Hello everyone, I just got an 88 4x4 5.0 short bed lariat. When I got the truck it leaked oil bad so I pulled the motor and replaced the seals and gaskets. I put the motor back in and now my fuel pumps won't kick on with the key in the run position. Relays are good eec and pump relay. When I short the pump relay out the pumps come on but do not pump enough pressure to start the truck. I pulled the mechanical tank selector and the diaphragm looks new and in good condition, it moved freely as well. I've pretty much tried everything I can think of except for running a new power wire from the relay to the pumps. I have not done this because even when running, the pumps don't pump enough pressure to the rail so I figure I may have a different problem. So someone please help. And just to get this one out of the way I have not put a multi meter on it yet because truthfully I don't know where to start or what to look for with one lol. If there are any members around the louisville ky area that knows their way around these and could maybe make a visit and school me I will provide some food and of course beer.

Thanks

 

Ttt

 

Ready need help...some guidance

 

Shorting over the relay sounds like a bad relay. And possibly a bad frame pump. They have 2 pumps. Lo pressure intank pumps. And a high pressure frame pump. Check the frame pump.

 

I wanna find out why I'm not getting power to it first before I decide wether it is or isn't bad. Could a voltage drop to the pump cause the pump to pump less pursue?

 

Here is a diagram:
http://i608.photobucket.com/albums/t...Ifuel-sela.gif

Use a test light to check for power to the high pressure pump on the frame rail. Also check the grounds.
Did you reconnect the ground wire back to the engine block? On my '86 it is located on the engine near the driver side valve cover near the firewall.
Also check the inertia switch as shown int the diagram. There is a reset button on it.

Note if the in tank pumps are not working then the engine will start and run but the HP pump will strain and whine loudly.
If the HP pump is not working then the engine will not start at all.
The pumps only run for a few seconds if the engine does not start so you either need to have someone switch the ignition key on and off or ground the pump pin in the scan gauge port to force the pumps on all the time.

 

UPDATE: seems that I have electrical issues... Got a guru helping me out

 

Guru stopped helping, injectors do not pulse. Injector harness is good. Both eec and fp relays are good. And I have a wiring diagram on hand any more suggestions. Right now I'm checking the engine harness for broken wires. Most grounds are hooked up. One small wire from the back of the injector harness broke but I grounded that with new wire... Someone help please

 

I hope the wire you grounded was supposed to be grounded.
At this point I would get an OBDI scanner and go through all the diagnostics tests and see what codes turn up.

 

^^ can't find any diagnostic procedures, I've done all I know to do and then some. I've got a wiring diagram its the little orange ground from the back of the motor. At this point I'm starting to think I somehow fried the ecm... What kills power to the pumps AND injector pulse?