jake66

i have a 1985 firebird 2.8 mpfi that will not start i think i have it narrowed down to the fuel pump relay because when u squirt starting fluid into it it fires right up and im getting a very weak light from my test light at the fuel pump with a good ground. am i on the right track? if so, where is the relay located all anyone can tell me is the firewall and i just cant find it anywhere!!!! please help!

ItstillaV6

On the driver's side of the firewall, you will find a block of black relay boxes. I recommend you pick up a Chilton manual, or Haynes repair manual. All of them look the same, and all of them contol different areas of the car.

If you have a good ground and a weak signal from the pump, them the relay is most likely fine. Your fuel pump is probably burnt out and not supplying enough fuel to run the engine. The relay is nothing more than a switch that completes the circuit. If it was bad, you wouldn't even get voltage to your fuel pump. I would change the pump first.

To drop the tank properly, you will need to pull the two metal bars, above your rear axle. I do not know the name of them, you'll see what I mean when you get the car in the air. Next check your fittings. The last 85 F-Body I stripped with a 2.8L had fitting which you could use two crescent wrenches on. They will most likely be pretty rusty, unless you live somewhere in the southern US. Grab some PB Blaster or Liquid Wrench and spray them up. Make sure, when disconnecting your lines, that you don't twist the lines on the body of the car. Then disconnect your fuel tank straps, and manuver that tank out. The filler neck is soldered into the tank, and is not removeable. It will make getting the tank out more difficult.

Just take your time and be careful, and definitely get some help from a neighboor or friend. If the tank is full, it'll weigh close to 200 lbs. Gasolng weighs just under 9 lbs/gal, and it is close to or over a 17 gallon capacity.

LWCS561

I've been battling this for about two weeks now. Heres the list of parts ive replaced:

fuel pump, fuel filter, plugs, wires, cap, rotor. fuel injection regulator. None of these have worked. The car still doesnt want to start. No blockages in the lines either.

jake66

someone told me to take a look at the oil pressure sensor i think it was the way it was explained to me the oil pressure has to b at a certain psi to get the fuel pump goin im an old school machanic and this is my first car with fuel inj and all this sensor bull i might be talkin crazy but u might wanna check it out

ItstillaV6

It is possible. Some of the 2.8L and 3.1L V6's have an oil pressure sensor tied to the ECM. If the engine has less that 6psi of oil pressure, it cuts the power to the fuel pump. This is to prevent the engine from being destroyed from poor oil circulation. The oil pump is mechanical, and driven by the distributor shaft, just like small block chevys are. You ncould have a bad sensor, or even possible a bad oil pump. The sensor is apparently on the back of the block, probably near the driver's side cylinder head, in a similar position to the chevy small block placement of the sensor. It is hard for me to tell, because my 3.1L does not have that sensor at all. I found a webstie, that had all the specs, I cannot remember the name of it. You may have to pull your upper and middle intake manifolds to get to it as well. Good luck to you on this one.

89-bird

The oil pressure sending unit is by the filter . As for the car not running because of it or starting is a myth . Mine went out when I was a mechanic and the car still ran and I was almost to work so I pulled in and hooked a mechanical gauge up and restarted it to check my pressure and thats how I knew it was the sendor or sensor as some call it . IIRC you should have three wires going to the pump one for pump power , one for the gauge , and one for ground . After spraying the starting fluid in does it start and stay running ? If so the relay is working if not it needs to be replaced and on my car is the one closest to the brake booster . Make sure you have power at the relay before replacing it as the fuel pump has two fuses one under the dash and the other over by the charcoal canister and it looks like a connector with two wires plugged into a cap . As a last option if it isn,t primeing check that the computer is sending power to the relay when you turn the key on .

Maverick H1L

iTrader: (8)

The oil pressure sender/switch is on the oil filter adaptor. Check for a code 54, for one, and then check the voltage at the rear fuel pump connector (on the body above the rearend and driveshaft). If the voltage is low, there is probably an almost broken wire somewhere. One of those things where a test light isn't really useful as it only tells you that power is available, not how much.

Fuel pump relay has a large orange wire going into it and a tan/white wire coming out along with a fat red wire and a green/white wire. Put 12V and ground into the diagnostic connector by the radio, the 12V source into the lower left terminal and the ground in the top right. Fuel pump should run as this completely bypasses most of the wiring in the system. Try to start the engine. If it runs, then there is a problem with the supply to the relay (the orange wire). If not, then you should check for a problem with the tan/white wire.