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Discussion Starter #1
Car is a '78 2+2... For the past two years it has been in rebuild mode, currently in the paint shop. Once I reinstalled the rebuilt motor, it started fine everytime. I had a charging issue I was working out which ended up being I had the wrong year brake check warning lamp relay plugged in. Replaced that and solved the charging problems. Then came the starting problems.
The car will start on the first crank, but will die within 10 seconds. Trying to crank the motor will not start it... can crank till the cows come home and sometimes it will start, sometime wont.
I remember (could be wrong) that the fuel pump will energize when the key is in the "on" position. Now it is not doing that. I tested the EFI control relay, did'nt test properly so I went to the salvage yard and got another one (tested correct). Installed it and same problem. Tonight I cleaned up the wiring, soldered the factory crimps going to the EFI relays and still had the same problems. If I remove the plug to the oil pressure switch and turn the key to the "on" position the fuel pump will run, turn the key to start, everything works fine.
I reinstalled the old EFI relay and hooked the oil unit plug back in place, turned the key to "on" and the fuel pump came on. Turned the key to start, car started.
Before with the key in the "on" position there was no voltage to the fuel pump until the car was cranked. Tomorrow I will remove the "S" terminal to the starter and crank the car to see if the pump is operating.
The oil pressure switch is sending to the dash, but could it be busted internally causing the pump not to operate with the key in the "on" position?
I read some posts that the pump will only operate while the engine is cranking, but in the FSM there is a chart (page EF-16) saying with the key "on" the fuel pump is actuated and the relay is on...
Thanks!
John Bracken
 

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Yep, the oil pressure switch mode of operation replaced the AFM fuel pump contact points on later models. No oil pressure, no fuel pump. The FI video from Z therapy covered this quite well. 78's worked off the oil switch? I thought they didn't go to that mode until the 79. I'd try another oil pressure switch.

Kevin
 

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pump should only operate with the engine turning
i have a 78 with a similar problem. when i turn the key in the on position
the pump runs. i have the bosch factory troubleshooting guide on k -jetronic
and still cant figure the **** thing out.

i keep swapping relays/alternators/afm/oil pressure switches and the ****
thing still acts the same. wish i was in your shoes. change a part out and
you get different result.


one thing i have noticed is the relays up by the glove box in the 78 are
right below the windshield leaks. i noticed rust on relays in both my 78 z's
those **** windshield gaskets are all like that unfortunately
 

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John,
I'm not exactly sure on this one cuz I'm familar with 75 and 76.
Isn't there a fuel ignition relay under the dash, passenger side
behind the glove box?. I believe that also switches on/off power
to the fuel pump. Also when replacing the relay did you reattach the relay so its grounded to the chasiss. I believe the relays may or may not work if their not grounded.
Ron
 

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Discussion Starter #5
Thanks guys...

It seemed to fix its self. I followed the test in the FSM, by unhooking the spade connector to the starter. I put the key to on, no fuel pump sound then turned the key to start, and the fuel pump started. Although sometimes when the key was turned to start, the fuel pump did'nt start. May have a bad contact in the ignition switch. When I left the car this evening, it was starting everytime. So far so good. Real test will be monday when the paint shop opens up... Will it start???? Hope so!
 

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Re: Thanks guys...

Guys, i dunno if mabe my car is dif, but we both have EFI....


The fuel pump is supposed to pump when the key hits the on position, its a default for it to build up pressure in the system just incase you just took the gas cap off or sumtin.


If your Fuel pump doesn't start to purr like a kitten when the key hits the on position, check it out.

Matt


Again i might be wrong...diff years may mean diff cars
 

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Re: Thanks guys...

Actually, the pump won't run with the key to on and the engine not running. If it does on your car, it's broke. Period.

It wouldn't be a very good safety circuit if it allowed the fuel pump to spew fuel all over your engine bay after a crash, because your key is on, and the engine had died.

Early FI Z's used the AFM fuel pump cutoff contacts, in conjunction with the FI relay. Pump will run during START mode regardless, but will not run in ON mode if no air is being pulled into the engine.

Later FI Z's used the oil pressure switch and the alternator voltage sense (both of these, not just the oil pressure) to determine if the engine was running or not. If either one were missing, the pump will shut off. Of course, the pump will run in the START mode regardless.

This keeps popping up. Our fuel pumps should not "hum" when the key is turned to ON. If yours does, you should spend some time finding out why, and fix it. The horrible death you prevent could be your own.
 

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Discussion Starter #9
Jetblack, all is well...

on the '82-'83 ZX the fuel pump will run for about 5 sec with the key in the on position. it is a normal operation to build fuel pressure.
 

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Re: Jetblack, all is well...

whew thanks, i thought by what zuber said i was gonna blow up lol....there is that ticking commin from the engine....lolol


Thanks


Matt
 
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