pwdbychevy

I have a few questions. I just swapped in a TPI from TBI and as I expected, the engine won't start. I'm thinking now I should've left the TBI in if I knew it was going to be like this. The fuel pump primes when I turn on the ignition. The fuel pressure gauge goes up to around 20 psi since there was no fuel in the line. Is that right? I crank the engine but it won't start. I turn the ignition off and turn it back on and the fuel pump primes again. The fuel pressure gauge now reads around 60 psi and starts to groan like there's too much pressure. I crank the engine again and of course it doesn't start. I keep repeating this and the fuel pump keeps priming and the more I do this, the louder the groaning from the pump becomes. How is the pressure from the line being relieved? If the fuel injectors were squirting, wouldn't that relieve some of the pressure? Is the pump supposed to be priming everytime I turn on the ignition? What is the pump supposed to be doing while the engine is cranking? What is the fuel pressure supposed to be doing while the engine is cranking? Is it supposed to go down? The reason I ask is because my fuel gauge does not move at all while the engine is cranking. I hooked up a noid light to the injector connector so there is a signal going to the injectors. PLEASE HELP!!!

CaptPicardsZ28

As far as I can tell my pump always primes when I turn the key on. It almsot sounds as if your inlet and return lines are backwards but you do get pressure so I am not sure. Also, if your fpr is closed too much your car will not start. This happened to me before after I installed an afpr. Maybe someone slse can figure out the rest. I tried my best. Sorry if none of my answers help.

pwdbychevy

The inlet and return hoses are two different sizes and one of them is longer than the other. I think I hooked them right but now that you say that, I'm not sure. Is the longer hose supposed to go to the inlet or the oulet? Correct me if I'm wrong but doesn't the inlet hose have a larger diameter?

Trickster

Your fuel pressure line is 3/8" diameter and your fuel return line is 5/16" diameter.

Captain C

I hope that you changed fuel pumps when you converted. There is a serious difference in the fuel pressure between the two systems. The TBI runs at around 13# IIRC, where the TPI runs from 39# to 43.5# depending on the year. If you haven’t changed the pump, that’s the first thing to take care of. Also, a stock fuel pump is not going to be enough for a performance 350. I have a Buick Grand National pump and it’s too small......

pwdbychevy

I have a fuel pump from a 92 z28 TPI installed. It's been in there for a little over year now ever since my TBI pump took a dive.

pwdbychevy

I'm at work right now so I can't check the sizes but I have the longer hose as my return line. Does any body have any pictures they can attach?

Captain C

I'm in the same predicament.... However, if webshots works you might be able to see something. The top hose is the larger hose... Not as good a picture as I could get if I were home right now. I'd get you a clear shot of everything......

Excuse the dirt, the hood had been up for 4 months by this time, and my cousin was grinding the crack filler on my drive way and covered the engine in crud....

Driver's side engine compartment

pwdbychevy

I can't pull up the picture at work due to network filters. if you can send some more shots I'd appreciate it.

Captain C

I'll have to take some new ones when I get home that might help. Unfortunately, I haven't had a chance to detail the engine compartment yet. Right after I put the engine together this last time, I blew the rearend......Again. Once I fixed the rearend, I blew the transmission..... Again. Still waiting for my new transmission to show up

pwdbychevy

Wow, that really bites. I've already rowed through two T-5's already(power shifting). Ya can't beat my one-two shift! Too bad these T-5 tranny are so weak.

pwdbychevy

the link is not working, it's telling me I'm not the owner of that album.

CaptPicardsZ28

All I have are these shots of my lines out of the car. Sorry.

Captain C

It was really late when i got home last night so I didn't get any pictures to email to you. On the way to work I remembered taking some pictures of the intake and stuff while it was out of the car. The digital camera I used at the time wasn't very good, but it may help. Unfortunately, I didn't remember them until I got to work.......

I would download the picture off the web and email it to you but all it shows are the two lines as they come off the hardlines from the gas tank. You can't see them attach to the fuel rail. One thing to consider, You can't attach them wrong as they will only go on one way. I would consider backing off on the pressure regulator first and then checking for kinks in the return line. After that, double check your wiring harness to make sure you have everything wired correctly....

pwdbychevy

I did a wiring check and everything came out fine. I get a code 12 in diagnostic mode but something weird happened. When I ground the aldl terminals and turn the ignition on, one of my cooling fans came on. When I take the scanner out, the fan turns off.

Trickster

That is normal for the fans to come on when you put a scanner on the ALDL or jumper pins "A" & "B".

tom3

What year TPI did you use? The later ones, 89 and newer, have the VATS deal in them and the injectors won't pulse without a signal to the ECM. If you are getting 60 psi at the fuel rail something is not right, the regulator should bypass and keep pressure about 50 or so until the engine starts, then cut it to about 40 or so on the vacuum signal from the engine. The 12 code from the ECM is a normal code, just a hello.

pwdbychevy

That's good to know because I thought i screwed up the wiring somewhere. My TBI system never did that. I guess it's unique to TPI. Something else just surfaced a few minutes ago. When I turned on the ignition again, I heard a clicking noise coming from the plenum. I disconnected the IAC valve on the TB and it stopped the noise. Are IAC valves supposed to be making any noise at all?

pwdbychevy

I knew that 12 code is normal. The year TPI unit is 1991. VATS is not an issue because my car is a 92 and had it already installed. The security light comes on and then shuts off which means everything is ok. I'm pulling the timing cover off to nail down the timing and get this beeyatch started.

pwdbychevy

Something is not right here. When I turn the ignition on and the pump primes for a 2 seconds, my fuel gauge goes all the way up to around 70 psi and then bleeds back down to around 40 psi. Is that normal? WTF?

