Only getting 10.5 volts to fuel pump relay and fuse?

EDENYSJR

MEMBER
1994 BUICK REGAL
3.8L
V6
2WD
AUTOMATIC
120,000 MILES

The car listed above sat for 10 years in the garage. I had to install a new ignition and with new Passkey 2. The locksmith said the new key and vat coded correctly. Gas tank drained of old fuel. Gas tank washed. New fuel pump, fuel filter. Changed oil, oil filter, transmission filter and fluid.

Engine cranks but does not start. Here's what I've done:

Tested fuel pump with 12v battery, fuel pump working. New fuel pump

Fuel does not reach fuel filter nor do I hear fuel pump priming. Tested voltage at fuel pump connector has 8.5 volts with ignition on.

With ignition on tested voltage at fuel pump relay. Using pin 85 as ground, I got 10.94v on pin 86, 7.52 volts on pin 87a and 0 volts on pin 30.

With ignition on 20amp fuse #3 (Powertrain Control Module (PCM), Fuel Pump/Oil Pressure Switch, Fuel Pump Relay, Fan Control #1 Relay) I get 10.94 volts.

I don't have wiring diagram for ECM so I don't know where to test voltage at this source.

I haven't check spark or starter.

Buick dealer says car will crank but not start if VAT isn't coded correctly. Is this correct?

Will incorrect VAT configuration also reduce voltage to fuel pump relay and thus reduce voltage to fuel pump?

Is there something else I need to check?

3 Replies

KEN L

MASTER CERTIFIED MECHANIC
43,057 POSTS

Do you have a security light flashing when you crank the engine over? If not, the system is not enabled. Also, the fuel pump gets it power from the ECM BATT fuse in the under-hood fuse panel so I would test the voltage at the fuse.

this guide can help:

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Here are the PCM/fuel pump/engine wiring diagrams so you can see how the system works. You may have a fusible link that has gone bad and not supplying 12 volts to the systems. Check out the images (below). Please let us know how it goes.

Images (Click to make bigger)