fuel pump problem

I killed my battery last night, don't know how, the lights were off. I let the charger sit at 6 amps over night, this morning the batt put out

13.22 volts. I attempted to start the car but the fuel pump didn't pump. I can hear the relay clicking. The PCM and fuel pump relay are both clicking, but the FP relay clicks 3 or 4 times. I checked the voltage at C213(I hink - it's the connector behind the right kick panel that sends power out to the fuel pump) and it's only showing 6.8-7.1 volts when I turn the ignition to start or run. Well, next I applied voltage from the charger to the fuel pump at C213 and the pump turned on. If I pressurize the fuel system manually from there, I can start the car and it runs just fine.

What the heck is going on? I have two ideas, perhaps someone has more...

I'm thinking the battery may be too weak - The fuel pump relay is clicking so much because there is not enough juice to hold it on. Or, does the PCM keep trying to turn it on because the fuel system is not becoming pressurized?

Perhaps I have a ground loop or something somewhere that is preventing proper voltage? I did recently change some wiring.

This is 93 5.0

Thanks, Jim S. '82 Mutant

Reply to
Jim S.
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Reply to
69GT4spdtrac-loc

Nope, it's not the inertia switch. I never put one in. I have a Littelfuse

20A MAXI fuse in it's place.

If it would stop raining I could try a new battery, grrr.

Reply to
Jim S.

The F/P relay may not be fully passing 12 volts. If you checked C213 at the dark green/yellow stripe wire, that is the F/P relay output to the F/P. The next thing to do is check C103 (pink/black stripe) at the F/P relay inside the engine bay. This is the input power feed to the F/P relay. If the reading is similar to C213 @ 6.8-7.1 volts, suspect the battery. If C103 reads 12 volts, with C213 still at 6.8-7.1, replace the F/P relay. However before changing the relay, verify 12 volts @ C103 (red wire) feeding the F/P relay coil. If that is fluctuating (causing the F/P relay to click on/off 3 or 4 times as you mentioned), check up stream to the PCM power relay which supplies 12 volts to the F/P coil and go from there. Also clean, inspect and reseat C103 at the F/P relay for good measure...HTH

-- Mike

93 Cobra
Reply to
Mike R

I did what you suggested. At the fuel pump relay - C103- the red wire shows 12+ volts. The Pk/Bk shows no voltage. My multimeter just scans around. I did a continuity check; no continuity. The Pk/Bk should be Hot All Times. I checked up at Fuse Link D at the starter relay, it's connected and I assume intact.

Could an open ground after C103 be causing my problem? The DG/Y wire is spliced at C213 and going into pin 19 of the PCM. I checked pin 6 from the PCM to G100 by disconnecting it in the engine bay. The relays no longer click.

Or, is it even possible that if something else that goes to G100 is not grounded it could be causing my problem?

Thanks for the help!!

Reply to
Jim S.

First verify 12 volts at the battery side of fuse link D (located at the start relay terminal), which you've probably already done. If ok, the link is open or the wire has opened down stream between the link and C103 PK/BK. There may also be a bad crimp at the PK/BK wire inside C103 connector. You mentioned that you didn't get continuity. If it was between the fuse link and C103 PK/BK, then you've pretty much narrowed it down. In case of an open fuse link, you may first want to check for a short (pinched wire) between C103 PK/BK and chassis. This would prevent a replacement link from blowing again and could also explain the battery drain... Make sense???? HTH

-- Mike

93 Cobra
Reply to
Mike R

Woohoo! Thanks for the help Mike. That assumption I made - that Fuse Link D was intact - well, y'know what they say. Turns out it was blown. I soldered in a new one and everything works fine now :) I didn't bother to check it sooner because I thought those things never blew out.

Thanks again, Jim S. '82 Mutant

Reply to
Jim S.

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