OK,

Until I bought a donor chassis, (1988 TA TBI which runs), 2 weeks ago. I never gave TBI a single thought. Little did I know how much I did not know about TBI cars. (No Schrader Valve for checking fuel pressure, etc.) Well the car ran with no complaints for 2 weeks. Parked it at airport, ran in, ran out. It wouldn't restart.


Looking at throttle body show no fuel from injectors. It growls to life with starting fluid but stalls out. I just, now, replaced the fuel filter, and am aiming for the pump.

I disonnected the flex line at engine, and no pressure spurts when flicking key on and off. I opened up the fuel pump relay, and pushed contacts together (even cleaned them), and only the fans came on (???). Bad pump?

The car will have a TPI V8 dropped into it, within a few weeks, but for the now, the car must run. Can a TPI pump be used in place of a TBI V8 fuel pump? Wont the regulator just bleed of excess pressure? Or will the pump cause excess pressure byond the relief flow of the regulator of the TBI unit?

Hate to put any money or time into the TBI system, when it is going going gone in a few weeks.

 

Good luck, the TPI pump puts out around 43 PSI...the TBI..14 max. If you are going to scrap the TBI setup you may want to look into an inline pump to get you by till the swap happens.

 

Thanks for the reply.

Pump is a pump is a pump, and the TPI one is obviuosly higher capacity, and can endure higher pressures. But in the end, it's the regulator that determines pressure. I guess I'm just wondering if the regulator will be able to drop the pressure enough to the normal TBI range. 13psi?

Given the constant trickle of fuel through the pump side of the fuel filter, during filter R&R, it is still allowing flow, and an in-line should work, without having to pull out the tank mounted pump. But, I 'plan' on pulling it. Its more of a question of lighting $53 on fire for a TBI pump, or $83 for a TPI pump.

I plan on cutting a access panel, and replacing it with heavier gauge galvanized steel, and rtv. Pulling the tank is a joke. People have refered to this as a hack job, but anything done with a level of craftsmanship, is fine by me.

I did some reading in a 1990 Helm Firebird Manual, and 82-92 Haynes, and found that on TBI cars there should be a flexible line near the filter, and pressure should be checked there. All the lines where 'solid' under there, except under the hood where the normal high pressure flex was present. I either misread something, or something

I guess the only way of knowing is to test it. Anyone?

 

Nope, it won't back the pressure off far enough, the regulator just drops the incoming pressure by a percentage, designed knowing what the pump output pressure would be (within a few psi)
This is fine, except that the sending unit that the pump is mounted to won't come out through that hole. There are hard lines from the sending unit that go down the side of the tank. Most people just cut the lines and put rubber line back in between the cut ends, not wise in a system that can see as much as 75 psi. If it were me and I was going to cut the hard lines, I'd flare them and use AN "B" nuts and unions to reconnect the lines.

I would replace any rubber lines on the TBI system with High pressure fuel injection hoses for the swap to TPI. You don't want to split a hose and have gas spraying around under the car/ in the engine compartment at 45 psi...rolling Napalm cannister.

 

I did consider this. This was the plan. Sorta why I didn't want to do it all twice. Ugh.

Do you think single flare will be sufficient for fuel?

 

correct me if I'm wrong, but I don't think the tbi cars have a return line. Although a pump is a pump, I'm not sure how the TPI pump will react without a return line. I would think that it could overheat without the large levels of fuel keeping it cool, and I would also be concerned about over pressurization when there's no return line.

 

For steel lines, yes. Look in the Summit catalog, they have steel flare sleeves, these backup the flare and the first 1/4" back up the tube. We use single flare and backup sleeves in aviation all the time.

 

I installed a Walbro High Volume/Pressure pump on my 92 RS when the pump died, and it worked just fine. The TBI cars do have a return line. My BLMs stayed about the same as they had always been too, leading me to belive that the regulator was doing its job at least halfway decent. I'm not sure how long the regulator would have held up to that pressure, but I wasnt planning on running it like that for very long anyway. If you plan on switching to TPI in the near future, I say DEFINATELY go with a higher pressure pump.

 

TBI's do have a return line, just like every other fuel injection setup.

 

LS1's have no return line

 

The early ones did.

 

Of course there is a return line. There are four actually.

1) Pump output
2) Return (Pressure based on line restriction back into tank)
3) Vapor Canistor
4) Fuel Fill Air outlet

I was able to flare 3 of the 4 lines (restricted space). I used high pressure flex line and two clamps for the 4th one, which fortunately was the fuel fill air outlet line.

Runs great, and a 16 gauge plate will top off the opening. It was very, very tight, since all four lines are hard, and only 1/4-1/2 inches apart. I ground off half of a finger pipe cutting tool allow easier cutting.

When I drop in the TPI pump, it should be quite easy indeed. That is, of course, if the TPI sender assembly is the same. There was only a short rubber line and two 'plastic' clamps connecting the pump to the hard pump line. I suspect the TPI pump attachment to the sender assembly would be more robust.

Thanks for all of your input on this. It is greatly appriciated. I still think a TPI pump would have worked, but I dont have the time to experiment now.

 

Why?... Do LS1's have regulators in the tank? Where does extra pressure bleed off to?

 

I placed a High Volume Pump in my tbi car, because I was doing a tpi swap and wanted to get the pump part done before I tackled the engine. It ran fine, I moved the car around with the tpi pump in the tbi car. I did this for quite a while with no problems.

 

Was your 'high volume' pump OEM style? (in tank?) Was the setup (connections) the same as the TBI sender unit? Same plastic ratchet clamps? Same short rubber line?

 

I looked it up, yes, the LS1's that run a single line have the pressure regulator in the fuel tank.

 

yes i used the same internals of the sending unit and just swapped in the new pump. It was a Walbro unit.

 

NovaSS,

Thanks for the reply. Having never toyed with a TBI car before, I wasn't sure what to expect, in terms of differences.

I'm still shocked there is no Schrader valve. A 'T' fitting with a valve will change all of that.

I'm of high hopes I can just plug in the TPI harness to the firewall, and run with it, when the time comes.

I'm a little suprised that the pump hookups are the same, as you described.

This donor 305 is a nice body indeed. Perfectly straight, and the original water based faded paint. It's perfect, for, having never been painted, it's never been bent. I'm just wondering what suprises it has in store for me. Needs a bushing in the door hinge, but thats it.