Hey all,
I'm pretty sure my fuel pump is dead (ugh) but I wanted to run the situation by everyone first before I did anything about it. My car has been having difficult starts for awhile now. For both this and another reason I had the PCM and the prom ('93 Z28) replaced and this had little or no effect on the problem. So fast forward to the other day...I go to start it and I get the starter sound and that's about it...and there may have been some smoke coming in through the vents but my friend who was in the car wasn't so sure. So anyway, now when I turn on the car, I get no fuel pump noise at all. This would seem to indicate a pump problem but I also want to check the fuse or relay that controls the pump because I'd rather avoid spending 200 bucks when I didn't have to. The starter seems to turn ok. My car has been sitting quiet and still for like 2 weeks now! Please help!! hehe


Summary of my drivel:
-Do you think this situation really describes a dead fuel pump?
-Where is the fuse/relay for the pump?
-How much should I pay for an AC Delco pump? (they want 250 at the local shop)

Thanks all.

 

Disconnect the fuel line that goes into the fuel filter. Have someone turn the ignition on....if fuel comes out, you've eliminated one possibility.

If you don't know where the fuel filter and lines are...they run on the drivers side of the frame rail.

 

Never heard of that, but I guess it would work. If you don't want to get sprayed with fuel, though, just hook up a fuel pressure test gauge to the schrader valve on the fuel rail (I think 93s have those too). I got my gauge from Thunder Racing while I was picking up some other parts, but they can be had from AutoZone and the like for around $20.

 

The fuel pump relay is under your left foot.

I would be sure that your filter is not clogged. It's cheap enough to just replace anyway. Most people neglect it.

You can also jumper 12v to the fuel pump prime connector to run the pump continuously. On the 1993-1995, doing this bypasses the relay. So, if the pump ran with the prime connector jumpered, but not for two seconds when you first turn the key on, then your relay is probably bad. The relay is not the most common cause of problems, though.

 

Mine did something similar... but I actually ended up having a bad ground somewhere in the harness.. took me about 3 hours of diging and swearing heavily before I figured it out. I ended up cutting the harness behind the drivers seat, and grounding the fuel pump there to a spot I gound to bare metal. Worked great ever since.

I have a tool where I ran a + all teh way from teh battery to the fuel pump and it worked fine... checked the relay and it was working.. I was getting +12 to the pump... but I had no Ground connection to the pump... it was a nasty thing to find....

 

Hey all,
Thanks so much for your info/suggestions. Over the next day or two I will try the following:

-I will get a fuel pressure gauge from Autozone (I had been wondering about where/how much for awhile now thank you) and check the valve (tho I have to find it first)
-I will definitely try replacing that relay with a known working one from my friend's LT1. Thank you so much for the info and pics...no one else seemed to know where it was on a certain other forum that shall remain anonymous.
-Depending on the results of the last few, I will try jumpering to the connector (a very good suggestion I never would have thought of)
- Check for grounding problems and the filter.

I will report back in a couple days when I try all this stuff. Thanks again all.

 

Ok, great news! I connected the fuel pump prime connector to the battery as suggested by shoebox and the pump ran!! Woohoo!! So now I need to find the problem along the line. I'm gonna start with the relay. Does anyone know the part # and/or how much a replacement costs? Thanks soooo much. You guys just saved me like 200 bucks.

 

So, you're sure it is not coming on when you turn the key ON? It will only run for like 2 seconds. The relay is GM PART # 12193601
and is ~$15 wholesale. You might try your local auto supply if you don't want to pay list price of around $31 at the dealer.

If you want to do any testing at the relay plug, here is what you should have:

Your relay should be marked with some standard pin numbers.

Pink +12v /hot when key is ON/to relay pin 30

Grey- relay power to fuel pump and bridged to prime connector near pcm/to relay pin 87

Drk Grn/White- fuel pump relay control from pcm (should be hot for 2 seconds when key is turned ON and hot when engine is running)/to relay pin 85

Blk/White- ground/to relay pin 86

 

Ok cool...now all I need to do is pry that relay out of that strange clip contraption so I can find the pin numbers...the white relay does come out of that gray box right? shoebox, how do you know so much about this stuff? I will try your suggestion as soon as I can. Thanks a lot for the help to everyone...I just hope it's the relay and not a grounding problem like 97FormulaWS-6.

 

Ok, now I'm frustrated...the relay didn't change anything. I got my part # 12193601 and installed it but I am unhappy to report that there was no change at all....except that now I have a dead battery...and to boot it started to rain as I was considering what to do next. I think it's probably a short in the wiring. I dunno...I'm pretty frustrated right now... I gotta get out the multimeter I guess....too bad I wouldn't know what I should be doing...ugh...

 

Well here is the latest... Through some testing at the relay connection point, I have determined that the problem lies either in the ground connection or that the PCM (I recently bought and installed a GM remanufactured one) is not sending the signal to turn on the pump. The relay was most likely not the problem but oh well.

Anyway, the way by which I have come to this conclusion is by connecting ports 30 and 87 of the relay, that is, the two that should be connected for 2 seconds when the car comes on, the pump will run with key on. So that leaves the two connections I mentioned above. I tried sticking a wire in the ground connection and connecting it to a piece of metal on the car but that didn't seem to do anything. I'm not really an electrical genius if you haven't guessed already. How can I determine for sure which connection it is? (I saw with a multimeter that there was some voltage on the green/white connection when I turned the key, but I'm not sure if it was supposed to be 12 or not) Also does anyone know what port on the PCM that green/white connects to? Remember I have a '93. Thanks so much for everyone's help.

 

You should have 12v for 2 seconds when the key is first turned on, on the green/white wire at the relay connector. It should go back to A7 on the red pcm connector.

Since you said you had your hands on the pcm, there might be a loose connection, bent pin or pin pushed out in the connector. You can use your ohmmeter to check the continuity of the green/white wire from the relay to the pcm. You might need some extra wire to extend your meter leads.

 

Ok I ran the continuity test from the inside of the pcm connector to the relay and it checked out...so it's the PCM. I'm gonna get it exchanged as soon as I can and will update as soon as anything new happens. Again, much appreciation for the assistance so far. I hope this fixes everything up...

 

Well in a few hours I'll probably know whether or not the PCM was causing the problem. I brought the PCM back to the shop that put it in and the guy said he had it replaced under warranty (I'll be picking it up and putting it in tonight) but he very well could give me the old one back and call it new...especially since he gave me this line about how if the oil level sender isn't working, then the PCM won't activate the fuel pump and he wasn't sure the PCM was the problem. He also claimed that the fact that the service engine light isn't coming on could be because the bulb burnt out (that he just replaced about 3 weeks ago) at the same time. Is there any truth to that part about the oil level though? If that is true, then would I really get 2V on the green/white wire instead of 0 or 12? I'm not sure this guy is bein completely honest with me. Hopefully he won't give me the same part back because I didn't write down the serial # of the old one or anything....I'd be in bad shape then!! Well updates as they happen... :blah:

 

There is no low oil shutdown or low oil pressure shutdown on these cars..
Just the pressure guage, and idiot light for low oil level..