what would cause the fuel pump relay to fail frequently? i'm thinking a bad grounding strap? none of the other relays fuses are going out, except my tail light combo fuse once in a while.


i got my teener back on the road today after over a year, and the damn thing went out. it went out before, right after i installed a new dizzy. any good ideas on where to start looking first?

What in the world are you talking about!? First you say your relay is bad. Then you refer to the fuse. Then you go on to (of all things) a "tailight combo guage". FWIW, the aux air valve shares the fuel pump fuse. My aux air valve developed an internal short causing the pump fuse on the relay board to blow. If your pump fuse intermittantly blows, you might try disconnecting the lead to the aux valve and run the car, although it might be a little tough to start. If you confirm that your aux air valve is bad you can use a 1.8 valve instead since 2.0 valves are gone.

QUOTE (brp914 @ Feb 7 2005, 08:27 PM)

"tailight combo guage". My aux air valve developed an internal short causing the pump fuse on the relay board to blow.

edit: tail light/gauge light FUSE.

and my fuel pump RELAY on the relay board got fried or something, and that's why my fuel pump stopped working. as soon as i replaced the relay, the fuel pump worked fine.

my aar works fine, but that is good to know anyways.

the fuel pump relays do go after 30 years...

Sometimes the relay board is bad...there is someone putting a diagram up in the FAQ area (may be wrong, but its here somewhere)

The diagram shows the circuits inside the board...

I replaced mine when I got it...keep two in my glove box (new ones) and its been fine ever since...just musta been corroded.

Rich

guess i'll just carry some spares and hope for the best. i actually fried the relay right in front of my local kragen auto parts. i quickly found out that they have no idea what an FI relay for a porsche is, and that they have no such part in their database.

QUOTE (mattillac @ Feb 8 2005, 10:27 AM)

guess i'll just carry some spares and hope for the best. i actually fried the relay right in front of my local kragen auto parts. i quickly found out that they have no idea what an FI relay for a porsche is, and that they have no such part in their database.

so are you blowing fuses for you tail lights? if so, sounds like you have an electrical short and it'll keep on happening until you find the problem


the reason Kragens couldn't find "FI relay" is due to the fact that no such thing exists, it's a general/generic (at the time) relay, used for many other applications and vehicles

for certain items such as those, it's not Porsche part, but built by someone else so you might have better luck using the part number on item for the autoparts store to use for a cross referance

Attempting to buy parts for ANYTHING at one of the chain autoparts stores is usually a frustrating effort. They don't generally carry parts of the quality any self respecting shop would use, and, contrary to their frantic in-your-face advertising, threir prices are rarely the lowest. Patronize the listers and shops that support this and other enthusiast lists! That said, the most common use for this general purpose relay is for the headlight motors, the heater blower, and the 2 fuel system relays. If your fuel pump relay fails, you can use the heater blower relay or the HL motor relays. If the relay goes bad but not the fuse for the pump, you have other issues, such as a bad board, dirty or weak contacts, or a short in the AAR circuit. The Cap'n

Most common failure of the aux air valve I have found is that the little power wire that powers it gets shorted to the valve body where the wire enters the valve, the insulation degrades, and it will short, sometimes intermitantly as the wire vibrates. to test, unplug the aux air valve wire, and connect an ohm meter to the wire going to the valve, and to ground. You should see the resistance of the internal coil, if however you got a dead short (zero, or close to zero ohms) you will find it, try to wiggle the valve wire during the test to determine if it is an intermittant thing.

Air valves are pricey, i have been able to save some with this failure by slipping some thin tubing over the wire at the sort point, if too much insultation is gone, it becomes very difficult to repair. Once done with the insulation repair, I use a tie wrap around the valve to secure a loop of the wire, so that if the wire gets pulled, the strain is on the tie wrap, not the wire end that enters the valve.

The valve also could be internally shorted. At any rate, test it with the ohm meter to confirm its goodness or badness. make sure your fuel pump wire is insulated, and has a groment on it were it passes thru the sheet metal to prevent shorts there.