Trickster

No, that is not normal, it is way to much pressure for your system. What type fuel pump do you have in there?

pwdbychevy

It's a stock TPI pump from a 92 z28. What happens is the gauge needle will go all the way up to around 70-75 psi and slowly bleed back down to around 40 and stay there. All the manuals I've checked say the pressure should be around 34-47 psi but they don't tell me whether it's supposed to go the high at first then bleed back down. I have a homemade AFPR that's is backed out all the way so it's at it's stock setting.

Trickster

I wonder if your homemade AFPR might be the cause of your problems!!!!!!!!

pwdbychevy

That's what I wondered but how would it cause it to bleed back like that? I haven't yet to get the car started so I haven't been able to set the pressure correctly. Are IAC valves supposed to be ticking when the ignition is on? Mine does. I have alot of troubleshooting to do.

Trickster

On mine with the stock regulator, the pressure will shoot up to about 43 PSI when the pump primes and then drop to about 39 and hold. This is normal since there will be a little bleed off. Your pump is shooting almost twice the pressure to the regulator that mine is. Usually about 50 -52 PSI is the max these regulators should be set at or the system won't operate worth a crap.

pwdbychevy

do you think if i screwed in the adjuster bolt on the regulator that maybe the pressure would show correctly?

ploegi

Screwing it IN will INCREASE fuel pressure. You want just the opposite.....

I suspect a restriction in the return line may be causing your high fuel pressure. Check 'em, and make sure nothing is kinked, etc.

pwdbychevy

I removed the return line at the fuel rail and blew into it to the point of hearing the fuel bubble in the gas tank and it seemed to have some kind of restriction which seems to have removed itself. I screwed it back in and turned the ignition back on again and now what happens is the needle rapidly goes up to around 47 psi and then slowly goes back to around 20 psi after the fuel pump shuts off. I'm ASSuming that it's supposed to hold the pressure at around 47 psi max and 34 minimum..

grafx

The car cranks correct?? Maybe the injectors are not getting a signal or maybe there is no spark. I'd check for spark if you've got spark check to make sure your injectors are getting a signal from the ECM. A fast way to check for spark spray some carb cleaner down your are cleaner and crank the car over if it starts up then you have spark.

pwdbychevy

The car is cranking. I hooked up a noid light to all the connectors and it flashes when cranking so there is a signal to the injectors. All injectors are measuring around 16.8 ohms. There is spark. My next check is to pull the plenum, unbolt the fuel rail and lift it up with fuel hoses still connected and turn on the ignition and crank the engine so that i can see if the injectors are actually shooting fuel. I suspect that the injectors might be bad.

pwdbychevy

Okay folks here's an update. I pulled the fuel rail with fuel lines still attached and turned on the ignition. None of the injectors are leaking. A very good thing. I placed a towel under the injectors and decided to crank the engine over to see if the injectors are firing and guess what? NONE OF THE INJECTORS ARE FIRING! What are the chances of all eight injectors not working at all? Keep in mind that the noid light blinks on all eight connectors when cranking the engine and the fuel pressure gauge show 42 psi while cranking. Could it be that all the injectors are bad? Anybody else have this problem before?

Trickster

Hello Pwdbychevy,

I know these are probably going to be some dumb questions here, but since I haven't seen them addressed anywhere in this topic I have to ask. Are those new injectors, have you checked the OHM resistance on them, what size are they, and who makes them? Just curious!!

pwdbychevy

They're not new injectors. I believe they're the original 22 or 24lb injectors that came with the unit. They have a gray body. The unit is out of a 1991 Transam 350 TPI. One of them looks like the body of it was burned but still looked ok. I've checked ohm resistance on them and they measured around 16.8 ohms each.

Trickster

They are the 22 lb. injectors and the resistance of 16.8 is good. If they haven't been used in a while, they may be stuck. Try tapping lightly on the sides of each one and see if they work. You can also hold one with your fingers while cranking to see if you can feel it clicking.

pwdbychevy

I'll try that and see if it works. Is it normal for injectors to stick if they haven't been used in a while? Would it hurt if I sprayed the WD40 in them to loosen them up?

grafx

could be a possability, try some carb cleaner on the undersides of the injectors

pwdbychevy

IT"S ALIIIIIIIIVE!!!! :lala: I got that beeyatch started! I bought 25lb SLP injectors but decided to mess around with the stock injectors while waiting for SLP injectors to arrive, I got all of them to fire away and decided to put away the SLP injectors for later use. I figured they would make my 305 run too rich. The engine started kinda rough I guess because the computer was relearning parameters but this thing is purring like a kitten now after adjusting the timing. I can safely say that my TBI to TPI swap is now officially complete. Thanks for all of your help guys. I'm sure many questions will arise later on. Now, about this burning your own chip thing...

Trickster

Cool!!!!!!!!!

I see by your profile that you're down in Tampa. Not out at MacDill by any chance?

pwdbychevy

I live in the New Tampa area on CrossCreek Blvd. Macdill AFB is about 12 miles south of me.