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1979 Monza V6 3.2 fuel pump not working

PostPosted: Sun Jul 09, 2017 3:47 pm
by mendez
My fuel delivery recently stopped so I replaced the fuel pump. Electric pump is in
the fuel tank. Fuel pump is still not working so I took out the fuel tank again and tested
the fuel pump. Fuel pump tested out good. I also tested the pump I had originally
removed, it also tested out good. I also changed the fuse with no results.

Re: 1979 Monza V6 3.2 fuel pump not working

PostPosted: Sun Jul 09, 2017 6:22 pm
by Monza Harry
Mendez welcome aboard! Thanx for joining our little piece of H-Body Heaven! There are many threads that deal with these somewhat troubling fuel pump issues, please take some time and peruse them, they will answer many questions. This said the "Search kinda function" isn't the best we all Know! So getting to your question, first as a primer the fuel pump has a safety function, 1970's style the power is routed through the oil pressure switch so that if the engine stalls [or runs out of pressure] say in a collision the fuel will stop. Now those switches are usually pretty reliable, but when they do "GO Bad" the pump is usually the first to know. Also there is a "bypass" for starting that uses the "IGN" terminal on the starter solenoid that will power up the pump, many newer style solenoids no longer have that terminal as "Electronic ign." doesn't need a +12V boost at start, so if a newer starter has been swapped in that could be causing you some problems at start up. So read up, there are many more detailed threads including a few different wiring diagrams. I hope this gets you to some resolution, and check in with us maybe with some "pic's" of your Baby. :th: :D Harry

Re: 1979 Monza V6 3.2 fuel pump not working

PostPosted: Sun Jul 09, 2017 7:04 pm
by mendez
Thanks for the great tips. I will buy the oil sending unit, cheap at O'Reilly’s
I bought my 1979 Monza new in 1979. Is the sending unit located by the oil filter?
Sam

Re: 1979 Monza V6 3.2 fuel pump not working

PostPosted: Sun Jul 09, 2017 7:25 pm
by Monza Harry
I don't ever remember seeing a 3.2L Chevy V6, it is there on the 3.8L Buick towards the front, and ~under the distributor on the SBC [V8] Sorry I can't help with that but others will come along. I wouldn't jump to that conclusion, first if you can find it and reach it, pull it out and test it, that will need a little pressure [air will be good] about 3# IIRC for a Chevy no more than ten though the terminals are marked on the OEM ones and my aftermarket was, I would check to see if all the terminals on the starter have wires and none hanging with nowhere to go [lift it up and look good they could have been tucked way up or even trimmed of so this will need a good look] . If the car has sat for, sometimes as little as a week, there will not be enough fuel in the carb to start, so probably not enough oil pressure while cranking to run the pump so it will not start, a cheat would be to fill the carb through the top vent and try it. If it starts and quits, try a second time to ensure the pump has time enough to fill the lines and some in the bowl, then if it starts you can play detective with a helper, one watches if the light goes out, while the other listens for the pump, [I wouldn't rule out adding a test light to determine if you have power at the pump while running with the dash oil light out] you may have a hard time even with a quiet exhaust as these aren't like the external High Pressure EFI pumps much quieter. Then you should also verify the engine does have oil pressure. I know this sounds like a lot of work but most of this is time only, not more than $3.00 for a squirt of fuel and maybe a test light. You now have an old car and you will need the test light eventually! Harry
Monza Harry added wrote:
Chevy Starter.jpg
Solenoid Connections should look like this one with every terminal used
Chevy Starter.jpg (27.99 KiB) Viewed 502 times

Re: 1979 Monza V6 3.2 fuel pump not working

PostPosted: Sun Jul 09, 2017 9:25 pm
by spencerforhire
I think Harry might be going down the wrong road here; the purple start wire is actually spliced directly to the oil pressure switch, not through the "ign" terminal at the starter solenoid.
download/file.php?id=5152

Re: 1979 Monza V6 3.2 fuel pump not working

PostPosted: Mon Jul 10, 2017 8:25 am
by cosvega76
Here is another thread where this was discussed. I supplied a simplified wiring diagram concerning the fuel pump circuit.

viewtopic.php?f=44&t=41060


Chuck

Re: 1979 Monza V6 3.2 fuel pump not working

PostPosted: Tue Jul 11, 2017 2:03 pm
by mendez
Sorry but where exactly is the oil pressure switch on my 1979 Monza located.

Re: 1979 Monza V6 3.2 fuel pump not working

PostPosted: Sun Jul 16, 2017 6:31 pm
by mendez
Well I replaced the oil pressure switch. NO GO!! My fuel pump is still not running?

Re: 1979 Monza V6 3.2 fuel pump not working

PostPosted: Mon Jul 17, 2017 6:26 am
by spencerforhire
It's a pretty simple circuit; best place to start testing is at the oil pressure switch. You can use a test light or multi-meter. The pink ignition wire should have +12v power when the key is on. The blue pump wire is connected to the purple start wire at rest so the pump will run while you're cranking the engine. Then when the engine is started, oil pressure switches the pump contact over to ignition. If you install a jumper(paper clip, short piece of wire, cotter pin, etc.) between the pink and blue wires and leave the key on, you can then check further along the circuit. Both sides of the fuel pump fuse in the box under the dash should be powered, then you can go to the rear and check right at the connector at the top of the tank. There is also a possibility that the tank has lost it's ground, but that would also make the fuel level gauge inoperable.

Re: 1979 Monza V6 3.2 fuel pump not working

PostPosted: Mon Jul 17, 2017 9:17 am
by mendez
All the connections on the fuse box are live except for the fuel pump connection

Re: 1979 Monza V6 3.2 fuel pump not working

PostPosted: Mon Jul 17, 2017 4:21 pm
by spencerforhire
Fuel pump fuse will only be live while cranking the starter or vehicle running with the pressure switch hooked up. Install jumper, turn key on and check fuse for power. If still no power, problem is between pressure switch and fuse box. if there now is power, problem is along the way from the box to the tank.