please help kids walken 90 chevy

[clarkboyz]

i just bought a 90 chevy crew cab with 350,they said needed a new fuel pump so i put one in checked it first ran also checked old one also ran,seems like theres no power,someone said i need a ignition modular is this true or is it something else cant find any fuses for pump,if you put gas in fires right up please help

[crabtruck]

Fuse for the fuel pump should be on the firewall, eng side near heater, perhaps under a big plastic cover. Fuel relay in same place.

From your other thread :

Originally Posted by clarkboyz

i just bought a 90 chevy crew cab with 350 motor,they told me needed fuel pump so i put one in only to find it ran,also checked new one before in stall,seems like i have no power,if u pour gas in starts right up for a minute,i was told needs new ignition modual is this true dont hve hole lot money to be wrong again please help if you can to cold kids walking to school thanks ken

Originally Posted by crabtruck

I'm a little confused. Are you saying it will not start unless you pour gas in ?
And when it does start from you pouring gas in it, it will die a minute after starting ?
Or are will it run, just poorly, after you prime start it ?
Have you checked to see if fuel is getting to engine ?
How long do you crank it when trying to start ?
If you have an oil pressure gauge, does it move while you arte cranking ?
Have you checked the fuel filter ?

Just keeping it together...

[Stoney]

I'd check the cap and rotor first thing.

[crabtruck]

You said in PM that pump is not running at all. Good idea to check fuse first.

http://i202.photobucket.com/albums/a...RELAY-FUSE.jpg

[crabtruck]

Originally Posted by clarkboyz

i checked the hole firewall no fuse,my truck looks like your picture but theres no fuse and the one plug on right of your plug i have two,and yes the oil gauge does move and no theres nothing pumping like i said like no power

By "plug" I'm guessing you're referring to the relays.
Usually the left one is the fuel pump relay and the right one is an aux relay depending on truck.
(Like a downshift relay for the THM 400)

You should be able to trace the wires from the pump relay to the fuse (and to the oil pressure sender and elsewhere).
Could be someone else working on truck in past has tucked the fuse up somewhere since there is slack to play with
instead of putting it back in the factory clip (my pic shows it free from the clip).
You can free the relay plug from it's holder to get access for wiring checks.

You will have voltage there A) when trying to crank for the first ~10secs via the relay,
B) after that, and while normal running, via the oil pressure sender if oil pressure is coming up a few lbs.

Basic circuit: voltage comes through one of the fusible links off the battery junction block in that pic.
Then goes either through the relay (controlled by computer) OR through oil pressure switch.
Those two output paths are spliced together and run to the fuse.
Output from fuse is to pump and also a wire back to computer for info.

Must have voltage at fuse for pump to run so that is your first check point so you can divide the problem.
Good voltage tells you problem to pump side: connectors, grounds,etc.
No voltage tells you front end problem: relay,oil sender, pcm,etc.

Just for reference you may want to look for the ALDL connector under the dash near brake release
you may be able to use it for trouble shooting the fuel pump.

[chuckphillips]

What did you find out...