White93z34

iTrader: (1)

alright earlier this year my buddy and i put a new (79k) 305TBI in his 91 RS to replace the old one that had a cracked block. at the time if pulling the old engine the car would start and run... badly, and we would hear the pump prime each time, now months later we are ready to run the new engine however we have no fuel makeing its way to the TB. and if i put my ear to the area behind the rear seat i can barely hear the pump turn on.

so now before i drop the tank down, could it be anything else aside of the pump? because droping the tank down does not seem like fun.

and what kinds of fuel pumps would you recomend?

84z28350

Well it can only be power to the pump or the pump itself. If you can hear it humming but no fuel check fuel filter if you havent done so already, might possibly be a blockage in the line too.

White93z34

iTrader: (1)

the filter looks OLD, but i'd think i'd still hear the pump prime like i used to

i hooked up a test light up to the wires that feed the fuel pump, i think the colors were gray, black, and purple. and the light would light but not very bright at all.

camaronewbie

Try the Oil Pressure Sending Unit - located usually above the oil filter on the block. If it's bad, it'll keep power from going to the pump. Power feeds directly from the battery, through the OPSU, to the pump. It's $28 at Autozone, but worth it BEFORE you assume the pump is bad and drop the tank.

When my pump went out, it went completely out - you heard NOTHING from it at all. However, when my OPSU went bad, car would run, but sometimes ran bad, acted like it was out of gas, hard to start sometimes, and other times ran like nothing was wrong at all.

I also had another car, where the OPSU went bad in a way that made the pump run constantly, given that the power feeds directly from battery - as long as battery was connected, the pump ran, causing my battery to die every 3 days. This drove me crazy till I figured it out!

White93z34

iTrader: (1)

i'll check that out, however i know when we pulled the old engine the car did not have a full tank of gas, close mabie but not totally full, now the gas gauge reads totally full, think that would have anything to do with it?

ploegi

The oil pressure sending unit above the oil filter is a backup for the fuel pump relay. It will in no way, shape, or form protect your engine from running with zero oil pressure. This is a myth. (otherwise, your engine would NEVER start until oil pressure came up.)

If you pour some gas down the throttle body will it start?

Try listening at the fuel filler. See if the pump primes when the ignition is turned on.

If not, check the relay.

If it does, find a way to check pressure. (I know, that is a real pain on throttle body cars.....)

White93z34

iTrader: (1)

if i hit the TB with some starting fluid it will start right up and run till the starting fluid runs out. i also took both of the fuel lines off the TB and no gas came out when i turned the key.

and lastly i had my friend hit the key while i listened above the gas tank and i heard a very quiet prime noise, its not near as loud as it used to be.