84redta

iTrader: (34)

I have an '88 Firebird 5.0L TBI. I'm a basic home mechanic, so instead of sounding pompous and ignorant and act like I'm completely knowledgable in what I'm talking about, I'm asking as many questions as possible, so be gental. This is my first direct experience with tinkering with a GM v8, I am aware that for the most part, TBI is a carbed motor with a fuel injection throttle body unit atop a TBI intake. My issue lies with the fact that I have to sit there and turn the key for a couple of seconds and after about 5 to 10 seconds I see the pressure gauge start to go up and once it hits half way, the motor fires right up. Is that normal? Is this motor more like carbuerated than fuel injection in the start up characteristics? Also there is a bit of smoke everytime i start out coming out...normal??? It goes away after a couple of seconds...it's just initial fire-up.

The car idles near perfectly once it starts up. It is responsive and idles perfectly, it's just the start up. I'm not sure if it's the motor or the gas issue, as I haven't dealt with this and all the other v6's I've played with worked like fuel injection or carbeurated should (of which the v6's were MPFI or Carbed, this is my first TBI). The reason that people have lead me to believe that I have a gas issue is that at times I have to pump the gas (thought you didn't have to do that with FI?) and a couple of times it's had a hard time starting/idleing, and after a couple of revs, or after dying a couple times and restarting, it will run normally once again.

(If anyone thinks its the fuel pump...a thought before I drop the tank) Another thought as I surfed the web was a poor electrical issue to the fuel pump? I know with the restrictive wires used by GM the fuel pump is probably getting ~12 V nominally when the battery is at ~14V, so a page said to run a relay with bigger wires to the fuel pump to get 14V at the fuel pump. My issue with that is that do I have to rewire the ground (to a bigger wire)? and is this even worth it. Is the delay in starting up, and the building up pressure (I understand the motor runs under compression, just wondering if this all sounds normal) before fireing up all normal?

Another issue I'm having is that my radiator fan is electric, and only works when I have the climate control features on Air Conditioning function.

On the flip side of this topic, I would like to know any and all simple bolt on parts that will still provide reliability to the seals and the engine in general (I'm at 143K so I don't wanna push it too far). I'm not looking for incredible HP or anything, just a bit of a boost from what it has would be nice. I've stumbled upon the 2" ported intake made for the 2" TBI and I figured injectors from the 350, injector pod spacer and an adjustable fuel set-up to boost it to 14 PSI would give me 200-250 HP which would be nice, and i don't think extreme. Any help on this would be great. Thanks!

'88 Camaro RS MPFI V6 Auto - Parted
'86 Camaro Berlinetta T-Top MPFI V6 Auto - Parted
'87 Firebird T-Top MPFI V6 Auto - Parted
'84 Camaro Berlinetta T-Top 2BBL V6 Auto - For Sale
'88 Firebird T-Top 305 TBI 5 Speed

RFmaster

Welcome to TGO

First - you should lose the notion that TBI is a Carburetor. In fact TBI was one of the most successful FI systems GM has developed over the last 25 years. Yes, it is not sexy, but it did a fine job at a very low cost. Compared to TPI and later EFI systems TBI looks rather primitive and does have performance limitations which can be overcome. There are numerous examples of very hot cars (trucks and boats) running modified TBI systems.

About your car. During start up ECM looks for a DRP signal from dizzy. Once ECM sees that engine is turning over it will enable Fuel Pump relay which supplies +12 volts to Fuel pump in your gas tank. In parallel with Fuel Pump relay is an oil pressure switch. Its a safety device - just in case if FP relay goes belly up while engine is running - prevents a stall (found dead on the interstate syndrome).

From you description it appears that you may have a bad FP relay - pull it from its mount, disconnect and examine socket contacts. It is not uncommon to see chard contacts. Check it out and report your findings.

I have no comments on HP parts for 305. To get any real meaningful power increases (over stock) requires induction and exhaust mods, as well as head-cam combo.