Round relays are still around (no pun intended) but i believe out of production. with some wire, press on connectors, and some of the round bullet connectors, you can rig it up to run the more modern, and common square relays (old BMW's seem to be a great source). Just get the connections right, use the bullet male connector in the relay plate holes, and the 1/4" female press-on connectors on the square relay (use insulated connectors, or heat shrink them) Only need about two enches of wire on each lead. It is tacky, but works, and no-one knows unless they lift your relay plate cover.
However good used round relays can be had, carry at least one spare, or be prepared to use one from the head light motor found in the front trunk under the motors.

QUOTE (Cap'n Krusty @ Feb 8 2005, 10:19 AM)

Attempting to buy parts for ANYTHING at one of the chain autoparts stores is usually a frustrating effort. They don't generally carry parts of the quality any self respecting shop would use, and, contrary to their frantic in-your-face advertising, threir prices are rarely the lowest. Patronize the listers and shops that support this and other enthusiast lists! That said, the most common use for this general purpose relay is for the headlight motors, the heater blower, and the 2 fuel system relays. If your fuel pump relay fails, you can use the heater blower relay or the HL motor relays. If the relay goes bad but not the fuse for the pump, you have other issues, such as a bad board, dirty or weak contacts, or a short in the AAR circuit. The Cap'n

i actually used the blower relay to drive back home. i've tested my aar with an ohm meter and it checked ok. the fuse for the fuel pump isn't going out, just the relay. maybe it's time to rebuild the relay board. i saw a how-to on here somewhere a while ago. first i think i'll replace the wires at the pump and double check my wires eveywhere else.

QUOTE (dmenche914 @ Feb 8 2005, 11:10 AM)

Round relays are still around (no pun intended) but i believe out of production.  with some wire, press on connectors, and some of the round bullet connectors, you can rig it up to run the more modern, and common square relays (old BMW's seem to be a great source).  Just get the connections right, use the bullet male connector in the relay plate holes, and the 1/4" female press-on connectors on the square relay (use insulated connectors, or heat shrink them)  Only need about two enches of wire on each lead.   It is tacky, but works, and no-one knows unless they lift your relay plate cover.  However good used round relays can be had, carry at least one spare, or be prepared to use one from the head light motor found in the front trunk under the motors.

is there a specific square relay that works best for this application? i'd rather use a new relay, not an old one.

i talked to one of the technicians here at my work, and he said that blowing these relays is a pretty common. he mentioned adding another relay in line with the one thats already there. has anyone done this?

QUOTE (dmenche914 @ Feb 8 2005, 11:10 AM)

"Round relays are still around (no pun intended) but i believe out of production. "

Naaaahhhhhh. They're readily available from any of the aftermarket European car parts WDs, and therefore the shops they supply. In fact, the list price has come down a few bucks in the last couple of years. The failure rate is acceptably low, and I have a number of customers with most or all of the original relays in cars as early as 1970. The Cap'n

thanks for the good ideas everyone!

dude take the relay out and inspect the posts taht it plugs into. mine were like rusted to hell. I used some contact cleaner and then some dielectric grease to seal everything in . check that out first b4 tackling the relay board. Took one apart and i almost cried. it was like crappy.

QUOTE (bd1308 @ Feb 8 2005, 02:46 PM)

dude take the relay out and inspect the posts taht it plugs into. mine were like rusted to hell. I used some contact cleaner and then some dielectric grease to seal everything in . check that out first b4 tackling the relay board. Took one apart and i almost cried. it was like crappy.

good idea. i think they're pretty clean because the relay goes in and out easily. i'll take a look anyways. thanks for the idea!

all i have to say is thank GOD for AAA. I was trying to pass a 88 toyota tercel doing like 80 down a freeway getting ready to turn onto another ramp when the relay cuit out. stopped like 100 feet b4 the onramp turnoff thing. It was freaky. had no idea what it was either...to make a long story short, it kept on doing it and then i found out about the rusty part when i was fiddling with the relay....SPARK BRUMMMMM SPARK (nothing) CLICK BRUMMMMM CLICK.....sorta thing. cleaned it out and voila! also see the pic i will post momentarily.

nevermind the pic ...dont have a relay, just take a very thin knife and spread out those little prong things. that seems to help. Just not too far, or it'll blow up in your face. just a little bit.

i would have been scratching my head for a while before i figured out what happened, except i recently installed an in line fuel pressure gauge. it showed me my lack of pressure and i knew where to look right away. that was $30.00 well spent.