ktmrider

Hello,
New guy here with a problem. I own a 77 280z coupe that I Just put a Motor Sports areo kit on and had painted red. Now I can't get it to start. It turns over great but dose not get fuel. Just replaced pump and noticed that I don't have any power to the pump. Checked the fuse box and the "links", all good. Where do I look next?

Thanx for any help you can give. KTM Rider.

Someone I talked to last night suggested that there might be a relay that controlls the fuel pump. Any idea where that might be?
Thanx.

280Z4ME

Did you check the plug behind the passenger seat.mine came lose and killedmy car. Also get under the car and check all connections under there. i had 1 cable that was lose and would short out intermittantly.

ktmrider

Thank you for someplace to look. I have not seen a plug there before but I will go and check right now . Thanx so much! KTM rider

Can't finde a plug behind passenger seat.

ktmrider

Still need help.

theramz

With a voltmeter or line tester, check to see if you have power at the pump. If you have 12 volts there then you have a bad ground. If you don't have power there then you will just have to trace the harness.There is only a fusible link for the efi system.

ktmrider

Thank you guys for the sugestions. The pump is new and dose work. The problem is that there isnt any power to it. I have checked the fusible lins and they are hot. Keep looking I guess...

280Z4ME

Did you pick up the carpet that is behind the passenger seat. They should look like this.

ktmrider

280Z4ME,
When I looked behind the seat I did not relize that the plugs would be that small and that they would be covered by some sort of black foam. They were pluged in but I unpluged and repluged to no avail. But at least now I can start tracing them back to the source. THANX SO MUCH!!!
KTMRIDER

theramz

The 77 280z fuel pump gets power from the "S" terminal on the starter. With the key on you should be able to hear the pump run. If not then it is the fuseable link or wire harness. The '77 does not have a pump relay. Source-Chilton Z and ZX '70-88

Speed

From the 78 Z BooK:

Engine Cranks normally but will not start;

1. Lack of fuel
2. Damaged electronic fuel injection harness or relay
3. Malfunctioning fuel pump.
4. Damaged control unit
5. Seized injector
6. Seized cold start valve
7. Malfunctioning pressure regulator
8. Dirty or clogged fuel pipe.
9. Clogged fuel tank breather pipe.

I think you can rule out 1, 2, 3, 4, 5, 8 & 9. If the car was sitting in a body shop for awhile, I would be tempted to play with the movement of the Air Flow Meter plate, and the cold start valve. Electricty from the water temp. sensor, and AFM provide current to the Fuel Pump relay, which in turns says things are groovey and lets electricty on back to the fuel pump. If these two sensors don't stimulate the fuel pump relay, the relay isn't going to send any electricty to the pump. It may be a loose wire connection, or some corrosion in the wiring harness system. Electrical wiring is my biggest issue with these old Z cars.

Hope this helps!

Speed

Enjoy the Ride

theramz

It makes sense that the pump does have a relay although I couldn't find it in the book. I looked behind the DS kick panel of my parts car and there are three relays above the ecu. The larger rectangular one is probably it. Like SPEED said, the ecu closes the relay when all the other things are correct.

Speed

Uh!,

I think the fuel pump relay is located underneathed the steel plate, (which is underneath the front hood, behind the passenger strut tower and the steel plate is in front of the battery (- located between the battery and passenger front shock tower. If its a 77, all the wires run up underneath this steel plate. Under the steel plate, there is five relays. The steel plate also has the two fusible links attached to the side of it.

Two of the relays are small, square and mounted closest to the ground. They are an A/C relay and a Inhibitor relay. The closest one to the ground is the A/C relay.

The three top relays are the fuel pump relay, which is the longest of the five and is mounted vertically on the steel plate, and has five blades. The relay adjacent to the long horizontal one, and in the middle top position with four blades is the Fuel Pump Relay. The third, but mounted a bit lower than the fuel pump relay on the top, is the electronic fuel injector main relay.

Hope I haven't messed this up? Maybe its the 78 thats mounted underneath the steel plate with the fuse holders? On a 76, the relay is located above the hood release on the drivers side, but your car isn't a 76. ?? Now I'm wondering if its out underneath the plate on a 77?

Speed

BoulderZ

On 78's, at least, it's in that steel box on the right-hand (passenger) side shock tower under the hood. In the factory service manual wiring schematic, it's grouped with all the other items in the box labeled "Relay Bracket". There are five relays there at most. One is the Inhibitor Relay, once is the Air Conditioner Relay, one is the Fuel Pump Control Relay, one is the Electronic Fuel Injection Main Relay, and the one you want, the Fuel Pump Relay.

The fuel pump relay has a four wire plug, and the colored wires going to it are: black, green with blue stripe, green with blue stripe, and white with black stripe.

Here's how it works, more or less (abbreviated from the '78 factory service manual):
Your car's running, alternator's producing current, which closes the logic in the EFI relay (it's really got two relays in it on the schematic), which sends current to the Fuel Pump Relay, closing it and making it send current to the fuel pump. This is supposed to be a safety feature, the idea being that if you run into things, your alternator will stop, which will mean the fuel pump turns off and does not douse your engine compartment in gasoline with the chance of turning a fender bender into a Z barbeque. Personally, I find it annoying because if your alternator goes bad (and they all eventually do), you can't limp to a service station on battery, the car just dies from no fuel. To make it even harder to diagnose: the relay logic is removed from the system when the key is in the start position.

That means that to test your car, you crank it, which hardwires current to the fuel pump, which builds pressure in the lines and it starts and runs. You let off the key to the On position, and now the relay logic is back in play. If the fuel pump relay isn't closed, power to the fuel pump stops, and your pressure starts to drop. On my Z's, it seems it'll start to sputter and die at about 15 psi. This makes sense in that the alternator wouldn't produce enough current to close the relays at cranking rpms, so the Nissan engineers bypassed it. It does seem a bit Rube Goldberg-ish, though, when you're standing in a sub-freezing carport trying to figure out why your car doesn't run.

I was finally able to diagnose an intermittently failing alternator on mine (it would start and run cold, but never start and run if the engine was warm...) by removing the relay block and testing it with a 12 V DC source I got at radio shack for ~$5. Apply the current, and a good relay makes a solid positive click/clunk as it closes. Might take it a second. That'll confirm if your relay(s) is/are any good. I was also able to help narrow it down by putting in an in-line fuel gauge between the filter and the fuel rail (~$25 for a gauge and some brass fittings and a 10 inch section of injector fuel hose). That showed that I had pressure cranking and starting and that it then started to drop off.

Good luck! I agree, the electrical systems on the late S30s can be a pain, but you can always work with them if you've got the schematic and a multimeter (and the promise of a strong, cold drink when you're done doesn't hurt either...).
Dave

ktmrider

Thank you to all of you out there! Iam still working on it . I have Hot wired the pump and now im haveing problems with a couple of the injectors. I believe the old gas has varnished the closed. Iam hopeing some fuel injetor cleaner will solve that. Again... THANK YOU! ktmrider