92 Blazer wont start

[vector006]

My 92 blazer (with W motor) fuel pump wont turn on when the key is on. I had the fuel pump replaced a short time ago...Im not sure how diagnose this.

Fuel Pump:
The Haynes manual says i can check the fuel pump by hooking a fused 12Volts to the "G" teminal if the ALDL. But...there is no wire going to that terminal!!! and I do have a fuel pump! so, i was thinking of splicing into the wires at the pump and try applying 12V to the pump directly...does anyone know if this is a bad idea???

CPI unit:
And another question regarding the CPI units...ive bought two CPI units, and both were junk i assume, since im not getting fuel to cylinder #4. is there any possibility it is something else??? Why would one cylinder starve for fuel...and not the others???

Thanks to anyone that can help!!

-jer

[SpitAndDirt]

Have you tried looking at your fuel pump relay? You may also have a fuse that is not clearly marked under the hood. Should be near the relay. The diagrams don't always show it either. As for the misfire, try the EGR. See if it needs to be cleaned. Hope this helps-Chris

[BlazerLT]

The fuel pump relay is on the firewall just under the hood.

[vector006]

There are two identical looking relays on the firewall, I know one is the fuel pump, but i dont really have a way to find out which one it is. So I swapped them to verify if the relay was the problem...it didnt help. And now i forget which one goes to which...i hope they are the same relay :~o And i cant find a fuse...what would it look like, would it be disguised in the harness?

And in reply to the EGR...it looks clean inside, i even have a new one sitting here i could try, how would that make cylinder 4 misfire? Just curious.

Thanks to anyone that can help!

[BlazerLT]

you swapped them without knowing if they were the same relays?

Do you know how bad that sounds?

[SpitAndDirt]

Yes the fuse is semi disguised, if you have one. It looks like two red wires going into a connector. You disconnect that connector and there is a blade fuse right there. Don't spend hours looking however, because your year may not have it. I just remember seeing it on other s-10s and blazers. As for the EGR misfire, if the EGR stays open, it just recycles exhaust gas into the intake. Your right, I can't say that it may only cause #4 to misfire, although I have seen some weird things happen. It was worth a try to eliminate all possibilities. -Chris

[tom3]

One thing I ran into on my 93. The fuel pump assembly in the tank has a plug in connector at the top of the tank, inside. This was burned/corroded and was not making contact. Bad situation. If you want to try, you can put direct voltage to the pump. Look for a gray wire hanging out of the harness just over the heater housing (under the hood) and connect a wire to this and the positive post on battery, this is a factory prime wire and goes direct to the pump.

[vector006]

Thanks for the help guys...i will try applying 12V to the grey wire today.

as for the relay...yes, it might sound like a bad idea....but, chances are they are the same. Any car manufacturer wont use the same connector for two different relays that are right beside each other, you have to remmember that the people putting these cars together on the assembly line are pretty scarry. Car manufacturers have to make things dummy proof...so i figured if they could afford to have someone mix up the relays on the assembly line, i wasnt going to hurt much.

But just incase, can anyone tell me what color wires are going to the driverside relay so i can put it back the way it is suppose to be?


-jer

[BlazerLT]

Originally Posted by vector006

Thanks for the help guys...i will try applying 12V to the grey wire today.

as for the relay...yes, it might sound like a bad idea....but, chances are they are the same. Any car manufacturer wont use the same connector for two different relays that are right beside each other, you have to remmember that the people putting these cars together on the assembly line are pretty scary. Car manufacturers have to make things dummy proof...so i figured if they could afford to have someone mix up the relays on the assembly line, i wasnt going to hurt much.

But just incase, can anyone tell me what color wires are going to the driverside relay so i can put it back the way it is suppose to be?


-jer

Ummmm.......

No offense, but you theory doesn't hold water.

the word ASSUME had three words (ASS / U / ME)

Please don't assume things are the same just because they "look" the same.

[vector006]

Originally Posted by BlazerLT

Ummmm.......

No offense, but you theory doesn't hold water.

I wiped off the grime ontop of the relays today, same part number is moulded into each...so, in this case, my theory holds Auto manufactures spend alot of money making things like this dummy proof, it's in their best interest.

Anyways, I went looking for the grey wire...i found one, it was near the heater core, it came off a smaller harness, and has a flat connector at the end which goes no where. Is this the wire that i apply 12V to in order to fire up the fuel pump? I didnt want to go applying 12V to any old wires. I sure didnt want to ASSUME it was the right one

[tom3]

Yep, that would be it. Driver's side relay, green-gray-black-orange wires to it on my 93.

[vector006]

I hooked a fused 12V to the grey wire you mentioned...and I couldnt here the pump turn on...all i heard was a little "clunk" noise everytime i hit the wire with the 12V. I hope the little alegator clips were delivering enough current.

I am probably going to bring it into the mechanic tommorow, unless someone else has any ideas.

thanks for your help.

-jer