84 starter problem

[pete315]

hello. new to this site. I just started working on a 84 Vette that was left at my friends body shop. has not run for a couple of years. he pulled it into lot and he thought starter went so it sat. car only has 64K on the clock. I pulled the starter today and went to bench test it. starter works fine. put starter back in car, I get nothing, not even a click. I again dropped the starter but left wires hooked up. with a test light, I get a bright light when I put test light lead on big middle terminal with the 3 wire connections. I get no light on the start terminal. (So far things look normal). when I turn the key all the way to the start position, my test light on the start terminal lights up but only with half the brightness. if I jump the main terminal with the start terminal with a screw driver, starter works. question- why am I only getting half the voltage to that start terminal when I turn key? I actually ran a wire from the start terminal to another battery and car cranked over with no problem. with spray start, car started right up but died shortly afterwards. getting no gas. guage says full but I think guage is wrong. does this year Vette have an electric or mechanical fuel pump? I'm thinking of disconnecting the gas line by fuel filter and sticking a hose in a gas can to see if I get gas. any help appreciated.

 

[Schrade]

Welcome onto the boards there...

Great job doin' diags - especially jumpin the solenoid. Most folks would have bought a starter, battery, alternator, car, etc, before diags

So the external battery gets it spinnin' every time?

If so, I'm guessin' battery ground terminal. Check that, then get to the fuel pump pressure. can you hear the pump prime the rails when you turn the key?

edit:
I'm just seein' how you wanna' pull gas from a can. Ain't gonna' happen; the pump is in the tank. Can you hear it prime the rails?

 

[pete315]

thought the pump was up front. yeap, my plan removing the line from filter will not work. I will have to listen to see if pump is working. do you know the fuse # so I can check that first? there is no owners manual in car.

 

[Schrade]

Fuse panel schematic is coded on a sticker inside the fuse panel cover.

I think almost all fuel injected vehicles make pump noise when you turn the key and you can hear it...

Pullin' fuel will work on carb'ed cars with cam-drive pumps or electrics - did it once for diagnostics on a CJ-7.

Fuel pressure is really important - something you gotta' know and it will help lead you to MANY problems.

 

[pete315]

will check out fuel pump. stil have to find out about only get half the voltage to the start terminal on the starter.

 

[geekinavette]

Yep fuel pump is inside the tank...and yep if the ambient noise level is very low you should easily be able to hear the pump run for a couple of seconds when you turn the key on (wait 15 seconds at least between tests). Now of course IF it is running that doesn't mean its making enough pressure...at that point a FP test would be next. The fuel pump fuse is at the bottom right corner of the fuse panel...labeled "FP". If the pump is not running, in addition to the fuse there is also a fuel pump relay mounted on the driver's side of the firewall.

The starter...I would use a digital voltmeter, lights are nice for quick testing, but don't give an actual voltage. Comparing voltage at the battery vs. voltage at the starter can provide clues. Obviously the light is good enough to determine that there is a significant voltage drop through the start switch circuit...just a matter of tracing and finding it. I don't suspect a grounding issue (at least for this particular issue) since (I'm assuming) that you used the same ground location at both testing points and they show a different voltage.

If you need/want '84 wiring diagrams...find 'em here: misterbill.homeip.net - /vette/wiring/

 

[pete315]

I also don't think there is a ground issue. I actually took a jumper cables and grounded starter directly to the frame, still had no change. I know there should be 12 volts at the main terminal at starter cause it's a direct line from battery to starter. my question is, how many volts should be going to the start terminal when key is turned to the start position. I'm guessing by the brightness of the bulb that it's only getting 6 volts. when I apply 12 volts, the starter works.

 

[geekinavette]

You should see full battery voltage.

Here's a wiring diagram of the starter circuit:

You have the ignition switch, neutral/clutch safety switch, and the anti-theft module that the signal has to go through. Any one of those, or connections (firewall bulkheads...etc) could be the problem.