Fuel pump dual relay
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- Posts: 41
- Joined: Tue May 10, 2022 10:51 am
- Your car is a: 1980 Fiat 124 Spider Fuel Injected
Fuel pump dual relay
I haven't looked too far into this relay but from what I can tell, it doesn't work without both connectors in it. I know its failing because the relay clicks very rapidly when I manually actuate the AFM to activate the fuel pump. The engine runs for about a second before running out of pressure and stalling. I hit the dual relay a couple times and tried to manually actuate it again, the clicking became slower and there was more time on in between the pulses. Lo and behold the engine ran a bit longer before stalling because the pump got more power. Now, this relay is gonna end up running me upwards of 130 CAD which is a bit expensive for me, is there any way I can tie this into two separate relays? If anyone has a wiring diagram of this relay or of the car with this system in particular that'd be awesome!
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- Patron 2024
- Posts: 3015
- Joined: Fri Jan 27, 2006 11:45 pm
- Your car is a: 1981 Spider 2000
- Location: Wallingford,CT
Re: Fuel pump dual relay
Have you removed the relays from their cover. to give the circuit a good visual inspection?and tried to manually actuate it again,
There was a resistor on the relay PC board that could over heat and unsolder itself. The manufacturer increased the resistor wattage and cured the issue many years ago.
I have found the female pins in the relays connectors become loose over time especially the small ones. I hold the relay steady and wiggle each wire to see if it causes the relay or fuel pump operation to change. I purchased some male pins to test the friction on the female pins. I use one male pin and insert it into the female pins one at a time to check for defective female pins. It has proven to be worth while test tool.
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- Posts: 41
- Joined: Tue May 10, 2022 10:51 am
- Your car is a: 1980 Fiat 124 Spider Fuel Injected
Re: Fuel pump dual relay
Is there any way to take the cover off without destroying the relay? If not I'll continue on with your other troubleshooting steps which I can't believe I didn't think of myself! Side note, if I was to find the resistor desoldered, do you have a recommendation as to what type of resistor I should replace it with? Wouldn't want this happening again! Before reading your reply I had been thinking that it might be a faulty ground arcing to the chassis, could this be my problem too? As you can probably tell I am just absolutely clueless with this car's electrical system, it wasn't the most innovative design in hindsight lmao.
- focodave
- Patron 2018
- Posts: 704
- Joined: Sat Jun 30, 2012 10:35 am
- Your car is a: 1980 Spider 2000 F.I.
- Location: Fort Collins, CO
Re: Fuel pump dual relay
Here is a link to a wiring diagram for the dual relay (it is from a VW site, but don't let that scare you -- it is the exact same relay and Bosch system that the FIAT uses):
https://ratwell.com/technical/DoubleRelay.html
That write-up does a real good job of explaining it in simple terms.
https://ratwell.com/technical/DoubleRelay.html
That write-up does a real good job of explaining it in simple terms.
1980 Spider 2000 F.I. (my hobby)
1970 MGB GT (my other hobby)
2008 Ford Expedition (daily driver)
2019 Harley-Davidson Electra Glide Standard
2019 Harley-Davidson Iron 883 Sportster
1970 MGB GT (my other hobby)
2008 Ford Expedition (daily driver)
2019 Harley-Davidson Electra Glide Standard
2019 Harley-Davidson Iron 883 Sportster
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- Posts: 41
- Joined: Tue May 10, 2022 10:51 am
- Your car is a: 1980 Fiat 124 Spider Fuel Injected
Re: Fuel pump dual relay
I didn't expect much upon first place of the site but wow it has everything I seem to need! Just from a quick glance of the diagrams shown, I wanna say one relay provides power for the other relay as well, which I think is what lined up with my testing originally, either that or something is wrong with my testing procedure. I'll have a look later tonight, just to circle back to the taking apart the relay, any tips for not rendering it useless upon disassembly?
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- Patron 2024
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- Joined: Fri Jan 27, 2006 11:45 pm
- Your car is a: 1981 Spider 2000
- Location: Wallingford,CT
Re: Fuel pump dual relay
The cover is the rectangle with the mounting tab. The base (the part the pins pass through) snaps into the cover. A seam is usually visible on all sides about 3/16" above the bottom edge. Its a little tricky to release all the small locking tabs but I have opened a number of them. Sliding the base and PC board out of the cover. Sometime the cover is glued to the base but usually not. If it is glued I cut through the seam/glue with an exact knife. I personally have never seen any internal issues with the relays or the components. I have read on various forums that early relays had the overheating issue. I don't know the value of the resistor that was the cause of the problem. So I can't help you there.Is there any way to take the cover off without destroying the relay?
The website Mirafiori.com is a Fiat chat room that has a library available for sire members of Fiat publications. Fiat published a training booklet titled:
Spider 2000 Electrical Diagnostic Manual 1980-1981
This publication would be helpful to you also.
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- Location: San Francisco Bay Area
Re: Fuel pump dual relay
I don't know if this is helpful, but some of the relays that Fiat used tended to get erratic when their internal electrical contacts got worn or corroded. I know this is true for the relay that controls the intermittent wipers, and the symptom is wiper blades that erratically start and stop at odd positions, like right where you are trying to see. But of course.
Anyway, if you do remove the cover of the relay, use some fine emery paper (600 grit or more) to gently clean the internal electrical contacts. Don't bend the tabs that position the contacts or the relay functioning might be affected. Just gently draw the emery paper across the closed contacts to clean them up. Perhaps swirl the paper around a bit so the polish marks are more randomized. If you really want to get serious, you can start with a coarser grit like 400 and then move up to the finer polishing grits like 2000. The goal is a flat and polished contact surface.
-Bryan
Anyway, if you do remove the cover of the relay, use some fine emery paper (600 grit or more) to gently clean the internal electrical contacts. Don't bend the tabs that position the contacts or the relay functioning might be affected. Just gently draw the emery paper across the closed contacts to clean them up. Perhaps swirl the paper around a bit so the polish marks are more randomized. If you really want to get serious, you can start with a coarser grit like 400 and then move up to the finer polishing grits like 2000. The goal is a flat and polished contact surface.
-Bryan
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- Posts: 41
- Joined: Tue May 10, 2022 10:51 am
- Your car is a: 1980 Fiat 124 Spider Fuel Injected
Re: Fuel pump dual relay
I got the relay open and tried to just hold the contact closed so that it wouldn't just erratically click, but that didn't help the problem. I think I'm looking in the wrong place for this issue. I have a feeling it might be something to do with the injection system on the engine, maybe an injector isn't firing or the cold start injector isn't working. I have to check tonight, thanks for the help anyway guys.