taman86

iTrader: (4)

I got an '89 350 tpi. Car starts intermittently because fuel pump works off, and on.

If the car does start, then I can drive it fine for as long as I want to. If I try to restart it later, then there is about a 50% chance that it won't start, because there is no fuel pressure. Then if I wait for a period of time 1/2hour, or longer, then fuel pump works.

My questions:

If fuel pump is working off and on, then wouldn't it quit working as I am driving it, stranding me wherever?

What should I check 1st? I did swap in a used Fuel pump relay, and still getting same problem.

Can low Oil pressure cause this? Mine reads between 18 and 35 on my gauge.
I read on another post, that low Oil pressure can cause the fuel pump to shut off.

DENN_SHAH

iTrader: (1)

the pump could well be dying. its not too uncommon for them to act like your is.

to check to see if your getting power out of the relay, wire a test light up from a good ground to terminal A on the fuel pump relay. put the light somewhere you can see it from the drivers seat.
make sure to route the wires so that none of them can get caught or burned on anything.
when it won't start see if the light comes on when cranking, if it does come on then you'll need to look for problems with the wiring between the relay & the fuel pump.
if you find no problems then change the pump & pay close attention to the connector outside the tank & the wiring inside the tank looking signs of damage or overheating.

hwcoll95

iTrader: (6)

the engine will bypass fuel pump relay as soon as it sees 4psi of oil pressure,mine was starting with a bad relay,once engine is running,it kinda likes sucking the fuel thru a straw/with litle to no voltage,and then no restart,seems as if a restriction like a plugged fuel filter,except mine was real hard to start,once running had sporatic surging,after fuel filter change problem went away?

Stekman

The oil pressure switch does not over ride the fuel pump relay at any point during operation. At ~4psi, the pressure switch closes, supplying an alternate source of power to the fuel pump in case the fuel pump relay fails.