//RF

84redta

iTrader: (34)

I had a code pop-up stating a fuel pump relay failure, and I replaced the fuel pump relay with a new one, did the same thing, there was no instantanious start up or anything that I noticed. So I switched it back to the original that came with the car and it's doing the same thing. After switching back (to the orignal) the code stopped popping up. If the fuel pump relay was truely bad...wouldn't it not run correct at all? I mean this engine purrs once it starts, it just seems like it needs to build up pressure before starting (could it be the oil pressure switch!? The guage works perfectly). Now the car seems to run perfectly other than the startup delay.

Now the computer is popping up with a coolant temperature is low, code 15 (even though the radiator system is full in the overflow container and radiator itself)...yet I can't find any sensor on the radiator that would sense when it's low, and I checked the Haynes manual for the code, and it says (for code 15) among poor electrical connections and such, it says the coolant temperature sensor may be bad. I haven't had a chance to replace the temperature sensor yet because I need to flush the system because it's merky, but could that have anything to do with such a delay in start up? I don't know, Advance Auto Parts coudln't get me a coolant level sensor yet Car Quest was quick to find one, yet neither place knows where it goes on the cooling system.

RFmaster

Fuel pump relay may not be a problem, but a badly corroded Fuel pump relay socket contacts just may be creating the effect of a failed relay. Oil pressure NO switch will close its contacts once oil pressure is above 6 PSI. Start up with very cold engine might be very long! You can verify if you are running on oil pressure switch by temporarily disconnecting it. With functioning FP relay engine should start, otherwise code 54 may pop indicating that fuel pump voltage was not detected at fuel pump sense line for 2 seconds after the ECM has sent the fuel pump relay On command. Otherwise you are running on OPS - not good.

Typically, CTS is located a near thermostat housing to the left. It should have a two wire plug with yellow and black wires. This is ECM dedicated sensor, so it is completely independent from your gauges. Make sure that connector is fully plugged in. You can verify if CTS is good by measuring resistance with a DVM - engine cold (about 20 - 25C) CTS should measure about 2.6 to 2.7 kOhm.


//RF

84redta

iTrader: (34)

I go to college so I can't take a look at the car until tomorrow, but just so this goes faster, where exactly is the oil pressure sensor located? And if I unplug the OPS and the car doesn't start (what time frame should I stop trying to start it...10-15 seconds?), if the engine doesn't start, what does that mean, that the OPS is bad? Thanks for all this indepth info, i hate blindly replacing sensors without testing the old ones.

RFmaster

OPS - oil pressure switch should be just above oil filter. Oil pressure gauge sending module typically can be found in the back of the engine. Later models combined the two together into a single unit. Be careful with plastic connector body as these get fragile with age!
One way to check how good FP relay contacts are is to measure voltages on each side of the OPS connector. One side will always be hot (battery voltage) while the other pin will be switched. A good relay contact should have very little voltage drop. For example if battery is 11.80 the switched side should be very close - 11.70V. If it is much lower - say 6 to 7 volts you have to investigate, relay, socket, wiring harness.

With ign key off to on ECM will command FP relay to prime for about 2 seconds. You can use this self check routine to verify FP contact closure and resistance.

My cold engine starts within 3 seconds from initial cranking - 20 seconds is too long for a healthy system to turn. (just my opinion)

//RF

84redta

iTrader: (34)

Yea, mine takes about 5 seconds, but like i said it seems as though the pressure guage has to build up to get it started, i would love to actually try your theory above to try and figure this out, but now something blew and i really can get it started. If interested, the post is this link:

https://www.thirdgen.org/forums/elec...ml#post3496296

if that doesn't lead you to where it should, it's a fresh link under electronics entitled : "HELP! Absolutely Nothing Works"

Again thank you for your time in trying to help me, and as soon as I resolve this other issue i will get back to you about this OPS and FP relay issue. Thanks again!