Bob T.

This is my first post on this forum and I hope that someone of you might be able to identify the problem of no power to the fuel pump. This is a 1989 Chevrolet extended cab C1500 pick up truck, with a 5.7 engine and automatic transmission.
It has throttle body injection and HEI distributor.
There is no electrical power from the fuel pump relay to the pump. There is power on the “A” terminal of the relay, but no power out. The engine will crank over and there is spark at the plugs. There is power to the injectors. The engine will try to start (more or less) with a spray of Berryman B12, but it will not run. With the primary wires of the ignition coil disconnected (fire safety) and fuel line at the throttle body lossened, there is no fuel when the engine is cranked over.
The fuel filter is new. When a jumper is connected to the power and ground terminals at the tank, the fuel pump does run and produce pressure at the throttle body.
Any ideas what might be causing this problem?
Thanks in advance. B.T.

stew160

Could your problem be the relay? Can anyone tell me how to test a relay? I was reading a repair manual and one of the trouble shooting steps was "See the relay test procedure" The statement was referencing another part of the manual not available to me. What do you do check resistance or what? Is there a simple check short of changing out with another?

stew160

Nevermind found what I needed. Plenty of info on the web. Bob T. See the link to test the relay. The last link is great for understanding how they work.
How to Determine If a Fuel Pump Relay Is Bad | eHow.com
How to Check if a Relay is Bad | eHow.com
http://www.autoshop101.com/forms/hweb2.pdf

Sounds like the problem is between the ignition and the relay. Something is not giving the relay permission to close. I know you say "There is power on the “A” terminal of the relay, but no power out." But the way I understand it. You should have control power into it also to cause the relay to close. Fuse maybe?

good luck! Will be monitoring for progress.

dungholio

test all the wires at the relay with a buddie cycling the key from on to of and back. if your test light detects a signal change with the key cycle then more than likely its a bad relay. also check all your ignition and fuel pump fuses

brickman49240

I'm curious, I have exactly the same problem right now on my 92 c 1500. Did you solve the problem? If so, what did it turn out to be? I'm thinking the ECM unit?

thanks

lowdown112

Having same problem with 94 c1500 found out I'm not getting power to ecm. Test light on your battery feed an orange wire going to ecm. It should be hot. Mine isn't and I still havent found a solution either. And I just put a new ecm in mine.

brickman49240

I finally discovered the problem was the wiring coming from the transmission speed sensor. The speed sensor has to send a signal to the ecm to turn on the injectors. All I had to do (after replacing a number of things that were NOT the problem, was separate the wires near the speed sensor. Obviously there was some kind of short there.