So speaking of fuel pump relays....

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milehighXR
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So speaking of fuel pump relays....

Post by milehighXR »

If you've seen the last post in my "yikes" thread, you'll remember that I came to the conclusion that my fuel pump relay was NFG, or at least not up to the task of supplying fuel reliably anymore. I've been working to get my XR to pass smog for a minute(not because of a lack of skill, or knowledge, or willingness to ask dumb questions when my old brain goes smooth), but more due to other things(work, honey do list, bad back/work comp etc...) getting in the way. I've finally been able to put a semi reasonable amount of time to the cause over the last few weekends. As I have been working on it I had an issue with no start on a couple of occasions. I gave it no thought as I was able to get the car to start and run. Last weekend, I actually had to go thru the flow chart to diagnose the no start as she simply wouldn't start. Ended up replacing the fuel pump relay with the headlamp relay as they are the same 12v 40A rating, and pins.

Once that was done she ran great. Best idle ever glass smooth. Never seen her idle like that ever. Continued working the other issue of not being able to pass smog, and got to the EGR valve leaking(thats another thread on TF). Today as I was verifying the EGR fix, I noticed we're back to the old idling like poop, and miss fires(for lack of better term) etc... WTF over. I even got to a point where KOER I had no codes related to smog(I'm running an 8UA with big vam). Check continuous codes one last time, cuz "hey no 42 while KOER I can go to smog now :mrgreen: ", and BAM code 42 :banghead Did not recheck.

Found my super secret stash of Merkur relays(so secret I couldn't find it last weekend when I wanted the relay :roll: ). I found several spare relays that match the ones in my car now( I assume OEM, Ford numbers, I've never replaced them since I bought the car in 93, dunno about PO). I also found several other relays that are the same spec(12v 40A, and pin out). But they are different. My stock relays are metal encased 12v 40A P/N 81AG14N089CA. I have some yellow plastic encased relays that are the same ford P/N. I also have some red plastic encased relays Ford P/N 85BG6911AA. I also have some purple plastic encased relays Ford P/N 85GG2M036AA. I also have one 12v 40A relay with the same pinouts, however the pins are numbered differently, and it indicates a 1993 model year based on 93 prefix, dunno where this came from, a Scorpio that was repaired? My relay stash was amassed from various cars that I parted or form other parts I picked up along the way, all from Merkurs.

After the cars performance in the garage today, and the diagnostics for code 42 pointing towards fueling issues, I am suspect that the headlamp relay I swapped last weekend is also not up to the task of supplying fuel consistently. I do have a few more of the exact look relay that came in my car as spares. Though they are also the same age, and assuming(oh dear here go....) that the other relays are updates of the metal encased one, there must've been a reason to update the relay. Should I swap the 93 relay and see if I can "keep the smoke in it", or maybe the purple relay? Or just go buy one? Or is my socket in the fuse panel not tight anymore? If that's the case whats the fix?

I'm at a point right now where I am tempted to make a big honkin jumper to force the fuel pumps on and see how it performs during KOER. But that feels like a bad plan... That could isolate the fuse panel, maybe as long as the jumper doesn't force the socket further open :roll:
Johnny


1 86 XR aka Naomi- my first love, now project car
1 14 black Fiesta SE aka Fiona- my new DD

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thesameguy
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Re: So speaking of fuel pump relays....

Post by thesameguy »

My XR has a problem with the fuel pump relay SOCKET. The terminals are not properly held in place by the plastic and they will not properly engage the FP relay unless I lift the panel up and physically push them into place. If I remove the relay and reconnect it, it will be broken again.

The XR uses non-standard Bosch-style relays. I feel like this may have been an early German thing as I recall my '84 BMW had similar relays but my '86 did not. My memory is foggy. On the "normal" relay the 85/86 terminals and the 30/87 terminals are opposite each other, but the Ford relay is different. If you use a generic relay, it won't work. I'm sure Ford did not continue using this wonky layout for long.

You definitely have to look at the terminals (and hopefully the diagram on the relay) to be sure you've got the right one. On that '86 BMW, someone had put the wrong relay in so that with every key cycle the pump would prime, but the relay was in the wrong position when the key was in Run and the fuel pump was disabled. So it would start and run for a second off that initial prime, but then die. The jackass I'd bought it from had put a switch under the dash to force the pump on. :/

When the car is running (poorly), is fuel pressure good? You can definitely just run the pump through a switch for testing. Fuel pumps only draw like 5a or so, not much. I guess maybe more if you still have the dual pump. A Walbro 255 at full tilt uses about 9a (assuming 70psi in the rail, or 25psi of boost)
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milehighXR
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Re: So speaking of fuel pump relays....

Post by milehighXR »

Yeah I kinda figured I need to fiddle with the socket, or something like that. That'll be this weekends project.

Has anyone found a permanent fix for this issue? Or is it time to look for an aftermarket fuse box/ relay panel kit.
Johnny


1 86 XR aka Naomi- my first love, now project car
1 14 black Fiesta SE aka Fiona- my new DD

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Re: So speaking of fuel pump relays....

Post by thesameguy »

I keep thinking about rebuilding the thing, but it's so cramped I've been hesitating until there is a legitimate need. The good news is that everything in there is pretty straightforward, and once could save a lot of space using ATM fuses and mini ISO relays. Not that space is at a premium, but if the whole thing was smaller putting it back would be easier. :)

Edit: I'd also considered relocating it under the dashboard. I've used this in other places:

https://www.waytekwire.com/item/45999/L ... ini-Power/

I don't think one would be enough to do the XR, but it's quite small so maybe two would get the job done.
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milehighXR
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Re: So speaking of fuel pump relays....

Post by milehighXR »

That looks like a fuse panel only? Does that take relays too?

Like I said, this weekends project is gonna be figuring out just what is going on. Once I get past that, I'll determine what to do for the final fix. I do Like the idea of getting the fuse/relay panel into the car, but I also know what a pita it's gonna be. I once pulled the entire wire harness from a Scorpio I parted out, and it was not fun in the least.
Johnny


1 86 XR aka Naomi- my first love, now project car
1 14 black Fiesta SE aka Fiona- my new DD

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Re: So speaking of fuel pump relays....

Post by thesameguy »

ATM fuses and mini ISO relays use the same terminals and spacing so a panel that can take one can take the other... Six positions is a relay, two is a fuse.
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Re: So speaking of fuel pump relays....

Post by andyofcolumbusmerkur »

They switched from the metal relay to the yellow plastic relay. I still have a metal one behind the dash on the 86 car. Still working fine after all these years. Under the hood I made a dot with a sharpie marker on the forward most area of each relay. So I can pull them out and put them back quickly. I used a shop vac to suck out any junk that got down in there and visually inspected everything. Sure you can swap a different yellow relay doesn't make a difference. Sure you can bend the prongs a little to make a tight connection if you think it is loose. I may try a small dab of something like Kopr-Kote next time I do this after others on here have recommended it.
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