xrav22

esham

Yes. The fuse that supplies power to the ECM. On my 90 and 92 it is on the side of the dash (with the door open) on the passenger side behind a triangular plastic cover.

When I was replacing the stereo CDM on my 90 I must have shorted something and caused the ECM fuse to blow. The car would turn over, had spark but would not fire. It would start on starter fluid for a few seconds. The fuel pump would not run.

I then applied 12 volts directly to the fuel pump which caused the fuel pump to run and I had normal fuel pressure but it still wouldn't start. I then checked to see if the fuel injectors were getting power by using a noid light. The noid lights would not light up so I realized it must be the ECM.

I posted for help here and Cliff Harris suggested I check the ECM fuse. Yup, it was the fuse....

Joe C

now, I may be wrong here, but let me throw this out there for the folks leaning toward the ECM (and related fuse). earlier, the OP (maybe in another thread) indicated he applied 12V to pin G of the ALCL diagnostic port and to pin A of the fuel pump relay harness, and maybe even pin B of the oil pressure switch and was not able to activate the fuel pump. those three voltage tests would eliminate the ECM as being suspect - for now. IMO, the problem can only be somewhere from connector C237 (input to the fuse panel), to the (actual) fuel pump ground. since he bench tested fuel pump, we can eliminate the fuel pump, and since he applied 12V to pin A of the FP relay harness, we can also eliminate the relay.

i'm getting a little confused on what exactly what the OP's done, but I would run a continuity check from the fuel pump fuse - the "120" circuit side, to the FP harness connector. to me, that would indicate if the power side of the wiring is good. the only other thing would be the actual "chassis" ground for the FP (circuit ground "150" in the circuit schematic). if both of those checks are good, the problem has to be upstream of the FP fuse to either side of connector C237 (circuit 458 side of the fuse). one simple test would be continuity check from pin A of the relay harness to the "458" side of the FP fuse. we are only dealing with power and ground here - it can't be that difficult to get the pump to turn on. it's either an open voltage circuit, or the fuel pump is not grounded. personally, i'm leaning toward the fuel pump chassis ground -

playsdixie

I have run v to both sides of the fp fuse with no results....I'll let you know today, i'll be working on grounding the pump or finding a broken ground wire....also the continuity checks....I have some broken wires underneath, vss wires and and O2 sensor wires are cut...must have hit something this summer. But this problem has been off and on since summer.....probably happened to me 6 times over the summer, but always started right back up...

playsdixie

here's a revelation, I provided a new ground to the black wire past the connector going into the tank....stretched a wire from the battery to the grey wire, same place....nothing....yet the pump off the tree bench tested ok....wiring inside looks good but now I think there's something wrong with the plastic connector on top of the 9 bolt plate....going to pull it off and check continuity....think i'm getting closer....or the car hates me....can't even hot wire it....

WVZR-1

11/24 I suggested paying close attention to the bulk-head connector and also I believe that you likely needed to use a different connector for the pump OR it had to have been changed previously requiring a cut/splice below bulk-head

playsdixie

No, I bought and installed the unit complete 4-5 years ago....stainless unit from convette central....wiring is complete....only changed the pump once, just now, and the wiring fit perfectly...and,,,, the old pump bench tested good too.....changed it when I couldn't force it on through G on the aldl or pin A on the relay.....can/t see any way to inspect that bulkhead connector, except continuity which i'll be doing shortly...does't look like it comes apart...

Cliff Harris

Try unplugging the oil pressure switch and bridging across the two contacts on the connector. That should connect 12 volts to the fuel pump (comes directly from the battery, so the ignition does not need to be on).

Joe C

OP - have you applied 12V and ground directly the fuel pump connector with the pump mounted in the fuel tank? you might have an issue with the actual contact pins within the connector. something's not making contact. I think you getting close....

playsdixie

THANKS....After all that chasing/tracing wires and circuits around my car, kind of looks like it's going to be in that tank...if I wouldn't keep getting home from work in the dark, I'd get it done.. it's season in Florida, so everybody's busy....I'll let you know as soon I see....again, thanks to all you guys for the input.......

aklim

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If it is in the tank, might as well get a sending unit

playsdixie

probably will have to....that stainless unit I got from corvette central a few years ago looks just like I put it in......shines like new.....not like the factory one I took out....

WVZR-1

I wouldn't think you'll need a tank unit for this. I'd maybe consider getting a 3-pin WeatherPack that fits the tank unit and do diagnostics of the pump still in the tree.

You've got a bunch of torn-up electrical stuff on the car that you don't seem to know how it happened. Maybe rethink all that doesn't work. Related? Who knows.

What brand and part# did you buy from NAPA for the pump? On the CC tank unit was there any script on the pump that you removed? I'm assuming that the sender came with the pump. It might be interesting to know what is included with their sender.

aklim

Diagnostics out of the tank, sure. In tank, I'd want to be ABSOLUTELY SURE that the 3 pin WeatherPack is fuel resistant. I'd get very nervous about current in the tank, low voltage as it may be.

WVZR-1

The WeatherPack is a 10 - 12" pigtail on the tank unit - his mating connector will be 10 - 12" from the tank unit!! If the pump is on the tree and in the tank now he'd have no difficulties with diagnostics OR MAYBE SHOULDN'T have.

I have a couple LT5 2-pump trees here and the ground is actually soldered on the flange, the CC sender I've no idea but without removing it he should be able to do what he needs. If he's removed it already the plan might change!!!

playsdixie

it's going to rain fri nite and sat here, so I'll tell you Sunday....

playsdixie

WVZR-1 was correct....there was something wrong with a wire on the under side of the bulkhead connector.....fixed it,, fired up right away, lots of fuel pressure....thanks to all who helped me through this....I started at the aldl, and relay and worked backwards....should have started at the pump...but in the end, it's running and back to being the tire smoker...thanks to the guys in the forum....wouldn't have this car or be driving it without all the help i've gotten....Paul

Joe C