FB RX-7 fuel pump troubleshooting

Two weeks ago I slid off track in my RX-7, and 30 or so seconds later the car died when starved of fuel. I cycled the key and listened for the pump which is a noisy Carter, and couldn't hear it kick on, so once back to the pits I jacked up the car expecting that grass or gravel had knocked the push connectors of the pump, but they were still in place and snug. 

Now that the car is home, I've tested the pump with jumpers and it works, but using my multimeter to test the wiring to the pump behind the driver seat, I'm getting no power to the wires when I bump the key. Does the carbureted FB have a relay or fuel pump fuse somewhere? Or is there maybe a ground near the fuel pump tray I'm not aware of?

My car is an '84, there is a relay with a brass cover behind the driver strut tower stamped "check relay" but I'm not sure what that's for.. wiring is not my realm. Tomorrow morning I'll post a picture of the two relays I THINK could be involved, one of which had dirty prongs which I cleaned to no effect. Pictures of the offending track and hapless driver/mechanic:

And the relay(s) I think might be involved:

Almost certainly there will be a relay somewhere.  Also, I would presume your 30 seconds of running time was while you drained the carb, so you've busted something during your drive through the countryside.

Find a wiring diagram and see about fuse and relay locations.

What year?

Some early FBs have the fuel pump always on with ignition on.

Later FBs (Series 3 for sure, my current S3 was built 09/83 so it is about as early as those get) have a normally closed relay for the fuel pump.  Yes a NC relay.  It is attached to the right side of the steering column area and is controlled by the emissions computer under the passenger floor.  It powers up the relay when it doesn't see a signal coming from the trailing ignition.

Pete. (l33t FS) said:

What year?

 

Some early FBs have the fuel pump always on with ignition on.

Later FBs (Series 3 for sure, my current S3 was built 09/83 so it is about as early as those get) have a normally closed relay for the fuel pump.  Yes a NC relay.  It is attached to the right side of the steering column area and is controlled by the emissions computer under the passenger floor.  It powers up the relay when it doesn't see a signal coming from the trailing ignition.

'84

In reply to Pete. (l33t FS) :

Going to try and add a redundant ground wire today for test purposes, if that doesn't work I'll look for that relay 

Update: I didn't get anywhere by adding a ground wire, and I crawled under the dash looking for the NC relay, but what I have doesn't look like the ones I've seen online, so I talked to a friend who has a bunch of pre-RX-7 rotaries, he says the fuel pump will not get power if one of the ignition modules (Mazda calls them igniters) is bad. They look like this, though I haven't found any in stock under $100 for a used one: https://mazdatrix.com/product/ign-igniter-used-rx7-81-85-style/

My friend some old style GM V8 control modules to work on his stuff, which is the direction I might go if necessary, but first I need to check for spark to make sure this is actually my issue.. One of my teammates in Champcar racing likes to say, "At least aim the parts cannon before you fire it."

Could there be a bad contact in the ignition switch? There is a fuel pump cut relay, there's a 20 amp fuse before it.

In reply to sergio :

Could be, but I'm not positive where that cut relay is, or the 20 amp fuse. Also I would be lying if I said I fully understood that wiring diagram. I'll post pics of the relays I've found so far once I get home.

X-03 is the fuse box under the the dash, the fuse box cover will have all the labels.

dannyp84 said:

In reply to sergio :

Could be, but I'm not positive where that cut relay is, or the 20 amp fuse. Also I would be lying if I said I fully understood that wiring diagram. I'll post pics of the relays I've found so far once I get home.

Here's from the RX7 forum the location of the fuel cut relay. Basically what Pete said. 

It's under the dash on the right hand side where your right knee is all most to the center dash where the radio is.. Just past the front of the dash. It's a 6 pin reply. The connector can be jumpered. I forget the pin numbers. Pin numbers are reference looking at the back of the connector.

In reply to sergio :

this guy ?

Very humble update: it was a friggin fuse.. marked "engine." At the track when I checked fuses it looked fine but upon closer inspection with a flashlight it was indeed busted.. this is another classic example of my brain going straight to more complex issues rather than taking the time to check the little things. Like when I had a broken belt in the tire of my old truck but assumed I needed all new tie rods to cure the wobble I was experiencing. At least I didn't order the used igniter for $135..

Similar story: For a long time on my '82 RX-7 the headlights would only retract when switched to the parking light position, even with the center console switch. I thought there was a short somewhere and spent a long time going over the wiring the diagram, but it turned out to be the fuse marked "TAIL ILLUM". I never checked it because the taillights and every other light was working fine.

Annoying plot twist: Two days ago, after replacing the fuse the car fired right up and fuel pump was working fine, so last night I bolted the fuel pump tray back in place, and went to move the car to my smaller garage, as soon as I turned the key to on the fuse blew again. To try and rule it out, I replaced the fuse after disconnecting the plug to the fuel pump, and it still blew. That fuse is also connected to the emissions system (most of which is deleted) and the charging system. So now I guess I need to go through and look for damaged wiring or loose connectors.. I'm kinda stumped that it worked fine when I first replaced it, with the only change being the fuel pump laying on the floor vs bolted up in place..