AFM/ Fuel Pump

[Packerz]

Hello all!  I have a 77280 with a “stroker” modified engine.  PO replaced stock Throttle Body (with ZX?/larger intake?)and apparently the AFM (To fit the TB?  current AFB has fuel pump “pins” “bridged” thus creating FP engagement w/ key “ON” rather than mechanical w/ engine and starter.  Before I get “flamed”?..I recognize danger in wreck...this why desire to replace back to starter FP energize!  Can I just unbridge pins and return to factory electrical wiring energize? Replace AFM? Must I replace AFM, and TB, to stock-will all wiring be back to stock, etc.?  Plug and play with stock part(s)?  Thank you, all!

[Zed Head]

You should be able to.  Study how the little arm causes the contact points to close when air pushes the vane open.  Pretty easy to test, unbridge it, turn the key on, and move the vane.  The pump should get power.

Start power is through the relay, not the AFM.  The AFM takes over when the key comes off of Start.

Here are some good pictures.  You might need to recalibrate the AFM if it's been messed with.

http://www.atlanticz.ca/zclub/techtips/afm/index.html

[Packerz]

Thanks Zed!  Is replacing 280Z TB and AFM with ZX models common swap/upgrade?  Why would PO bridge the two pins?  Any good reason, or a requirement, if ZX components used?  If not,  can’t I just unbridgeable the pins and go on down the road?   Thanks again!    Doug

[Zed Head]

No, somebody has been hopping up your engine.  There might be other things besides the TB and AFM.  The fuel pump contact might be bridged because they had low air flow at low RPM and the pump kept losing power.  Might have a vacuum leak.  Might have a big cam that flops the AFM vane around, causing the contact to open and close.

I'd get all of the numbers that you can from the engine and try to figure out what you have.  Get the head number, check the area below the casting to see if the head has been shaved.  See if it's an N42 block or an  F54.  Might have flat tops or dished pistons.

I just looked back at your first post and see "stroker".  So, the PO has probably messed with a lot of things trying to get the stockish EFI to work. Might be quickest to just go to Megasquirt or Haltech or one of the other programmable EFI systems.  Or carbs.

 

Edited June 12, 2020 by Zed Head

[siteunseen]

Here's some info on bigger throttle bodies. I've always read about 240sx TBs on 280s.

https://www.google.com/search?client=ms-android-americamovil-us-revc&ei=LRPkXtafM6LhxgGAlZvwDw&q=240sx+throttle+body+classiczcars.com+&oq=240sx+throttle+body+classiczcars.com+&gs_lcp=ChNtb2JpbGUtZ3dzLXdpei1zZXJwEAwyBQghEKABMgUIIRCgATIFCCEQoAEyBQghEKsCMgUIIRCrAjoECAAQRzoCCAA6BggAEBYQHjoICAAQFhAKEB46BQgAEM0CUKcXWNY1YMdAaABwAXgAgAHIAYgBqAaSAQUwLjQuMZgBAKABAQ&sclient=mobile-gws-wiz-serp

[Packerz]

OK  Yes, stroker has all normal 3.1 mechanical/engine mods also with Stage 2 cam, headers and lightweight flywheel. The car runs and operates perfectly ...just the fuel pump “ON” issue. Don’t understand why the pin bridge And if the ZX AFM requires this bridge to operate FP or a simple unbridge remedy...?  Is there a (Ford) fuel line part that has FP auto-shutoff at engine stop? 
sorry about my lack of knowledge at this last Item/issue to become Regular driver- Fully Safe!  Thanks!!!       Doug

[Zed Head]

7 hours ago, Packerz said:

Hello all!  I have a 77280 with a “stroker” modified engine.  PO replaced stock Throttle Body (with ZX?/larger intake?)and apparently the AFM (To fit the TB?  current AFB has fuel pump “pins” “bridged” thus creating FP engagement w/ key “ON” r

Edit - actually that would be why it's bridged.  Because the 77 plug is expecting the fuel pump contacts.  The easiest way to short the wires is in the AFM itself.  The ZX's used the oil pump switch and two relays to control the pump.   They don't have the switch in the AFM.

Are you sure it's a ZX AFM?

 

Wouldn't be a surprise of the ZX AFM is a turbo AFM.  Maybe it delivers more fuel for the stroker.

You'll just have to cobble somehting together if you want the pump to run differently.  You're well off of the stock system.

 

 

Edited June 13, 2020 by Zed Head

[EuroDat]

I'm not sure I understand the upgrade. Isn't the ZX throttle body butterfly 50mm and smaller than the 280Z? It is certainly smaller for the rubber connection to the AFM. It would not be an upgrade.

Could it be a 280ZX turbo? I don't know the burrerfly size in them, but expect them to be bigger.

The common upgrade in the past was to use the early 240SX (JECS) 60mm throttle body on the early KA24E engine. It had the throttle body position switch in the same position as the 280Z & ZX.

The 280ZX tb was an upgrade for the 180B guys with the L18 engine.

 

[grannyknot]

Here is the KA24DE throttle body, 60 mm at the butterfly.

 

[EuroDat]

Hi Chris,

The throttle body I was meaning was in the KA24E sohc in line six with 12 valves. It was apparantly a bolt-in upgrade. Just swap your tps and go. Well king of.

I'm not sure the KA24DE is the same.

 

[Zed Head]

16 hours ago, Packerz said:

 The car runs and operates perfectly ...just the fuel pump “ON” issue. 

It looks like the PO did a good job of making a variety of parts work well together.  Nothing wrong with that, that's what half the people on the forum are doing.

I think he just needs a way to get the fuel pump to power up only at Start and with the engine running.  Like a normal 280Z.  The 77 fuel pump and EFI relay might already be doing the Start function.  Maybe running a relay off of the alternator charge lamp circuit could do the engine running function.  Like half of the ZX system.

Just brainstorming.  I'd guess that he's just tired of hearing the fuel pump run when he has the key on, besides the safety issue.

[EuroDat]

Could use a 78 280Z oil sender switch to activate a relay and the relay then bridges the two wires in the AFM.