1985 200SX Loses Fuel Pump Ground

Anyone experienced a problem with losing ground to the fuel pump?

The car will start (sometimes), then run for a few minutes, then die and not restart. When it will not start, there is no ground to the fuel pump. If I ground out the pump manually, the pump runs and the car will run.

As near as I can tell, teh computer controls the grounding of the fuel pump. I have changed the computer, but same results. Any other inputs to the computer that could make it think it should not be running?

Thanks in advance,

Tim Golike

Reply to
Tim Golike
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Then I'd ground the pump and get on with my life! :-)

Many of these cars used variable voltage to the pump to try to make them less noisy. Some used the computer, some had a seperate fuel pump control module. The only problem with grounding the pump is it's a little noisy at idle. Given the age of the car, I'm not sure it's worth the trouble trying to figure out this "problem" when there is a simple cheap solution.

Reply to
Steve T

Wow you spent all the $$$ on a new ECM , did ya ever think to check the relay that controls the fuel pump ?

BTW , relays are only about 18 bucks

Reply to
NissTech

Sheesh! Talk about putting the cart before the horse. The way you troubleshoot things like this is work your way back to the ECM, not start with the ECM.

Reply to
Meat-->Plow

Well given it's very likely on that car the pump IS grounded by the ECM itself with no relay, it might be the best first guess. Again given the age of the car, I'd just ground the pump and get on with life.

Reply to
Steve T

Could be what is actually controlled by the ECM is the B- side of the pump. I've seen that was the case in some US auto manufacturers.

Reply to
Meat-->Plow

Actually many of the nissans of this vintage have the -power/current- for the fuel pump routed THROUGH the ECM. I've seen dozens of mid 80's Z's not run because the power to the fuel pump wasn't being supplied because of burn up traces or bad solder joints in the ECM at the power transistor used for this function. The fuel pump relay only energized for the 1st 20 seconds, then variable voltage was supplied to the pump through the ECM. I can't remember if it was the power or ground that was supplied by the ECM, either way it could be jumped at the ECM or the traces repaired and the problem was solved.

Reply to
Steve T

Thanks to all for your input.

I know many of these cars have fuel pump relays, but apparently not this one. Can not find it listed/described any where in the 1985 model specific shop manual, nor can I find it physically in the car.....

Steve, you seem to be on track about the 20 secs. That is about how long it runs before it dies and will not restart. I am a little hesitant about grounding at the pump. The noise is not an issue. Just not interested in it putting out pressure if I have the key on and the motor not running. My plan is to get an oil pressure sender with dual contacts and ground it through one side. I hope that will get the job done.

Thanks again,

Tim

Reply to
Tim Golike

That should work fine, actually I'd just use a normally closed relay with the coil conected to the present oil switch if you're worried about the pump being on when the engine isn't running.

Just use the leg that is going to the light, which is grounded when there is no pressure. When it sees pressure it will lose ground, the relay coil will turn off which will close the points for the fuel pump to turn on. I'd also tie into the present wiring to the pump so you get the present 20 seconds of running before your added on relay kicks in, will make starting easier.

Reply to
Steve T

Steve,

Thanks for the suggestions! That's the way I'll head.

Tim

Reply to
Tim Golike

I had the exact same problem with my 85 200sx. The problem is the ground point on the pump itself is pretty weak.

You can try and solder it to the pump, but it'll fall off again eventually.

I ended up getting a wrecked pump with a ground that was in better shape, and it worked fine after that.

t
Reply to
disallow

Steve,

I grounded the pump w/o using a relay just to get it running to move it to another garage. Started fine, but no oil pressure. I expect oil pressure is an input to the computer and the that would certainly explain its reluctance to allow the fuel pump to run.....

Plenty of oil in the pan. Take off the filter and nothing comes out. Have not torn into it yet. Any suggestions where to start looking? Plugged pickup? Possible/likely for the pump not to be driven properly? Broken shaft/gears?

Thanks for your help,

Tim Golike

Reply to
Tim Golike

Nope, the computer doesn't get any signal from the oil sender..

Does it have an external pump on the front cover? If so I've seen these lose their prime if they sit long enough though is pretty rare, ussually have to sit with no oil in them for a few weeks to do this. If you have some compressed air you can try putting some light pressure on the crankcase while spinning the engine with the plugs out/filter off and see if it starts pumping. The oil light wasn't on when the pump quit was it? I've never seen a bad oil pump but I have seen the pickups plugged.

Reply to
Steve T

Thanks,

It does have an exernal pump. I kept messing with it and it finally started pumping oil.

I now have it rigged with another oil pressure sender T'd of the main one. Sometimes takes a little cranking to get it started (building up oil pressure?) but runs fine. We'll see how long this lasts... Feel like it's about time to donate it and move on!

Best Regards, Tim Golike

Reply to
Tim Golike

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