Fuel pump not priming, help needed

[Polyatomic]

Short of the long, I am not getting a signal to the fuel pump, and have no idea why.

I did a recent refresh on my AA2 UK spec. (in USA) including a rebuild of the fuel pump/pickup. Everything tested fine after completion, however, after re-install of the tank into the chassis I am no longer getting signal to the pump, so it does not prime nor powers up the fuel pump when trying to start. Fuses all check out ok now (a 10amp was blown), all the relays test ok, thinking it might be the Hondata tuned ECU. Any suggestions? Might help if there was a wiring diagram, but pretty sure that is non existent

Thanks for any insight
~Chad

[Karl V]

Sounds to me like the immobiliser Chad.

It prevents the fuel pump from priming until the immobiliser fob is presented. Have you checked the wiring in that area?

[Polyatomic]

The immobilizer was my first thought, however, it is engaging. The light flashes repeatedly until the fob is in close proximity, then I hear it click over and the light stops flashing. I assume it’s functional at that point. I will still triple check the wiring. Thx

[Karl V]

Sorry for the dumb question, but do you hold the fob up before switching on the ignition?

I THINK that if you hold the fob up after the ignition is switched on, you've missed the priming stage of the pump. If this happens to me, I usually turn the ignition off and on again to get the pump to prime.

But maybe I'm doing it wrong (?)

[autobackup]

Karl

You are spot on - the fob has to be close to the immobiliser aerial loop before turning on the ignition.

I usually lean in and disarm the immobiliser system while standing outside the car - then I can take my time setting everything up (music/phone etc), before climbing in, and strapping myself down before actually pressing the starter button to start the engine - I have left the ignition on for up to 10 minutes in the past and, providing the ignition hasn't been switch off in the interim, it simply starts!!

[Polyatomic]

I have actually tried both ways, originally I had the key fob on a lanyard attached to the dash and it was working fine. Trying to think of the best way to test it though.

[thomas_fr]

Ok, a few ideas :

- try to power the fuel pump directly (with large gauge wires) from battery, to be sure the pump works
- check that the fuses are all ok (but i think so)
- double check that the MFRU unit (that TRW box on the firewall, near the fuel filter) is correctly plugged in

I would inspect the Honda ECU in the end, it's reliable.
You did not change the ECU, right ?
If you changed it for a Kpro ECU for example, you got a PRB or PRC ECU ? they do not use the same pins for fuel pump relay control.

[Polyatomic]

Good ideas, thanks

-I have powered the fuel pump using the battery alone, it works fine; I even tested everything BEFORE putting the tank back in to be sure. Car ran until a fuel line blew off (Didn't fasten the hose clamp and needed a shower in 93 octane )
-all fuses are fine, minus 4th down on the left (10amp), replaced, no change.
-will triple check the plugs (TRW) box as I was having a challenging time getting the tank back in to position w/o removing the coolant lines which had just replaced and filled with new 50/50 coolant. There is a good chance a wire, or harness got pinched as I was putting the tank back in.

[thomas_fr]

Did you only refurb the car or also upgrade the fuel system ?
On my atom, i did change the fuel system to a 255l/h pump, without changing the wire gauge size : i ended with a blown harness on the fuel system

[Polyatomic]

Did you only refurb the car or also upgrade the fuel system ?
On my atom, i did change the fuel system to a 255l/h pump, without changing the wire gauge size : i ended with a blown harness on the fuel system

Well after purchasing it a couple yrs ago I originally just planned to refresh the hoses and tidy things up w/ a good detail but after getting into it the mod bug bit me on the ass and I started to update most of the car, (OCD) had the black panels painted in a matte finish, cleaned/powder coated the shifter assembly, added all 3.5 lights, including 3rd b-light, installed a pair of Tillett B6 CF seats, fire suppression, CF dash, silicone hoses, changed out the the solid motor mounts, few sensors, dissembled fuel tank, cleaned it out, new gaskets and rebuilt the pickup. The factory told me the Walbro GRJ235 pump was the update version, had planed on purchasing but the original seemed fine. Has 17k miles on it...still need to sort the parking brake out, repack bell cranks, finish flushing all fluids. Also have the clear plexi panels to install -Once on the rd again I’ll probably update the ECU to KPro and do a retune...always open to suggestions.

[Polyatomic]

Oh, I think I might have fixed the issue Thomas; I pulled the TRW box, saw some copper sticking out, sure enough 2 wires were loose. Pulled the pins in the harness, re-crimped, plugged back in and tested..nada. Checked all the plugs and found 2 others loose behind firewall, so pulled them and repeated, tested and Voilà!!! Pump primed, will test w/ fuel tomorrow but that’s gotta be the fix. Loose wires in the harnesses combined w/ me wiggling the tank back into place.

Will update; seriously appreciate you all chiming in, long distance high-five from across the pond!

[Karl V]

Reading your experience / mods on the car, I now feel dumb asking if you've presented the immobiliser fob!

Glad it's heading in the right direction. That engine firing noise will be the sweetest sound ever

[John Scherrer]

Glad it sounds like you fixed it!

In my experience, it's no problem to switch ignition on first, then present the fob.

[thomas_fr]

Perfect if it"s now working !

[Polyatomic]

Thanks for all the suggestions and insight, it’s certainly working now! -A fantastic sound of relief and anticipation... really excited to finished getting her buttoned up and back on the road. I did drink a good 4+ gallons (15 ltrs) to get the pumped primed. I could search this but what is the lowest amount of fuel we can run in these? I know the fuel level sender is less than reliable. Cheers