black85vette

I need the GM test procedure for 84' fuel pump systemm and the wiring diagram, can anyone help me out please?

mcm95403

The FSM says:

1. Remove the air cleaner and plug THERMAC vacuum port on TBI
2. Remove steel fuel line between the front and rear TBI's Use back-up wrench J-28698 to hold fuel nut on TBI's when removing fuel line.
3. Install fuel pressure gage (they spelled it wrong!) between TBI's. A 9-15 psu gage (TWICE!) such as J-29658 should be used.
4. Start the car and observe fuel pressure reading. It should be 62-90kPa (9-13 psi); if not, refer to charts A-5 or A-6
5. Remove fuel pressure gage (I'm gonna go nuts at this!)
6. Reinstall steel fuel line between TBIs.
7. Start car and check for fuel leaks.
8. Remove plug covering THERMAC vacuum port on TBI and install air cleaner.

Now I have to find those charts.
OK, found them. I'll just post the links to the pics instead of embedding them since they are hi-res:

www.marcmedina.com/84corvettes/techfiles/chart_a-5.JPG
www.marcmedina.com/84corvettes/techfiles/chart_a-6.JPG
www.marcmedina.com/84corvettes/techfiles/fuel_pump_wiring.JPG

mundo

Throw out the '84 fuel pump. Get an '85+ fuel pump. You will have to make a minor wiring connector mod. The pump is in the gas tank. Easy to get to. 4 bolts at the fuel tank inlet hold it. The '84 pump only puts out 19 psi where the '85 puts out 56 psi. The FPR regulates the pressure to 13.4 psi. Anything less and and the '84 CFI car hesitates and sputters off the line. The '84 pump is a weak sister. If it doesn't give a steady 19 psi the FPR can't hold 13.4 psi and you're screwed.

mcm95403

That pretty much covers it.

black85vette

Trying to help someone else with there 84' thats why I ask, thank you for the great info.
Is this a popular upgrade to install the 85 pump? there are no ill effects from this conversion? can anyone chime in on experience with long term results?The 84's owner says he replaced the pump last year and drove less than 20 miles and has lost fuel again so thats why I think we need to verify there are no electrical issues before replacing the pump!

qws

You are right, verify before replacement.
84 fuel pressure should be 9-13 psi. The 84 pump does not put out 19psi. Fuel reg is located on the "rear" tb and can be made adjustable if needed. (free mod)

If you do have to replace the pump then its a good idea to use an 85 or up pump.

Another common problem is also the rubber hose that goes from the pump to the hard line in the tank. Mine split once and needed replacement since it would loose pressure. Or the sock may need replacement if it wasn't replaced with the first pump change.

Troubleshoot, verify then replace.

mundo

I had an '84 and know what I'm talking about. The 85 fuel pump will NOT hurt your car. It will help. The '84 and '85 pumps look the same only difference is the wiring connector. Put in the 85 fuel pump a lot of gremlins will go away such as hesitation and mini-stalls.

qws

I have one to.

I don't believe anyone every stated that it would hurt the car


Agreed... so does all the L98 fuel pumps along with the LT1. Matter of fact that what I use. But I also needed that to get 43 psi.


Not true at all. If you have "gremlins" then your not troublshooting and correctly fixing your problem. Your advice is just feed it more fuel which covers a problem but doesn't solve it.


For the OP- here you'll find ever diagram you'll need for the wiring

http://misterbill.homeip.net/Vette/

black85vette

Thank you all for the great info.