projexladen

Hello everyone!
I have an 87 NA that is now failing to start. No fuel is getting to the engine. I replaced the fuel filter, no change.
I haven't yet diagnosed the wires to the fuel pump, but relay, fuse links and fuses seem to be ok.
Before going further, I will confirm power is getting to the fuel pump. If it isn't, I'll find out why.

My quick question, I have an 87 T2 shell with fuel tank and pump, and am wondering if I could use the T2 pump in my NA?
I've researched a little and saw the pumps have different part numbers, but thought I'd ask you guys if swap could be done...
Thanks!

RotaryRocket88

iTrader: (7)

The pumps are the same physical size/shape, but the TII pump will flow much more. You can swap them for testing purposes, but it'd be best to stick to an NA pump in the long run. There's really no need to extra flow on most NAs, and you'll likely see a small dip in fuel economy.

Pump flow: https://www.rx7club.com/showthread.p...=1#post9154530

projexladen

Wow, thanks for the very informative link!
After pondering this for a little while, I wonder, would it be possible to regulate voltage going to the TII pump, step it down just slightly, say to 11 or 11.5V, to get the flow rate to be near that of the stock NA pump? Or would that damage the pump...

I'm glad the TII pump will help for troubleshooting. Unfortunately, I haven't been able to get to it yet, with other things that keep coming up.

Thanks again!

RotaryRocket88

iTrader: (7)

S4 TIIs and all S5s used a resistor/relay setup to switch fuel pump voltage down to 9v at idle. S4 NAs don't have this system, and it is generally something people don't want on the car when chasing power goals (potential failure point that can lean out the mixture). You could rig one up if you really wanted to, but in my experience the additional flow at low pressures only has a marginal effect on fuel pressure. My car has an OEM FD fuel pump (which is a step up from a TII pump), and idle fuel pressure is only about 1 psi above the stock spec.

projexladen

Sounds like it'd be a fair amount of work, to install something that could later be a problem. Something like that would probably be useful for the hyper-milers out there...

I swapped the pumps, to no success. I am getting 12 volts at the harness connection, and checked all the wires to the fuel pump, very little to no resistance in them, and ground wire is good (was hoping for a free easy fix, no dice).
Unless there's something else to it, looks like I have not one, but, two, dead fuel pumps...

RotaryRocket88

iTrader: (7)

It may be worth doing a quick bench test on both pumps. Attach some wire to both terminals, and touch them to a car battery. It just seems unlikely (but possible) to me that both would be dead.

And just in case, be sure you're jumping the fuel pump test connector (yellow 2-wire plug on passenger strut tower) and turning the key to 'ON' to test the pumps. Alternatively, you can prop the AFM door open to get power to the pump (w/ key 'ON').

projexladen

It seems kinda odd to me too. Found a clue today, when disassembling the parts car, another fuel pump. it was in a bag with a new seat gasket, hose, and two hose clamps. Looks like someone may have been planning to change the fuel pump.
The bag had been opened, and the pump was scratched up a little bit, but was clean. I couldn't see any model numbers on it. The inlet port looked fine. I can't be sure what it's story is, so I plan to bench test it and the other two.
I have to jump power from a battery to open the moonroof anyway, so it won't be much extra work to test them out.

Thanks for that suggestion, I'll try it. I didn't realize there was a fuel pump test connector.
I was testing for voltage at the harness connector the pump's wires attach to, on the driver strut tower.

Also, have you ever a pump whose seat gasket looks melted? The one on the assembly from the parts car looks like it. I've done a few fuel pumps, never seen that...