Garth Knight

iTrader: (1)

Hello, I have a 1988 tbi firebird, and every day, I have to crank up to 5 seconds before the engine starts.

This happens in all the situations: hot and cold engine.

I have replaced the fuel pressure regulator and fuel filter but the problem has not been fixed.

I have tried with the search button w/o results...

Can you help me? I'd like my engine starts immediately...

turbinator3

oil pressure switch is bad I bet. watch the gauge and see if car fires right after the gauge picks up pressure

Garth Knight

iTrader: (1)

have to try thank you

Matt trans am

Yep need oil pressure. Like having no juice in the battery.

Garth Knight

iTrader: (1)

Thank you! Where is the oil pressure switch located? Is the one near the distributor or the other one above the oil filter?

RBob

iTrader: (1)

I'd say the opposite, the oil pressure switch is good, while the fuel pump relay is not being activated. The relay and oil pressure switch are in parallel. So once oil pressure rises (from cranking) the switch closes and powers the fuel pump.

It is the fuel pump relay that is not being activated or is bad.

RBob.

Garth Knight

iTrader: (1)

Thank you, I will check it, too.

RBob

iTrader: (1)

Some troubleshooting tips. At key-on, engine-off the ECM supplies +12 volts to the fuel pump relay for 2 seconds. It is the GRN/WHT wire from ECM pin A1 to the relay terminal C.

To get the ECM to apply power to the relay again do a key-off for at least 10 seconds.

Be careful to not short this 12 volt source to ground. There is a small transistor in the ECM that will pop. Which may be the issue with the fuel pump relay as it is. If so it is easy to replace using a PN2907.

RBob.

Jono4820

iTrader: (1)

Had a similar problem several years ago with mine. New fuel pump did the trick as my fuel pressure was also low.

Garth Knight

iTrader: (1)

Thank you for your reply.

Yes, I am going to swap my fuel pump with the EP381 60psi which should be a great upgrade...

OrangeBird

iTrader: (1)

Wow , really ???? Your gonna replace the pump without having followed Rob's 100% spot on advice first ? And what happens when your new fuel pump doesn't fix the problem , what part are we gonna just up and change next in the hopes & prayers that it cures the problem ? Anyone can replace parts till it finally runs right , Hell you may even end up with a whole new car one part at a time till it's finally fixed doing it that way , at GREAT financial cost , or you could do what all real mechanics do , namely TROUBLESHOOT the problem using established methods to isolate the one bad part that's causing the problem .

Course , if you have baskets of money to blow and don't care about spending hundreds to fix what may be a $20 or $30 relay , go right ahead , but for us mere financial mortals without baskets of bucks to aimlessly **** away , the troubleshooting method is really the only way to go .

I wish you luck , cause it sounds like that's what it's gonna take when using the "replace every part till it runs right" method .....

battman

iTrader: (2)

a 60 PSI pump is not an upgrade, your car will drown in fuel. you need to purchase a replacement pump for a TBI system.

Garth Knight

iTrader: (1)

OrangeBird, I have to replace my fuel pump for other reasons, so it is a good chance to see if it solves my problem or not.
Of course I am not going to waste my money replacing all the possible parts of the car...

This is a controversial problem because there are people for and people against to use a 60 psi fuel pump on a TBI system. As they are people who replace the fuel pump cutting the fuel lines and others that do it in the "standard" way...

OrangeBird

iTrader: (1)

Cool , if your pump is screamin or otherwise giving notice of it's impending doom then Hell yea , get it outta there before ya end up stuck somewhere (It's a built in design , they NEVER fail at home) . Now as to the 60 PSI pump idea , I gotta admit I'm with battman here , a stock engine using a TBI will run just fine with the lower pressure TBI intended pump . If you were building this thing up a few more hundred HP I guess I could see looking into fuel system modifications but if this is gonna remain mostly stock I think the called for pump is the way to go .

Schurkey

Why does the fuel pump pressure make any difference UNLESS it supplies more volume than the regulator can return to the tank?

My 45-ish psi EP241 supplies a rock-solid 11.5 psi on my TBI K1500. The pressure regulator regulates the pressure, not the pump. (Unless the pump can't make enough pressure to pop the regulator, (system is below regulated pressure) or the pump supplies more volume than the regulator system can return. (System is above regulated pressure.))

There was a time that the EP241 was a "recommended" upgrade to the TBI fuel system. I think folks believed that it supplied more volume, (supported higher horsepower) in addition to being capable of more pressure. I am not sure that the "higher volume" claim is correct. I haven't done any actual testing to confirm or deny the volume claim; and I haven't seen any published data on GM in-tank fuel pump capacities.

DynoDave43

iTrader: (11)

I thought this was still the "std." recommendation...using a TPI pump as a replacement in TBI applications. The impression I was left with from reading here was that the TBI likes / is happiest to run around 13psi, and the factory TBI pumps don't make that much, even on a good day (and many make less). The TPI pump may largely be overkill in a stock TBI application, but the assurance that you are getting a full, steady 13psi (checked and adjusted as needed) made it money well spent.

Given the same size of fuel line in both instances, would not the higher pressure pump deliver more volume? There are restrictions as pressure climbs, the regulator has to allow for greater pressure, etc., but all else being equal, you'd move more fuel (volume) at a higher pressure, right?

Schurkey

I don't think that's a given.

In-tank electric pumps come in multiple designs--gearotor, turbine, vane, etc. In the end, it's about pump design along with the electric motor that powers the pump.

In other words, RPM x displacement (or turbine size, in the case of centrifugal pumps)

First Guess: There's going to be no definite answer to this question until someone buys a TBI pump and a TPI pump (and other pumps as desired) and flow-tests them at some realistic TBI pressure., and with the same voltage (considering vehicle-harness voltage drop.)