1987 Interstate fuel relay -

[desertrefugee]

The two grounds I spoke of above are not entirely accurate as it pertains to the illustration below in this fuel pump configuration. Sorry about the confusing information. However, one side is the supply on the other side is the return… the return is not always necessarily ground.

This diagram is fairly indicative of the circuit you’re gonna want to mimic. In this case, the alternator signal is actually coming from the coil. The other side actually will be ground. Or whatever the OEM harness was using. I suspect it’s ground. Haven’t looked.


The pin out/numbering scheme in this diagram is standard across all automotive relays.

 

[Ansimp]

The only problem I have with your relay diagram Darrell is the coil terminals 85 and 86. The 85 terminal as per the Bosch numbering system is the negative trigger and 86 is the positive trigger. As it is a coil you can reverse the connections except when the relay has diode anti spike protection and then it will only work when correctly polarised.

 

[Ansimp]

desertrefugee » Mon Jul 13, 2020 2:09 pm[/url]":1twm7y20]
The two grounds I spoke of above are not entirely accurate as it pertains to the illustration below in this fuel pump configuration. Sorry about the confusing information. However, one side is the supply on the other side is the return… the return is not always necessarily ground.

This diagram is fairly indicative of the circuit you’re gonna want to mimic. In this case, the alternator signal is actually coming from the coil. The other side actually will be ground. Or whatever the OEM harness was using. I suspect it’s ground. Haven’t looked.


The pin out/numbering scheme in this diagram is standard across all automotive relays.

The only problem I have with your relay diagram Darrell is the coil terminals 85 and 86. The 85 terminal as per the Bosch numbering system is the negative trigger and 86 is the positive trigger. As it is a coil you can reverse the connections except when the relay has diode anti spike protection and then it will only work when correctly polarised.

 

[desertrefugee]

Good point Tony. However, the majority of off-the-shelf automotive relays do not incorporate a flyback diode. I am not sure whether the GL1200 harness incorporates one. And I’m too lazy to look. Also not sure if it needs it. While an inductive spike is not a desirable artifact and without researching the inductance involved, I wouldn’t expect a problem in this application.

I suspect that any transients that might be present would be of such short duration that they would be essentially harmless.

All I can say for sure is that my automotive-relay-driven GL1200 fuel pump has been working fine sans diode. For several years!

 

[TheRepoGuy]

Again, the key is finding the right relay...two auto parts stores down and the only 4 prong relays are the ones for flashers, not for “regular” use [emoji21]


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[desertrefugee]

Strange. Every auto parts store around here I’ve seen supplies them. Very common. I would be astonished if your local Napa did not carry them.

 

[TheRepoGuy]

The folks at the local Napa aren’t the brightest cookies in the box around here. I’ll likely end up ordering one and just being done with it honestly


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[pidjones]

Most parts people can only look up on the computer these days. They haven't any real mechanical or dealership experience. I once had to go through three stores to find one that would order me some plain solid-core 7mm spark plug wire without demanding to know what car it went on. Finally found an O'Reilly's with a guy that pulled out a PAPER catalog and ordered some for me to pick up the next morning. They ordered a 100 foot spool, cut off what I wanted, then sent the rest back to the warehouse.

 

[saganaga]

My NAPA seemed really concerned I bought Rotella T4 for a motorcycle.

 

[desertrefugee]

NAPA has always been my go-to auto parts store. When I was a youngster, I can remember that the folks in there ( in NC ) had a depth of knowledge about vehicles and mechanics and freely offered advice. So I sort of became a customer for life. Here in Arizona, they have also moved with the times, but are still a cut above the rest of the crowd. Most of the guys behind the counter are middle-aged and know one end of a screwdriver from another. At least at the one near me.

 

[sledge]

my 86 SE-I quit on me a couple months ago , out on a ride ... i found the trouble was the fuel pump relay , and I also found that almost all the relays in it has the same numbers on them , so I just pulled another relay out, and put it in the Fuel Pump Relay spot ....... fixed it in a second . that way you can ride it while you look for some new Relay's .... thats what I did anyway. good luck