I'm frustrating my self with an ongoing non-start issue in a TPI from TBI swap. Maybe I found a clue.

New in tank pump TPI (OEM), new lines, old TPI pressure regulator.

When cranking, I hear the relay go on for a few seconds, then it clicks.
During cranking, at first fuel pressure goes up to 42Lbs (measured via a gauge at the Schrader valve) but drops off immediatley after the click is heard to about 20 lbs.

inspection of plugs-- they seem dry.


I suspect the click is the relay disengaging, and the pump is being turned off.

If I simply tune to the "key on" Position, you can see the fuel pressure bump up, click occurs, then immediately starts back down. It doesn't hold. If you turn off and turn on again, pressure stays down without an additional click being heard.

Is the ECM looking for pressure but not seeing it? If so where is the sensor?
Or is it not seeing something else that forces a fuel pump shutdown?

thanks for your help to all kind enough to respond.

seems pretty straight forward its the FP or the reg or the intank lines for the FP should start by testing out that reg

I just returned from clamping off the return line to test the regulator.

Same condition occurs. Pressure goes up to 42lbs, I hear a click from the relay and it immediately and visible drops off to about 15-20 lbs in a matter of ten seconds.

I should have mentioned as well, that the fuel gauge stays pegged at full, even though there's not more than five gallons in the tank


Keep in mind no start has ever occured on this engine in over 2 years of trying.
this is a 400block with TPI stuffed into a Caprice wagon. Should be hearing 450 horses but all I get is the sound of my hair being ripped out.

if you clamped the return line and pressure still dropped.. then its your injectors or one of the intake lines is split?

When you say "intake lines", do you mean "supply line". from the tank to rail?

initial comment was "inspection of plugs-- they seem dry."

Granted I only checked two. (one and three) Will need to check the others to confirm that one isn't hung open and therefore soaking wet in the cylinder. injectors are new but sat all winter.

If there's a split in the line, I would suspect in the tank, as no fuel seemed visible on the ground afterward, though there was a strong odor..


Was also told at a GM dealership there is supposedly a ball check in the pump to keep the fuel from retuning via the supply line, which is what would keep the pressure up in the line for the next starting event? Sounds good- don't know the truth of it.
for certain

What's with the relay turned off after a few seconds... why not stay on while cranking?


Is there a ball check? (OEM replacement pump for 5.7L 1992 Z28)

i believe there is a check valve of some sort in the pump to prevent the drop in pressure...
and the relay is functioning exactly how it should on for a few secounds to build pressure then off... once the engine starts the relay will again turn on and the pump will run continually...


i wouldnt bother pulling plugs at this point just check your oil you will have a fair amount of gas in it if it is indeed a leaky injector...
but i suspect a split intank fuel line.. not bad enough that the pump cant build pressure but once it stops it just drains right back out

I've pulled the fuel pump out. I didn't see any visible rips or points of obvious leakage in the sender assembly,

I would like to somehow bench test it to see if the check ball is holding.

ANY BODY GOT SOME IDEAS? I HATE TO JUST THROW MONEY AT A NEW PUMP WHEN THIS UNIT IS ALREADY BRAND NEW. ZERO MILES... LOTS OF CRANKING.

I pulled the pump out of the tank and the fuel rail off the manifold

I set up a "test Bench" (picnic table) with a battery, fuel pump, hose, Manifold with injectors in place, fuel pressure gauge, and wires. I used screw type clamps instead of the little plastic squeeze type supplied with pump.

When giving the Pump voltage, pressure went up to 42lbs and would hold there with pump off. If kept on, the regulator would open up to keep it around 42.

Injectors could be individually fired by appying 12 volts to their contacts.

I reassembled into car, tested for pressure, hold at 42 during initial crank.
So I'm content now that the pump is working, and there are no leaks
The drop off of pressure seems related to when the injectors are firing during crankings of startup attempts, but since it's NOT starting. the fuel is likely going into non-firing cylinders. Oddly, plugs still seem dry?

The initial engine was a 350 with 19lb injectors, this is a 406 with 32lbs injectors. So here's the question:

Should cranking injector pulse width be greater for a larger displacement, or is that compensated by the fact of having larger injectors? Both those items have been accounted for via chznge in the program tables already
I'm thinking I should be increasing crank pulsewidth and pump "on" time before the relay kicks it out.

you have answered you own question

yes you need to be programed

This is same issue as the other thread...

Your ECM is not getting reference pulses, otherwise it would be keeping the fuel pump running. IN this case, it should also not be pulsing the injectors. If it is pulsing the injectors and not running the fuel pump, you have an ecm problem.

maybe i can help you, i have a 1987 corvette that i had the same problem, after replacing the entire fuel system with the same problem i found out that when you pull out the fuel pump there is a fuel seperator between the fuel pump and the fuel line, you need to replace this with a new one or i used a piece of fuel injected hose with clamps on it. believe it this fixed my problem $200.00 dollars that i spent for nothing. everyone i talked to had no idea.