decades of dubious electrical repairs and mods made by previous owners...

You can fix this yourself, no problem. Just buy some adequately rated relays on eBay for about a 1/4 of Porsche OEM and go for it, pretty simple.
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Old 04-15-2013, 06:53 AM
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Thanks for the replies I am sure I can handle fixing this but I will have to find the sockets for the relays. Is there any immediate trouble with having these fuses instead of relays? I will need time to get to this. Why would anyone go through all of this trouble to replace those relays with fuses?
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Old 04-15-2013, 01:06 PM
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There are other relays in the overly complex system that when energized create grounds for those fuel relays to operate. A couple come to mind, such as the yellow one in the rear relay tray, and the overspeed relay under the drivers seat.

I don't know if it's necessarily a bad thing what the PO has done, other than maybe creating some amperage draw or voltage drop issues due to longer wire runs (I know what I'm thinking but not enough to put it into words that make sense). Ordinarily a relay is used to complete an electrical connection that draws significantly more current (such as pumps) vs. the relatively small control current needed to actuate the relay itself.

Anyway, to be safe you should probably replace the relays. But in so doing, you may inadvertantly find out why he wired it that was in the first place!
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Old 04-15-2013, 01:33 PM
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I cant see the back but the fuses are not fused, the power coming from the 30A is fused. Might be a popular 930 fuel pump upgrade, if done right the relays are not taken out of the equation. I did it myself on my car, it keeps power for two pumps from having to go through a single fuse block. If the relays are hacked out an aftermarket would suffice. Looks like there's a couple wire nuts tucked back in there.

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Old 04-15-2013, 01:42 PM
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Mark that is what I was thinking there must be a reason this was done and putting the relays back in maybe opening up a whole new can of worms. Sly those wire nuts appear to be the way he wired the fuses in when he connected them to the wires from the relay connector. At the very least I would like to clean it up remove the wire nuts and solder the connection with shrink tube. If this is acceptable I might just do that instead of putting the relays back.
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Last edited by Mike80911; 04-15-2013 at 03:46 PM..
Old 04-15-2013, 02:45 PM
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Mike
I have four of the relay sockets I just cut from my old wiring harness, you can have them if you want them.
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Old 04-15-2013, 03:02 PM
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Thank you Sly is there still some wire attached to them? I think I need two of them. Are all of the relay sockets the same or are the FP ones specific for those relays? Let me know how much you want for them, how much to ship them to 11360 and how to pay you.
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Last edited by Mike80911; 04-15-2013 at 03:47 PM..
Old 04-15-2013, 03:45 PM
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Yeah theres plenty wire attached and you can have them. Don't think Ill be rewiring one of these cars again any time soon... fire me your contact info and Ill get them out

my reg email is slivan@verizon.net

Tom
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Old 04-15-2013, 03:52 PM
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some people should not be allowed to own a car like this. remember the trunk monkey? when people start to hack into the wiring or doing something else stupid to cars like this, a monkey should pop out of the trunk and whack them on the head with a bat.

look at the WIRE NUTS in the back.

the 930 FP circuit is simple but complicated at the same time becuase there are relays operating relays. my biggest question as to the design is if you are going to use one fuse to run 2 pumps, why bother with 2 relays? this is the big problem. one fuse with 2 pumps drawing a lot of current.

do your FP's run with the key on and the engine off? i am betting they do.
there may be other reasons they did this. it could be the FP's were not working and to fix it, they wired them on all the time.

here is how the FP system works:
lets start with the yellow relay in the engine compartment. that relay is controlled by the switch in the AFM. this relays purpose is to provide ground to the red FP relays to energize them.
this ground comes from the overboost switch on the IC. that ground goes thru the 14 pin connector on the relay baord to the speed realy under the seat. this is your rev limiter. it turns off the FP's at redline, hopefully. from here it goes thru the yellow relay then to the 2 FP relays turning them on. simple right?
the other purpose of the replay under the seat is to cut out the O2 sensor after about 3k RPM.


if you want to fix it back to mostly original, search for threads on splitting the circuit off to 2 fuses and go from there.




i would also look into the green wire and the red/w wire with heat shrink on it.
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88 BMW 325is 200K+ SOLD
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Old 04-16-2013, 03:16 AM
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T77 thank you for the explanation on the system. There are 2 fuses there I think he used one for each relay. The brown/red wire is just taped together not heat shrinked and that is the one I was saying that was stuck between the battery terminal and post. There was not even a connector on it just stripped and stuck between there. I do not think the PO did this himself he really was not very knowledgable and would not even attempt something like this I think it was either done before he got the car or he took it somewhere and they hacked it up.
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Old 04-16-2013, 03:53 AM
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"do your FP's run with the key on and the engine off? i am betting they do.
there may be other reasons they did this. it could be the FP's were not working and to fix it, they wired them on all the time."

If your FPs are running before the engine starts = no good, it is a Safety hazard. Just imaging the case of a wreck, the engine cuts off BUT fuel continues running every where... easy to fix/reverse with an OEM relay. You want the FPs to run only when the engine is running. It might take a couple of more seconds of crank at start but it's money in the bank.
Old 04-16-2013, 06:26 AM
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This might help understand the fuel pump wiring.

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Old 04-16-2013, 07:17 AM
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Yes they do run as soon as the key is turned on to the acc position I know that is not supposed to be but I thought there was a relay in the read that controlled that
Old 04-16-2013, 07:19 AM
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This diagram shows how to bypass (jump) various devices to get home!

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Old 04-16-2013, 07:28 AM
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yes, the green is taped, the red ones behind have heat shrink, i would investigate them too.

wire nuts are very bad.

i look at the 930 system as 2 circuits. one for cutting out the pumps when not running, the yellow relay circuit, and the main circuit.


dont forget, im sure there is a reason they did this. probably the FP's were not working. so when you fix it, you have to take that into account as to why it does not work when you are sure you did everything right.

if your O2 is out of the circuit, i would look into the relay under the seat not working. my brother had a problem with that realy and was able to fix the relay i think. (that was what got me to resarch this circuit).
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86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:
Old 04-16-2013, 08:16 AM
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I love this topic, as it comes up fairly frequently. Those diagrams are gold...everyone should save a copy.
I wouldn't be suprised if Mike's car has had all the nasty gremlin relays and such removed or bypassed. The yellow relay, the overboost sensor, and the overspeed relay to be exact...or any combination of them. In the long run it makes for a more dependable car, but depending on what has been done you could lose the safety feature (pumps off when car stalled) and/or the overboost protection (if the sensor wire has been grounded).
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Old 04-16-2013, 09:40 AM
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I will update the thread and see exactly what is bypassed when I get into the fix. Might not be for a while but will get to it eventually

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Old 04-16-2013, 11:19 AM
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