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I have recently picked up an 88 f250 with the 460 bb. I have worked on many sbf's but this is my first 460. It is efi, I am more familiar with carburated. I bought a new fuel pump relay for the truck because the pumps weren't engaging. The new relay and the old one both have 5 prongs in them, neither worked. The one out of my 5.0l f150 has 4. I plugged it in and one pump ran but there was no fuel pressure at the engine. I jumped a wire in the plug and both engaged and i had fuel pressure at the engine. Still no fire, truck has spark, and ran (coughed and farted) on ether. any idea what might cause this? Injectors? Again, im not too familiar with efi. And i don't understand why my new relay wont turn the pumps on if using a wire to jump it did. Maybe its not suppose to have the extra prong? Wrong relay? In the plug there are only 4 wires. Will include pictures. Any and all information/suggestions would be greatly appreciated, would love to get this lariat back on the road.
The NC pin #5 is not used.
Yellow wire is the power to the common contact from the fuse link at the starter relay on the passenger fender.
The red wire is the power to the Fuel Pump relay coil from the the EEC Power relay.
The brown wire is power to the fuel pump system from the NO contact.
The tan wire is the ground wire to the Fuel Pump relay coil from the the EEC Computer and pin #6 of the self-test plug.
Note the below diagrams relay numbers is information to use when switching from the factory relay to the Bosh type relay that is used in the 1992 and newer F-series trucks.
subford, do you think i have the wrong relay? Or will it make a difference having the 5th pin or not? A relay out of my f150 with 4 pins turned the pumps on, but i still had no fuel pressure. Using wire to jump power to the pumps i had pressure.
Thanks
Will
No.
If when you jump pin #2 to pin #6 or pin #6 to ground of the self-test plug and the fuel pumps run with the key on then the fuel pump relay is working and all of the fuel pump circuits after the fuel pump relay are OK.
The EEC relay is also working OK.
When you jump pin #2 to pin #6 or pin #6 to ground you are bypassing the computer.
The relay you bought is probably just faulty. The extra contact is just unused.
The connector only has 1 wire that feeds power to both pumps. If one pump turned on, they both should have, so you either have wiring issues, or iffy fuel pumps.
The relay you bought is probably just faulty. The extra contact is just unused.
The connector only has 1 wire that feeds power to both pumps. If one pump turned on, they both should have, so you either have wiring issues, or iffy fuel pumps.
Got a new relay, all pumps are running and i have perfect fuel pressure, but still won't run. There was constant power on both pins on the fuel injector plugs with key on engine off and key on cranking. I have spark, pulled and cleaned the plugs. Now I'm leaning towards injectors or maybe a module that runs the injectors? Obviously it still isn't getting fuel. Any suggestions? Maybe a MAP sensor?
Thanks
Will
Sounds like it. Next step is try pulling and checking for codes.
When you turn the key on, the fuel pumps prime for 1 second then shut off, correct? What happens when you release the key from the "start" position? You should hear the fuel pumps continue to run for one second again after the engine has stopped turning.
Sounds like it. Next step is try pulling and checking for codes.
When you turn the key on, the fuel pumps prime for 1 second then shut off, correct? What happens when you release the key from the "start" position? You should hear the fuel pumps continue to run for one second again after the engine has stopped turning.
After doing a bunch of research on these problems i came across a youtube video on how to check the codes, did it, and nothing came up. Yes thats exactly what happens with the pumps. I thought it was odd that they turn on and then off, but priming makes sense.
There was constant power on both pins on the fuel injector plugs with key on engine off and key on cranking. I have spark, pulled and cleaned the plugs. Now I'm leaning towards injectors or maybe a module that runs the injectors?
Im pretty sure there is always power to the injectors. The computer grounds each one in turn to actuate them.
Are you sure the grounds are all connected?
Can you borrow a noid light, or make one with an led?
10-19-2016, 04:00 PM
