I have a 90' power ram with a 318 and TBI. i can not for the life of me figure out why its not gettin fuel. The fuel pump is working, the relays are working. I got a brand new Idles speed control. new fuel filter the lines are not clogged. but some how there is no fuel getting to the tbi... the connector on the top of the fuel pump was getting 3 volts, i think it should be getting around 12, i followed it up and its not pinched or anything...i am stumped

 

without the truck running i don't think your pump would even get any voltage. have you checked the fuel pressure regulator?

 

How do you know the pump is working?

Have you put a fuel pressure gauge on it? Are you actually getting fuel to the injectors but they are not firing?

When you first turn on the key the pump comes on for a couple seconds to pressurize the system but then turns off. Try checking the voltage at the pump and have someone turn on the key and recheck or if you meter has a "high\low" memory function set it and recheck.

What was your initial problem?

 

Key on truck not running there should be battery voltage at the pump connector. If there isn't look at the ASD relay. If there is battery voltage and the lines are clear and you aren't getting fuel either the tank is empty or the pump is not working. The pump can run without pumping fuel when it goes bad.

PS. Nice to be back on line with electrical power and internet access.

 

This is not completely correct...the pump will only have power for a couple seconds once the key is turned on. After that the pump is not reactivated until the engine is cranking or running.

When the key is first turned into the "Run" position the computer grounds the ASD relay momentarily, which sends power to the fuel pump to prime the system on the DG\BK wire at the pump.

Once cranking the engine the computer will again ground the ASD relay for the fuel pump but if the engine doesn't start within 3 seconds it removes the ground from the ASD relay until the engine either starts or the cycle is restarted.

This can be verified in the 1990 FSM and by referencing page 14-19 (Fuel System) and the wiring diagrams on pages 8W-57 (SBEC\ASD Relay) and 8W-117 (Fuel Pump).

To verify the ASD relay; you need to verify the SBEC supplies the ground and that the ASD has constant power on J1 (Red) and once grounded sends power out over Z1 (DB\BK)

 

Maybe the diagram I have is wrong but it shows the ASD providing power to the fuel pump, ignition coil, and injectors. If the ASD is shut down after 3 seconds where do the coil and the injectors get their power from after the first 3 seconds of cranking?

 

You are correct; I got carried away with my statement: it should say:

Once cranking the engine the computer will again ground the ASD relay for the fuel pump but if the engine doesn't see a hall effect signal within 3 seconds it removes the ground from the ASD relay until the cycle is restarted.

It is different on vehicles with both an ASD and fuel pump relay.

 

I think we can agree on this. The bottom line for the OPs original question is connect your volt meter to the fuel pump connector at the tank and you should see battery voltage at the connector when you first turn the key to the on position. If there isn't look at the ASD relay.

 

Yes, agree 100%, I was just trying to explain that there is only power there (key on) for a couple seconds so he will need to have help or a meter with a High\low memory.

Seal; I want to apologize if my comment came off as condescending or in a negative tone...it is sometimes hard to convey information on a "1 dimensional" format such as this w\o seeming negative.

To the OP sorry to clutter up your thread.

 

No problem. I obviously wasn't totally clear in my first post or you wouldn't have had to clarify it for me. I am always willing to learn, and anyone that uses a manual for information knows that manuals can be wrong. The main thing is we need to get it right and in a form that everyone can understand.

I almost always work alone so I have a bunch of wire jumpers of varying lengths that have alligator clips on both ends so I can attach my meter and have both hands free for things like turning the key.